Vehicle Tips

A SELECTION OF TIT BITS FROM FUELTECH'S MONTHLY TRADE NEWSLETTERS

WET & COLD CAN PLAY HAVOC
"Engine hard to start on a cold wet morning. Once it's started, its fine." You've probably heard something similar. I suggest that it is more than likely going to be a contact problem - a relay, earth connection, harness plug corroded, etc. A connection that is perhaps worn or corroded, that with a little moisture the resistance rises to a point where small current cannot travel. It is often hard to induce the fault - you usually have to flog Mum's indoor-plant water spray bottle in an effort to create the atmosphere. Be aware manufacturers go to a lot of trouble to locate harness plugs close to batteries & radiator header/overflow bottles (they must get bonus points!!). On Toyota it's the earth strap on the battery box (covered in acid) and the igniter bracket earth just below the battery box, the fusible links on Rodeo, the front main harness plug on Mazda B2600, the injector harness on 300ZX, and so on. It's not a bad idea to pull apart every harness connection you can find under the bonnet - you'll be surprised at the condition of some. It can be difficult to find, but remember that it is the customers problem, not yours.

A RETARD!
Young bloke brought his VL in the other day complaining that it gets "really hot". Call me dumb but "on the gauge?" I asked. "It gets so hot it stinks of burning. It'll almost burn your legs when you get out," he said. Well that's a bit different - a look underneath revealed the catalytic converter was indeed hot. The long & the short came tumbling out when he revealed (probing questions - they'll even diagnose it for you!) that the problem started after he'd installed a crank angle sensor - one of those mat black Taiwanese things. A check with the Labscope revealed that as the rpm rose, the engine speed signal collapsed which affected timing - the thing would retard right back to base timing. A "proper" crank sensor was fitted from FUELTECH, the "counter jumper" graciously gave him his money back (methinks that's happened before!) and away he went happy having learnt that valuable lesson in life that you do indeed, get what you pay for.

HYUNDAI STUMBLES
Had a number of occasions in recent months where late model Hyundai Excels intermittently run rough/no power, turn CEL (check engine light) on & log a coolant temperature code or just turn the CEL on without storing a code. In all these cases we have found a wiring fault close to the temp. Sensor (read within 10cm) just before it joins the main efi harness. In the Siemens computer system, the computer substitutes "not-quite-operating-temperature" of 80 degrees so it can be quite hard to pick without watching computer inputs for the clue, when no codes are logged.

POWER & GROUNDS STILL IMPORTANT
Had a couple of instances recently of hard starting, rough running and/or poor fuel consumption complaints. While not intermittent necessarily, the complaints could be induced fairly easily. On other occasions the engine ran fine - any testing would reveal, as you would expect, everything fine. However, when in trouble, a gas analyser revealed the mixture excessively rich. Injectors were found to be opening too long, but why? All normal input sensors (load, temp. etc) all tested fine. That left just the ECU? No - don't forget power & grounds to the ECU. In one of these the Nissan Pulsar had a stuffed earth strap between engine & body (nearly 3 volts difference - old age starting to creep in). The other was a lazy alternator on a L/R Discovery (give it a rev and it behaved itself then after a few minutes at idle, it would run like a pig again). Appreciate all systems have some form of injector open-time compensation for voltage variation - the lower the voltage the slower and therefore longer it takes to open the injector so we'd better open it a bit longer to compensate. Trouble is, the compensation is usually too much for a warm - hot engine.

MITSUBISHI TIT BITS
Surprise of the month was to learn that Bosch would no longer manufacture the TR-TS Magna 2.6 ltr distributor. Apparently the things have had few crank sensor problems, they're over 10 years old, so bugger it - no more. As you know the crank sensor is only available as a complete distributor. They do use a pretty bullet proof Hall sensor in the dissy, so if they fail in the future (after residual stocks run out), we'll have to get all cunning and just replace the Hall cell themselves. =No spark Mitsubishi 4 & 6 cylinders are all basically the same. It's a similar system to the VL Commodore, except they use a Hall sensor rather than LED. Unlike VL/Skyline, the Mitsubishi weak link is the power transistor beside the coil. An oldie but a goody, is to use an old test light (non-LED type) from battery positive to coil negative. The light will flash when the coil is grounded through the Power Transistor (just like a points system). If no flash then P/T is not being triggered (see below) or is being triggered but P/T has failed. =So, on the dissy is a 4-pin plug - that's the crank sensor. It'll have ignition power & ground & two 5 volt outputs from the ECU. Check those with the ignition on & plug removed from the dissy. Those 5 volt signals are the ones we're after - one will give you 4 Bips (off/on - 0v/5v) and the other 1 Bip per revolution of the distributor shaft. I find it easier to remove the dissy, earth it out on the head and with ignition "On", turn it by hand. If no 5v output from ECU, then ECU has no power (efi relay) or is stuffed. If no 12v supply then ignition switch problem. If no Bips from dissy, then crank sensor stuffed. If we're getting all the Bips and still no spark, then check for corresponding Bips from the ECU to power transistor - usually the blue wire (centre black is earth, big fat one is coil negative.). If no voltage then ECU is stuffed. If 0.0v to 0.4v on/off Bips, then power transistor should be triggering the coil (see above). =Appreciate Mitsubishi along with Ford EEC V (EF Falcon on) computers appear to have little worthwhile voltage surge protection. If you smell smoke where the electricity got out, then chances are high it'll be toast! Appreciate that your customer could well be up for a core charge ON TOP OF the normal cost of a remanufactured computer - IF the core is repairable. When you order, we'll be able to clarify. Don't get caught - don't quote when you're not sure. Remember, it is the customer's problem - he bought it, he broke it, you just fix them!!! Now if Mitsubishi spent another 14 cents on computer over voltage protection ………. =While we're all on about ignition systems - don't loose sight of the most common problem with Mitsubishi - poor servicing affecting driveability. You know - wrong/thick oil causing stalling/no power, high fuel problems from dirty injectors, stuffed spark plugs, incorrect timing, oxygen sensors not checked, etc. - all those old things that are not part of the $29.95 "service" from your friendly discount super market that your customer uses 'cos they're so cheap!! Wonder why!!

SERVICING OR LACK THERE OF.
Had some doozey problems recently that involved Magna TS, Subaru Liberty, Mazda MX6, VW Transporter. The complaints centred on driveability problems - unstable low engine rpm, stalling, rough idle, no initial power, hard starting. In all cases the systems were thoroughly tested for correct input signals, fuel pressure & delivery checked, etc. No codes were recorded so that meant no short cuts. Eventually in each case it was a matter of sitting down and looking at the facts. Determine first what actually was causing the instability - it could only be fuel, spark or mechanical. The ignition pattern was perfect, timing spot on, plugs good - they were nice and clean (that indicated they were burning and on the lean side). The injector "on" time did not alter, making richer/leaner had no affect on the stumble. Therefore it was not an engine management problem. It had to be mechanical and yet the engines all performed well under aggressive driving. It had to be a burn problem - suck, puff, bang or blow. The gas analyser kept indicating that these engines were all carrying too much oxygen in the exhaust, yet they were not excessively lean - as revs came up the oxygen dropped. We had to have a problem with valves/timing. Further investigation revealed the lifters/lash adjusters were pumping up under these conditions. A leisurely engine flush and change onto the CORRECT grade of oil, in all these cases fixed the problem. Be aware of oils - many manufacturers specify 10w/30w oils not 20/50. Be aware of service interval history. The moment these things slip past their scheduled service period - it's only a few thousand overdue - the more the contaminated and thickened oil is going to cause lifter type problems especially at low engine rpm.

EF FALCON IDLE PROBLEMS
The EF is developing a few idle problems. Most common is dropping the odd cylinder at idle. Appreciate the EF is the first of the really lean Falcons - 90% of the problems are dirty injectors - they are NOT like the previous models that can idle with filthy injectors. In the EF this will lead to ignition lead and/or coil problems. We strongly recommend the genuine leads - they last longer and appear less prone to cross firing. The coils should be tested just like on the V6 Commodores - that is, they should be able to jump 30Kv or 1" in atmosphere when you add in the gap. Coils available from those fine chaps at FUELTECH for less than $100. The other common problem is the severely flaring idle - sometimes as much as 2000 rpm. While we have had a few problems with the idle speed motor sealing (usually only flares a few hundred rpm after high manifold vacuum) most common is the idle speed motor driver in the computer. This is the EF that stalls or screams its head off for no reason - makes it a bitch to drive around town. While there are a huge number of different EF ECU's, we can now supply overnight for $300 if we know the part code affixed to the harness plug - 94 DA 12A650 xx (where the xx tells us the application).

PETROL FOULING PLUGS.
I don't know what they've been putting in our petrol lately, but it's been causing missing and starting problems - usually after they've just had the whiz-bang tune-up. NGK are aware of it - ("we get this sort of thing from time to time in outlying regional centres") it puts a coating on the new spark plug fairly quickly (often within a few Kms). They suggest that if this happens then go one range hotter for the time being until the "doctored" fuel is used up. Our friendly Oil Coy. Person denied all knowledge and is surprised that we could even suggest their fuel is anything other than as pure as the driven snow itself!!!!!!!!

WHO SAID THEY CAN ONLY HAVE ONE PROBLEM!
A dear old VL just about had me stuffed the other week! Customer driving along and it just died (the car, not the customer!). The thing would crank over fine, give a couple of hiccups and die. Checked the fuel pressure & quantity - fine. Checked injector pulse and after a few beats it would give a couple of shots then nothing - just too easy!! It had to be one of those Taiwanese crank sensors - replaced with a proper unit and we had injector pulse every time, good spark - nice crack and at the right time. The old girl should go, but she'd give a couple of twitches then nothing. Bugger! If it has got suck, spark, injector pulse - then it's gotta go. If it had too much or not enough fuel that would cause the problem - better check injector open time - 4ms then drops to 2ms - nothing abnormal. It has to be mechanical. Getting late in the afternoon - time to walk away and have a think. Rang back the next morning to suggest check manifold vacuum during cranking - do we have a suck problem. Verdict - vacuum was less than 3"Hg - pathetic despite the high mileage. A blocked catalytic converter could cause this. A phone call a little later confirmed that yes the cat was blocked, and she fired but stalled - when he put a replacement ECU in, away she went. How would you believe a faulty ECU, crank sensor AND a blocked cat. That dress shop was starting to look like a promising career move!!

ENGINE MISS - keep it simple.
A Magna V6 was sent in with a miss under load, a problem apparently rectified only a few weeks back, but it could have been any modern vehicle. Generally we expect a "load-breakdown" like this as being a secondary voltage fault - but there is a reason for it. This miss under load is because there are no spark plugs/leads/coil or not enough fuel to burn. In the absence of a Gas Analyser or a Scope, we can use the oxygen sensor (if it's working - replace if not). As we load the engine up we would expect to see an enrichment of the mixture, just like the accelerator pump on a carby system. If not then is the throttle position switch giving the ECU the correct signal? Or is the mixture just so lean because the injectors are blocked or there is a fuel delivery problem. We could clamp off the return line to confirm. Check fuel pressure/quantity - the pump in the Magna is tiny and is prone to failure close to the 150K mark - you expect a minimum off the return line of 600ml in 30 secs at 250kpa. Appreciate injectors do get dirty regularly, some cars are more prone to this than others, and there has been a little dodgy fuel around lately (premium will help here). Having rectified the mixture shortfall, checking the plugs, leads and coil is the next step. Work on the principal that if it can't fire the plugs then the spark is going to be looking for a shortcut. In so doing, it could have damaged a component by damaging the insulation. Appreciate some new after-market leads absolutely hate water, such that a sprinkling of water over the "new" leads once they are hot can have them missing within a few miles. Genuine leads seem to be the answer on these modern high-energy ignition systems. Why the vehicle returned with the problem was that the CAUSE of the problem was not fixed. In the efforts to save a buck only half the job was done, then some weeks later almost the whole thing had to be repeated.

IDLE PROBLEMS ON THE EA
A spate of flaring/high idle problems recently with EA-on Falcons. Be aware the power steering switch is a normally CLOSED switch and can lift the idle up to around 1200rpm plus, pretty easily. If it were bridged-out then that wouldn't happen!! Bad or loose earths will signal an unstable system voltage to the ECU and it will react accordingly with the idle speed motor. A thermostat problem will also fool the ECU as to the correct engine temperature and it will also react accordingly - probably surges at idle as well. Make sure the voltage at the coolant temp. Sensor is 0.6 to 0.7v at normal operating temperature - if not then replace with genuine thermostat. If they struggle to idle then check the MAP sensor frequency at KOEO (key on engine off) is between 156Hz to 160Hz - no more no less, and that the vacuum pipe is secure with no holes. Appreciate the CFI throttle body Falcons will do 61kph in drive with feet off the throttle - that is normal. If the idle speed motor is disconnected on the CFI Falcons (because it's faulty and the owner just unplugged it) it'll retard timing and run like a bucket - they are only about $60 new to you (from FUELTECH I hasten to add). Most of the multi point Falcons are pretty good with their idle speed motors, BUT we are now getting the odd one where the neoprene seal in the ISM is damaged and will not seal - hence high idle - pretty common when on gas.

IT'S THAT TIME OF YEAR AGAIN
Just when you thought all those old KJetronic injected Volvos, BMWs & Mercs had driven off over the horizon, never to be seen again - the weather cools down and out they all come again - just like the penguins at sunset. Hard starting cold, rough running, won't accept throttle, etc. You've just got to love the old dears!!! I know they all want them fixed for nothing, but they don't really mean that, its just something they've read in their owner's handbook! Best advice I can give you is don't assume. Back to basics. Check ignition system then fuel flow, system & control pressures before you give them the bad news. Don't expect the problem to be a 5-minute fix - try and keep the car overnight to ensure it's fine when cold. Invariably it'll be the control pressure regulator - probably locked at around 3.5Bar cold instead of a lower 1.2Bar, stuffed injectors and/or problems with the fuel distributor head. Spend the time to get this information and it'll save you a lot of time in the long run. Don't be afraid to lay the injectors over the rocker cover and activate the plate with the pump on to see what is happening. Look for fuel lying in the air flow sensor housing - the FDH piston is worn or leaking - it needs replacement. Check the cold start injector system - it'll probably be blocked. Don't compromise your high standards by taking short cuts - it'll bite you on the butt. They've bought it to you to be fixed properly. Let them have their shock/horror tantrum at the high cost. They'll eventually agree they really do want it fixed - under great financial suffering of course. They all do that - it's in the owner's handbook! It's a game they play!!

THE OLD BANG THE FUEL TANK TRICK NOT ALWAYS CONCLUSIVE!
EA Falcon won't go. But give the fuel tank a smack and away she fired. Must be the fuel pump. New one installed and bugger me she wouldn't go either. We'd better blame the supplier of the pump before we do anything else. If we check for power at the pump with the plug disconnected it is fine, BUT check with the pump connected and we've got no volts - we have a dodgy power supply. At the FP relay if you hot wire direct from the battery to pump feed, the pump fires. But when you hot wire across the relay power to pump feed, no go. The harness plug below the battery that feeds the FP relay & others had suffered the Famous Falcon Folly of corrosion from coolant dribbled into/from the header tank immediately above. A vigorous clean and the problem fixed. - absolute darlings dreaming up ways to make us a dollar !!!

CAMRY LACKING SUCK.
A '96 Toyota V6 Camry where the customer complained of poor performance, especially when cold - it had got worse over the years. He'd had it back several times to be told that it was normal - "nothing wrong Mate, it's the way you drive". It wasn't until he had a drive in a friend's similar car that he realised it wasn't him, it was the bloody car. Anyway, he called in for our thoughts - even when hot this thing wouldn't get into it like a 3 litre V6 should. Once the revs were up, it would go, but not down low. We checked the basics - cam & ignition timing, acceleration enrichment - plenty of fuel, ignition OK, it seemed short of suck. Let's check the variable length manifold butterfly system - they were stuck solid on the long runners. The manifold was full of gunk. After a clean, injectors too, she was a different beast. I would suggest we're going to see more of this as their mileage increases - a good idea to keep the induction system clean. We've seen 2 previously where the actuating solenoid has failed causing similar problems.

GASPING JEEP.
Had a Jeep Cherokee in trouble the other day. Idle away sweet, but once you cracked the throttle it was increasingly rough until about 3000 rpm where it would "hunt" something shocking. That "hunt" was injector shut-off controlled by the ECU. Appreciate the thing must be in deep stuff for that to happen - what could cause it? A loss of a major input would do it - loss of load signal, throttle position, coolant temp, possibly the crankshaft position signal or the ECU itself. Let's check these major inputs - the TPS is a potentiometer type so you would expect a low voltage at idle (say 0.5v) rising towards 5v at wide open (just like any other car). With the load sensor it is a Map sensor - similar to a VN Commodore - so you'd expect a low voltage (around 1.0 - 1.5v) at idle rising toward 5v at zero vacuum. So if you saw 3.9v constant on the Map signal, that would cause the problem - because the vacuum line had a big hole in it. The old story - keep it simple. By the way there were no codes logged in the ECU!

ASTRA/VECTRA TROUBLES.
Had a few check engine light (CEL) problems recently with the late model Holden Astra & Vectra's. They use the Australian Holden exported engine with the Lotus/Opel twin cam head and use a Bosch or Siemens engine management system. The crank angle & cam angle sensors are the magnetic pick-up type and are like all similar units, prone to heat problems. Ensure when you order them you get the correct unit - there must be quite a few different units for the various models.

HOT START PORSCHE
Surprised to find the other day with a Porsche 924 KJetronic fuel system, that in order to save money, someone had decided to unsuccessfully mix & match pressure regulator plungers & slides in the fuel distributor head (FDH) from other cars to get the desired pressure - a real NO NO. Of all the KJet systems to work on, I've always found the 924 the hardest to achieve easy hot start. This slant 4 engine has very low manifold vacuum during hot cranking and will not deflect the plate sufficient to inject fuel. Whether they like it or not, under hot cranking conditions the driver must depress the accelerator pedal to allow what little suck there is to deflect the plate. That's even in the owner's manual, but the poor dears do get confused between hot & cold cranking. Don't take short cuts, take all your pressure & flow readings first. Talk to the customer, ensure he is willing to pay, and then take your time to do a top job - the customer will be so pleased..

SUBARU IN TROUBLE.
Here's a doozey for you! Subaru 2.5ltr drives fine. Pull up at Claudia's place on the hill - being careful to select first or reverse gear and pull hand brake on hard. In the morning, engine won't go. Eventually get the vehicle towed to a repairer and discover the cam belt has slipped a couple of teeth. What has happened is the engine has been left in gear, and as the hand-brake has crept overnight with the weight of the car, the engine has rotated backwards taking all the tension out of the hydraulic tensioner. As soon as you wind it over in the morning, there is initially no tension on the belt, and bingo - 2 or 3 teeth jump on the crankshaft before the tension is taken up again. Hopefully it hasn't popped any valves in the process. Any manual cam belted engine (or chain for that matter) that uses a hydraulic tensioner and is parked in gear where the weight of the vehicle could turn the engine backwards, is at risk of this sort of problem. Got to be worth sharing with your customers.

MAZDA PURRING.
Mentioned a few months back the problems we've had with rough running engines which has been traced back to the wrong engine oil - too thick. Just the other day we had a little late model Mazda 323 that would stall cold. It purred like a kitten, but would stall every time you decelerated around town. The lifters/lash adjusters would pump up and engine would die. It would start-up straight away though and purr. A change to lighter 10w30 oil solved the problem. That's about the 4th Mazda 1800 twin cam we've noticed with this problem these last few months.

NISSAN STUMBLES.
Late model Nissan Navara V6 fire up in the morning and run like a pig for the first 8-10 minutes. Once it got hot it ran fine, no surging, fuel consumption normal, power fine. After it got the mandatory injector clean and a new coolant temperature sensor for good measure, it was exactly the same. Sh…t, better actually find out what's going on this time!! When cold the oxygen sensor read 0.8v (rich), but the gas analyser said the mixture wasn't as rich as it should be - down around 1%CO not the 3% plus you'd expect. Hydrocarbons were high, as was Oxygen - almost lean misfiring. Once it got hot, the mixture would reduce to 0.3%CO and the Oxy. Sensor sat on 0.2 volts (lean). Run at 1300rpm and the Oxy. Sensor would sit on 0.2v and NOT cycle. It was the Oxygen Sensor causing all the grief. Because the Oxygen Sensor would not respond to the ECU inputs at hot-cruise (it didn't cycle), then the ECU ignored the sensor. It substituted its own mixture across the board based on memory and based on its own program bias. With late Nissan systems, when they loose their Oxy. Sensor, they tend to bias their substituted mixture LEAN - whether it's hot or cold. Holden, for example, bias their substituted mixture rich, pretty rich for Ford, and bloody great billowing black smoke rich for Volvo. A new Oxygen Sensor and a moment to learn and the Navara was happy again. It even had more power and improved fuel economy much to the surprise of the owner - been like that for awhile methinks.

VL CRANK SENSOR STRIKES BACK
Just a reminder - the modern exchange remanufactured Crank Angle sensors (original shiny finish/RSB04 cast into the surface) are of an extremely high quality. They rarely fail. That's why we continue to offer them, and why they have a 2-year warranty. On the other hand, the Taiwanese units (with the matt plastic finish) seem to fail regularly with the resultant customer blame. BUT, it doesn't matter which unit is used if the top bearing of the distributor runs dry and pumps out orange/red metallic dust which will cover the light emitting diodes and shut the sensor down. Replacing the crank sensor will get the vehicle going, but it will stop in a few days or weeks time. A good idea is to remove the distributor from the engine to check the condition of that top bearing. It only takes a few moments - a good investment. Don't be like the chap who replaced 3 crank sensors and the ECU (for good measure) until the customer took it to one of FUELTECH's customers who fixed it properly for a $9 bearing!!!!

THIRSTY JACKAROO.
Customer complained of high fuel consumption on his normal bog standard Jackaroo V6 - was there anything we could do to improve it? We took it for a spin with the high-speed air fuel ratio meter and found it had 9:1 under full load, and best cruise out to 14.4:1 AFR. After a chat, we fitted a HALTECH E6GM computer to it and after some good tuning work by our Peter, we produced more power at around 13.2:1 full throttle, and we could get it to step out to 15.2:1 at cruise. The long and short was an extra 20kmh up the steep Southern Outlet, better low engine rpm response, but close to 600km from a tank of juice compared to 380km before!!!! Some of these modern vehicles honk the fuel in under load, hence high fuel consumption complaints in "normal" non-highway driving. I think Peter has done quite a few Haltech conversions like this now to improve driveability & fuel consumption on Jackaroos & Range Rover/Discovery.

STALLING XF EFI FALCONS
A common problem in automatic XF Falcon & ZL Fairlane. Because the engine is such a long stroke device, the air flow meter setting is very important. Any air leaks from inlet manifold, EGR valve, rear main seal will cause the engine grief - fix them first. After a basic tune of timing, plugs, fuel etc., and after ensuring the transmission is OK - should stall test 1850 to 2000 rpm - the following sequence should have the old girl purring.

Disconnect idle speed motor, select drive against hand brake, set idle to 550 rpm from the throttle body air screw.
At air flow meter (AFM), wind CO bypass screw OUT max. 3 to 4 turns. Flip top off AFM and adjust spring tension for the flap as close as possible to 1.0v on load pin.
Make necessary adjustments to maintain a smooth idle of 500 to 550 rpm in gear by dabbing on throttle to ensure engine will return to idle without attempting to stall. Final adjustment on airscrew will help (clockwise to richer). Appreciate the engine needs to be leaner than you think.
Turn engine off, reconnect idle speed motor, and do not adjust throttle airscrew because NORMALLY the thing will idle in neutral at around 850-900rpm.
To avoid the transmission bangs selecting reverse, FIRST select DRIVE with foot on brake, then select reverse - the thump will be reduced. When the transmission is repaired is the time to make pressure solenoid adjustments to reduce this ageing problem.

NO SPARK VL COMMODORES
System uses an LED crank angle sensor (CAS) within the distributor to generate a speed signal (360-degree for timing) and a position signal (120-degree signal) for the computer (ECU). The ECU then uses these 2 signals to generate a trigger to the power transistor (PT) bolted to the outside of the distributor. The PT uses this trigger to switch the -ve coil to ground to generate spark.

On top of the distributor is a 4 pin harness plug - this is the crank angle sensor. With this plug removed test the voltage on each pin of the female harness plug against ground (engine earth/battery -ve) with the ignition on (KOEO).
Should have 12v (battery volts from the EFI relay), earth (Ov), and on the remaining 2 pins - 5v on each (from ECU).
Ensure the distributor shaft is turning during cranking - cam belt.
With the engine cranking these 2 wires which had 5v on each are the important signals you are after - expect approx. 2.3v on one and 0.3v on the other. If the CAS has failed expect close to 5v OR close to 0.0v on one or both. If the signals are BOTH within 20% of specs., then
Check the signal from the ECU to the PT (fawn wire onto PT). If ECU is generating the correct signal expect approx. 0.4v. If a greater voltage, then you have an earth problem. If 0.0v then the ECU is not outputting the signal - ECU failed. If correct signal but still no spark then the PT has failed to switch the coil (rare) or the coil has failed (common).
To check the PT is switching the coil, use a normal test light from the +ve battery to the -ve coil (brown/red at PT). Your light should illuminate with KOF (ignition key off), and when the coil is switched to ground through the PT during cranking. If your test light flashes during cranking then PT is doing its job so coil has failed. If no flashing then PT has failed. Or if test light constantly lit, then PT has failed.

ROUGH IDLE VL COMMODORES
A common problem with the 3-litre Nissan engine is where the idle deteriorates to the point where it will not even run. Before that happens there is an initial loss of power, which just gets worse. A prime cause of this is the Air Mass Meter drifting beyond specifications - check the load pin (3rd in from back of engine - white wire) against an earth should have KOEO no less than 1.26v (excessive lean) and no more 1.32v (rich). If this load setting base is out, you won't be able to adjust the idle mixture (1st pin in from front of AMM) factory lean at 3.6v to richer say 2.0v to a satisfactory mixture - AMM will need replacing.

DELCO SYSTEMS THAT ONLY IDLE.
A common problem with all the Delco 808 computer systems in N13 Pulsar/Astra, VN-VP Commodore & Camira was the incidence where the engine would not accept any throttle. The engine would idle happily, but not respond to throttle. This was usually an intermittent problem, and sometimes even accompanied by the radiator fans running (sure sign ECU in trouble). In 95% of these cases a faulty computer causes the problem.

PINTARA FLATSPOTS.
Appreciate these old dears really do need both sets of spark plugs to fire. In other words, don't take short cuts with tuning - replace plugs after setting gap, check leads, cap & rotor button for damage (they are hard on their ignition components). Ensure the coils are both the same - don't mix & match. Ensure oxygen sensor actually works. Ignition timing - make sure you have vacuum advance mechanism working - Nissan dealers still have parts. We re-route the vac. advance line to full manifold vacuum - not throttle sensitive as standard - and find an increase in timing from 4 (standard) to around 8-12 degrees transforms throttle response. If mixture has to be adjusted then disconnect oxygen sensor during adjustment - otherwise it'll fight you! In standard form, the air flow meter bypass screw was set 5 to 7 turns out - pull that back to 2-3 turns out for improved response. Mixture adjustment can be done through air flow meter spring tension changes after flipping AFM around to adjust while running.

LETHARGIC CAMRY
Once Camry has exceeded about 160,000Km, they tend to get quite lethargic. Appreciate that as suck reduces from old age, the mixture leans. Regular injector cleans are recommended. Air flow meter adjustment after 160K is usually 2 to 4 clicks richer for best results (I leave the bypass screw). EGR valve spring weakens & they tend to open too early causing a flatspot (if vacuum line to EGR blocked problem won't appear). They also like a few extra degrees of ignition timing.

REPLACING FUEL PUMPS
When replacing fuel pumps, it is always worth while investigating why the pump failed in the first place. If the pump has done over 150,000Km - that's called old age. Any less, then find out why, otherwise the new pump will go the same way. Most common causes of premature pump failure is running the tank continually too low, starving the pump of fuel because the pump has slipped in the carrier, tank floor is dented/buckled, water in fuel, dirt in fuel. Strongly advise the tank be removed & cleaned before pump replaced - takes a little longer but a wise investment.