Does anyone know what type of signal the ECU outputs to trigger the Ignitors.

[cdndub]

I've been hunting for an intermittent misfire on my Q45 for the last while that occured between 1500 and 2000 rpm at light load, it would dissapear above 2100rpm and is probably related to load on the engine as well as either a failing spark plug, coilpack or ignitor.

I've done almost everything else in an effort to track it down short of having the injectors ultrasonically cleaned and flowchecked but they all ohm out within .2ohms of each other and all between 11.4 and 11.8 without the harness.

I made an entirely new Injector, Temp sensor and Knock sensor harness a few weeks ago without any effect and found a few leaks in the PCV system that I corrected and made 100% sure there are no leaks anymore even using two clamps on some of the hoses that are hard to reach once the upper intake goes on.

However what lead to the intake removal and all this work in the first place is that suddenly the stumbling and mis got a LOT worse where it now feels like its running on 7cylinders.

I'm going to try making up a Consult interface today so i can do a balance test and see if i can narrow down which side is causing it.

Power is still decent and the motor still seems to smooth out above 2000rpm. But its definitely lower than stock power the car feels sluggish compared to have i've felt it run at different times.

I will probably just go and get out the oscilloscope and check the signal from the ECU to the ignitor but I happen to have a brand new <off of a Crate engine> set of GM LS3 Ignition coils. These are great coils with excellent spark output 65-85KV depending on dwell.

I'm hooked on the idea of ditching the ugly ignitor units, and the annoyingly expensive and hard to work on and hard to find replacements for stock coilpacks and mounting the GM ones off to the side with short plug wires down to the cylinders. It seems like it would make all kinds of things easier to work on in future and given the advancements in coilpack technology between 1992 and 2009 I think they probably put out a lot more Voltage and Current than the stock ones. I dont see any downsides other than making sure the stock ECU will trigger them properly.

If its not the case I can look into manufacturing interface boards that take care of converting the signals and making sure the Dwell is correct.

Its getting to the point now where I'm tempted to rip off the stock fuel rails, and injectors and make up adapters to take the new 4th or 5th gen Laser Drilled injectors, and toss the stock ECU in the bin in favor of a good standalone. However If i'm going that far then a Turbo system or supercharger and 5speed swap isnt far behind either. And at this point i'm quite happy with how the car runs and works when it does run properly.

Sorry for the long ramble just wanted to give some background and yes I've tried jumpering the fuel pump controller with no effect, fuel pressure is good, filter is new, etc etc and on and on.

Dave
Modified by cdndub at 3:05 PM 7/20/2009

[Q45tech]

Why?I've had the same coils and ignitors and harness for 19.5 years and 332,900 miles.

Why redesign something that works perfectly, unless you are a manufacturer to reduce cost and decrease reliability to sell replacement parts.

Of course to avoid oil leaking into well I've removed cleaned and resealed valve covers twice about every 7 years or 100k.

There is nothing electronic in coil assembly only the coil and connector. The ignitors are so robust be have never replaced one, same with coils.

The usual problem is owner abuse in not resealing and not cleaning coil extension.

Since you can probe the input to coil and view with oscilloscope you can see the waveform and the resulting field collaspe waveform and feedback from the spark plug firing.

Most misfiring is from leanness caused by soot on intake valve heads from poor quality gasoline. Why one uses a quality detergent additive in gasoline and a periodic vapor cleaning of entire intake all the way thru plenum into combustion chamber.

[Q45tech]

Just like with any motor, fuel pump, or injector the current waveform of the coils [input] can be observed by removing the fuse and substituting a small value resistor or wire loop to allow the use of an amplified dc current probe to feed digital storage oscilloscope..............use the delayed offset triggering from #1 to lockin time base and count and observe firing order.

"The primary coil generates a flyback waveform that has a peak voltage of 40 to 400 V and is usually on the order of 10 ms in duration. Therefore, an instrument with the ability to measure voltages over 100 V and at a sampling rate over 100 kS/sec is needed. Traditionally, you could measure this waveform using a specialized and expensive digitizer that has high-voltage capabilities. Alternatively, you could use a general-purpose 8-bit oscilloscope with an attenuation probe, but this method reduces your accuracy dramatically. "

http://www.lindertech.com/ign_coil.htm

[cdndub]

Q45Tech that was probably the most useful post reply i've ever had to a question/idea I guess I'm just at a place of frustration and having recently <last summer> resealed both valve covers and checked the boots and put new OEM spark plugs in etc, and then done the list and more that I detailed above trying to hunt down this intermittent problem. I've verified EGR valve is working as it should, the Purge valve, my idle valve actually did bite the dust but I managed to open it up the solenoid and found that the coil itself was ok and it had broken the lead from the connector to the coil somewhere inside the plastic end piece. I simply drilled out some access holes to get to the leads for the solenoid coil, soldered in some legs so that they would extend outside the end of the cover and then drilled around the legs on the connector so i could expose the metal. Then simply soldered some short jumper wires externally so that I could keep the factory harness but make the Idle Stabilizer valve work again. Once the cap was back on I used some two part epoxy potting compound to seal things back up so mother nature wouldnt destroy it anytime soon.

Since it had to come apart I also took the whole Idle valve apart and cleaned it thoroughly and then checked it for adjustment and leaks.

So i'm still feeling totally stumped The coils were something that I had heard from others were a fairly common failure point on the G50's but what your saying is totally the opposite. I think in fact I will have to just scope the coil negative wire and see if in fact things are working. I suppose its also possible that I've just had a sparkplug fail on me.

I cleaned all of the upper plenum while i had it off, soaking and then scrubbing etc where things looked stubborn but it wasnt all that bad to begin with since I'd done this as well when it was off for the Valve cover resealing.

I'm starting to wonder if with a leaking PCV system if maybe the seal into one of the spark plug holes failed and filled the plug hole up with oil again like i'd found before I did the covers.

Theres also the ever possible notion that its just a brittle wiring harness thats causing the ignition coil problems. I completely agree with you that the Stock coils are robust units and didnt look like they would be failure prone other than being located in a fairly high temperature area for the last 340,000km's

I think i'll go back to finishing my consult interface now that I've found the Crystal and two IC's i was missing and see what the computer actually thinks. What does still surprise me is how the car can misfire this badly, and run this poorly and not trip the CEL.

[cdndub]

Oh I also forgot to mention that After I finished the work I detailed in my first post and the engine was running exactly the same as it had before other than the Idle motor working again which meant it didnt want to stall when you started it after it was warm. I decided to try and give it some Water injection to clean out any remaining carbon on the valves/combustion chambers. I just held the idle high at 3000 rpm and let it suck the water in Via one of the ported Vacuum fittings on the Throttle body. I gave it 200ml of water 3 times over a 5min period once it was warm and the motor did sound smoother afterwards but the misfire persisted. I was hoping it might clean up a plug if it was just fouled.

I've just tried adding some Fuel system/Fuel injector cleaner to my last tank of 92 octane Chevron and will see if it makes any further difference. I'm also changing the transmission fluid as soon as my filter kits arrive.

I was also wondering if it might just be a sticky lifter causing a valve not to actuate properly before I changed the oil. It has been on ELF 5W40 Full Synthetic since I bought it and wondered if i'd let it go to long before a change. After draining and changing with a new filter it also made zero change even after another 2-3days of driving.

I'm hestitant to drive it much at this point and its my Wifes car So i guess i'm grasping at straws but should do like you say and just be logical and test things. I'm sure once I do finally find this annoying gremlin, I will probably laugh at how simple it probably was. It = was so intermittent in the past and is now at least a nice Stable failure which will make hunting for it simpler I hope.

Thanks Dave

[Q45tech]

Hopefully members understand that the ecu pulses to trigger ignitors or coils with built in ignitor control transistors are identical.

The purpose of the ignitor transistor is to allow a small low wattage [low ampere] transistor to be used in ecu for low heat and extremely high reliability.

This has applied to every car for 30 years whether a single, dual or 8 coils.

I have warned members since 2002 that they will need to reeducate themselves in basic electronics and microprocessor software if they have any hope of self repairs in the future.

Just think of all those battery/alternator idiots [challenged] we have here and how difficult it is to get them to perform simple voltage and current tests.

I get frustrated with members who don't follow advice and plow ahead blindly in replacing components because someone else on a different car said that helped without understanding even the basics!

I see the same situation with trained technicans they want to fix not test and work too hard and make to many mistakes [wasted effort] to avoid letting their mind do the majority of the work.

[maxnix]

In those long and articulate expositions, I do not see any mention of basic intake maintenance nor cleaning. If you are not starting with an as new specification system (or systems if interdependant), small problems are easily masked by deferred maintenance and cumulative maladjustments (deviations from as designed OEM).

[Q45tech]

If we redesigned VH45 so that it had multiple extra gigantic air filters to remove the oil vapors from PCV return and EGR air and maintained the oem gas vapor filter better..................we would have virtually no need to CLEAN the throttle body, plenum, and runners.

[cdndub]

They were lengthy and poorly written which I apologize for. I can type 120wpm when its coming straight from my head and tend to get carried away with run on sentences and To much information.

I've done all the basic maintenance I can without having a consult interface. I've even replaced the worn Throttle position sensor with a new one <It very likely could have been cleaned if taken apart and the carbon tracking removed>. I verified that it had several dead spots when I checked it with a multimeter over its range slowly.

I'm not complaining about the overall reliability its been a good car however I have spent quite a bit of time under the hood and replacing things. Not things I wouldn't expect to replace on a high mileage 1992 vehicle.

In fact I'm about to change the transmission fluid again since the two filter kits I ordered just arrived this morning.

The intake was hand scrubbed with lacquer thinner <upper intake> along with the throttle plates in the throttle body, and anything I could reach was cleaned when i had it off a few weeks ago.

I should with any luck have time to finish up the consult interface today and see What/If the computer has to say about the misfire once I do the transmission fluid change.

[Infinitiguy19]

Now I know I am nowhere near you guys when it comes to knowledge on the Q or just working on cars.

But do you have any exhaust leaks?

How new are the motor and transmission mounts?

And your sure you got all the intake/vacuum leaks?

Did you test the injectors hot and cold with a good VOM?

Is the car perfectly quiet right now?

If not what does it sound like and can you record the sound or even make a video?

And according to Ty at T3 when I gave him my results of a power balance test using OBD Scan Tech Nissan, He said the results were backwards and I would have to do some math to find out that actual change in RPM's between cylinders.

Welcome to NICO.

[cdndub]

Well i've got some interesting results after spending a few hours working on the Q today.

One I think I finally tracked down another annoying Issue that also likely explains my 2nd find.

So before I got started on anything I took the car out and picked up 24L of AGIP Dexron3 trans fluid. Making sure I took it easy on the drive to and from the shop but got things warm enough to be at operating temp etc.

When I arrived back home I thought why not start with the standard AT Check transmission diagnostic. The results showed the number 3.. I sat scratching my head for a few minutes realizing that was the code for the TPS sensor again. Now that code and error is what lead to me checking the TPS and changing it out origionally.

I decided enough was enough it was time to get out the multimeter and scope and check the signals right at the TCU and ECU for the TPS.

As soon as I got the kick panel off and pulled the TCU out I thought why dont I just start by undoing the harness and checking to see if there are bent or corroded pins etc. I do Automotive Electrical work for a living and see sadly a LOT of downright horrible electrical work as well as just plain old 20 year old + corrosion.

As soon as i pulled the plug off the TCU I realized that there was oil inside the connector near the bottom. Right at the pins for the TPS input and Temp input. Thinking maybe its just leftover deoxidizer spray from the previous owner etc I put some on a rag and tried smelling it.. It smells just like plain old engine oil.

I find a little more on the harness near the connector and another small amount on another harness nearby but see no other oil anywhere and this is INSIDE the car. I admit I felt really puzzled at this point but decided to just spray it clean with some degreaser and then deoxidizing/electrical contact cleaner and put it back together before taking any measurements. I also opened up the TCU and checked the solder connections on all the pins inside and found no cold solder joints.

After hooking it all back together and powering up the car the Voltmeter measures 0.398Volts with the throttle closed and 3.98Volts with it wide open <my throttle cable is slightly stretched i think and is probably origional so may only get to 98% throttle>

With the car running the values changed only slightly probably due to the charging voltage coming up and raising the 5V reference voltage slightly <its 5.2volts for the record I measured that too.

So what i'm thinking now is that some of the weird behavior i've felt with the car since I bought it and moreso in the last 10,000km's where it would run great and feel like it was shifting to match the throttle pedal sometimes.. and then other times you'd put your foot down and suddenly realize the motor was just loading up and you were going to get hit if you didnt get into traffic faster etc and would mash it to the floor to get it to kick down a gear.

I think that it was probably losing the TPS signal sometimes. I never did see a Transmission Malfunction error ever come up. Nor a MIL light come on.

I think the TPS signal must've gotten worse when the outside temps got warmer here <in the 30's lately>

The negative impact of all this is that its made my trans fluid go from a decent red color with nice clean dexron3 smell the last time I checked it around 3-4k ago to a slightly burned smelling dark red/brown color. which was my second find of the day.

So i did the standard drain 4L of oil from the pan, fill 4 L of fresh ATF up, run it for exactly 2minutes at idle, and then shut it down and drain etc. Doing this until i hit 16L of fresh fluid having gone into the PAN and 16L coming out. Then I decided to take it for a drive and get it warm again and check the trans codes.. All Clear now no TPS error. So then it was back under the car. Drain another 4-5L of fluid off and then pull the pan and change the pan gasket and filter.

The filter looked well used and the magnet was definitely dirty..

Its all clean now and after letting it warm up to operating temp at idle for 5minutes I took it for a spin. What a HUGE difference, the shifts are smoother, firmer it seems to hold the gears longer and harder as well. I let it get nice and hot and then tried some good WOT runs and it holds strong in 2nd and 3rd to 6500rpm before shifting.

I also forgot to mention this is a 95transmission and TCU in a 1992 Q45, a swap the previous owner had performed, and there is already a front mounted B&M trans cooler.

The misfire at idle is still present, but slightly better on occasion, it definitely seems to come and go and the motor is smoother above 2200rpm still.

The last interesting thing I found is that My feeling about it being an ignition problem is very likely true.

When I got back home the first thing i did when parking the car was look under it for an oil leak.

To my surprise I noticed that the exhaust pipe just after the catalytic converter on the drivers side, and drivers side only, was glowing red hot, the passenger side was warm but not glowing.

This means unburnt fuel on the drivers side giving the Cat lots to burn and making the exhaust temp climb.

The sound also matches i've thought the miss sounded like it was on the drivers side exhaust bank for a while.

I can try to record the sound but if you've been around cars for any length of time you'll know what it sounds like when a V8 turning 600rpm is dropping 1 or 2 cylinders every single rotation.

Time for bed on this end, but at least i know what bank to look at for ignition related problems <likely just broken wires or connectors and not a coil at all.

Dave

[maxnix]

I've done all the basic maintenance I can without having a consult interface.

The intake was hand scrubbed with lacquer thinner <upper intake> along with the throttle plates in the throttle body, and anything I could reach was cleaned when i had it off a few weeks ago.

OK, so that only leaves EGR system, IAC valve, and lower runners.

[cdndub]

Actually in my post <long rambling ones> above I do mention that I just entirely rebuilt the IAC valve and the EGR valve is functional.. I didnt clean it this last time It the intake was off but did the time prior and have checked it manually in the past and it still seems to function properly as the motor will definitely stumble and die or nearly die if I apply vacuum to it at idle and cause it to open.

SO i guess that leaves the lower runnings as a potential problem, I did clean inside them as far as i could get a rag with some laquar thinner but that doesnt mean the valves are super clean. However I was hoping the water injection cleaning I did recently would help clean up the intake valves as well as the exhaust even slightly. at least enough to cause the condition to improve slightly.

I've never come across ANY engine where the lower intake runners were contaminated enough to cause a complete misfire on one cylinder. I could see that happening if i had left a rag down one port but know thats not the case.

I did however realize after making the long post above about hoping that i've now narrowed things down further that A lean Misfire would also cause a rich condition at the Catalytic converter so its still possible its a clogged injector etc.

I'll try cleaning the intake but am going to turn my mechanics intuition back to where I think the problem lies which is somewhere in the ignition system.

I will post an update as I check/find things in case anyone else ever comes across problems as strange as these ones. I am still totally stumped about the oil inside the TCU connector causing an intermittent sensor reading. Stumped about how it got there not that it would cause a problem.

I'm not going to rule out the lower runners or intake valves being a problem. anything is certainly possible now.

[Infinitiguy19]

Did you check the ECU pins and connector for any oil or other substances?

[cdndub]

ECU pins are clean as is the ECU, I checked it for cold solder joints as well and damaged components a few weeks ago.

I do apologize for my horrible grammar and run on sentences.. My wife just gave birth to our Baby daughter <first child> 10 days ago and sleep has been something I've come to realize is a truly undervalued commodity. The Q45 is also the car thats got the babyseat currently in it and the most comfortable for us to all go out in so I'm trying to get it back in tip top shape asap. I'm heading outside to pull the coils and check the harness, plugs and coils to see if i can visually identify which cylinder is having the misfire problem by looking at the plugs. I'll take some photos of what I find and will post an update later.

I'm just hoping its not oil leaking through the Valve cover and down into the plug valley causing it as I just resealed the covers coming up on 1 year ago <20,000km's> and its not a Job I'm looking to do again all that soon. I think i'd probably rather do it with the motor out of the car next time.

[silkysmoothyjud]

Kinda off the tech stuff, but my a/c belt tension wheel just failed, froze and broke my belt. But the failing tension wheel felt like a random misfire at idle and at low rpm before it completely froze. I couldn't figure it out for the longest. I thought I would just throw it out there.

[cdndub]

Belts are fine.. My mechanics intuition didnt let me down.. I just pulled everything off the drivers side to get to the plugs.. Plug number 3 is wet and black the other 3 look decent mixture looks excellent on 5 and 7 and 1 may even be a little lean <which could be a result of dragging cylinder 3 along for a ride>.

I was also right about the failing coils. I'll take measurements but they have literally physically failed i'll post up some pictures later. The epoxy has failed on two coils, cylinder 3 and cylinder 5 and I can see heat damage around the core where its been arcing to the side instead of into the spark plug.

Trying desperately now to find replacement coils locally that wont bankrupt me.

THe LS3 coils are now becoming a much more considered option as well.

Dave

[Infinitiguy19]

So did the coils fail because of the oil that was on them?

How long do you think they were leaking on to the coil?

And if you don't mind, How long can oil stay on the coils before they fail?

I would try a local junk yard for the coils, Low ball them too because not many people need couild for a G50 Q45.

[silkysmoothyjud]

Try "infinitioptions" on ebay, my part guy will hook you up cheap. Do the transaction outside of ebay and save even more. Tell em Justin sent ya..

[Infinitiguy19]

That seller was not found, I did find this guy however: http://stores.shop.ebay.com/In...mrsZ1

This Store currently has 0 listings. You can come back later or check other Stores.

So how do we see what he has?

[silkysmoothyjud]

he has 9 cars or so...shoot him an email....

[silkysmoothyjud]

oops, brb with proper spelling

[silkysmoothyjud]

infinitoptions, His name is Alex, tell him Justin sent ya and do the transaction via invoice off of ebay. I got my a/c wheel for 15 bucks delivered.....

[cdndub]

Problem SOLVED!! this intermittent miss has been plaguing me for almost a year it would change with temperature and often disappear entirely after i'd worked on the car doing minor maintenance or fixing a vacuum leak etc

It was in fact 1 completely dead coil that still passed the ohm test that the manual tells you to do.

And a 2nd coil had also cracked and was on its way out as well. I replaced both with good used units from a local Nissan shop that was kind enough to stay open on a saturday night and meet up with me so I could buy 4 coils off of him.

I now have 2 spares and 2 dead ones I'll post pictures of the offenders as soon as I copy the images off my camera and upload them. The epoxy center is definitely yellowed and showing its age. The coils on the drivers side were also more yellowed than the passenger which leads me to believe that the engine bay layout lets more heat <or maybe just the coolant gallery design> build up on the drivers side of the engine than the passenger side.

THe coils I replaced them with are much closer to clear/white fresh epoxy than the ones I removed.

I dont think oil caused the failure at all I think once the epoxy failed it was just a matter of time before the windings are able to short to the metal core instead of firing off a spark on the plug.

THe car runs beautifully now honestly its a whole new car with the intermittent TPS issue for the transmission computer fixed and the misfires gone its sooo butter smooth on the freeway and has torque again on the bottom end.

I'm glad I didnt give up on the car and toss in the towel I knew it had potential still in her.

Dave