1G Missing, Stumbling, Undriveable when Hot!

[Blitzking]

First off, there are no boost leaks.
Car runs perfect when cold, no missing, no stumbling. Plenty of boost and power.
Once the car has started to heat up I start to hear little pops thru exhaust, which progressively get worse as the car warms up. The car becomes undriveable after about 15 to 20 minutes of driving. If I park the car for about a half hour it will drive perfect again until it heats up.
There is no check engine light.
Everything is stock except exhaust manifold and aluminum 2-row radiator, there is no play in newly rebuilt turbo shaft.
The plugs, plug wires, fuel filter, air filter, oil, oil filter, are all new.
I removed the waste gate actuator and temporarily fixed the valve to stay open to help verify if it was and engine or turbo issue. The issue still persists.
The plugs appear to be fouling out. Removing the FPR hose does make a difference. Car starts fine hot or cold, car idles fine hot or cold. Just misses under throttle or load above 2500 rpm. Engine is tight, no smoke other than steam, no coolant leaks, no oil leaks.
Has original SMIC and hoses. Modified air box and removed silencer.

Please Help! I had a buyer for the car, but have to fix this issue first. I'm in Southern Michigan if anyone is near by and is an expert with the 1G DSM.

 

[DSM1G90]

First clue is fouling plugs. Sudden rich condition when getting warm.

Modified air box and removed silencer .. might have messed up with the MAF sensor inside the honeycomb. One honeycomb needs to remain. ECU doesn't like that at all.

 

[my dreamt dsm]

I am having a similar problem and it has been bugging me for 2 years. No engine light or anything. The only thing I found out is that it knocks around 2500 rpm via evoscan.
Compression is good, boost leak is good, plugs are good. I'm starting to think it's something related to coolant sensor or something.
But man! If any one could figure this out. It'll be so cool.

 

[Blitzking]

I removed the card board disc shaped silencer, did not touch honeycomb.
Car acts as though it's losing cylinders, I replaced the coil pack and relocated it and the power transistor module to allow for better cooling, though the problem still persists it is not nearly as bad. Any chance a CAS or the transistor could lead to this issue. I hooked up my timing light and it fires flawlessly until the engine starts to miss then the light cuts out. Does this on every wire. It behaves much like the old MAP sensors did on GM 4 cylinders in the 90's.
Any Ideas People?

I can only drive around town, as soon as I try to take out on highway she fails to the point that you cannot drive it. I have to pull over and let it cool down. The car is not overheating at all, in fact it runs extremely cool as the gauge never goes passed the halfway mark. So I disconnected the O2 and drove it for a while thinking that I would keep it in open loop mode, It did take longer but eventually it failed with O2 disconnected as well.
Need help DSm guys?

 

[DSM1G90]

I bet your ECU is going out on you, or at least, getting tired.....and this won't throw a CEL.

You need an MD128625 ECU. If it's the original ECU for that vehicle, 22 yrs on an ECU is about enough before dying.

Why the light cuts out is that your coil isn't putting out the current for the light to sense any current to trigger the cap to discharge, which ignites the xenon tube in the gun.

Temp needle SHOULD be close to the 12:00 position if you got a 195* T-stat installed when fully warmed up.

Thing HAS to run hot to run effectively for it's the way the ECU is programmed - to sense 195* from the temp sensor to go into a closed loop condition.

You run it cold and it's hating every day you drive it.

 

[Blitzking]

Thanks for the feedback, I understood why the timing light wasn't firing was just using that info for reference. Just wanted ideas on why the engine is not firing. This only happens under load or off idle, it will return to idle just fine, never stalls. Idle is a bit rougher and searches a bit though once it's hot. The CEL does work as it lights when first starting the car and then shuts off within a few seconds. I am a former State Certified Master Mechanic here in Michigan and I was a drivability specialist. If I was getting paid to fix this car I would be fired!!!!! This DSM has been the biggest nightmare I have ever owned. I have put over 3k into this car. Wish I had bought a V8 non turbo vehicle instead.

 

[DSM1G90]

The CEL does work as it lights when first starting the car and then shuts off within a few seconds.

Which is normal for the startup for any DSM (and any vehicle in that matter) since it achieves "closed loop" condition after the initial start.

This shows that all sensors are behaving normally and communicating with the ECU.

What other forms of test have been accomplished, or needs accomplished - like TPS settings, CAS setting (base timing, with the ECU disable connector connected to ground and then the 5* BTDC timing), et. al .. which all of these are perforned under idle situations?

Still say that the ECU is fading quickly on you. (sorry on the timing light comment-didn't know of your qualifications, which should be praised in the meantime...)

Time for the obvious questions: any vacuum leaks or PCV issues?

Another one: Does it still have the stock CAT on it? If so, do this small test. at the head of the CAT, drill a small 1/16" hole at the head of the CAT, then try the power thing. If power comes back, that CAT is totally plugged up - which will rob any motor of power when fuel is applied.

Good luck - DSM

 

[Blitzking]

I have the repair manuals (3) from the Manufacturer. I have done all tests and all basic settings. I even have a permanent fuel pressure gauge under the hood connected to the top of the fuel filter via a special eye bolt adapter, pressure at idle reads 30psi and goes up above 40 psi with acceleration. Vacuum at idle is the normal 20 inch range. Not sure about the EGR valve. I do have a block off kit but I'm kinda big on not hacking things up, i.e. Vacuum lines, and wiring harnesses. The ECU could be the culprit, but I did make sure that the CEL works by disconnecting different sensors to verify that it will set a light, i.e. Knock sensor, IAC, etc... The light came on and then went off when reconnected. All the symptoms of a bad ECU are not any issues that I am having, at least from what I've read about.
I built a Boost leak adapter with a gauge and air chuck, made attempts to use it, would never hold any pressures for very long so I set the line at a constant 10 PSI and sprayed everything down with soapy water. Found leaks at intake gasket (tightened and it went away), injector gaskets (replaced), some vacuum lines to EGR and the rest seemed to be internally in the engine, I installed a check valve in the PCV line to the manifold so there was never any feedback. I tried holding the engine in place (via cam sprocket bolt) but I never felt really confident, basically I pressurized the crankcase. Dipstick blew out the first time I tried. I tried it on the intake side and the turbo. I can say without a doubt that I don't feel like there are any vacuum leaks. I've tried the old carb cleaner trick and never found anything that way. Like I said it will idle forever even when it's running bad. The coolant level is perfect the oil level is perfect. Get a little oil out the oil cap when running hard, but it needs replacement as it is 22 years old. I also observed the timing mark during acceleration and it was advancing appropriately but once the engine started to miss the timing would jump back to base timing with each miss. So I deduce that it has something to do with the spark ignition system. It misses because it losing spark to the cylinders, therefore fouling the plugs, running rich and choking out the engine. I drove it at least 10 times today all short trips and it ran perfectly, didn't miss a beat. But if I try to take it for a long ride, it will fail. Another thing is the stock boost gauge seems to correlate with the miss, I can tell it's missing because the gauge jumps at the same time. When it's really choking the gauge goes to full boost, but the car is not actually boosting just flooding out.

 

[DSM1G90]

The ECU could be the culprit, but I did make sure that the CEL works by disconnecting different sensors to verify that it will set a light, i.e. Knock sensor, IAC, etc... The light came on and then went off when reconnected. All the symptoms of a bad ECU are not any issues that I am having, at least from what I've read about.

True this with the ECU making closed loops with the sensors, but doing this trick is dangerous for the drivers that works with these sensors are touchy and can easily be blown open. But, there are other sections of the ECU that communicates with the ignition system -like the CAS, TPS, coils and power transistor - this area of the ECU could be your problem.

If you can take it out (disconnect the battery first), crack it open and see if the CAPS on the momboard are swollen or leaking .... or any dead short or similar.

Why I'm suggesting all of this, for my Laser did almost the same thing before the ECU took a major dump to the moon-hard starts, fouling plugs, lack of power, et.al. .

Got it replaced and the car ran like it never ran before with tonnage of more power (and I'm a stock Laser) ... and I never had any CEL's either to let me know of things going bad.

Good luck, again - DSM

 

[Blitzking]

Thanks, for the input. I will take a look at it and see if the caps are bad. I'll let you know.

 

[300hpbound]

I completely agree with the leaking caps on the ECU. I had a similar problem with my N/A talon. When hot it would act as though it was misfiring. It doesn't sound like it was to the extent that yours is at currently, but I think I caught it early. I pulled my ECU and I had the two main caps leaking and it was spreading corrosion in about a quarter inch circle around one cap. Was not triggering a CEL either. I've only driven it once since having them replaced and the board cleaned but it seems to have gone away ( I currently have the luxury of having a little beater truck to drive during winter so she's resting comfortably in a garage).

 

[Blitzking]

Well I replaced the ECU and the car is finally fixed!!!!
What a nightmare! I also had to replace the the turbo as the rebuilt 14b started pushing oil out the exhaust. I installed a Godspeed TD06h 20G. Basically had to do a little modding to get it to fit. The power ban is also higher now it makes boost around 4000 rpm to 6500 rpm. So not much kick for around the town driving like the 16G had.
Tried a MBC but car gets fuel cut at 5000 rpm with that installed at any setting.

 

[dsmboise]

Glad to hear that you got it fixed!

Please also keep in mind that if you have the A/T, there is at least one capacitor in the TCU that will leak and eventually cause third gear starts. There's a great thread here for TCU diagnosis. Sorry, I can't paste the link. Stupid tablet! But it's called TCU Guide. Better to change it out before you have trouble. Again, this is obviously only if you have the A /T. I tried to check before posting, but I didn't see it in your profile. I remember you saying you were going to sell it.

Good luck!