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Resolved 1G Losing power when trying to make boost

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bastich32121

Probationary Member
19
3
Mar 20, 2023
Raleigh, North_Carolina
First post here. I've been working on a 93 Talon TSI with my son for over a year at this point I think. The car sat for over a decade in my brother in laws garage with a cooling issue.

So far we've had the fuel tank reconditioned, replaced the fuel pump, fuel filter, plugs (NGKs gapped to .030), plug wires, timing belt, water pump, every other accessory belt, air filter, oil filter, oil, coolant, brake fluid, pads, rotors and tires. There were also some pretty bad vacuum/boost leaks which have been sorted out by rebuilding the throttle body and replacing all the injector seals and o-rings.

So now that the car is road worthy, it's consistently exhibiting a loss of power when under throttle and trying to make boost. This issue only happens after the car has been running for a while, maybe 20+ minutes. I've done quite a bit of searching in this specific issue and the typical suggestions are, check the coil pack, check the ICM/ignitor/PTU (how many names does this part have?), check the ECU.

So far, we tried a new coil pack, 2 new (old Mitsubishi OEM) ICMs, and even had the ECU sent to ECMTuning for inspection.

I'm looking for any suggestions on where to go from here because I'm almost out of ideas.

Tomorrow I'll try and close the plug gap down to .028, but even if that does improve things, it feels like it would only be masking the actual problem.
 
Did you ever check to see if the exhaust is flowing properly?
 
You don't have to pull it. When it starts goofing up on you, have someone give the car some good revs and FEEL the volume of fumes that come out of the tail pipe. If it feels like a pretty good flow then good. If it seems like it should spit out more when it's revved up but isn't, that is a sign to then check it physically.
 
If the car is knocking badly, will it throw a CEL?
Not in stock form, but ECMLink does.

You have a temperature-dependent issue. That oftentimes points to a failing electronic component. Seems you have replaced a lot of it, but what about the fuel pump and injectors?
 
You don't have to pull it. When it starts goofing up on you, have someone give the car some good revs and FEEL the volume of fumes that come out of the tail pipe. If it feels like a pretty good flow then good. If it seems like it should spit out more when it's revved up but isn't, that is a sign to then check it physically.
Aight, took it for a spin tonight. Had a tough time getting it really missing badly but shortly before I parked it, it was missing some but still accelerating slowly. When I parked it I had my son rev it while I felt the exhaust, it seemed pretty good with a lot of exhaust gasses blowing out.

I really would like to run it with a test pipe to see how it does though.
 
Get a laser thermometer and check the temperature of the SMIC before and after it starts doing the misfire stuff. Should be able to buy one cheap at harbor freight or wally world.

I forget the actual name for them but you know what I mean. Little gun thermometer that shoots FRICKIN' LASERS to take a temperature. :p
 
If the turbo spools up quicker but it accelerates/rev slow especially under load in mid/high range like above 4000 rpm, you should check the base ignition timing with a timing light. You may have very late ignition timing. Also you should make sure the CAS is installed properly. not 180 degree off. Those would cause this kind of issue, too.
 
So, quick update. I purchased one of these cheap spark testers that allow you to gauge the strength of the spark. I tested out 4 3 and 2, and the 3rd cylinder seemed to have a much weaker spark than 4 and 2, this seems confusing though since both 3 and 2 are driven by the same coil pack. I swapped the plug wire between 2 and 3 and the problem was the same, ruling out the plug wire.

At this point we turned the boost back up a little and went for a drive to get the issue happening. Once it occurred I put the gauge on the number 3 cylinder again and I had to close the gauge all the way down to about 10kv to get it to spark, and even then I could tell it was missing some. The number 2 cylinder was still getting spark at around 30kv if I'm reading this thing correctly.

Any chance this could be the ignitor, or does this sound like a definite coil issue?

Here is what I was using in case that description was confusing.

OriGlam Spark Plug Tester, Adjustable Ignition System Coil Tester, Coil-on Plug Ignition Spark Circuit Tester, Autos Diagnostic Test Tool https://a.co/d/hQovb6q
 
Final update on this thread. Replaced the coil pack again. Made sure to check resistance between the outputs and between the posts at the rear and then between the pins in the connector, everything was in spec. We fired up the car and tested spark on each cylinder, they all measured 30kv with that gauge.

Finally we took the car for a drive and after an hour or so, mixed driving on the highway and in town and the car pulled cleanly every time, making 17psi.

Thanks for all the input and suggestions here. It's a relief to have this issue sorted out finally (hopefully).
 
Thanks for the update. I have a 2g, but basically what sounds like the same issue. I've suspected the coil pack as its basically one of the last things I haven't replaced yet. I was just hesitant because they tested good. Ordered some new coils and hope the outcome is the same as yours.
 
A couple things, I don't know if it would have made a big difference, but when the new coil pack arrived, I did the resistance testing between the pins on the connector and one of them was bouncing around and way too high >20 ohms. I transferred the 2 modules from the new pack to the old bracket and wiring and checked resistance there and it was measuring in spec.

Before replacing the coil packs a second time, I did put a cheap oscilloscope on the PTU by back pinning the connector and running the car. The resolution wasn't great but it was clear waveforms were present and 12v.
 
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