Resolved 1G Losing power when trying to make boost

[bastich32121]

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.

 

[CrackedDSM]

I know you said you sent the ECU out to get inspected, but does it have ECMLink? Do you have any kind of way to log? Also, 100% need to make a profile thread so we can have details on the car. Like what engine it has, what's done to the engine if anything, what turbo, what injectors, what supporting mods, etc.

And what exactly do you mean by "loss of power" under throttle. Does it noticeably bog down, or does it just seem to rev and sound fine, but not go anywhere?

If you do have ECMLink, a log will help infinitely.

 

[curt-s]

My bottle of now empty scotch says log pls.

If no ECMLink, it seems like a heat issue. If you mash the throttle and can throw it into open loop, does it exhibit the same problem? You might have a MAF issue and it may be reporting the wrong airflow. Otherwise slow rolling it into boost may indicate an O2 sensor problem. May.

Otherwise it could be fuel, related to FPR. Unable to keep up with a proper 1:1 pressure balance

Plus everything @CrackedDSM says

Do you have a wideband?

 

[CrackedDSM]

My bottle of scotch says log pls

In order to keep this thread on topic, I am NOT going to ask what kind/brand of Scotch.

This is me. Not asking. Do not reply and tell me.

 

[curt-s]

In order to keep this thread on topic, I am NOT going to ask what kind/brand of Scotch.

This is me. Not asking. Do not reply and tell me.

Ok
This thread remains on topic whether or not it was a 12 year Balblair

 

[bastich32121]

I don't have ECMLink. I did have the ECU socketed while it was there (the diagnostic fee covered it), but no cable or software. Are there any logging options outside of purchasing ECMLink? If I get logging setup, what should I be looking at?

When I say loss of power, I mean it goes from making plenty of boost (gauge says it hit 17psi peak) and pulling strong to redline, to violently misfiring and making less than 5psi. After shutting the car off and letting it cool, it runs fine again.

The car is mostly stock as far as I can tell:

Td05h turbo, has the small hot side
7 bolt engine
Stock intake
Stock side mount intercooler
Stock bypass valve, not crushed

The only modification I found is what looks like a TurboXS manual boost controller. I haven't adjusted this at all yet, though I'll probably lower the boost

 

[curt-s]

Td05 covers a few different compressors.
14b or 16g? What's the PN on the compressor housing


There's a few considerations here.

For instance a 1g MAF with a 16g hitting fuel cut.

 

[bastich32121]

I'll see if I can get the numbers off the compressor this weekend to make sure, I'm expecting it to be a 14b.

I'll update the thread once I confirm that.

If you mash the throttle and can throw it into open loop, does it exhibit the same problem?

My instinct has been to take my foot off the gas when the issue started. I'll take the car for a spin tomorrow and give this a try.

 

[curt-s]

My instinct has been to take my foot off the gas when the issue started. I'll take the car for a spin tomorrow and give this a try.

This would just be a test for open vs closed loop, however, at 17psi or so even on a 14b should be enough to kick the ECU into open loop. However it still relies on the MAF to provide an airflow reading either way.

If you can back it off to, say, 15 at max and it doesn't happen, at least you have a running car until we can get some extra data somehow

 

[CrackedDSM]

Take the lower honeycomb out of the MAF and see if it still does it.


As far as logging options...that's a toughie. Honestly, IDK what even exists anymore. 15 years ago I'd have said grab an Ostrich and I'll send you Jackal to log with, or use TMOlogger, or a palm pilot emulator w/ pocketlogger software. But now IDK.

 

[1990TSIAWDTALON]

Nobody has asked, but does the car still have a catalytic converter that could be plugged up?

 

[bastich32121]

Nobody has asked, but does the car still have a catalytic converter that could be plugged up?

I haven't even checked, would that present a problem only after the car has been run for some time?

 

[1990TSIAWDTALON]

It would get worse as it gets hot as the inside expands and plugs the exhaust more. It was a common problem back in the 80s. They would plug up, car would loose power and it was hard to diagnose other than not much exhaust coming out of the tail pipe. Just something that came to my mind from long ago. You may not even have a cat but bad mufflers can collapse and do the same. It's just something to check off the list of things.

 

[bastich32121]

Thanks for the suggestion, I will check it out.

 

[CrackedDSM]

I think it’s more probably due to fuel cut when trying to run above 15-16lbs on a stock 1g fuel pump and injectors.

Turn the boost controller down, or better yet delete it entirely and just run a line straight from wastegate to the J pipe and see if it does it still.

 

[bastich32121]

I don't think its getting to fuel cut, when the problem starts the car is losing power trying to make any boost at all, it won't even hit 5psi.

 

[CrackedDSM]

I don't think its getting to fuel cut, when the problem starts the car is losing power trying to make any boost at all, it won't even hit 5psi.

So what it does is you floor it, and it pops and cuts out then continues accelerating briefly then pops and cuts out, rinse repeat?

 

[bastich32121]

So what it does is you floor it, and it pops and cuts out then continues accelerating briefly then pops and cuts out, rinse repeat?

Not quite, I haven't tried flooring it when the issue is happening. I am part throttle, accelerating, and as the boost pressure rises, it starts cutting out. The longer I drive the car, the worse it gets until I stop the car and let it cool down.

Per curt-s's suggestion, I'm going to dial the mbc down and then take it out tonight. When the problem starts happening, I'll try flooring it to try and get it into open loop to see if the problem still happens.

I may try your suggestion as well, removing the lower honeycomb out of the MAF.

 

[CrackedDSM]

Not quite, I haven't tried flooring it when the issue is happening. I am part throttle, accelerating, and as the boost pressure rises, it starts cutting out. The longer I drive the car, the worse it gets until I stop the car and let it cool down.

Per curt-s's suggestion, I'm going to dial the mbc down and then take it out tonight. When the problem starts happening, I'll try flooring it to try and get it into open loop to see if the problem still happens.

I may try your suggestion as well, removing the lower honeycomb out of the MAF.

If it does anything like what I mentioned, that's fuel cut. It'll repeatedly cut out because it's freaking out over the signals it's seeing.

It's also why I mentioned turning the boost down or just running a line direct from turbo to WGA, to limit the boost it makes. Very curious what turbo is on there.

 

[bastich32121]

So this evening, I dialed the manual boost controller all the way down, then backed 3 full turns off it. The car is making about 12psi now.

I took it for a drive and made 6-7 3rd gear WOT pulls up to 6k or 6500 over a 10 minute period with no issue, the car was running very smooth, though noticeably slower at 12psi. I continued to drive around for another 10 minutes or so and the same issue started as before. The car started stumbling when trying to give it throttle and it was trying to build some boost. WOT exhibited the same issues as part throttle, so I suppose my issue is present in both closed loop and open loop. Before I got home and parked, when I gave the car full throttle in second gear it was able to make boost, but was still stumbling badly and hardly accelerating. At this point I backed it off and drove with much lower throttle inputs, keeping the car from building any boost pressure but still accelerating smoothly, and the car ran fine.

 

[CrackedDSM]

Take a video of it? You can upload the video here on Tuners or on youtube itself.

I wonder how your intercooler looks. Is it beat to hell and back or blocked somehow?

 

[bo0st2]

A video would be helpful + getting ECMLink would be wise if you plan on keeping this car

 

[bastich32121]

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Took about 30 minutes of driving before it started behaving this way, it's a cool night. I'm not sure how well you can hear it in the video, but you can clearly see the boost reach ~10psi but the car isn't accelerating. Then when he gives the car easy throttle and keeps the engine in vacuum or very low boost the car behaves normally.

 

[CrackedDSM]

Really curious how your intercooler setup looks. This screams detonation/spark knock to me. Reminds me of when I would heat soak the shit out of my stock SMIC. It didn't bog down quite that bad, but it was noticeable. Letting it cool down fixing the problem also makes me curious.


Somethings up, wish I was closer. I'd love to pick this thing over in person.

 

[bastich32121]

If the car is knocking badly, will it throw a CEL?