ecu problem?

[greg666]

i have a 1992 tsi, automatic, with 5spd motor. reset the ecu and it drives like a champ, for about 20 min. At this point i loose all kinds of power and the exhaust temp spikes. it continues to get worse power from that point foreward. dissconnect the battery, reset the ecu, starts all over again running strong and falling on its face after 20 min.

 

[Lofty]

What's a 5spd motor?

 

[delta448]

If you don't reset the ECU, but park the car, shut it off and let it cool down for a few hours, do you get this problem as soon as the car is restarted or does it only come back after reaching operating temp?

If this is the case and the problem only starts once you reach operating temp and go into closed loop fueling, I'd start by looking for a short in the front O2 sensor wiring and checking the coolant level.

If this is not the case, I'd pull the ECU out and take a look for leaky capacitors.

Also, you might double check that the MAS is securely connected to the intake and there is no possibility that the turbo could be sucking in unmetered air.

 

[jrohner]

+1 on the leaky caps. You may even have a hole fried in your ecu.

 

[rush2252]

+2 on the leaky caps. I think nearly every 1g is affected by this kinda like all 2gs are affected by crankwalk at some point. The ECU is behind the radio under the center console. there are tons of Threads on this try the search I bet this is your problem

 

[greg666]

the car is an automatic. it had the motor from a 5spd put in it. i was told that the ecu will react differently to different motors, and am not sure that the ecu that is in it is the right one. it is not an overheating issue, cause once it starts running like that, it doesn't run right again untill you reset the ecu.

 

[delta448]

Did you swap the injectors and the fuel pressure regulators between the two engines? If you're using the ones from the manual trans vehicle's engine then that could be part of it...

Automatic trans 1G turbos have smaller 390cc injectors and a smaller 13G turbo, manual trans 1G turbos have larger 450cc injectors and the 14B turbo. The auto cars also ran a higher base fuel pressure than the manual cars. Obviously, if the injector size or fuel pressure are not what the ECU thinks they are, you can have issues.

But, the difference is only roughly 5% extra fuel if you're using both the manual FPR and injectors.

I don't know if this is your only problem, but if the fuel delivery is incorrect for the ECU you're using it's probably not helping.

 

[habitatguy187]

Did you swap the injectors?

Automatic trans 1G turbos have smaller 390cc injectors and a smaller 13G turbo, manual trans 1G turbos have larger 450cc injectors and the 14B turbo.

Obviously, if the injectors are not the size the ECU thinks they are, you will have issues.

+1

High exhaust temps are caused by running lean. So if you have a manual ecu (which thinks you have 450cc injectors) but really you have 390cc injectors (from the automatic 1g's) then you'll be running way lean, causing exhaust temps to spike.

However you still need to pull out your ecu and check it. I had 8 holes in mine plus many burnt connections!

 

[delta448]

Measuring EGT is tricky. Probe placement affects a good bit.

Sometimes running rich causes the sensor to read hot, because the extra fuel is still burning as it passes the probe or at least burns within a closer distance to the probe and loses less heat.

 

[habitatguy187]

^^^ Hmmm, good food for thought.

 

[DSM1G90]

The Ox sensor is having fits with this and the ECU can't keep things in balance due to the thinner injectors. Put the 390's back in and you should be set to go.

I had a situation in reverse: I have a Galant VR4 motor in mine that came with 510's, but the stock ECU only knew about 450's and I was running terribly rich as the result due to the Ox sensor was trying to tell the ECU to lean it out, but the ECU couldn't.

I put in the correct 450's and the running rich problem got solved.

-DSM

 

[rush2252]

quick question? Is it true the 2g autos and the 2g 5spds have different injectors as well? I heard they have diff injectors and tunes. I know they run the smaller T25 mines running really rich and sometimes at night the turbo mani glows red after driving awhile EGT is through the roof i assume??

 

[snowborder714]

2g's all have 450cc injectors.

 

[greg666]

mine does have the larger injectors. the ecu in it is in perfect shape, but its the wrong one for the motor. i just ordered an eprom so i hope that wil solve my problem. thanks for the ideas

 

[greg666]

if its not one thing its another. put in the eprom, rewired the fuel pump and put in a walbro 255. then added a fuel labs fuel pressure regulator. now its all good, running at 14 pounds of boost no lagging at all. the egt is still spiking, but not quite as bad, and now it runs good, holds at 14, but then cuts to 10, then down to 7 without moving the peddal. anyone know why i would be loosing boost like that? what should the egt be runing at?

 

[rush2252]

Go back to the basics. Boost leak test. etc etc etc

Kolby