1G Replaced ECU suddenly have idle surge/hunting

[jakes97gs]

Hi guys, I've been looking around the forums and it seems an ECU can be the culprit in regards to idle surge/hunting.

I just recently replaced the ECU in my 1g TSi with a rebuilt non-EPROM unit from eBay. Up until my previous ECU died due to leaking caps the car ran flawlessly. I just recently replaced my ECU with this one from ebay (which the seller assured me was from a turbo 5 speed and under the case looks clean and fresh) and the car runs good except idling when it's cold, until the car is fully warmed up it idles somewhere between 1400-2000 rpms and surges like the ignition is being cut until idle drops 300 rpms or so and then it idles back up and repeats the cycle.

It usually goes away when the car is warm, and from what I've been reading the ECU could potentially be the culprit among many other things. Does this sound like a bad ECU behavior, or more like ISC or another idle control piece. I will begin checking other things, but my real question is whether my ECU could be the culprit or if it's just a coincidence that the surge began now.

Also if the seller was mistaken and sold me an auto ECU for the 1g turbo what kind of effect would that have on my 5 speed? Thanks!

 

[92AWDHX40]

Could be leaks bad drivers could be a bad computer you got.

 

[wevo1985]

Try cleaning the throttle body, the old ecu probably learned to idle with all the carbon in the iac. The new one probably can't learn fast enough because their is so much in it. I know when you replace a battery on a Toyota it won't idle if their is too much carbon in the throttle.

 

[pauleyman]

How about this, old ECU could not control idle. New one can but ISC/BISS is not set correctly. ISC could also be bad which is why you should test it. Bad ISC can fry the drivers in the ECU. Test ISC and set BISS properly.

 

[KRYPYONIGHT]

I had an issue with an ECU, my car died while driving because the the fuel pump stopped working as a result of the ECU going out.

After buying an ECU off of ebay (that was suppose to work in my car) .
Then finding a guy all the way across the country who actually had the right one & informed me that you need the same one that came out of your car. If the options on your car are different than the car the ECU came out of, there's a likely chance that something won't work when you hook up the new one.

I recommend finding one from your exact year & model with all your options (sunroof, power options, transmission). You have to remember, the ECU runs everything, so if the ECU you buy isn't programmed to support some of the options your car has, some things aren't going to work & the opposite is also true, if the ECU is set up to run options your car doesn't the pins in the connectors won't go to the proper corresponding part of the car & other things won't get the correct signal to work.

 

[2gmitsueclipse]

After buying an ECU off of ebay (that was suppose to work in my car) .
Then finding a guy all the way across the country who actually had the right one & informed me that you need the same one that came out of your car. If the options on your car are different than the car the ECU came out of, there's a likely chance that something won't work when you hook up the new one.

This is a misinformed post in regard to the DSM platform. Please do some research before posting something like this.

 

[gofast63]

I had the same problem a while back. I adjusted my TPS and it solved my problem. The BISS screw could be the culprit.

 

[KRYPYONIGHT]

This is a misinformed post in regard to the DSM platform. Please do some research before posting something like this.

Sorry, just going off of what I was told. What part of this was wrong ?
Also, in my situation, this seemed to be true.

 

[gofast63]

Sorry, just going off of what I was told. What part of this was wrong ?
Also, in my situation, this seemed to be true.

The ECUs are pretty much interchangeable. Of course 1g & 2g are different.

 

[2gmitsueclipse]

Sorry, just going off of what I was told. What part of this was wrong ?
Also, in my situation, this seemed to be true.

The ECU has nothing directly to do with a trans-axle type. The difference is in the fuel (for turbo). Auto came with 390cc fuel injectors, m/t came with 450cc (for turbo).

***For turbo models only***
90 is an oddball
91-94 ECUs are pretty much the same with only differences between auto and m/t (because of fuel injectors are tune)
95-96 any will work in 95-96 car
97-99 any will work in 97-99 car

The only other difference would be cali spec ECUs (emissions).

I know there are a couple other details that are build date specific, but this is a good guide.

Other options such as trim/package options do not matter.

For example:

A 99 GST M/T ECU w/o ABS will swap into a 98 GSX M/T with ABS.

The ecu s are pretty much interchangeable. Of course 1g & 2g are different.

Not in stock form.

 

[gofast63]

The ecu has nothing to do with a trans-axle type. The difference is in the fuel (for turbo) . Auto came with 390cc fuel injectors, m/t came with 450cc (for turbo).
***For turbo only***
90 is an oddball
91-94 ecu is the same with only differences between auto and m/t (because of fuel)
95-96 any will work
97-99 any will work

The only other difference would be cali spec ecu (emissions).

I know there are a couple other details that are build date specific, but this is a good guide.

Other options such as trim/package options do not matter.

For example:

A 99 GST M/T ecu w/o ABS will swap into a 98 GSX M/T with ABS.[DOUBLEPOST=1414901568][/DOUBLEPOST]

Not in stock form.

Lol. I forgot they put autos in these cars. I think it's time for me to go to bed.