strange idle surge problem

[SHEARER_TSI]

Ok, so a friend of mine bought a 91 tsi yesterday and it has a strange problem, then again it's a strange car. The car is a 91, someone put a 1990 harness in it and switched all the components (ignition, throttle body, cas) with 90 parts yet the edu is from a 91. The car wants to run rough and idle surge if you try and rev it, if you just turn the key and start it it will idle pretty good. When you first start the car you can rev it. If you do that then let it idle it will not rev and sounds almost like it is wanting to backfiring or stumble. The timing was off by one tooth, we fixed it, the base ignition timing was off, we fixed it....no change. We have tried 3 ecu's and 2 MAFs...no change. We drained the fuel out and put fresh fuel in it..no change. We swapped pins 6 and 14 on the edu...no change. We put another 90 TB on it thinking the tps was bad..no change. New plugs or wires yep you guessed it no change. Nothing seems to make it better, nothing seems to make it worse.

 

[92AWDHX40]

http://www.dsmtuners.com/forums/articles-engine-fuel/191137-how-fix-your-idle-surge-problem.html

try any of these things yet?

 

[SHEARER_TSI]

all but the FIAV,O2 sensor and boost leak. I ran out of time and he is on vacation until monday. I will continue to check for problems when he gets back. I replaced the entire tb with the one I had on my car which everything ran perfectly as all the sensors only had 50k miles on them. What would cause it not to take throttle?

 

[92AWDHX40]

Well first of all do boost leak test that's a big one right there I had bad o2 sensor and replaced that and still had idle issues until I fixed my leaks.

 

[SHEARER_TSI]

Yeah I should have started there but I was to lazy to drive and get my tester . I can not wait to get this figured out, the car is super clean and been sitting in a garage since 1995. The guy my friend bought it off of had had it for about a year and never even drove it

 

[92AWDHX40]

yeah I havnet see you on here in a while.

 

[SHEARER_TSI]

yeah I have been pretty busy with school. I really regret selling my car, I don't regret getting rid of the parts but the shell, that was a mistake.

 

[92AWDHX40]

Yeah I understand dsms and school it ll pay off, youll find another one day.

 

[SHEARER_TSI]

going to be hard to replace that car considering it only had 55000 miles on it but then again I may just build another evo.

 

[92AWDHX40]

oooo yeah.

 

[SHEARER_TSI]

My main concern with this car is that it will not rev up, when you first start it it will but as soon as you let it idle is will not. it just bogs down.

 

[92AWDHX40]

Faulty fuel system perhaps.

 

[lasershark]

i had a similiar problem with my 90 laser I used to have it didn't surge but did the rev/bog thing, after looking through a bunch of different things it turned out to be just the maf; just throwing it out there.

 

[SHEARER_TSI]

hard to imagine having two bad mafs but who knows

 

[lasershark]

hard to imagine having two bad mafs but who knows

I overlooked that part

 

[SHEARER_TSI]

I'm starting to wonder if it isn't the Walbro.

 

[SHEARER_TSI]

fixed

 

[92AWDHX40]

Good what did you find out?

 

[SHEARER_TSI]

The walbro had a bad o-ring causing it to loose pressure.

 

[92AWDHX40]

Ah that's good to know glad you fixed that issue.

 

[SHEARER_TSI]

yep still has a few bugs in it but at least it will go down the road now

 

[SHEARER_TSI]

New problem now, last night we took it out for a drive and the boost controller was out of wack, car was running like 23 psi. We turned it down to about 12 psi and the car wants to stumble and miss real bad. We tried new plugs and wires, another MAF and discovered a major boost leak. We fixed the leak and still nothing. It feels like it's running pig rich yet the plugs look like they are running lean. Going to install a wideband tonight. Any ideas?