danny951

just under 1k rpm

special tool

You do not have any error codes then. You have a mechanical issue. If it was my car, I would dissasemble the intake and check the turbo, also make sure there is nothing impeding intake air INTO the turbo.

And when I say, "if it was my car", please understand that I know what the hell I am talking about.

danny951

So you're saying that I do not have a bad TPS or a vacuum leak?

One other thing, when the car is idling (warm) I hear a hiss sound under the hood near the airbox, possibly right under the airbox. I thought that was where I would find my vacuum leak, but I couldn't find anything without taking the airbox off.

special tool

Nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo oooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

Take it apart and make sure nothing is in there. This is not your TPS. You would not have a good idle with a faulty TPS signal, a disconnected TPS, or a PARTIALLY disconnected TPS (yes there is a code for that)

If there is nothing there, I wil tell you how to check the wastegate with a COLD engine when I get back from taking my daughter to see "ROBOT" at the movies.

danny951

alright. I'll take a look, but if something was clogging my intake would the car run smooth before getting into boost? I'm sure you know more than I do about these cars, but I figured that my intake was good because the car runs strong until the turbo tries to make boost and that intake has to feed the motor.

Dal Heger

Actually, I have seen a faulty TPS partially fail. Still good idle, but intermittent boost at the midrange and top end. The other thing that someone mentioned is the air flow meter. It could be an intermittent failure there. The carbon trace does wear out. Yes, there are blink codes for both of these problems.

Other option is a collapsed downpipe, or right after the downpipe going into the cat (assuming that this car still has a stock exhaust). These are both double walled and the inner wall can collapse leading to a major restriction in the exhaust.

I'm also assuming that you checked ALL the hose connections/intercooler connections to make sure that they are nice and tight.
You might want to take the intercooler boots off and roll them in your hands to check for any cuts/cracks/holes that might open up under boost, but stay closed under normal idle/non-boost.

Just be systematic in your approach and you'll find the culprit.

Good luck!

Dal.

special tool

Dal - I am talking about fault codes. You are not getting a good idle with a fault code.
You can have intermittant failure/function, but when it fails, the car will not idle correctly.

Dal Heger

Yup, you are totally correct.

Did he check fault codes? That should narrow down the search quickly.

Dal.

danny951

How do I "check fault codes"? I get a red (!) flash when I boost higher than 1.5bar on the stock guage (it is rare that I can do this, but when I do the red light flashes at me) but I figured that was the LSD kicking in and letting me know it was functioning.. (?)

Dal Heger

Wow, I've never heard of that. As far as I know the master caution isn't hooked up to the DME at all. The 1991 S2 had a check engine light, but that's it. LSD doesn't have a warning light... Limited Slip Differentials just work (or not if the clutches are worn out). Do you even have a limited slip diff? Pretty rare if it's not a M030 package car.

To check fault codes, or blink codes you need to make yourself a little LED tester from parts gathered from your local radio shack. Check out http://www.lindseyracing.com/misctech.htm for the setup.

That will give you a good place to start.

Funny that Charlesworth didn't catch any of these things.

Dal.

danny951

Funny indeed.... yeah, my car supposedly has the LSD (option code 220).. not sure why else the caution would come on when hitting the boost hard. I'll put together that fault code check and see what comes up..

danny951

alright i got a tester put together... something i noticed in the picture ..



What is the thicker RED jumper that is going into the port on the right? My car doesn't have that and there are only 2 jumpers on the tester. (?)

awilson40

As far as a TPS fault.
When I first got my car, I would have this same problem with "limp mode" boost.
When it would happen I would get a TPS error code output. The TPS checked good
but after I replaced it, I never had another problem. So dont just assume its good.
Look on Lindsey's site, they give directions on building a test light and how to use it.

http://www.lindseyracing.com/Merchan...ode=TECHGARAGE

danny951

I did as suggested on the lindsey site and the light didn't blink at all. I guess this means no fault codes.. ?

I've got the airbox off now and the intercooler hose on the driver side off.. now I'm trying to find how to get to where I can check the turbo compressor wheel. What else has to come off??

awilson40

The only way you can retrieve fault codes is to be in limp mode IE boosting to only 1.2 bar, then connect the LED while the engine is running as the faults are cleared each time the engine is shut down. Dont worry about that large redwire. Its not there, some one is grabbing switched power for something.

You have to remove the VAF meter, 'J' tube and hoses connected to it inorder to see the input to the compressor impeller