86' n/a s4.

so my idle was at 850... i naturally wanted it down at 750. took off the TB and started messin with the cam adjusting screw and the damn fast idle screw... yeah the one they say not to touch, just leave it... but no, i had to be a dumb *** and screw with it. gah.

so, when cold it always starts fine... then goes into a 1700rpm fast idle sequence for about 30-60 sec. then for a bout 2 minutes it starts hesitating and fluctuating... kind of like bouncing between 1450 and 1600. the thermovalve fully extends after warming up and does in fact make the fast idle cam separate from the roller, and once it does the car idles smooth (even though it's at 900 now). i'm wondering if anyone has experience adjusting the primary plate/bore clearance using the fast idle screw? what is a good method? i'm pretty sure that is what is causing the bouncing... because once the car is fully warmed up it drives completely normal... just the whole cold starting procedure.

i've also set the TPS once the car is warm using the lamp method (which works great). i do realize that the tps will need to be readjusted again after getting the fast idle crap figured out... bah i must have taken that thing off at least 10 times...

i've read the FSM + Haynes + multiple threads in the forum and various other pages...

hmm, i know that the primary plate is supposed to have a gap of 0.4-0.5mm when the secondary flaps just start to open. but is the primary supposed to be completely closed tight otherwise? this is confusing me...

 

I tried to using the FSM procedure (this was on a turbo car though). Even with a feeler gauge it's hard to get everything totally accurately set, and even when you think you did it right the car doesn't idle where you want it to. You're better off getting the car fully warmed up and just playing with the throttle stop screw that controls how open the primary butterfly is (forgive me, I haven't messed with the TB on an n/a car and I know they are a little different).

the thing about an n/a though is that it has the idle adjust screw thing on the top and if you still have the BAC it can get a little confusing which screw to turn, which way to turn it, and how far to turn it.

 

Did you tighten or loosen the fast-idle cam? It sounds like you loosened it (and caused your cold idle to drop)? If so, just tighten it back up so that you don't get stuck in that deadly "transition" zone where the TPS likes to freak out around 1500 RPMS's... Once the thermowax does it's thing--then it shouldn't matter where you've set the fast-idle cam. It should be doing nothing once the engine is warm.

And yes, you should always adjust/check the TPS after fiddling with the idle. That, and since you're running the thermowax, I'm guessing you also have your BAC still installed... IN that case, you must ground your 'initial set coupler' every time you mess with the idle--otherwise the ECU will try to compensate for your changes and basically cause even more annoying issues.

 

well unfortunately with the n/a it's a really hard for me to get in a good position with my hands to turn either the cam adjusting screw or the fast idles screw because they are between the firewall and the TB. i have to take the thing off every time i make more than a 1/4 turn on either screw. i appreciate the help.

 

thanks for the reply erik. i think you're bang on. yes, still running thermowax and BAC. i guess i'll do a little trial and error to see how much to tighten that fast idle screw... because i definitely loosened it up to the point where there was a gap between the primary plate and bore before the secondaries even move.

the thing i keep forgetting is to set the initial set coupler when i adjust that idle screw on top of the TB. i always assumed that i could set the idle without it in, but now i understand that it needs to be in to cut the ECU connection to the BAC (i think that's what it does). I read somewhere that I could just disconnect the BAC while adjusting the idle and it would be the same as the initial set coupler. either way i'll go the coupler route.

so, this is the order i will adjust all this stuff in:

*) remove TB
1) tighten the fast idle screw
2) check clearance between primary throttle plate and the the primary bore when secondaries just start to move (0.4 to 0.5mm) i use a small wire to test that
3) check cam adjusting screw (although i thinks its fine because the cam separates from the roller after the thermowax does it's job)
*) install TB
4) warm up the car and shut it off
5) install initial set coupler wire
6) start er up and set the idle turning the idle adjust screw on top of the TB (750rpm)
6) turn off the car and attach the TPS check lamps to the green 3 pin connector near the intake arm.
7) adjust the TPS screw so that only one lamp comes on

holy ****! lol

does this sound right? thanks for all the help! i really don't think my car would be running if it weren't for the people on this forum... so cheers to you all.

 

I would personally just use a multimeter to set the TPS on an s4. Either way, you've got the right idea.

 

About the gap. Just get a piece of electrical wire. Strip the insulation. Unwind one of the strands. Measure the strand with a mic or dial calipers. Too fat. Get a piece of emery cloth and stroke the strand of wire til it is whatever the FSM indicates. I think it's .017 give or take.

Then use that piece of wire as your gauge. In other words it is NOT a big *** piece of feeler gauge that is inaccurate, but instead a small piece of wire just the right size.

Don't mess with the throttle stop screw and when you finally get things adjusted, then adjust the TPS for an output of one volt dc when the engine is HOT and idling. See the FSM, OUTPUT/INPUT page in the FUEL SECTION.