Alright... now that i set the tps for the third time (it was off AGAIN.. different method... now its perfect)... idle is quite a bit better... but i think i found out what my idle problem is. When i start it, the rpms jump to like 1500, then take a dive to about 500, and slowly the idle goes back up to 750-800. WTF is going on! BAC?
Thanks
-Ross

 

buuuuuuuump

 

did you do the TB mod???

 

no sir

 

i think it is the BAC... so i adjusted the idle screw a bit... as soon as i let off the gas, it stays at 1000 for about five seconds then drops to 750. Later on in the day... it was going to just under 750 back to 750. This inconsistent idle **** is really pissing me off!!
Oh yeah, and i still have that warm idle misfire... as though the engine is running out of air when i start it... then it slowly recovers by itself.

what would be to blame for an inconsistent idle? I do not think it's a vacuum leak because the guy that i purchased it from brought it to the dealer to have the rough idle diagnosed, they replaced the UIM gasket, and it fixed the problem, so a vacuum leak check was done a few months back.

Thanks
-Ross

 

once again, today the idle is yet again different,

 

Buuump?

 

Check for vac leaks, clean the BAC, check for vac leaks, make sure your dashpot/thermowax is functioning properly, check for vac leaks, readjust TPS accordingly (only after warm!), and check for vac leaks

 

Sorry kinda off-topic, but.. You said that you adjusted the BAC screw. Is this the allen head thing on the side of the bac? On my car that thing will not turn, and I have several other BACs that it will not budge on either, so I was wondering if its even the right screw....

 

It should just be a flat head screw, no allen head.


As for my car, it does the same thing on idle. After revving it comes back down to random RPMs. Sometimes 1000, sometimes 600. It doesn't misfire or anything, just doesn't go to a consitant spot. Mine is a fresh rebuild though, so I have that to blame for it. I will try to further adjust the TPS as well.

 

Ok, so here's what i did... Tested for vacuum leaks - found none. Adjusted TPS again, this time TO THE T... as per the Mitchell manual... but the short-range tps only went up to 3900ohms.

Anyways... when revving the car from the engine bay... if i go over 1000RPM it stumbles and hesitates and backfires... up until 2000RPM... and it sounds like the BAC is buzzing when that happens. I thought the BAC was only active at idle????


FURTHERMORE... ON TOP OF ALL THIS CRAP... i have now confirmed that the car, unless ABSOLUTELY WARMED UP, hesitates every once in a while over 5000RPM... boost or not.

The plugs ARE new. I doubt its the wires...

So here's what i'm thinking... the fuel mixture must be off... so either I have:
A) Bad TPS with temperature-sensitive blow-opens.
B) Bad AFM with temperature-sensitive blow-opens.
C) BAAAAAAAAAADLY leaking injector(s).

So the next course of action, when I have a free weekend, is to pull the UIM and get the injectors cleaned professionally.

It has all the symptoms of a bad ground, but i redid the grounds already!!!! All except the ECU and the boost sensor one. Are those neccesary?

 

OH BTW, the inconsistent idle quirk went away after I re-re-readjusted the tps and set the idle speed with the jumper.

 

Oh and i also pulled the TID off to check for cracks, found none... went around on a hose tightening spree... no change.

 

I have same problem as yours-sometimes idle will be 1000 rpm sometimes 700 when I stop at a light. Adjusted TPS and idle did not seem to help. Car runs great across entire powerband, should I just accept it and stop nitpicking about a 15 yr old cars idle?

 

Fingers,
not too familiar with the TII,
but it sure looks like you have a bad TPS

hugues -

 

pmr2000:

make sure you set idle speed as per FSM
make sure you TPS is adjusted correctly as per FSM
make sure BAC is working (and that ECU sends the correct signal to BAC) as per FSM
make sure your charging system is up-to-snuff (battery, alt, cables)
make sure you have good grounds
make sure you have no vac leaks (check EGR and ACV diaphragms)

Even with a 10-15 yr old car, the idle should be pretty steady if the engine is decent.

Hugues -

 

hugues, could it possibly be a bad AFM? Would a bad boost sensor cause this also?

 

The reason why I ask is because I tested the TPS for any blow-opens... there were none, but when i put everything back together, it still did that thing between 1000-2000 RPM. So i'm thinking something else is the problem, like the boost/pressure sensor, or the AFM

Thanks
-Ross

 

Are you *positive* you don't have vac leaks? Boost sensor won't do that, AFM could but is unlikely.

 

Positive. My mechanic used propane, and went all around the engine, and we found NOTHING. The idle did not change at all.

 

Have any error codes at all? Crappy grounds? Try to press the AFM flapper open a alittle and see if it smoothes out.

 

No error codes. Grounds have all been redone except the boost sensor, and the ecu. I'm sure the afm works... i just think it works intermittently

 

Do like I said and press on the afm flapper while it's running and see if you can get it to smooth out/idle more closely. If that fails, check your dashpot/linkage/etc and make sure nothings snagging or getting caught up.

 

already checked if everything's moving like its supposed to, and it is. I will check the afm tonight, as well as doing a resistance test on it.
Thanks SR.

BTW, is it neccesary to ground the boost sensor ground wire? why?

 

Not really, it's just providing a better ground for the ECU. Are you positive your dashpot isn't maybe holding it open a tad bit too far? Or maybe your throttle cable is too tight to release fully closed?