New TTA owner...rough idle questions

[brn agn]

I just purchased an 89 TTA and I am having some idle problems. Re-setting the IAC and adjusting the TPS didn't seem to help. BLM's are close to 128 at idle, IAC is low to mid teens. TPS is at .44 VDC The oxygen sensor is transitioning really well. No trouble codes...everything looks "right" on the scan tool. Sometimes the car will stumble a little when accelerating, but once the boost starts to build, it smooths out. I hooked a timing light up to each individual spark plug wire. Some of the wires had a definite "miss" as I was watching the light. I installed new spark plugs and spark plug wires tonight. It starts much easier, but the rough idle is still there. I hooked the timing light back up to the wires and you can still see the "miss" when you watch the strobe. It seems like it is worse on the right hand cylinders (it was like that before the new plug wires too). What do you suggest I change next...the ignition module or the coil pack? I don't have a tester or access to spare parts at this point. Thanks in advance!

 

[U1ARUNIT]

Test out the coil pack with an ohm meter across the top of each pair of secondary terminals . They should be 11-13k ohms give or take.

What injectors and chip? Stock chips don't usually have a very smooth idle.

 

[fly89gta]

i was reading around 10 on mine? time for a new one?

 

[brn agn]

Thanks for the advice on testing the coils. I'll do that tomorrow. The car has the stock injectors and stock chip. One thing I forgot to mention is that I can rev the car to 2000 rpm in park (I had to do this during a recent emissions test) and you can hear the engine miss ever so slightly. No real rythym, but it is missing. Thanks again for the advice.

 

[Dean]

First invest in a coil / module tester (#102020 CCCI Ignition Simulator 86-89 turbo engines) from Caspers Electronics to figure out which one might (of might not!) be amiss. Well worh the ~$110... you will be surprised how often it is used, particularly if you hang around other Buick folk!

 

[rastaz]

The stock chip in TTA's is notorious for erratic and choppy idle. Mine hardly ran when it was cold. I suggest you get a Thrasher 92 chip for $25 before you start changing expensive ignition parts. You'll be pleasantly suprised how much smoother the car will run and it might solve your other problems.
HTH

 

[brn agn]

Update...

Well, I checked out the resistance of the coils...they were all within 12.8-12.9. I did find out why the car will not pass emissions...the catalytic converter is gutted. I've got cars to pass the sniffer test here before (it is an idle test) without a converter...but I don't want to go through the trouble this time. I'm just going to buy a converter and install it. Does anyone have any advice on the best brand? What do you guys do that have to go through emissions? Do you run a high flow cat year round, or do you just swap out your gutted one every year for the test? I would like to hear your opinions. Thanks again for the advice!

 

[striker_29]

Dont know about your emissions situation, but what about your idle? Does it hunt up and down to find idle? Does it idle low? With tps and everything in spec you might want to check for vacuum leaks. Crank the car and then unplug the cam sensor, see if it gets better. Might also wanna remove the iac valve and spray some carb cleaner up thru the tb. Hth and good luck!

 

[87SFI]

Originally posted by striker_29
Dont know about your emissions situation, but what about your idle? Does it hunt up and down to find idle? Does it idle low? With tps and everything in spec you might want to check for vacuum leaks. Crank the car and then unplug the cam sensor, see if it gets better. Might also wanna remove the iac valve and spray some carb cleaner up thru the tb. Hth and good luck!

I thought the car would die if you unplug the cam sensor.
I'm having idle problems myself that i'm working on.

George

 

[striker_29]

Originally posted by 87SFI

I thought the car would die if you unplug the cam sensor.
I'm having idle problems myself that i'm working on.

George

No the car should not die when you unplug the cam sensor (maybe the maf), but it wont start without it. If you unplug it while running, and idle improves, you may have something flaky going on with it. May be bad, or not set correctly. Thats what I have learned so far anyhow. Good luck man!

 

[brn agn]

The idle doesn't hunt...it just has an audible "miss". I have unplugged the cam sensor while the car is running...no change. I also unplugged the MAF (after plugging the cam sensor back in)...no change. I cleaned the throttle body, IAC passages and intercooler about two weeks ago. I'm going to put a catalytic converter on the car so it will get through emissions...then I will worry about the idle problem. It is more of an annoyance right now. My "hunch" is that it is either the ignition module or coil pack (or the wiring related to one of those things). I'll keep everyone updated on what I find.