rbrcka

I just got done with an overall tune-up to try and correct a horribly rich running condition that my car had when I bought it. I have put in new O2 sensors (fixed a burnt wire to the passenger side O2), plug wires, plugs, optispark and opti harness, coil, and ICM. I also found that the IAT sensor plug that goes into my procharger inlet elbow did not have a sensor at all! So I now have a IAT sensor.

Last night I put in my 2nd set of plugs, because the first set had carbon fouled since that was one of the very first things I did when I got the car. The new plugs last night made a HUGE difference and the car runs really smooth and revs freely with no off-idle bog like it had before.

Now for the new problem.... The car is idling pretty fast at around 1200-1300 rpm and will be steady with vacuum around 14-16 that is steady as well. This is both with the car cold and once it is warmed up to normal operating temp. Sometimes if I have rev'd it up a time or two it will act like it is trying to idle down and once it goes under 1000 rpm it gets rough for a second and then dies. When I start it back up it goes back to the 1200-1300 rpm and revs up fine, but if it starts to slow down like a normal idle it dies again. My initial thought was a vacuum leak, but I wasn't getting any revs spraying carb cleaner around the intake manifold, throttle body or vacuum fittings. Any ideas from past experience?

FAD2BLK93

Not having the IAT plugged in, the computer saw -32 degrees of air temp and goes super rich. My car has a similar problem, it wont idle down...holds at about 900 then goes to 1200, then you drive and come to a stop and the idle pulls the car along at 1000 rpm...I was told that my IAC counts were to low...11 and they should be between 30 and 50...what are your IAC counts?
The first thing I thought of was vacuum leak as well...haven't found one either.

rbrcka

I'm going to try to hook up my laptop tonight and see what kind of output I'm getting on it so I will check for the IAC count.

rbrcka

I didn't take the car out tonight since it is like 9 degrees out currently, but I cleaned the IAC. I will see if that makes a difference over the next day or so and try to log to see how things are looking.

sdm1234

iTrader: (8)

how do u find out your IAC counts?

FAD2BLK93

I hooked up a tech 1 scanner to find out what my counts are.

porksoda

iTrader: (39)

^^^Exactly

You have to hook up a scanner and see what the counts are. I wish I could check mine but I have OBD I and scanning tools are few and far between.

rbrcka

I haven't found any vacuum leaks yet, but I stumbled across something that could be part of (hopefully all of) my problem. My car came with a BBK 58mm TB installed. I found a forum discussion on here that the BBK's don't have the IAC bleeder air hole drilled like a stock TB does. To compensate a lot of times people will adjust the flappers open so it will idle. Mine are open part way when no throttle is applied.

I think I'm going to pull the TB back off and see if they had drilled a hole to allow the IAC bleed off. If not, I will drill that out, adjust the flappers shut and make sure the TPS is adjusted correctly. Does this seem like a good idea?

rbrcka

Well I did find that my throttle body did not have the IAC bleeder hole through it. I also found that the intake manifold was not ported out to the 58mm size. So, I have decided to get a stock throttle body bored out to 52mm that has been all rebuilt.

I closed down the tb flappers on my BBK and it did slow the idle down, but I could tell the IAC was having trouble trying to get the idle smooth without the extra flow of the bleeder. I think the new 52mm should clear up my idle issues and also get me a better end result for flow since the intake manifold isn't ported to 58mm. (and I don't feel like doing that now) I'll post how it turns out.

NovaTodd

Also make sure the IAC motor is working. I had the exact opposite problem. Had to crack open the throttle blades, drilled the IA port in the throttle body, ect. Checked the motor with a plug in the hole and it was dead. Replaced it and it idles right at 850 per my tune.

buffman

iTrader: (9)

IAC counts are supposed to be around 25-30 at warm operating temps in neutral. IIRC you can reset the IAC. Turn ignition on but don't start engine. Depress gas pedal about 1/3 down and hold for 10 seconds. Release gas pedal and turn key off. Wait 10 seconds and start engine. This aligns IAC with PCM.

rbrcka

That's a good idea to check the IAC too. I cleaned it when I had the TB off, but if it wasn't working that would definitely cause problems. How exactly did you test yours?

rbrcka

I put my new bored 52mm stocker on and just broke down and put a new IAC on because. I also did a little tune modification to the pcm to raise the idle timing some as well as the idle speed up a little. The little that I've had it running the idle seems to be real good now.

NovaTodd

Good deal

Has it been warm enough to actually get out on the road?

rbrcka

We just got hit with another snow storm, so I haven't been able to take it out yet. I also found out my fuel pressure regulator was going bad and had been pulling some gas into the intake manifold at idle. I have a new one ordered and I'm just waiting for it and the weather to get better. Hopefully it will be ready to rock and roll then.

NovaTodd

Haven't been there to miss a snow storm since 1982....Something to say about 300 sunny days a year

rbrcka

I just wanted to check back in now that my issues are resolved. The throttle body did help some and I also found a faulty fuel pressure regulator; however, the main source of the trouble was my damn Opti! Another victim of the good old optispark.