Not for me. A local guy has a 94 T/A, and is experiencing a pretty hefty idle surge with the car in park, neutral, or drive (A4).

I took a log today using Datamaster, and other than running on the rich end of things (112/108 @ idle LTerms, STerms were in the range of 114-118 for both sides) everything looked normal. When the surge was happening, I could watch the IAC go from it's idle position of 20-21 up to anywhere from mid 40's to the max value I saw of 78. There's no screaming issues that I can see looking at the logs. It's intermintent, every 15-30 seconds or so it would happen, and it's only in closed loop with engine coolant temps above 190* F.

If anyone wants to see the log just let me know. Any ideas??

 

Thanks for helping me out Fastbird. Also the car still has the stock Thermostat. I guess that why It was running on the hot end but still don't know what to think of the Idle surge. Thank you all help and suggestions in advance.

 

If this is a stock cam and heads car, there is no reason for it to be pulling that much fuel (108 BLM is bottomed out). You've got sensor issues or a mechanical problem. I guess I'd start looking at the MAF first (no one tampered with it, right?) . Then check for leaking injectors. Then Opti, Then O2 sensors, Then MAP.

Just my approach to things.

Steve

 

As far as I know, no one tempered with it. I bought the car last summer. The car does have new opti, plugs, wires, and O2 sensors, all done over the last summer after I bought it. Would a MAF tell the IAC to open up or cause those surges.It is a stock head's and cam car.

 

IAC is probably just reacting (as it should) to rpm fluctuations cause by another problem somewhere. You'll have to post a log of idle MAP, RPM,MAF,O2's, BLM's,etc. Also take a look for a big vacuum leak. That'l cause huge problems.

Steve

 

SABLT194
Fastbird93 has a log that he did for me when the car was ideling and having the surges. If you want you can pm for for it and he'll email it to you.

 

I sent him the log so he can host it up.

I really don't think it's a leaking fuel injector because of how intermintent the surging is. It's every 15-30 seconds. Plus there's no extended cranking time which is commonly found with a leaking injector.

 

Here's the link for the guys who wants to take a look
http://clam.rutgers.edu/~amitr/Amit4_17.uni

Hopefully someone will have a idea what the hell is going on. Thank you again.

 

I took a quick look at your DM file this AM and nothing stuck out like a sore thumb. The AFGS (MAF) doesn't seem to track RPM perfectly but im not convinced thats a show stopper. Here's a couple of more things to check:

Verify that it is running a stock .bin file in the ECM - ie: no one monkeyed with it.

Might try to unplug the MAF and fire it up on Speed Density mode and relog data to see if that cleans it up.

Any other ideas?

Steve

 

First I notice is it looks like a stock cam or very small cam?

Second, coolant is a bit on the hot side but that shouldn't matter, here are my thoughts.

First, For the idle under overspeed timing change it to 0 up to about 150 rpm, then 1* after that.

What happens is once she over revs a bit the timing drops to compensate, then it's too low so timing goes back up.

Second, close your blades a bit more, seems like they are too far open for the IAC to have nice control over, keep closing them until idle is around 40 counts, bring the idle up to about 700 if you can.

Third, lean her out a bit.

Fourth, check for misfires but it may not be the case.

Biggest thing, reduce timng compensation and close those blades a bit, PCM looks like wants to keep IAC values higher then 20 and sometimes brings them up, becuase IAC counts going up means PCM commands it.

Other then thats, you should be fine, doesn't look like a misfire from what I can tell although its hard, doesn't look mechanical either, definately just looks like the PCM doesn't like those IAC low counts and the idle overspeed timing table doesn't help by robbing all that timing either.

Once you're done, I recommend loosing the TPS and have her read around .62 at idle, closing those blades will bring what is already there lower, PCM prefers to keep everything at .62 at idle or so.


PS. Your alternator doesn't seems to be charging too well should be 13.2-14.0 volts

 

Bunker so I basically need that adjusted in the PCM. What kind of tool do i need to adjust those things in the PCM. Sorry for the stupid question but I am a novice at this. Anybody else have any other thoughts?? Thank you for all the help and advice.

 

We can adjust your IAC counts with just the throttle stop. The leaning out and timing changes however, I don't have the software to reflash a 94+ PCM. I'm free pretty much every evening this week, just give me a buzz.

 

Looked at the datalog, noticed pulse widths in open loop desired AFR 14.3 hot engine are 3.5ms with a rock solid idle. Closed loop pulse widths in the 2.5ms range and a typical lean surge... my bet's on the o2 sensor or exhaust leak pre-sensor, or a vac leak although the MAP and MAF are reading normal so that's unlikely.

 

I am throwing the Bosch one's out. And called few places no one really has AC delco's not even NAPA. Where do you guys pick up the Ac delco's from. Called the dealer they wanted $77 for one .

 

Call 877-726-8295 and ask for Jason in Parts (Jason Cromer). $35 each, you only need 2.