3.4, stock ECM. Idles at nearly 2k rpms on cold starts. Temperature doesn't matter, just that the car has been sitting. It idles high, then slowly works its way down to a good 1k idle. If I restart the car after its recently run, it idles fine.

I changed the IAC, which solved the fact that it wouldn't idle at all cold. Coolant temp sensor was replaced, but made no difference. Throttle body was cleaned recently. No vacuum leaks. No codes.

Thoughts?

[This message has been edited by onesexyfiero (edited 04-22-2013).]

Maybe the IAC is not set up just right....Have you reset the computer and driven around a while?

[This message has been edited by Gall757 (edited 04-22-2013).]

It was set up according to the instructions, and its been driven for a while.

I thought that this was normal. I let my 3.4L warm up for about 3 to 5 minutes in the morning until the idle speed comes down.

My old 86 GT 2.8 auto idled at maybe 1,500-1,700 on a cold-cold start IIRC. This is idling at 2k even on a warm (ambient temp) cold (engine hasn't been running) start. Doesn't seem right.

Anyone?

Mine always takes about 5' to warm up, then settles into 900-1000 rpm. Nature of the beast, I think.

So a 2k RPM idle on a 70* degree day for the first 5 minutes of operation is normal? That just doesn't sound right. And why didn't my 86 do it? On a hot day, cold start it settled in after the initial flare of startup right into a good 1k idle.

A bad thermostat would make the warm-up time longer.

Sure, I get that if its cold out a bad thermostat might reduce the engines ability to heat coolant, but my understanding is that if it isn't that cold out, it should bring the idle down, at least below 2k, almost immediately.

Do you have continuity from the temp sensor to the ECM? Are you able to scan the ECM to determine the sensor function?

If he didn't have continuity, the idle speed would not vary due to engine temperature.

Also if the IAC circuit was not operating at all, the engine would idle slower when cold and warmer once the engine warmed up.

Normal operation with the stock chip. If you want a reduced idle chip they are available.

This is my site where I sell them - http://www.reddevilriver.com/Related_Products.html

Blame the government for your high idle.

Haha, but really you can. Temperature is relative and all ambient air temps on this earth are low. Anyone recall part of the reason the Fiero was approved as a project? What social problems we had back in that era? OK GET TO THE POINT MAN!

The catalytic converter much be hot in order to "catalyze" your exhaust gases into more environmentally friends compounds. This is called Catalyst "Light Off Temperature" and is very hot, upwards of 300C. Your car emits more pollution in the first 5 minutes than at any other time because the CC is not doing its job. To get it hotter quicker and pass emissions we calibrate the engine for a high idle on "cold" startup. The cold means engine cold which is monitored by the coolant temp sensor. When the engine is warm, the cat is presumed warm since there are no exhaust thermocouples. This was a strategy employed by all OEMs in the day and we still do it today to a point. New three-way catalysts are much closer to the engine to reduce the time to 'light off" because the engine gases are more hot close to the head. Most are incorporated into the exhaust manifold now and we call them "maniverters" or "headiverters." They are also more efficient in design. If you live in a state with emissions checks did you ever wonder why your replacement cat is so much smaller than the giant original? "Well that sucks" you are probably saying! Yes but consider the alternative that could have been employed. You could have a bunch of secondary air junk on your car! The secondary air system makes the exhaust gas hotter by injecting air (containing more oxygen) into the exhaust manifold or directly at the base of the valve seat when employed on today's modern engines. The engine is then calibrated to run very rich for 20-30ish seconds and the unburnt fuel is burned outside the combustion chamber. Once the cat is hot, the pump shuts off but you are still carrying all that garbage and heavy hardware around.

There are also issues with heat soak effecting the IAT sensor on restart (some of your Fieros have them and some do not) and some people probably bad sensors and vacuum leaks. This explains all the "but my car doesn't do that" scenarios.

So high idle at cold startup, lower emissions.

I get that its to some degree the nature of the beast, but I still don't get why my 86, and even the 88 back when it had the 2.8 in it didn't idle as high.

Phonedawgs: I'm in the process of a 7730/DIS swap. Think I actually bought my ECM from you. Seems like maybe I should just push on with the swap and hope this gets resolved in the process.

Cheeze: I don't have a cat installed on my motor, so all I'm doing is polluting worse with my high idle.

[This message has been edited by onesexyfiero (edited 04-26-2013).]