Idle hang.

[ThomS]

I have A fast idle when driving the car and I reach an intersection or stop light it takes 5 to 10 sec for idle to come down. When foot is off the gas for a time and I stop the car the idle is at 1500 to 2000 rpm and all of a sudden it drops to 900 rpm. IS something sticking or is there an adjustment to be made?

[Tom @ Fast Forward]

Might be something sticking but more kely thr idle adjustment I mentioned when you were here. Easy way to tell is to warm up the car and unplug the IAC valve electrical connector. The idle shouldn't change. Let us know.

[99mx5]

I would suppose it is normal to an extent. My car had a bit of idle hang when it was stock (It also had the infamous factory idle dip). The ECU is adjusting the IAC valve to adjust for the change in running conditions when you stop the car. This also happens when you use the power steering and AC.

I agree, do the idle adjust procedure in the install instructions.

[sinuous]

Maybe check the taughtness of your throttle cable. Might be a little tight?

Jared.

[Banshee]

Its a idle hang.

I didn't have any problems when I had the Pill in the IAC hose, but since I moved it to the Intake side of the cam cover, I get it occassionally. You can blip the throttle when it happens, and it'll correct itself.

[Tom @ Fast Forward]

His install has never had the idle adjusted other than the day we got it running properly. It just needed runs under various conditions for the ECU do do it's 'learning' curve. When we set it up, we set the idle a little high at the time so it would idle while it was cleaning out the half gallon of fuel in the cylinders from the grounded fuel injector that literally poured fuel into the cylinder.

I'll bet that when he pulls the plug on the IAC, the idle rises a couple hundred RPM.

[elerner]

I went through the exact same thing, Thom. Lower the idle a tad, do the unplug IAC dance and drive it for a couple of days. If it still happens, lower it a tad more.

[ThomS]

Thanks Tom and elerner. I will try that after some driving and see what happens

[ThomS]

It seems to have disapeared as fast as it came. and the idle is right on at 900 RPM with or without the IAC attached for the test.

[Kyp J]

I'm assuming Thoms's last post meant it went away by itself. Mine had been doing the same thing before I put it in jail along with the same codes Thoms was getting. Mine must be linked with his somehow. I will be getting mine back next weekend to play with it.

[ThomS]

I'm assuming Thoms's last post meant it went away by itself. Mine had been doing the same thing before I put it in jail along with the same codes Thoms was getting. Mine must be linked with his somehow. I will be getting mine back next weekend to play with it.

Yes you are right. It went away by itself. Really crazy I know. Kurt worked on my car and so did Tom, now all my codes are gone with what they did to the wiring and vacumn hoses. Still get 1518 once in a while. will fig that out if it kills me. I understand I think our two cars are brother/sisters or something.

[Phil]

I've got the same problem as the first message with the exeption that the idle does not drop, but stays around 1300rpm even with the idle screw all the way in. The second post said that if you unplug the IAC there should be no change, but when I do it the rpm drops about 500rpm. Any ideas?
Thanks

[Tom @ Fast Forward]

Vacuum leak. If it is a 94-97, have you connected the water lines to the IAC. That is required for the 94-97.

[Phil]

Tom,
It's a 2002 with the BRP set-up (remember, the broken finger). They recommended not hooking-up the water lines to the TB.

[Tom @ Fast Forward]

Yep. The 99+ don't need the water lines. It just sounded so much like the idle problems incurred with the 94-97 if the water lines are not connected.

My eyes still tear when I think about your fingers. Hope they heal just like original and soon. I said a prayer for their quick recovery.

[Phil]

Thanks for the help and the prayer Tom. The pins get removed on Monday. Does this still sound like a vacuum leak?
With idle adjust screw one turn from closed, rpm is 1300
Disconnect IAC plug and rpm goes down 500rpm and stays that way even if IAC is reconnected as long as the engine is running.
If engine stalls, rpm goes back to 1300.
Thanks for your advice and I'm looking forward to your help down the road in making my car fun to drive again.
Phil

[Tom @ Fast Forward]

In order for the engine to idle at 1300 RPM, it has to get air from someplace.

One other possibility just came to mind. Check the bypass valve actuator and see if it moves freely. If the bypass is sticking in the boost mode, the SC will suck more air through the small opening in the throttle body than engine vacuum alone would do. At idle the valve should be wide open and, if you blip the throttle, it should close to the stop momentarily.

In any case, you are getting extra air from someplace? Check the hose between the throttle body and MAF too. Unmetered air coming in through a hole in that hose might confuse the ECU into opening the IAC a bit to allow more air as it might think it is not getting enough.

Idle is controlled by the ECU based on :

Intake Air Temperature (check the IAT probe)
Throttle position (TPS feedback)
Measured intake air flow (Mass Air Flow meter) (Check for leaks between the MAF and TB.

To control idle, the ECU adjusts:

Timing (Are you still stock timing?)
Idle Air (IAC valve could be sticking?)
Fuel (Do you know if it goes rich at that point? A/F gauge?)

Should have the CARB Test Letter any day. Then testing and then we can make a lot of Californians happy. :) Think positive, we will get CARB approval and the board will let us include our hotside in the approval. Upgrading your hotside will be a pleasure. You will probably be a lot easier to satisfy than Chuck. ;) His power appetite is becoming insatiable.

[ThomS]

All of a sudden the car is idling little fast again and hanging up again.
Whats up with that.Guys any ideas.

[chuckerants]

You will probably be a lot easier to satisfy than Chuck. ;) His power appetite is becoming insatiable.

:lol: :lol: :lol: :lol:

[Kyp J]

All of a sudden the car is idling list fast again and hanging up again.
Whats up with that.Guys any ideas.

This may mean nothing since I haven't driven it enough yet since I worked on it yesterday (got caught in a huge rain storm so went home on an attempt to test drive).

I had been having similar problems including the erratic codes and occasional idle problems. I found my alternator tension bolt missing and the bottom pivot bolt loose. I guess I never finished tightening things up on final assembly. From past history reading the various forums, I know the pivot bolt is ground for the alternator and will cause a lot of voltage variations which confuses the signals from the different sensors. Especially those with analog signals (temp, mass air flow, etc.) I am hoping in my case that cured the above problems.

Since you had all the alternator/ECM problems, maybe some residue of that problem still exists. If you haven't already, double check the pivot bolt (the one you can't remove with the brace in place luckily for me since I didn't have to order that one too.)

[Tom @ Fast Forward]

More likely it is just time to calibrate. We set it on the high side when it was here. Just needs a tweak to the down side and all will be well.

[ThomS]

Ok guys I will check the pivot bolt and re check the EGR valve test too.
Thanks