3.2 carrera idle problems

[deeksvaleting]

Hi
I have just purchased a 1988 3.2 carrera R.O.W.
the car has an intermittent idle problem. it fluctuates between 1200 rpm & 400RPM ,then stalls
I have retorqued the inlet manifold studs and cleaned the idle control valve, but this has not helped. I bought a second hand idle valve & the car would not run at all with that one.
when the idle is fluctuating i have tried disconnecting the electrical plug to the idle valve , this sorts out the fluctuating but the car then idles at 1100rpm .

Does this sound like the idle valve is at fault?

Can anyone help
Deek

[ChkbookMechanic]

I don't think I can completely help you, but have you tried to set the idle using the idle set screw on the intake? I had to have the idle adjusted on my car when I got it and also when I installed the SW chip.

http://www.911chips.com/dmeconvr.htm

[T77911S]

no, the fluctuating is the idle valve working. when power is removed, it opens all the way, thats why the 1100 idle. may be an o2 sensor?

[deeksvaleting]

Thanks for the reply
I had the chance of a Brand new valve but I think I probably will be wasting my money .
I will try adjusting the idle at the screw
I have been told there is an O ring behind the idle screw that can become perished and leak sometimes?

[donporfi]

Check for vacuum leaks.
Check the oil tank breather hoses, oil cap it has a seal and is a source of vacuum leaks. The throttle body has some rubber plugs, one can be leaking or be missing.

[dshepp806]

Originally Posted by donporfi

Check for vacuum leaks.
Check the oil tank breather hoses, oil cap it has a seal and is a source of vacuum leaks. The throttle body has some rubber plugs, one can be leaking or be missing.

+1: eliminate any vacuum leaks first. Standard testing for these leak types applies.

Base idle good?

Best,

Doyle

[deeksvaleting]

whats the best way too check for vacum leaks ?
is it advisable too spray carb cleaner and listen for idle increase?

[Zef]

Originally Posted by deeksvaleting

whats the best way too check for vacum leaks ?
is it advisable too spray carb cleaner and listen for idle increase?

Ether is good....if you have a surge in RPM...there is the leak.

[84 911 WideBody]

First, Please do not make a habit of unpluging the two coil idle control motors (3 wire) with the motor running. This can spike a Bosch ECM idle circuit. The defalt on the ICV is to over cam and alow a fixed fast idle... The 1100 you had when it is unpluged. I would be looking unmetered air leak/ Vac leak, oil tank as already mentioned.

[Ned, NYNA11]

Before doing anything else, plug the hoses to the ICV and get it out of the equation.

With the hoses plugged, the idle speed should be adjustable with the adjusting screw. If the speed is now ok, the problem is with the ICV.

If the speed is still high, the throttle plate is not closed or there is a vacuum leak into the manifold on the engine side of the throttle.

[dfink]

There are many posts about this problem and the process is fairly straight forward. First as others have said check for leaks. On your 88 the rubber is likely shot on most of the vacuum lines. First places to look are the rubber adapters for the PVC valve, the brake line, and the back side of the large rubber 90* between the throttle body and AFM. All other rubber parts are also likely suspect.

The next step is to jumper I believe B to C at the test block on the left side of the engine compartment. This is the round plug that looks like it should have a relay in it but doesn't. This centers the ICV so you can adjust the base idle. Unplug the O2 sensor when doing this. The turn the idle adjustment screw which may have a yellow cover on it. Turning clockwise lowers CC raises the base idle. You should try to set the idle speed so that when you disconnect the test block jumper the speed does not change.

Beyond that there are several other things that can be done that require a longer explanation. Fix the vacuum leaks and the rest will follow.

[Por_sha911]

+1 with what dfink said.
One other thought: Do visual inspections first and be careful with spraying ether around a running motor. There is nothing worse than an vac leak caused by a big honking engine fire.
Next, welcome aboard. In case you don't know, we have a friendly and informal tradition that newbies should post a pic of their car so we can all ooh and aah.
Finally, there are a ton of threads already posted about checking for leaks and fluctuating idle. The search button will help you.

[deeksvaleting]

Thanks for the help . Luckily I am a firefighter so should the car go bang I will know who to phone !!
I will post pics soon
many thanks