Hi guys, new member! I have an 87 Fuel Injected that Idles somewhat high, I will not get past inspection. Last year it was at a comfortable 800 or so, now it's at around 1300 in park, and drops down to 1100 or so in drive. What could be causing this? I have no Idea where an idle screw would be- i'm more of a Small Block man myself :). And EFI works differently than carburation... any hints/pointers would be greatly appreciated. engine is non-turbo. Thanks very much!

Mikey

Mr. Webb's posting puts you on the right track; check out the 700/900 FAQ on the topic, also - same injection systems - there's a lot of good info there which also applies to the 200 series.

The "solenoid-looking" thing with the hoses beneath the TB & intake manifold is an air valve (Idle Air Controller) run by an electric motor in response to instruction from the EFI computer to set the idle speed. It has a plastic knob on the side which can be used to set the base idle speed - details are in the FAQ.

I'd clean out the throttle body first; if that's part of the problem, anything else you do will only be partially successful. If the throttle body is gunked up to the point that the buttterfly plate isn't closing completely, the IAC can't get the idle speed down even when fully closed. When cleaning it out, be careful not to get solvent into the plastic switch housing on the side of the throttle body.

If, on the other hand, pinching off the hoses connecting the IAC to the intake manifold causes the idle to drop, it's possible the IAC may be sticking... Rap on it with a screwdriver handle & see if that causes the idle to drop. A bad electrical connection (as Mr. Webb pointed out) can also cause the IAC to quit regulating the idle.

The computer is supposed to control idle, keeping it around 750 RPM or something like that.

This doesn't specifically pertain to Volvo, but here is a typical diagnosis path:

1. See if the idle switch is being closed when at idle. If not, make sure the throttle cable isn't binding, and then adjust the switch so it closes at idle. Without the idle switch, the computer doesn't try to force the engine speed to be 750 (or whatever). If the switch clicks, it is probably working, but check for resistance with a meter. If it doesn't change with open/close of throttle, replace the switch.

2. Make sure the wiring to the switch is good.

3. Clamp off one of the hoses going to the idle air stabilizer valve (gently, don't tear the hose) with needle nose vise grips, or similar. This may make the car stall, and should at least drop the idle WAY down. If it doesnt, then your base idle adjustment is out of whack, or you have a vacuum leak. If it does, then your valve is staying open for some reason, either your computer is telling it to, or it's stuck.

-Steve

Steve,

Thanks very much for the insight. I just got back from tinkering with it myself. The line you're talking about connects to the Main air intake pipe right in front of the TB, i pinched it by chance because I saw a solenoid of some kind below the I.M. when I pincched it, the Idle did indeed go way down. What exactly is this? It got dark and I could not see anyrthing anymore. Thanks again for the suggestions.

Mike

Mike -

The thing you saw was the Idle Air Control, aka IAC, it's a motor not a solenoid. With the throttle plate closed, the engine gets no air and dies. So, there's a Throttle Position Switch, aka TPS, that trip when the throttle is closed. Tells the ECU computer to turn on the IAC, which then allows air to get around the throttle plate. The IAC has two same-size vacuum hoses, one you closed for the test, the other goes into the intake manifold underside.

A properly working IAC regulates the idle at 750, higher when a/c is on. If your idle is whacky, any link in the chain can be failing.
TPS - bad only if the throttle body is really crudded up or someone messed it up.

IAC - valve can be glopped up, can sometimes be loosened with carb cleaner.
AND, motor can be shot. Pull off harness, check for ohm readings between each pair of terminals. Haynes has some specs. But, if any pair shows open circuit, IAC is shot. Another unit with the exact same Bosch p/n will swap in, regardless of model of car or engine.

Good Luck,

Bob

:>)

Muleskinner & Bob

Thank you very much for your help. I looked up what the IAC is and I will agree that it is probably stuck open due to one of the failures that you listed. I will look at the TB tomorrow and also take out the IAC and see why it is sticking. I've read that 700series FAQ on Fuel Injection, very helpful aswell. I'm gonna start working on it early tomorrow and will let you guys know how progress goes. Thanks!

Mike

One small point.
After correcting the IAC problem check your base idle to be 700 or so. This is the black knob on throttle body. It is set with the IAC disabaled by squeezing off all air or using the test jumper. The car should not stall when IAC is disabled, it should only drop down to base idle speed. This is explained in the FAQ's. If all is working correctly idle speed is 750 rpm and 900 rpm with air on.
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David Hunter