I have a 98 v90 that the idle air system is driving 6 or 7 of us nuts, I have a 98 v90 that the idle air keeps intermittently illuminating the check engine lite. We have been thru the system and the only thing we have not tried is changing the engine computer. After resetting the lite it will last up to 3 weeks or only 1 day.
I have traced the wires to under the air box. All like new. Wires have been meg out and all seems well. No intermittent grounds. Wiring diagram leaves a lot to be desired. Any one have any suggestions?

 

Dear Sir,

Please tell us what you've done so far so that we can isolate each item and boil down the problem.

I'm not savvy to your model so this is the best I can do at the moment.

JPN

 

First of all,when ever the system is reset, it will be ok for as long as 3 weeks or as little as 1 day.
Most common cause is a malfunctioning idle air motor.Two things can cause that either an electrical problem with the motor itself or it gets gummed up and sticks.We have replace it 2 times with known good motors.I have checked power to the motors and have meged out the wires to eliminate short to ground.We have traced the wires from the motor to under the air box and the connector. This bundle appears to be secure and not compromised.Wires look as new.Trying to figure the route and bundle to the computer is not readily apparent and I'm not going to tear it apart without reason.In my lifetime very few electrical problems are cured by tearing wire bundles apart. Usually connectors,solders, or relays.not wires in a bundle.
Thank you for the consideration, Ed

 

First of all. What codes are the computer throwing? Without that theres nothing much we could do. What symptoms are you experiencing with this issue?

 

Code is idle air motor only code that comes up.no other symptoms. Maybe a fast idle on startup for 2-3 seconds. Again it is intermittent.

 

I think, your point of view about volvo diagnostic software is really good. The best volvo diagnostic software is vadis. It's a one kind of program as well as software that designed to be used by Volvo experts in stores. It operates as a stand-alone program in Microsoft windows.

 

If you are talking about the electric motor that forces air into the head at cold engine start, I've normally seen two issues. The more unusual is a bad Air Pump Check Valve, if you draw a vacuum to the part you should hear it move and it may just need to be cleaned / lubricated. The more common cause, which hits a lot of other stuff on Volvos this old, is that the vacuum system rubber fittings start to leak. The connection to the Air Pump Check Valve from the intake side of the engine is actually one of the easier ones to fix, normally a piece of vacuum hose / hose clamps at the Air Pump Check Valve will have everything working again.

As I've described previously, a number of the Volvo little rubber vacuum fittings are unique, in that they connect a hard vacuum pipe of one diameter with a fitting using a different diameter. I simply had a dealer identify all the fittings and ordered everything, this fixed a lot of the OBD/SMOG problems with our S90.