jnsluft

My 1995 90Q has developed an idle issue. The car starts fine and will idle at a constant 800-900 rpm until warm. After warm-up the idle will drop enough to make the dash lights flicker on and then jump back to normal speed. This happens every 15-30 seconds or so.

There are no other driveability issues and the car otherwise runs normally.

Where should I look first?

Shawn

E=MC^2

Check Everything basic

check your air filter, replace your fuel filter, check all your vacuum lines, check your cats make sure they arnt bad. just take a hammer and lightly tap them. They are a big honey comb on the inside if they are bad you will hear them bounce around on the inside because they are broken.


Keep us posted, good luck.

-Brian

maineman

Clean your Idle Control Valve. ICV

https://www.audiworld.com/tech/eng.html

RIAudiCab

ICV is definitely the place to start as just stated above. Clean it out w/ carb cleaner and compressed air. Next place would be vacuum lines for air leaks.

lgibson

X3 on the ICV. I had same symptoms. The valve was actually clean but the three attaching bolts were loose and the sealing surfaces a bit dirty.

jnsluft

That was it. Problem solved. A nice simple job. The car's idle is now butter smooth. I even replaced some vacuum lines while it was apart.

Thank you for directing me to the tech article section. I feel dumb for not knowing it was there.

Now I have to figure out why the check engine light was flashing today. It just never ends.

To everyone, a big thank you,
Shawn

Luxus Panzer

Is your ISV black or metallic?

If you can ever find the metallic version at a junck yard....get it.

one is Bosch and one is Hitachi (I think)

jnsluft

I don't remember what brand it was. I went to look and couldn't tell. It looks exactly like the one in the tech article.

Thanks for the heads-up on the metallic version. I'll be on the lookout for those.

Thanks,
Shawn