1990 Q45 low idle

[spectre173]

My 90 Q45 is idling too low and sometimes stalls when takeing off from a stop. Check engine light is not on.

Anyone have any ideas?

[Q451990]

How low is it? My first guess would be a dirty intake system, dirty throttle body, dirty IAC/AAC valve, etc. As a temporary cover-up, you might try opening the idle adjustment screw on the AAC valve. Do you have your FSM (factory service manual) that came with your Q?

Another possibility is a dirty Mass Air Flow sensor or a weak or corroded connection to it. Typically this will show up as a surging issue, but you might want to check that too.

Welcome to NICO!

Heath

[maxnix]

If you haven't replaced your chahin guides, please read the article.

[spectre173]

Thanks for the input.The car has 76,000 miles. The idle is 600 no A/C and 500 with A/C on. The idle is steady.

[Q451990]

That's not really that low. Spec is 750 +/- 50 at idle in neutral. The stalling isn't normal though. What is the service history on the car regarding intake an injector cleaning?

I second Brian's recommendation to investigate the chain guide issue. A low mileage 90Q is worth keeping alive, assuming it's in good condition...

Heath

[elwesso]

600 would sound about right from the factory assuming that the intake hasnt been cleaned. I wouldnt fiddle with the IAC, but rather clean everything up.

Do you hear any humming coming from the back of the car? The stalling might be fuel pump related (among other things) but FP's are always to be checked first on Q.

[spectre173]

HI,

I was wrong. It doesn't stall when taking off from a stop. When restarting a warm engine, the engine cranks and starts then the rpm drops below 400 and engine stops. I must use the throttle and let the rpm stabilize and then it will idle. All maintence items have been performed including the 60,000 mile check.

Do I set the idle via the aac valve with the wiring harness hoocked up?

Thanks, D2

[silkysmoothyjud]

MAF for sure, Mine did that and I used some "electrical parts cleaner" (q45.org) and it cleared it up (for now)

Modified by silkysmoothyjud at 2:59 AM 6/16/2007
Modified by silkysmoothyjud at 3:01 AM 6/16/2007

[silkysmoothyjud]

Big update from someone who just resolved the same problem!!!!!!!!!!!!!!!!!!!!!!!! Restricted vacuum lines will do just that my friend. Look behind the throttle body for a medium sized "L" shaped vacuum line that starts along the side of the plenum and goes just right under the plenum (check all other visible vacuum lines for a pinch). If you grip said line with a pliers does your idle go up? Then there you have it!! Buy the "L" shaped hose from auto zone, its like 20 dollars to make the Q run like a million bucks!!

[Q45tech]

This common hose has a slang name " The PxxxY Hose" because of the way it looks when in fails and sinks inward blocking air flow.

Why one replaces every hose PERIODICALLY.