RepairPal is your advocate for car care advice and guidance

Q: At stop or signal a/c on,in gear idle speed drops to 500 with annoying shimmy on 1994 Volvo 940

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
Volvo tech performed throttle body clean & idle adjusted, injector service, BG upper valve clean, new air & fuel filter, IAC & AMM Cleaned. When you stop idle is about 700 but then you see it drop to a stable 500 but shimmy starts. Increase idle screw enough for 100 RPM’s at stop, in gear, a/c on, when engine is turned off and restarted RPM is 1300-1400 & snatches heck out of tansmission putting into reverse. Any suggestions?
No car image 94a1663db56199c5353592009e34aaa51078a2469bed068bb8d6f0ba43accf97
Get a Repair Estimate
Guaranteed by certified locations nationwide. Learn more
RepairPal estimates are guaranteed at over 1,700 quality certified locations nationwide. Learn more
| |
big no-no to try to adjust idle speed as this is handled through the ecm. everything needs to return to factory settings and see if problem persists(probably not). if it does persist check to see if idle drops when cooling fan comes on(probably so). if that is the case then fix will be an updated e-prom as the is a voltage drop to iac when fans operate.
original setting applied. Idle is ok in gear @ stop, foot brake applied & radiator fan engaged. Problem is only when a/c engages, of course the radiator fan engages simultaneusly but the additional drag of the a/c drops the rpm's to 500. Idle is stable idle @ 500 but for the shimmy develops due to the drag of the a/c at that low idle. Turn off a/c or take it out of gear, either option, and the idle is ok at 700-800 and no shimmy. I'll consider the e-prom as you mentioned.
Didn't find what you were looking for?