1996 850R idles at 3000rpm

Volvovlo · Post by **Volvovlo** » 14 Oct 2022, 22:56

Hi guys,

My car starts and runs for 3-5 minutes normally, then will Rev up to 3000rpm and stay there. Has also happened once while driving. Seems to happen every time it's started.

Unplugging the idle air control valve makes the revs drop back to normal. I changed this with a used part, but same problem again. Something is telling the aic to idle higher. The CEL is on, however I cannot read codes as my obd port is damaged.

I have read other threads with similar problems, checking my tps and temp sensor connection. Still no change.

I'm not sure if it's related, but sometimes my car won't start when hot, sometimes it will. Using starting fluid usually helps it.

Any advice on what to look at/change next is appreciated. Tia.

Post by **Clemens** » 14 Oct 2022, 23:04

My guess would be the temp sensor. you said you checked the wiring. Try replacing the temp sensor.

Post by **scot850** » 15 Oct 2022, 03:57

Clemans, do you mean the ECT (coolant temp sensor)?

Even if the ECT is not working correctly, I would not expect it to rev passed about 1500 rpm if it thought the ambient air temp was low. Having said that it would affect the hot starting issue. Does the sensor read correctly on the dashboard when the car is warm and does it take a long time to get to normal operating temperature?

You may have an air leak or vacuum leak in a hose somewhere.

I did think about a sticking throttle cable or the pivot/spring at the engine end.

It is likely one issue but may coincidently be 2 separate issues.

Neil.

Post by **hausmeister** » 15 Oct 2022, 08:25

Can you repair the obd port? Without codes it is just guesswork on where to start.

Post by **Clemens** » 15 Oct 2022, 13:32

scot850 wrote: ↑15 Oct 2022, 03:57 Clemans, do you mean the ECT (coolant temp sensor)?

Even if the ECT is not working correctly, I would not expect it to rev passed about 1500 rpm if it thought the ambient air temp was low. Having said that it would affect the hot starting issue. Does the sensor read correctly on the dashboard when the car is warm and does it take a long time to get to normal operating temperature?

You may have an air leak or vacuum leak in a hose somewhere.

I did think about a sticking throttle cable or the pivot/spring at the engine end.

It is likely one issue but may coincidently be 2 separate issues.

Neil.

yes, the EcT is what came to my mind.

Post by **misha** » 15 Oct 2022, 16:13

Unplugging IAC valve while engine is idling should kill the engine instantly... unless there is a vacuum/air leak on the intake side.