1996 850 turbo. Iac valve keeps running even after key is off and sometimes will run until battery is dead if not disconnected. I'm guessing a hung up relay? anybody know which one or where to begin looking.
Thanks, Roy

 

this might help. any indication of engine having a rough idle when engine temp is rising? check the temp gauge on the cluster and see if the temp gauge will rise to the mid point when engine is warming up. usually when the temp sensor is going bad the IAC will run on its own. clean the connector of the temp sensor and pay much attention to the female socket of the connector which usually gets contaminated with the gunk retainer that the manufacturer usually use to retain the terminals to the plastic socket. i hope this helps.

 

I will try that first. Awesome, Thanks so much
Roy

 

I am having this problem almost exactly as you both describe.
Let me ask you this: when I unplug the temp sensor, should the IAC valve stop running on its own? Thank you, Dan
1995 850 T5-R

 

Actually I think I want to try to expand on my issue in hopes of getting help.

Intermittently, the car idles high, about 1000 rpm.
When this problem happens, the in-dash temp gauge needle suddenly goes all the way down as if it's cold.

When this problem occurs, if I put it the car in park, the idle quickly rises to 2500 rpm or so.
I have noticed that when I unplug the IAC valve while the car is idling high, it will return to normal.

The first time this happened (wife driving) the coolant overflow reservoir cracked on the top and steamed out a lot of coolant.

Also when this problem first occurred, I eventually got some ODB II codes from it.
Going by memory, I think there were codes for the throttle position sensor and the wastegate solenoid.

Here's what I've done so far:
- Replaced the coolant overflow reservoir.
- Cleaned the throttle body.
- Replaced the throttle position sensor.
- Replaced the idle air control valve (with one from a junk yard).
- Replaced the wastegate solenoid and related vacuum hoses.

Even with these things done, I am still having this problem intermittently.

One existing problem that may or may not be related, there's an intermittent water leak coming from one of the hoses that go to the heater core. It causes some steam after driving 10 min. on the freeway. Could the steam be playing a role in things?

Deeply appreciative,
Dan

 

Hey Dan, old cars usually have multiple problems, especially when you let some things go.

Deal with the problems seprately. Fix the leak at the heater hose, check your coolant temp with live data on the obd-ii port. If the temp is off like mine was (-37 degrees), change the coolant temp sensor. I used one from the jy. Make sure your coolant reservoir isn't building pressure while you're driving.

 

Thank you very much for your reply.
I plan on changing the temp sensor next week.

How can I make sure the coolant reservoir isn't building pressure while driving?
Because when I first got the car, a couple years ago, I replaced a leaky radiator and later a heater core.
It has always seemed to build pressure since I've had it.
I say this because it always seems to find a way spring a new leak.

But this idle problem really has me stumped.
That's what I really hope to seek advice about.

Thanks again,
Dan

P.S. Nice wagon.

 

You can't stop it from building it's designed to build pressure because that raises the temperature the engine can safely operate at and not allow the coolant to start to boil. I'm guessing but I know it gets at least 10 psi and might be as high as 17 or 18.

Everything in the cooling system is designed to handle this pressure when new. As the items age they will fail, you can delay it with good maintenance and regular coolant flushes but getting rid of the pressure isn't a realistic option.

You could leave the cap loose but your engine would overheat easier.