Hi all,

My 1987 740 has a very high idle when in park. When in drive, the idle is fine (750 - 800 rpm).

When I cold start the car in the morning the idle speed is approximately ~1000rpm - all normal.

After approximately 20 - 30 seconds, the RPM jumps up to 1500 - 1600 and stays there. It does not go down. The wiring harnesses have been redone in 2012, i have removed the idle air valve, cleaned the electrical connection with contact cleaner, and cleaned the insides with carburetor cleaner. It does not stick at all and i can feel the valve moving freely when i shake it in my hand. There are no vacuum leaks, i have cleaned the throttle body and put a new gasket on it, and even if i turn the **** on the throttle body that regulates the amount of air going in all the way in, the RPM DOES NOT go to normal idle speed of 750 and stays up in the 1.5k range. The oil trap was removed and cleaned.

Maybe its the temp sensor? I ordered one in and it should be here in 4 days time but could anyone suggest anything else to look out for?

Thanks.

 

Doesn't the '87 have a manual **** adjustment for the idle, a knurled black thing under the throttle body?

 

Yep, that's it.
I've grounded out the IAC and the **** is all the way in but the idle is still 1k rpm. I'm thinking its a vacuum leak... Not sure where...
I know you can test using carb cleaner, but are there any better methods?

 

Any highly flammable spray... Or I've had MAFS do that, affect idle speed.

 

check the airboot to the throttle body connection, too. make sure your throttle butterfly is closing fully too.

keep me posted, having this same issue with my 85 240.

 

I came looking exactly for this. Thanks for posting. Mine is an 83 240 and I'm on my 3rd MAFS. Hoping there's something else that's a simple fix for this.