1981 244 Idle Issue

[RollinRoland]

Hi all;
Been a member for a while but this is my first time posting. I am looking to see if anyone has any advise on what might be wrong with my 81 B21f k-jet m46 244.

Background:
This car was my primary daily driver for about 2 years. I trailered it across the country due to a move and it sat for about 3 months. I never had an issue with the car other than an occasional rough start in the winter. I started driving the car daily again until one day I had driven it on the interstate for about 40 minutes and noticed it was idling high when I was on the clutch or in neutral. I pressed in on the throttle and it seemed to stop. When I started the car after running into a store, the problem was gone. When I got back home, it started idling high again. The next day, it started fine but began to idle high once it got to temperature. I've tried quite a few things to fix this but was hoping someone might be able to point me in the right direction. It idles at around 3k-4k rpm.

What I've tried so far:
Replaced IAC (I have 5 of them -same issue with all)
Checked Throttle Position micro-switch with ohmmeter (no issues)
Hooked up smoke machine (no vacuum leaks)
Took off throttle body/cleaned/replaced gasket
Cleaned flame trap
Checked all grounds
Checked connections to ECM from IAC/throttle switch
Re-wired all terrible decomposed wires
Set idle with IAC unplugged

-Will replace coolant sensor (fuel injection) on Monday when the sensor is delivered. Pulled the old one, it looks rough.

Things to consider:
The idle does go down when I pinch the vacuum hose on the IAC
I got gas at Walmart (for the first time ever in this car) right before this started happening
I had the heater on when this started happening (happens with it off as well)

I appreciate any help offered!

 

[OVERDRIVE]

If your wires looked bad just there, I'm sure they're bad where you can't see them. Considering it seems intermittent It's got to be the wiring harness. The ~92-96 EFI MB's will start acting up when their harnesses just show the slightest signs of the sheath cracking and crumbling at the exposed ends.

 

[RollinRoland]

Thank you for the response. I should add, it is no longer intermittent. As soon as I start the car, it jumps up to 2k rpm and rises to 3k within a few minutes. I will definitely run down some more wires though. I pulled back some of the stock wire sheathing and it wasn't too bad where the wires were not exposed to heat/air.

 

[VolvoLatAm]

email this guy with year/vin/engine/
he might have some harnesses in stock

elbertbos.nl

 

[hessam69]

You need a new wiring harness if you're going to be running this car and expect any form of reliability from it.

All volvos from this era need new harnesses

 

[the_hairy_baboon]

could the distributor sometimes be bumping timing in a way that makes a bit more torque than needed so idle runs away, even with IAC fighting it?

Pop out spark plug #1 and check where the timing mark is sitting when at TDC (base alignment correct) and then I guess run a timing light to see if spark is not when it's expected to be when the issue occurs.

 

[johfraser]

 

[johfraser]

 

[bobxyz]

You need a new harness - most likely, the IAC wires, or the sensor wires to the CIS control box are shorting out somewhere. Looks like a blue Cali plate? If so, try Dave Barton's 240turbo.com for harnesses.

There's also a harness in for sale here, but I don't know if it's compatible with your '81 NA

 

[johfraser]

Hi all;
Been a member for a while but this is my first time posting. I am looking to see if anyone has any advise on what might be wrong with my 81 B21f k-jet m46 244.

Background:
This car was my primary daily driver for about 2 years. I trailered it across the country due to a move and it sat for about 3 months. I never had an issue with the car other than an occasional rough start in the winter. I started driving the car daily again until one day I had driven it on the interstate for about 40 minutes and noticed it was idling high when I was on the clutch or in neutral. I pressed in on the throttle and it seemed to stop. When I started the car after running into a store, the problem was gone. When I got back home, it started idling high again. The next day, it started fine but began to idle high once it got to temperature. I've tried quite a few things to fix this but was hoping someone might be able to point me in the right direction. It idles at around 3k-4k rpm.

What I've tried so far:
Replaced IAC (I have 5 of them -same issue with all)
Checked Throttle Position micro-switch with ohmmeter (no issues)
Hooked up smoke machine (no vacuum leaks)
Took off throttle body/cleaned/replaced gasket
Cleaned flame trap
Checked all grounds
Checked connections to ECM from IAC/throttle switch
Re-wired all terrible decomposed wires
Set idle with IAC unplugged

-Will replace coolant sensor (fuel injection) on Monday when the sensor is delivered. Pulled the old one, it looks rough.

Things to consider:
The idle does go down when I pinch the vacuum hose on the IAC
I got gas at Walmart (for the first time ever in this car) right before this started happening
I had the heater on when this started happening (happens with it off as well)

I appreciate any help offered!

The basic idle speed and other adjustments cannot be done successfully by just unplugging something.