924s runing rough at idle

[BOJAN]

This is regarding my 87 924s, always ran great till 2 couple of days ago. Starts fine from cold, runs fine for first min or so, but within min or min and a half the idle would get very rough, if I press gas not much happens, stumbles hesitates, occasional back fire. Car will not stall, keeps running rough. If I restart, it always starts, sometimes would be excellent with first jab off throttle, but as soon as it comes to idle , roughness returns, sometimes runs rough immediately after restart..

My idle was always bit shaky, but not like this...

Only thing I did prior to this is I unplugged and reconnected the o2 sensor...
the following day I cleaned the contacts to speed and reference sensor connectors , but this happened prior to cleaning them...

Has anyone experienced theses symptoms like I said...it always restars fine, and will not stall completely.....

THX!

[v2rocket_aka944]

try unplugging the idle control valve (plug is between the intake manifold runners for cylinders 2 and 3) and see how it runs.

[Bradical]

Sounds like you are dropping a cylinder to me. I’d suspect an injector, but it could be as simple as a spark plug wire or something. Probably amplified by a tired set of engine mounts.

[John_AZ]

I repaired this problem in 2017---same symptoms.

The larger hoses under the intake had rotted and cracked.
I did not need a new ICV or throttle valve switch.

Check all air hose connections you can see from the top---and the small tube rubber connections.

Have the throttle body BIG round seal on hand ---WYAIT

Have 4 intake gaskets on hand.

Look at the PET.

I wasted a lot of time X3 doing the smoke test and then one part , then another , then another.

J_AZ

[BOJAN]

Thank you all for taking the time!

Battling a bad cold or something, so as soon as the wife oks my further tinkering will give it another look.

THX!