1991 240 Engine misses and shakes at idle when warm

[injection]

My dad's 240 when the coolant temp needle gets to the middle the engine has a bad habit of violently shaking but when the engine is cold it runs smooth.

What's been replaced: intake gasket, spark plugs/wires/dist, fuel filter, coolant temperature sensor, cat, and the harmonic balancer.

What's been checked: injectors, TPS, and ignition coil.

Any help is appreciated.

[lindy8_man]

Generally for what is left, I would test at your MAF, verify timing, and check your motor mounts.

You would do well to also narrow down the problem to Air, Gas or Spark. then trace back from there.

[Richard-Bundy]

hi,
if you haven't already checked it, try the idle air control valve. if its not the problem, cleaning it wont hurt. my sons 940 had all sorts of rev control problems until the IACV was cleaned. also it wouldn't hurt to clean inside the throttle body. the other 2 things I found are common , are a dirty MAF ( easily cleaned with MAF cleaner or circuit cleaner ), and a stuck flap at the airbox entry. I just temporarily fixed one by making some holes and zip tying the flap in the cold intake position.( I live in a warm climate). when I get a chance I will totally remove the flap and cover the hot air duct hole.
all the best !

[rgk]

I second the idle air control valve. It's at the driver's side of the engine, underneath the intake, and has two vacuum and one electrical wire running to it. It's a small cylindrical object.

[rgk]

I would also check the coolant temperature sensor.