M20B25 Intermittent High Idle (Confused)

[Eddie25]

Hi All

This one has got me a bit stumped. Earlier this year the E30 was suffering with a high idle. It would jump up to 1500rpm or so and stick there rigidly.

The car was checked extensively for vacuum leaks and none were found. Most hoses and boots are new. The ICV was then replaced with a brand new unit but this did not repair the fault.

The TPS was checked and appeared to function correctly. The fault was eventually cured when a specialist fitted a Pre Face Lift throttle body with air bleed screw and adjusted it in conjunction with the emissions readings to get the desired idle.

The car is now mostly fine but still occasionally idles high. The other fault that has remained from previous is the car will be quite slow to return to idle. i.e when driving and the clutch is pressed in for a gear change the revs will take some time to drop down.

Could this potentially still be a TPS fault if it was swapped from the originally throttle body? Or perhaps a fault in the ECU/AFM? I'm running out of ideas.

[Brianmoooore]

The fault was eventually cured when a specialist fitted a Pre Face Lift throttle body with air bleed screw and adjusted it in conjunction with the emissions readings to get the desired idle.

This is not a cure, this is a bodge! The type of bodge that makes it impossible to get your car running correctly.
Whatever whoever did it is a 'specialist' at, it's not repairing E30s!

The first thing you need to do is to fit a good, unmolested throttle body and AFM, whose adjustments have been untouched since they left the factory. These components only have one correct setting, and that's the one BMW left it at.
When that's done, we can start looking for the real fault(s).

[Eddie25]

Many thanks Brian this will be the first job after Christmas I think.