Idle Issue After Rev.

[Prototyp3]

Vehicle: 1988 E30, 325is

The car starts great when Cold (it takes a second or two longer) and great when its warmed up, after engine has started it idles stronge around 500rpm.
However, when rev the motor at all while in neutral and then let off the car nearly dies (drops down to what look like 150rpm) and comes back up to 500rpm, if I start the car wait 30 seconds put it into first and drive out of the driveway and let off the gas the car will die, and will not start backup for several minutes. If it idles for a few minutes the drop in RPMs after revving in neutral is much less and it drives fine with no death or hesitation.

Any ideas of what is causing this problem?

[nando]

500rpm is about 150-200rpm too low. it should be 650 +/- 50rpm.

is your ICV functioning? has your throttle stop/TPS setting been tampered with?

[jlevie]

Actually, standard idle on an M20B25 should be 750rpm.

As to the OP's question, intake leaks, a bad or sticky ICV, a bad TPS, or a combination of those is probably responsible.

[Prototyp3]

Thank you for the reply's I will have to research these things further.

[zig553]

I had this exact same problem so check your Oxygen sensor and make sure its been replaced within the scheduled period and make sure your sparkplugs are copper ones , I changed both these things and reset the ECU by unplugging the battery for 30min-1hr and haven't had a problem since.

[Prototyp3]

Update

So I took another look at my idle issue after reading through you guys responses and found that I am idling more around 650-700rpm mark, but I am still dropping down around 200-300rpm mark when I rev it in the first 5-7 minutes of it idling. This weekend I am going to take a further look into your suggestions and I will let you know how it goes.

Thank you