E30 rough idle

[Tyler325i]

So I have a rough idle out of no where. It was running smooth to my friends house. I stopped at a stop sign, took off pretty hard then boom my car started shaking prettier erratically. I towed it to my house and started doing some testing. I tested my fuel pressure, cap an rotor, spark plugs, tips, cps, ecu, and did a compression test and all those are fine. I just can't figure out what's causing this? Is there anyone that had this problem and fixed it?

[blocke]

Did you check: AFM adjustment, AFM connector plug, and your ICV?

My afm connector plug came loose the freeway at 65, felt like my car was slamming through multiple bricks walls. Idle was also terrible.

[smackley]

Throttle position switch. I just had mine go bad and was a headache to diagnose. Cheap enough part if you are looking for a place to start. Theres a way to test your current one if you'd like as well. Check the idle micro switch in both the engaged and disengaged positions.

My TPS locked into the idle position in the switch and caused my ICV to stay open during WOT which equals too much air.

[Tyler325i]

Yea I already check the tips with a voltmeter and also olmed it an it's fine it opens and closes, and for my maf, I made sure it was plugged in and and everything. Although it might be the mad too because whenever I plug my launch into it it throws a code saying its bad. But the code old got thrown yesterday and this all happened about two weeks ago

[jlevie]

The first thing to do with an engine that has a rough idle is to smoke test the intake. Once intake leaks are ruled out a fuel rail pressure check, new plugs, and valve adjustment would be the next step. If the idle is only rough when the engine is at normal temperature, change the O2 sensor. Otherwise change the distributor cap, rotor, and ignition wires.

[Tyler325i]

I did a rail check, brand new cap rotor, spark plugs, and O2 sensor and i already checked all the valves.And how do I do a smoke test? And I don't think the intake is leaking I just rebuilt this motor with brand new everything inside the motor and gaskets.

[Tyler325i]

I need a new harmonic balancer... I figured out that mine is all jacked up... And I kinda broke it...

[shoshottz]

did the harmonic balancer fix your issue?

[flumph]

6 year thread necro.

For the googlers reading this, if you have an Eta, the HB wouldn't do this because the crank trigger on Etas isn't on the HB. B25/i motors have the toothed wheel for the crank position sensor on the HB. B27/e motors have the toothed wheel on the flywheel.