Idle Speed Motor Question - Rough Idle and Hesitation on Acceleration

[DeLorean937]

Im currently trying to diagnose my idle speed and roughness on acceleration. When I accelerate the car is pops and sputters and has no power. The only way I get it to speed is to nurse the throttle up above 2000 RPM then it takes off fine. I checked timing and got the mixture set to get the car started and running and not die when I place it into gear. I seem to get things adjusted perfect then sometimes in goes back to ruff driving. I took things apart to check around. I found the CSV brass pipe was moving around and leaking so I got it secured down.

I'm checking my idle speed motor at the moment. I have it in my hand connected, engine is cold, when I depress the micro switch the rotor inside moves only about a quarter of the way? Is it suppose to open all the way or only when hot?

[DeLorean937]

Forgot to mention that I tested the ISM but powering the center pin and grounding each side and valve open and shuts to the max without issue.

[Bitsyncmaster]

If you adjusted the mixture to get the best idle, your mixture is probably way rich. You really need a meter to adjust the mixture correctly.

[DeLorean937]

If you adjusted the mixture to get the best idle, your mixture is probably way rich. You really need a meter to adjust the mixture correctly.

I adjusted the mixture to get best performance on acceleration. Idle was high but I lowered it using the lower arm screw and micro switch screw still hesitates on acceleration of i can get into gear without dying.

[Bitsyncmaster]

I adjusted the mixture to get best performance on acceleration. Idle was high but I lowered it using the lower arm screw and micro switch screw still hesitates on acceleration of i can get into gear without dying.

A lot of things can cause your problem. For it to be missing at low RPM it could be ignition but that usually has problems more so with higher RPM. I'm just guessing your to rich and fouling the plugs or the rich mixture is causing pre-ignition.

[Michael]

I can guarantee you your mixture is off, probably way off. You can not adjust the mixture by sound, you can barely get it ballpark close (which is a nice way of saying it's way off). Some say you can get it close by unhooking the o2 sensor and going clockwise until the engine stumbles. 1/8 of a turn makes all the difference in the world, there is no close.

You need a 20 dollar meter and only after you have confirmed all vacuum leaks and linkage settings are correct as well as dist. advance and confirm the idle circuit is working properly and the stops are adjusted correctly. There is a lot to check there. Mixture is usually the very last thing to adjust.

Over the years of P.O.'s many mixtures were tampered with to compensate for something else, then adjusted again to correct yet other problems.

[David T]

The common causes are a bad CPR, vacuum leaks, dirty injectors, fouled O2 sensor and now that you messed with the mixture adjustment, the mixture is way off. You probably need a tune-up too. Before you can even attempt to adjust the mixture you need to make sure all of the secondary ignition components are good and you have NO vacuum leaks. Depending on the mileage you may also need a valve adjustment. You cannot adjust your way out of these problems, they have to be fixed and THEN you might have to make a minor adjustment. The mixture screw is VERY sensitive, a 1/16 turn is a lot. In most cases you are better off not touching it, it is closer to where it needs to be than you will be able to set it (assuming no one got to it yet!).

[dn010]

Make sure the 3 brass air screws are fully seated too, the PO of my car had these all open back when I ran the stock engine and it caused all kinds of problems!

[mluder]

Make sure the 3 brass air screws are fully seated too, the PO of my car had these all open back when I ran the stock engine and it caused all kinds of problems!

And sometimes opening them slightly can SOLVE all sorts of problems.

Cheers
Steven

[DeLorean937]

And sometimes opening them slightly can SOLVE all sorts of problems.

Cheers
Steven

It helped a little bit by lightly seating them. But I was wondering if the micro switch is depressed when cold, is the idle speed motor suppose to open all the way?