M20B25 choppy Idle....

[Valvebounce 2]

So after a lengthy break from trying to make my e34 go, I made time this weekend, and found success,

However, it runs kinda choppy at idle. Not really how an old luxobarge should idle.

A brief skim of the forum found a thread about cleaning the idle air valve. I guess that's a good place to start. Would brake kleen be OK to use for this?

What else should I try?

Many thanks,

Bart.

[Young Thrash Driver 1020]

Give carb cleaner a whirl. Isopropyl alcohol should be safe too.

[Mark 178]

Clean the ICV and also the mechanical flap in your AFM. Both can get gummed up with gunk and cause idling problems.

[Valvebounce 2]

Cheers fullas!

The guy I bought that car off has a brand new can of throttle body cleaner. I might see if he'll unroll his foreskin and let me borrow it. (Since he sold me such a lemon in the first place!) lololol

[Lucan 196]

Check for leaks in the intake while your at it.

[Valvebounce 2]

I got some carb cleaner, and got the AFM, and ICV spotless. I also held the rubber elbow up to the light, and checked to see if it had any holes. Put it all back together, and made sure all the hoseclips were both properly seated, and correctly tightened.

Still idles like a Carburated engine with the choke out.

Any other ideas?

[Mark 178]

Did you clean the throttle body while you were in there?

Do the revs surge and then drop or is it just idling low. Where does the tach needle sit at idle? Does it improve when warm?

[alisterh 26]

Does the ICV buzz with the ignition on?

[Valvebounce 2]

I think it's idling around 650.

I don't think there is any change when the engine is warm.

The ICV might buzz. I've been doing battle with this car for a while now. I might duck outside now, and see if it does.

[Valvebounce 2]

Yes.

It does kind of buzz. Is that good or bad?

[alisterh 26]

Yeah it should buzz, have you checked the Throttle position sensor?

[Valvebounce 2]

Checked it how?

[Valvebounce 2]

Any more ideas peeps?

When It very first starts, it idles great for 30-45 seconds.

Then it gets that choke on too hard/almost sounds like a miss sound about it.

I wonder if the tappets are too tight?

[actletpone 43]

Common causes:

You can test the ICV, AFM and TPS with a multi-meter following steps in the haynes / bentley manual. Other common air leak sources (dip stick o-rings, b*tch tube seals, intake gaskets, vacuum tube to fpr, tube from valve cover to throttle body, injector o-rings, oil filler cap, throttle body elbow fittings, brake booster + fittings, also some cars have a rubber blanking plug under the throttle body where the charcoal canister used to connect which can crack). Best way to check air leaks is smoke test.

Fuel Filter, Fuel Pressure, Fuel Injectors, connections in c191 plug

Dizzy cap + rotor, Spark plugs - gap + condition + type ('apparently' m20's do not like platinum plugs)

Does the idle increase when the air con is turned on?

Does the idle sound change if you remove the oil filler cap?

Are the first 30 - 45 seconds at an increased idle speed?