Car hesistates at idle when putting the trottle down

[BigKriss]

Symptoms are, at the the traffic lights in drive, normal idle is 700 - 800 rpms. when i put throttle down, it goes to about 500rpms almost stalls and then pulls away fine again. it only happens at idle and not elsewhere. what can i check / do to fix this problem. i think it's afm (air flow meter) related, but i'm not sure and i've never mucked around / cleaned the afm before.

I searched through he old posts here http://www.bimmernut.com/forum/searc...d=531698&pp=25 but couldn't find much.

[tim eh?]

Symptoms are, at the the traffic lights in drive, normal idle is 700 - 800 rpms. when i put throttle down, it goes to about 500rpms almost stalls and then pulls away fine again. it only happens at idle and not elsewhere. what can i check / do to fix this problem. i think it's afm (air flow meter) related, but i'm not sure and i've never mucked around / cleaned the afm before.

I searched through he old posts here http://www.bimmernut.com/forum/searc...d=531698&pp=25 but couldn't find much.

i have this but only when it's just been started.
i wonder about the fuel pressure regulator sometimes but i really have no idea.

[BMW4LIFE]

mine does the same thing if i dont drive the car for a couple days right at start up...after 10 sec...its totally fine

[Jeff N.]

Maybe try cleaning the carbon wiper on the AFM. Wouldn't recommend mucking with the spring tension. Seems to make things worse overall.

[BigKriss]

I very much think it's afm related. around 30% throttle from idle, the car almost stalls. what product do you I use to clean the carbon wiper on the afm Jeff?

[632 Regal]

Wrong Jeff but you can use spray carburetor cleaner, very safe.

I very much think it's afm related. around 30% throttle from idle, the car almost stalls. what product do you I use to clean the carbon wiper on the afm Jeff?

[BigKriss]

okay, thanks for that.

[Bill R.]

mixture across the entire range, if its a little too lean it will do what yours is doing, look for cracks or leaks in the hose between your afm and the throttle body, if none are found i would readjust the idle mixture with the idle air bypass screw. a little bit makes a big difference so its better if you hook it up to an exhaust gas analyzer while doing it since you can see small changes there easily. A poor connection at the coolant temp sensor will also do this. Check and clean connections

[Jeff N.]

Hello Bill!

Yes - those are better suggestions and simpler than cleaning the AFM wiper area. I can second that if the car has a slight vacuum leak and is running a bit lean, it will definitely have problems on throttle tip in. Funky tracks in the AFM could cause a similar response but these would be more likely.

[Rus]

I had the same symptom of hesitation off the line before I replaced the crankshaft position sensor. Upon replacement, the symptoms completely disappeared. The CPS was the only change....because it failed on me. My guess is that an old CPS doesn't provide a clean enough signal and the ECM doesn't respond properly to the throttle opening. Worth a look if the other suggestions don't work.