Laggy throttle response

[RobertK]

Regardless... a MAF will always give much better throttle response than a flap door AFM. No matter how you tune it the flap door does add to the throttle response time.

[skuyler]

Now with more video

http://www.youtube.com/watch?v=1wlJ13I5LZg

[NC325iC]

i still think id call it an afm problem, you said you looked at it when you take it out push the flap with your hand and see if it binds or anything

dont worry about your icv your car seemed to be idling fine

[skuyler]

i still think id call it an afm problem, you said you looked at it when you take it out push the flap with your hand and see if it binds or anything

dont worry about your icv your car seemed to be idling fine

I appreciate the reply, but the AFM may be in the clear. We did take it out/clean it/inspect it. When pushing it slowly by hand, it had even resistance throughout the range of motion and nothing obvious

[turbo_negro69]

Now with more video

http://www.youtube.com/watch?v=1wlJ13I5LZg

looked fine to me
i think you're not used to owning a car with an AFM.

[NC325iC]

no i dont think thats normal, it seems like its bogging down before it picks back up, you dont have a spare afm around do you? any friends with e30s around?

i dont know enough about the wiring of the afm to tell you about that 5th wire, is there a pin for it on the afm?

[turbo_negro69]

maybe it's because the sound didn't match up with the video speed? i'll try watching it again later when i'm not downloading all this porn.

[euroshark]

Find the ADJUSTMENT SCREW on the AFM. This is something everyone here is missing... If it's bogging down, it may be too rich at idle, causing it to bog down before the RPM climbs. Clockwise makes it richer, counter makes it leaner... Try leaning it out 1/2 turn or so...

That looks like the only problem... The delay in reaction time is caused my the AFM. There is like 14 inches x the area of the diameter of the intake hose that has to be sucked through the throttle before the AFM catches up completely... Unfortunately the AFM does not react instantaneously. I'll get a video of my E28 for reference...

[euroshark]

This is an M30 AFM, but it should be similar.

[PeaveyBassist]

I wouldnt mess with the screw unless you KNOW what the mixture is for sure. Like... a number from a dyno/wideband. The reason it would drop a little before picking back up is because when you open the throttle the mixture will go way lean for a second until it opens the injectors longer to richen it back up and make the engine speed climb.

Will

[nando]

looked fine to me
i think you're not used to owning a car with an AFM.

I just watched the video of the throttle response

that is defnitely not "normal" response time, and is not inherrent to an AFM car. I think most of you are just not used to owning a car that runs properly..

I still vote vaccum leaks.

if I get a chance I'll post a video of my car's throttle response, but it will be a while.

[euroshark]

I wouldnt mess with the screw unless you KNOW what the mixture is for sure.

It won't hurt anything, it mostly control the idle mixture. You can basically tell by smell and response if it's about correct, and if running a little too rich / lean at idle makes it run better, most people won't complain. I have adjusted the AFM idle mixture screw on every car I've owned. It can help smooth out the idle, clean up the mixture for emissions, and smooth out irregularities in the powerband.

I think most of you are just not used to owning a car that runs properly..

This is probably very true!! While the AFM doesn't react instantly, the noticeable "lag" should be very small... If it weren't snowing, I'd get a video of my 533i. It's very "crisp". (And I have adjusted the AFM mixture screw).

[NC325iC]

i think you should go with nandos suggestion, get some carb cleaner (O2 sensor safe) and spray it around on the vac hoses with engine running if idle changes thats your leak.

but if you can find another afm to test in there i think its worth a try ,your contacts may be worn out, that lag is def not normal

[skuyler]

Update: I fiddled with the TPS, cleaned the throttle body, changed the fuel filter (needed it anyway), and fiddled with the AFM mixture screw.

Doing all that seemed to make the car MARGINALLY better, but it still lags. Looks like I'll be shopping for an AFM.

Thank you guys!

[delphini]

any updates skuyler ??