Laggy throttle response

[nando]

In my honest opinion.. Your throttle response is fine and so is your AFM. You can try fine tuning it but like I said before. If you are used to driving a car with a MAF then you will always notice the difference in response when compared to a car with an AFM.

The only time I ever had almost instant throttle response on my car is when it was idling too high (950-1100 RPM) DUE TO a vacuum leak on my boot. Your AFM does not open itself up as soon as you touch your pedal. It opens up because of the vacuum created by your engine which in turn opens the AFM's spring tensioned door and thus causes the delay. You can try loosening your AFM spring to make the door open easier but I would not suggest it as those things are laser calibrated.

When you close the throttle quickly the same thing happens to recover to idle. Our DMEs are pretty ancient when compared to newer cars and considering the fuel management technology available in the 80s I really don't expect them to respond instantaneously to throttle input.

I'll say it again. the amount of lag he is getting is NOT normal, even for our ancient ECUs and AFMs. when I get a chance I'll make a video of my car's throttle response and you'll see what I mean.

[RobertK]

In my honest opinion.. Your throttle response is fine and so is your AFM. You can try fine tuning it but like I said before. If you are used to driving a car with a MAF then you will always notice the difference in response when compared to a car with an AFM.

The only time I ever had almost instant throttle response on my car is when it was idling too high (950-1100 RPM) DUE TO a vacuum leak on my boot. Your AFM does not open itself up as soon as you touch your pedal. It opens up because of the vacuum created by your engine which in turn opens the AFM's spring tensioned door and thus causes the delay. You can try loosening your AFM spring to make the door open easier but I would not suggest it as those things are laser calibrated.

When you close the throttle quickly the same thing happens to recover to idle. Our DMEs are pretty ancient when compared to newer cars and considering the fuel management technology available in the 80s I really don't expect them to respond instantaneously to throttle input.

[jrabbit]

tps

you should feel an audible click from throttle switch as soon as the throttle plate opens [engine not running] thats your injector shutoff. as the cars age the throttle switch will fill up with oil [blowby] and cause problems.

[ptownTSI]

noisy ass m20's, i thought just mine had that clackety clackety under there.

[skuyler]

After fiddling with all that stuff, it made a little improvement, at least enough for me to feel satisfied with and/or stop caring about. If i find a cheap AFM at the junkyard, I'll pick it up, otherwise, I give up

[delphini]

any updates skuyler ??

[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!

[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

[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).

[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.

[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

[euroshark]

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

[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...

[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.

[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?