Laggy throttle response

[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

[ptownTSI]

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

[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.

[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.

[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]

Please do so because every e30 I've ever heard sounded just like that. That "hiccup" noise is the sound of the AFM door opening up from the intake manifold vacuum pressure. If there was a failed sensor then there would at least be a CEL and if it was a vacuum leak then he would have the opposite of this problem including a high or abnormal idle.

[nando]

Please do so because every e30 I've ever heard sounded just like that. That "hiccup" noise is the sound of the AFM door opening up from the intake manifold vacuum pressure. If there was a failed sensor then there would be a CEL and if it was a vacuum leak then he would have the opposite of this problem including a high or abnormal idle.

give me a month :D

[NC325iC]

RK makes good points about the vac leak his idle would be off, i think its likely worn contacts inside the afm

[nando]

RK makes good points about the vac leak his idle would be off, i think its likely worn contacts inside the afm

not necessarily. the ICV could compensate for a vac leak by closing a bit more. my car originally had a huge hole in the intake boot but my idle was still normal. and incidentally when I replaced the intake boot my throttle response got a lot better..

[bddog]

Replace the intake Boot and check hoses for hardness and cracking.The boot can look fine from the top, when you get it off it will be shredded. Keep it simple.

[RobertK]

not necessarily. the ICV could compensate for a vac leak by closing a bit more. my car originally had a huge hole in the intake boot but my idle was still normal. and incidentally when I replaced the intake boot my throttle response got a lot better..

That's odd. I had a relatively small vacuum leak and even though my ICV tried to overcompensate it still idled around between 950-1100 RPM. Even still more air getting into the boot will not cause lag since the AFM cannot measure air coming int through the leaks it would essentially be leaning out the mixture if it was bad enough it would backfire through the intake. The exact opposite would cause lag... that is less air getting into the boot.

[nando]

the hole in the underside of my boot was about the size of a dime. and it was also cracked around most of the circumference.. no idle problems, but laggy throttle for sure.

[a3ternus]

Recently I had my valves adjusted and also had the sop do a general electrical maintenance/repair to the whole idle/injection/AFM system...
Now my throttle lags exactly like in the video,whereas before it wasnt...
I mean,I know,we re dealing with supercars really,but for me it somehow spoiled the fun of worn tyres and 110bhp at the rear wheels...:(
No intake air leaks here as well as they were all taken care of professionally...
N.

[b*saint]

Its lags like my 98 Honda. Sounds normal, just not for an E30. My M20 and S38 are SO sensitive.

[ummagawd]

any updates to this? the hiccup really bothers me

even stalled a few times when i first started driving it