Laggy throttle response

[silversleeper]

Seafoam?

Yes, that is my answer to everything.

[87-325ic]

i had vacuum leak in my mind too. i think its a slight mix of both.

afm does cause some lag, (this is why people convert to maf) and vacuum leaks do cause poor running and idle/ problems like this.

[AndrewBird]

I'm with Nando and a few others. I think it's a vacuum leak.

Vacuum leak causing a leaner then normal mixture, then when given a sudden "shock" of throttle, leans to the point it can't keep up and lags. That definitely sounds like a lean bog, not a rich bog. If it were rich, it would stumble as it recovered. A lean bog will just pop back to normal running like your car is doing in the videos.

[Mr Deagle]

The screw on the AFM is the Bypass adjustment, to tune the mixture.

[87-325ic]

ummmm.... how is that screw on the AFM the IDLE adjustment screw? i thought motronic controlled idle via the icv...

also.. does that afm screw just "tweak" in either direction the entire A/f ratio along the entire rpm range in the same amount?

[ummagawd]

any updates to this? the hiccup really bothers me

even stalled a few times when i first started driving it

[b*saint]

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

[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.

[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.

[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.

[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.

[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..

[NC325iC]

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

[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

[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.