strange throttle lag question

[More&Faster]

i've searched and not found a solution that works yet. the problem is that at or near idle, if i hit the gas, it bogs for a second before revving, regardless of throttle angle. i can floor it and it wont do anything for about a second. as you can imagine, this makes driving smoothly a bit of a challenge. i thought the TPS might be misaligned but i adjusted it and i'm positive it's calibrated right. i still need to check the terminals for continuity. i was thinking maybe this could be a spark problem? since it bogs a bit i was thinking maybe the ecu is pumping extra fuel in and the rich mixture doesnt burn right away. i'm stuck on this one.


halp!

[MikeE30325i]

try spraying your throttle linkage down with a bit of wd-40. maybe it is dirty. thats my only suggestion.

[RobertK]

i've searched and not found a solution that works yet. the problem is that at or near idle, if i hit the gas, it bogs for a second before revving, regardless of throttle angle. i can floor it and it wont do anything for about a second. as you can imagine, this makes driving smoothly a bit of a challenge. i thought the TPS might be misaligned but i adjusted it and i'm positive it's calibrated right. i still need to check the terminals for continuity. i was thinking maybe this could be a spark problem? since it bogs a bit i was thinking maybe the ecu is pumping extra fuel in and the rich mixture doesnt burn right away. i'm stuck on this one.


halp!

In my own experience ever E30 I've ever driven has had some level of pause before you hit the gas pedal. This is usually attributed to the fact that the M20 has an AFM and not a MAF like newer cars do.

The pause is usually the reaction time between you hitting the pedal and the flap door opening on the AFM.

I know some people might not agree but I've yet to see an E30 in person or on video that did not have some degree of throttle pause because of the AFM.

The only E30 I have seen that did not have throttle pause / bog was Ely's stroked eta w/ the MAF conversion.

[More&Faster]

In my own experience ever E30 I've ever driven has had some level of pause before you hit the gas pedal. This is usually attributed to the fact that the M20 has an AFM and not a MAF like newer cars do.

The pause is usually the reaction time between you hitting the pedal and the flap door opening on the AFM.

I know some people might not agree but I've yet to see an E30 in person or on video that did not have some degree of throttle pause because of the AFM.

The only E30 I have seen that did not have throttle pause / bog was Ely's stroked eta w/ the MAF conversion.

wow. if this is how e30s are normally, then that's pretty bad. they should have stuck with carbs.

the only 80s cars i can compare are a diesel and a honda, which uses an MAP sensor. both have instant throttle response.

i was gonna go turbo down the road so maybe getting megasquirt now would be worth it just to ditch the afm.

[More&Faster]

try spraying your throttle linkage down with a bit of wd-40. maybe it is dirty. thats my only suggestion.

as i said, it's just off idle. it's not the cable. i can activate the throttle directly with the same result.

[NC325iC]

mike that was a dumb suggestion,
robertk is right it is likely just the flap taking a long time to open, pull your afm out and clean it thouroughly

[More&Faster]

mike that was a dumb suggestion,
robertk is right it is likely just the flap taking a long time to open, pull your afm out and clean it thouroughly

done that. its clean and operates smoothly. is this as good as it's gonna get? :(

[nando]

again there should be a SMALL lag, but not a huge amount. my plugs are all fouled up and my air filter is filthy so it's not quite running right, but when I get it back to where it was before I'll post a video.

[RobertK]

wow. if this is how e30s are normally, then that's pretty bad. they should have stuck with carbs.

the only 80s cars i can compare are a diesel and a honda, which uses an MAP sensor. both have instant throttle response.

i was gonna go turbo down the road so maybe getting megasquirt now would be worth it just to ditch the afm.

If it pauses like the video in the first post of this thread:

http://www.r3vlimited.com/board/showthread.php?t=81017

If it's any longer than that then you probably need a good tune up.

BTW.. most people who go turbo usually do a MAF conversion.

[More&Faster]

If it pauses like the video in the first post of this thread:

http://www.r3vlimited.com/board/showthread.php?t=81017

If it's any longer than that then you probably need a good tune up.

BTW.. most people who go turbo usually do a MAF conversion.

it's about like that or maybe a bit worse.

what do you mean by tune up?

[Mr Deagle]

i've searched and not found a solution that works yet. the problem is that at or near idle, if i hit the gas, it bogs for a second before revving, regardless of throttle angle. i can floor it and it wont do anything for about a second. as you can imagine, this makes driving smoothly a bit of a challenge. i thought the TPS might be misaligned but i adjusted it and i'm positive it's calibrated right. i still need to check the terminals for continuity. i was thinking maybe this could be a spark problem? since it bogs a bit i was thinking maybe the ecu is pumping extra fuel in and the rich mixture doesnt burn right away. i'm stuck on this one.


halp!

btw, the "TPS" is a Throttle position SWITCH, and is only for sensing closed throttle

[RobertK]

it's about like that or maybe a bit worse.

what do you mean by tune up?

Plugs, wires, air filter, new vacuum line, check boot for cracks, clean the ICV & AFM.

[More&Faster]

quoted from the other thread

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...

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

i looked at my M20 AFM today and my screw there is a hex head and seems to control nothing at all. (i had to pull out an inch of plastic to get to it). i turned it half a turn, a whole turn, five turns, and finally took it out with nothing changing at all.

and you're wrong on principle regarding the AFM's reaction time anyways. the afm will begin to open when the pressure in the manifold drops. this happens as soon as the throttle opens and travels at the speed of sound. the engine doesnt have to consume all that air before the AFM notices it.

[MrK]

All this talk about throttle lag made me go down and try my own car (M30 powered, but its totally stock with an AFM and all).

Negligible lag IF THAT. Leading me to believe that there may be something wrong with your engine, most probably a failing or maladjusted AFM.

[NC325iC]

quoted from the other thread



i looked at my M20 AFM today and my screw there is a hex head and seems to control nothing at all. (i had to pull out an inch of plastic to get to it). i turned it half a turn, a whole turn, five turns, and finally took it out with nothing changing at all.

and you're wrong on principle regarding the AFM's reaction time anyways. the afm will begin to open when the pressure in the manifold drops. this happens as soon as the throttle opens and travels at the speed of sound. the engine doesnt have to consume all that air before the AFM notices it.

no air/vacuum does not travel at the speed of sound