random hiccup 91 m42

[B-well]

when the motor is up to temp or very close to it, and im in low revs and put a load on the motor it will medium-lightly buck or hiccup. once im in the upper RPMs there are no problems.

It occurs mostly when im accelerating from a stop in a normal way.
sometimes its only one buck but sometimes its like a bunch of times in a row.

It normally only occurs when the vehicle is up to temp and if i remember correctly it never happens when the motor is cold or slightly warm. so it seems it only happens when at operating temp.

Any suggestions would greatly appreciated

[gearheadE30]

Crank sensor caused that on my car. When it gets hot the waveform amplitude drops and sometimes will 'miss' the trigger gap, especially at lower rpm. Noise in the circuit can also cause this. The computer then loses sync for1 revolution, and then all is normal again. It's a pretty noticeable lurch when it happens though.. if yours is really light and the car just feels like it's a little down on power in that instant, especially at small throttle opening, the car might be running lean for a second, which could be a number of things, most probably the 02 sensor.

[vpilarrt]

I had this once and I cleaned out the AFM barn door valve by spraying 1/4 - 1/2 can of choke cleaner all around inside the airbox. That fixed it.

[B-well]

Crank sensor caused that on my car. When it gets hot the waveform amplitude drops and sometimes will 'miss' the trigger gap, especially at lower rpm. Noise in the circuit can also cause this. The computer then loses sync for1 revolution, and then all is normal again. It's a pretty noticeable lurch when it happens though.. if yours is really light and the car just feels like it's a little down on power in that instant, especially at small throttle opening, the car might be running lean for a second, which could be a number of things, most probably the 02 sensor.

I had this once and I cleaned out the AFM barn door valve by spraying 1/4 - 1/2 can of choke cleaner all around inside the airbox. That fixed it.

ill check the crank sensor and air meter and let y'all know how it goes

[grippymonkey]

I get a random kick from time to time also. Sometimes it'll do it real quick while sitting at idle for a long time... or when I just start out in 1st gear.

[B-well]

crank sensor replaced with no result and i cleaned the afm with CRC5110 and it seamed to help a little but i think it was more that i wanted it to help and it still the same.

Any other suggestions. its only when the car is warmed up and under load under 2k rpms

[B-well]

?

[bwawuz02]

exhaust, i.e. muffler or cat, could be clogged causing back pressure?
or possibly an injector that is clogged?

[B-well]

exhaust, i.e. muffler or cat, could be clogged causing back pressure?
or possibly an injector that is clogged?

ill check it out. flows pretty decent out of the tip. I've got a loud track exhaust i can put on.

[bwawuz02]

I would try swapping the AFM too, sometimes the connection gets warn right where the sweeping arm contacts the board, especially in the low load region.

[vpilarrt]

How old is your O2 sensor?

[B-well]

I would try swapping the AFM too, sometimes the connection gets warn right where the sweeping arm contacts the board, especially in the low load region.

waiting to hear from a buddy when he gets off work to swap it out.

How old is your O2 sensor?

no idea. car has 92k, 10k of that which i've drove and never replaced it.

the hotter the engine gets the worse the problem gets. nearly exponentially

[Ryann]

In my experience Bosch Motronic drivability issues that go away with high rpms or at WOT are usually vacuum leaks. AFM issues usually will give you a CEL. Have you viewed the Bosch AFM home repair video?

[B-well]

I extremely appreciate that. thank you

[VANOS714]

I had that problem, changed the spark plugs and good bye hiccups.