stumbling issue not the usual.
Thread Starter
whats that smell!?
Joined: Aug 2005
Posts: 339
Likes: 0
From: Port Orchard, WA
stumbling issue not the usual.
ok i have a 86 S4 n/a and i am stumped on what my problem is i never noticed it before it was slight but no it is obvious really obvious am have a hestiation and stumbling problem. it won't mater if it's cold or warm. it's so intermitant one day the car will run fine the other will be running crappy, ill be driving then it will stumble for half a sec then pick back up, this morning it stumbled when i was decelled!?, and occaionaly in idle but it wont die. any ideas?
You could have a plug wire that's intermittant arcing. Check the plug wires to make sure they're firmly seated at both ends. Then route them such that they're not touching another plug wire. And, finally, learn how to punctuate!
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 27
From: FORT WORTH, TEXAS,USA
The FSM gives you a way to check the AFM. Fuel and Emissions section.
It's not really that great though. There's no way a person can really check it out at home. I've no idea where you'd send one to have it checked out, either.
There's a *carbon track* the afm wiper rides on. It's been riding that track for a couple of decades on your car. Saying this does not mean THAT is your problem.
Stumbled under deceleration. Could be a TPS problem. One of the things a TPS does is cut fuel to the injectors during deceleration. Cuts only one primary injector if you let off the pedal just a touch.....cuts both primary injectors if you let off all the way on the pedal. Then the ECU senses when the rpm have dropped to around 1100rpm or so, and the primary injectors come back online.
Seems you could take a meter and put it on the TPS output wire, and with key ON engine OFF, watch the volage as you press the pedal slowly. You wouldn't want to see any *opens* or really erratic voltage changes. Green/red is the output wire as shown in the free online wiring diagrams.
A lean condition can cause bucking/jerking type hesitation. Too much fuel and imho it feels like stepping into a bit of mush. Unlike the lean condition. Just imho.
AFM's that have been fucked with can cause your problem. But it'd be a consistant thing, not intermittent. Fucked with means someone has removed the large plastic *D* shaped cover and played with the afm spring tension and got it wrong.
IF the pressure sensors vacuum line has no orifice in it, that can, on some cars, cause hesitation. The orifice dampens the input pressure. Smooths things out.
It's not really that great though. There's no way a person can really check it out at home. I've no idea where you'd send one to have it checked out, either.
There's a *carbon track* the afm wiper rides on. It's been riding that track for a couple of decades on your car. Saying this does not mean THAT is your problem.
Stumbled under deceleration. Could be a TPS problem. One of the things a TPS does is cut fuel to the injectors during deceleration. Cuts only one primary injector if you let off the pedal just a touch.....cuts both primary injectors if you let off all the way on the pedal. Then the ECU senses when the rpm have dropped to around 1100rpm or so, and the primary injectors come back online.
Seems you could take a meter and put it on the TPS output wire, and with key ON engine OFF, watch the volage as you press the pedal slowly. You wouldn't want to see any *opens* or really erratic voltage changes. Green/red is the output wire as shown in the free online wiring diagrams.
A lean condition can cause bucking/jerking type hesitation. Too much fuel and imho it feels like stepping into a bit of mush. Unlike the lean condition. Just imho.
AFM's that have been fucked with can cause your problem. But it'd be a consistant thing, not intermittent. Fucked with means someone has removed the large plastic *D* shaped cover and played with the afm spring tension and got it wrong.
IF the pressure sensors vacuum line has no orifice in it, that can, on some cars, cause hesitation. The orifice dampens the input pressure. Smooths things out.
Last edited by HAILERS; Sep 3, 2008 at 09:13 AM.
Thread Starter
whats that smell!?
Joined: Aug 2005
Posts: 339
Likes: 0
From: Port Orchard, WA
The FSM gives you a way to check the AFM. Fuel and Emissions section.
It's not really that great though. There's no way a person can really check it out at home. I've no idea where you'd send one to have it checked out, either.
There's a *carbon track* the afm wiper rides on. It's been riding that track for a couple of decades on your car. Saying this does not mean THAT is your problem.
Stumbled under deceleration. Could be a TPS problem. One of the things a TPS does is cut fuel to the injectors during deceleration. Cuts only one primary injector if you let off the pedal just a touch.....cuts both primary injectors if you let off all the way on the pedal. Then the ECU senses when the rpm have dropped to around 1100rpm or so, and the primary injectors come back online.
Seems you could take a meter and put it on the TPS output wire, and with key ON engine OFF, watch the volage as you press the pedal slowly. You wouldn't want to see any *opens* or really erratic voltage changes. Green/red is the output wire as shown in the free online wiring diagrams.
A lean condition can cause bucking/jerking type hesitation. Too much fuel and imho it feels like stepping into a bit of mush. Unlike the lean condition. Just imho.
AFM's that have been fucked with can cause your problem. But it'd be a consistant thing, not intermittent. Fucked with means someone has removed the large plastic *D* shaped cover and played with the afm spring tension and got it wrong.
IF the pressure sensors vacuum line has no orifice in it, that can, on some cars, cause hesitation. The orifice dampens the input pressure. Smooths things out.
It's not really that great though. There's no way a person can really check it out at home. I've no idea where you'd send one to have it checked out, either.
There's a *carbon track* the afm wiper rides on. It's been riding that track for a couple of decades on your car. Saying this does not mean THAT is your problem.
Stumbled under deceleration. Could be a TPS problem. One of the things a TPS does is cut fuel to the injectors during deceleration. Cuts only one primary injector if you let off the pedal just a touch.....cuts both primary injectors if you let off all the way on the pedal. Then the ECU senses when the rpm have dropped to around 1100rpm or so, and the primary injectors come back online.
Seems you could take a meter and put it on the TPS output wire, and with key ON engine OFF, watch the volage as you press the pedal slowly. You wouldn't want to see any *opens* or really erratic voltage changes. Green/red is the output wire as shown in the free online wiring diagrams.
A lean condition can cause bucking/jerking type hesitation. Too much fuel and imho it feels like stepping into a bit of mush. Unlike the lean condition. Just imho.
AFM's that have been fucked with can cause your problem. But it'd be a consistant thing, not intermittent. Fucked with means someone has removed the large plastic *D* shaped cover and played with the afm spring tension and got it wrong.
IF the pressure sensors vacuum line has no orifice in it, that can, on some cars, cause hesitation. The orifice dampens the input pressure. Smooths things out.
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