Checked the throttle potentiometer today, trying to find the cause for engine hesitation when accelerating.
First tried to take it out and check it at home. But it wasn't very cooperative. On this engine, it is on the underside of the throttle body, bolted with two torx screws. Outer screw came out after about 15 minutes with damaged head, inner one didn't want to, so finally I gave up. Tightened the screws back, disconnected the connector and checked the pot on the car. Didn't bothered with disconnecting the battery first, as stated in Haynes for all operations concerning electrical systems in the car.
(Un)fortunately, there is nothing wrong with it. Resistance was changing perfectly smoothly between 900 and 2400 Ohm as I was opening and closing the throttle. Potentiometer is made by Bosch.
Started the engine with disconnected pot. It was at 30-40 degrees, because I returned from town about an hour earlier. Engine started normally. Unexpectedly, yellow warning light didn't lit after starting. But the idle was higher, at the beginning slowly varying between 1300 and 900 rpm, then after 2-3 min stabilized at about 1500, when engine reached its operating temperature. Pushed the throttle. Engine was missing about half a second, rpm dropped like it's gonna stall, then started raising, but not very fast. Tried several times, definitively much worse that with connected potentiometer. It is possible to drive in this condition anyway, although not very comfortable. With connected potentiometer, engine is not missing, but just hesitating to deliver the power for fraction of a second.
Hmmm, any ideas ?
How to check the throttle potentiometer
Moderator: RichardW
It's not your TP Alex.
If the TP is faulty, it will make for strange idle revs if you leave the acc pedal. It's like the car gets a mind of it's own.
The TP wears out in the carbon tracks, and this causes unexpected behaviour when the slider is exactly over a worn out position.
It can be tried during drive by sloooowly accelerating. Then suddenly the engine will jump in power.
The MAP sensor would cause a hesitation on fault as it decides the fuel on air pressure. If faulty the fuel enrichment does not occur correctly when accelerating.
If the TP is faulty, it will make for strange idle revs if you leave the acc pedal. It's like the car gets a mind of it's own.
The TP wears out in the carbon tracks, and this causes unexpected behaviour when the slider is exactly over a worn out position.
It can be tried during drive by sloooowly accelerating. Then suddenly the engine will jump in power.
The MAP sensor would cause a hesitation on fault as it decides the fuel on air pressure. If faulty the fuel enrichment does not occur correctly when accelerating.
Hi Anders,
I'll try to check the MAP sensor. But, more than a visual check of it probably can't be done without some equipment. But I've got a feeling that it will be looking good. As I said, diagnostics didn't show anything wrong with any of sensors. New MAP sensor is about 100 EUR.
Any ideas, what else to check
I'll try to check the MAP sensor. But, more than a visual check of it probably can't be done without some equipment. But I've got a feeling that it will be looking good. As I said, diagnostics didn't show anything wrong with any of sensors. New MAP sensor is about 100 EUR.
Any ideas, what else to check