2007 Jeep Compass 2.4L
The car has recently started developing a lurch when I back off the gas after accelerating. It usually happens at medium throttle or higher, like when accelerating up an on-ramp or something. It accelerates fine, but then has a single, brief lurch like the throttle gets fully closed for a moment as I slowly back off the throttle when getting to the speed I want, or get over the crest of the hill, or whatever. After the lurch the revs return to normal. It’s the same effect as if I quickly took my foot right off the gas pedal, then immediately pushed the pedal back to where it was.
It’s drive-by-wire. I’m thinking that a bad spot has developed in the gas pedal sensor. I probably won’t be able to figure out very much about it before I give up and take it to the shop.
- Before I start playing around with the pedal, are there any other obvious places I should be looking?
- If it goes to the shop, would this be a dealer-only option because of _____?
I think the throttle pedal sensor is a pretty good bet. As far as the “playing around”, that depends on the tools you have to play with. Do you have a scanner that can data-log the sensor signal? That would show any signal noise to verify sensor problems. Do you own a digital voltmeter that you can probe the output signal from the sensor to look for noise in the signal? If you don’t own this stuff you could take a chance and just change the pedal and sensor assembly.
No, it is not a dealer-only thing. Aftermarket parts are available (see link below from RockAuto) and you could just change it yourself ($65 part) as a pretty simple DIY job. Not much of a gamble at $65 and 3-4 bolts and an electrical connector.
http://www.rockauto.com/en/moreinfo.php?pk=2064234&cc=1433554&jsn=434
No, no scanner. For the pedal I was mostly thinking about a multi-meter on the bench. Beyond that I’d have to pay somebody for diagnostics.
New complication: it did it once yesterday with the cruise control on. I’m starting to think there’s some programming glitch that closes the throttle too fast - some self-learn thing gone awry?
It could be an occasional misfire.
I once saw this symptom due to a cracked spark plug.
Thanks, but would that always happen only when just backing off the throttle after accelerating?
Not much cost or effort to inspect the plugs.
If it were the pedal sensor wouldn’t the engine “hiccup” every/most times the pedal moves past the bad spot, not just coming off acceleration?
Does this have a hot wire MAF sensor? That could just be dirty.
You’re not using an oiled air filter, are you?
Another idea if you haven’t solved it yet, sometimes the injectors get a little clogged and it causes problems in metering out small volume flows of gas. No effect on medium to high fuel flow rates, but when you just need a small amount of gas to keep the engine running during deceleration, instead of a little, at first you get too much, then none at all, as you back off the gas pedal, which causes a jerk sensation. Try running a can of fuel injector cleaner through the tank, see if that has any effect.