Jerking/Lurching During Deceleration

v40driver68 · Post by **v40driver68** » 10 Sep 2012, 17:54

2002 v40, 100,000miles

Multiple trips to mechanics have not solved this!
After driving on freeway or local for about 30min to an hr, when I take my foot off gas pedal to prepar to stop, car decelerates normally then around 5mph it jerks forward slightly. Any engine or tranny mount that needed repair was taken care of over a year ago. That seem to solve a previous more prominent jerking problem. But this more subtle one is a real puzzle. Also, a/c is running when this occurs.

Post by **MadeInJapan** » 23 Sep 2012, 03:32

I don't think your Volvo has the dreaded ETM but you might check to see if it does. Sure sounds like it could be a break in a vacuum line or possibly a dirty Throttle Body. Do you know if these have been checked or cleaned recently? Do you get a trouble code (check engine light) pop up? Even if you don't, it might be worth reading your codes to see if you have anything impending.

dielawnsupremo · Post by **dielawnsupremo** » 06 Nov 2012, 18:39

I"m having an IDENTICAL issue in my newly-bought V70 XC...have you found out the issue yet?

Post by **zulu-v40** » 06 Nov 2012, 20:42

The V40 has a fly-by-wire throttle, so an ETM issue is luckily out of the question. Maybe it's a misfire? You might explore the spark plugs and engine coil packs for wear. Removing and cleaning the throttle body is fairly simple and well worth your time. Use a toothbrush and Throttle Body spray cleaner. While your at it, remove and inspect the throttle position sensor attached to the body. That thing gets really gunked up. Checking for vacuum leaks like MadeInJapan suggested is also a great idea. Gently bend the vacuum hoses and look for cracks. Even if there's a superficial crack, I like to replace the hose.

Post by **JimBee** » 06 Nov 2012, 20:53

While you have clear access to the TPS, bench test it. Inside it is a variable resistor, like a potentiometer. You can use your multimeter to check variable resistance. Find the ground (middle pin?) and test the others for continuity.

I've been told that generally if they click at one end of the rotation, they're good and that they don't go bad often. But it's easy to test. With your meter connected, use a screwdriver to turn the shaft, slowly but steadily one end to the other. Your meter should show steady increase of decrease in resistance (ohms) through the range. If there are flat spots or any irregular jumps or stops as you turn that would be an indication of a bad TPS.

dielawnsupremo · Post by **dielawnsupremo** » 08 Nov 2012, 19:34

Found out mine is misfiring, cyl 3. Will find out why tomorrow.