BB's,

My stumbling/hesitation problem on acceleration continues...

Quick problem summation: Car has been stumbling on acceleration for a month or two now. Started hesitating a couple of times during heavy rain only, then began doing it all the time. Starts and idles fine.

Work done: Checked for vacuum leaks. Checked AMM connection, cleaned bellows and IAC hoses. Cleaned and replaced flame trap. Replaced plugs, cap, rotor, air filter about 15K ago. Recently replaced wires, fuel filter, FPR. Last night I replaced pre-pump and sending unit (rusted-out).

I don't have any test equipment so I have been forced to take the replace parts approach. Might be forced to go to a mechanic soon if I can't fix.

Could this be a bad knock or oxygen sensor? Going to check those next.

Any other thoughts folks??

Thanks all,
Jim

This may not be applicable since my problem occurred on a '81 with CIS.. But there's a ground wire that attaches under the intake manifold. I think it goes to the IGN computer. Mine was falling apart and the car would hesitate then run then hesitate but would idle fine. When the gnd wire finally broke, it would ONLY idle. Just reattaching it worked!

Jim,

With rainy weather come potential electrical problems, I've found.

Be sure to check/clean all the fuses (especially the 25A fuse in the engine compartment - left(US driver side) next to fender.)

Clean all contacts at the battery and coil.

Also, run a batch of Chevron Techron (that stuff is great) in the tank.

Give it a good "eyetalian tuneup" out on the highway.

Good Luck!

TomD
'86 240
'93 240

What about your coil? Couple of thoughts: take a look under the hood at night in your garage with the lights off. Check for visible electrical leaks around the coil tower, where the coil wire plugs in, also the spark plug wires and distributor cap, now with a helper, put the engine under load (foot on brake with car in gear with some acceleration, but stand off to the side) watch for the same stuff. If okay, take off the small electrical wires at the coil and give the terminals and the threaded connections a light wire brushing and test drive. Lastly, if you can borrow a known good coil give that a try, however Volvo coils are pretty robust and long lasting, mines 15 years old, but I did have trouble like you and it was a loose connection at the terminals.

Does it rev up fine under park? I am assuming the hesitation is when the engine's under load, correct? If that's the case, it is related to ignition. Happened to me less than a year ago. The igntion wire going from the coil to the dist. had corroded and sparks were flying all over!! Hence it would idle or had hesistation under load. I replaced the coil with Bosch unit, but I bought wires from NAPA. Well, wouldn't you know it!! It didn't even last a year!! Two months ago, hesiatation came back...I replaced the FPR, cleaned intake system, spent countless # of hours diagnosing, but all this time i refused to check the wires (since in my mind it was still 'new'). My buddy had a German-made set from his last service which he gave me, and bingo!! The car runs and idles like new!!

Cheers,
SM
--
90 BMW 325is, 98 BMW 528i, 90 Volvo 240DL