Bucking while driving

I have a 93 Plymouth Voyager. Yesterday it started bucking while driving. It loses power when trying to accelerate. Then it comes back full force. Shifting seems fine. It just seems like there is not enough power at times. We drove another 15 miles home with the same issues coming and going. I had this issue before - less noticable though - and the shop replaced the O2 filter, exhaust system and engine wiring. Any ideas? FYI - I got gas the day before.

Sounds like leaking ignition components might be a possibility! Does it do it when you accelerate and then its fine once you are at cruising speed?

I was crusing at 65 mph and it just started. Then it was fine again for a while until it started again. We got off the highway and took some less busy road. Sometimes it accelerated fine and shifted great, then it started bucking while accelerating and crusing. The engine never died, we stopped at a gas station and had it idle for a bit. That was fine. Like I said it comes and goes. A friend of our suspects bad gas.

Does the engine sound like it is loosing power - or are are loosing power somewhere else?

It could be the "bucking" could be issues with the torque converter in the transmissition.

How full is the tank fuel wise, if less than 1/2 try this, put the contents of a bottle or two of HEET, Water Out, Dry Gas in the tank, if you have a condensation problem in the tank she will buck, stall, hesitate and just run rotten. If this does not do the trick, you have at lest eliminated condensation and the cost is minimal.

Thanks for all the help. I bought some gas treatment last night and will test drive today. It was raining like crazy Saturday and the car was sitting outside. You could be right with the condensation.

Damp conditions and weak ignition problems go hand in hand!

I also like the torque converter slipping theory. If it only does it at a steady cruise this could be likely. I'm not sure when they switched to the "7176" trans fluid but I do remember a TSB on transmission shudder do to the use of the wrong trans fluid. The fix was to flush and more often than not it worked.

As far as the heet in the gas tank. Seriously I have been in this business a long time and have never run into "moisture" in the tank. I have run into "water" in the tank. If you have "water" in the tank it likely happened while you where just filling up and I doubt if you made it a mile down the road before your car became incapacitated! "Moisture" in the tank is so unlikely that it is not even worth mentioning!

Reference water or condensation in the tank, I am 72 years of age and i have seen up close and personal condensation in the tank at least four times in the last six to eight years (not much but it does happen), generally occurs when we let the tank get low on fuel and let it sit for a period of time. Daughters Mustang II was so bad I dropped the tank and poured contents out and had a quart of what looked like water but smelled like gas.

Good news! After adding the gas treatment and letting it sit for 2 days, I drove to work this morning without any problems. I took it for a test drive last night and had some minor shacking - especially when accelerating, but it went away after a couple of miles. It is still a little sluggish when accelerating, but I take it easy on my baby until the next fill up. Thanks for all your help!!