What causes a 1997 Buick Park Avenue engine with 39000 miles to miss when power is applied at medium speeds?

Answer 1

Missing is usually attributed to the "spark" but can be fuel related or mechanical for that matter. As for the spark: pull the spark plugs and see if any are different looking lighter or darker or wetter etc. It's also a good thing if you can "Read" the plugs to see if you engine is getting enough (or too much) fuel. Also look for one or more to be "Oil Fouled" which could indicate bad valve seals or a broken ring (if it's just one cylinder with the problem). If one plug is "Wet" then it may be that that cylinder is not firing due to the plug being bad or the plug wire or the coil or the computer is not firing that cylinder at times, etc. etc. Also could be a "Burnt" valve not seating properly and leaking too much (usually the exhaust valve). Conducting a compression check couldn't hurt either. Will let you know if all the cylinders are sealing ok. If it's happening during medium speed under "Light" load then that's when the engine is pulling a very high vacuum and one of more cylinders may be pulling too much oil and fouling the plug or (since this is where the computer will run the engine the leanest) it may be one or more cylinders aren't getting enough fuel. Had a car once that was intermittently missing and it was a bad rockerarm. Also had one where the cam lobes were going away and that was causing a miss (among other things) LOL. The spark plugs can tell you alot about what could be wrong, let them "talk" to you ;-) TommyTrouble Could be either the plugs, wires or even the coil packs, check the plugs and if the look bad at all, replace them. Look and listen for your wires arcing out, also check for cracks in your coil packs, if one is cracked, replace it.