i have a 1996 pontiac sunfire GT with 2.4L engine.
symptoms are multiple misfires accompanied by a very prominent engine vibration that "seems" electrical in nature and continues for a second or two after the engine is shut off. other symptoms are reduced power and acceleration at low speeds or RPMs, going uphill etc. it is also using gas at 2 or 3 times the normal rate.
this problem started at the same time that there has been some road construction on a long hill on my commute, causing me to drive at low speeds for a prolonged period of time and raising the engine temperature a bit. it has never overheated, but the temp gague has gone up significantly a couple of times - occasionally there has been a slight "burned" smell, leading me to think that a wire or cable in the ignition system may have burned the insulation off, causing the vibration mentioned above, but so far we have been unable to find any damaged wire.
to date we have replaced the spark plugs, coil housing, spark plug boots (wires) and the MAP sensor hose. i have taken it to two mechanics, including a GM dealer. they have switched out coils etc. and have determined that as far as they can tell, the problem is not mechanical. they did not seem to think the problem was with the ignition control module or computer. they also report that the catalytic converter is now plugged as a result of the problem. as far as i know, none of the original symptoms were related to the catalytic converter.
their best suggestion is to replace the spark plugs i just replaced with a different type than what we are now using, even though the type we have been using (bosch platinum) was working fine for years and the recommended delco plugs did not work, which led is to the bosch platinums. i understand that bosch platinums are out of favour in some circles, but please keep in mind that the vehicle had been running very well for years using bosch platinum plugs, so i am reluctant to believe that this is the problem, in spite of the mechanic's suggestion; in fact, they cannot guarantee that this will fix the problem.
any other ideas?
thanks in advance. i have a wife and four kids - this vehicle is primarily used for putting food on the table as i commute 25 miles to work and back each day. any help i can get would be greatly appreciated.