NEED ADVICE - 1996 Pontiac Sunfire GT 2.4L engine ignition problems

[tasunkawitko]

hello -

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.

ron

chinook, montana

[tasunkawitko]

UPDATE -

i just received a call from the mechanic who said that the new spark plugs (original delco type) took care of the misfire. i am not sure how this is the case, since as stated above, the car ran beautifully for many years on the bosch platinums, but i do trust this mechanic, so if he said it fixed it, then i do believe him.

what i think is that the original problem must have been the MAP sensor hose, which was old, cracked and rotted and came disconnected undetected, probably due to the jarring of the road construction. as i drove the car, the existing plugs (before i replaced them) must have fouled up and the converter must have plugged up, causing the troubles mentioned above. the only one i can't account for is the vibration - i'll see if it's still doing that when i get home from work tonight and pick up the car. this is the best scenario i can come up with based on what little i know - if anyone has any other ideas, please advise.

two days in the shop, a lot of diagnostic work and four spark plugs: 259$. i'm not happy about that kind of money, but i do understand that a lot of time was put into figuring out the problem. as long as it takes care of it, then i am satisfied.

this still leaves the plugged catalytic comverter - at first he said this may cost several hundred dollars - i found a matching catalytic converter for 79$:

http://www.oreillyauto.com/site/c/de...2404&ppt=C0022

some research informed that the job should take around 1.5 hours in a shop.

can someone please explain why his estimated cost was so high? it's not that i am a cheapskate, but with a wife, four kids, a mortgage etc. we do need to be careful with our money and cannot afford to pay more than necessary on things like this. i am definitely not ranting against mechanics and i agree wholeheartedly with the "pay it now or pay more later" philosophy, but i don't see where this job should cost more than a couple of hundred dollars.

thanks again in advance - i welcome any replies, advice or opinions.

ron

chinook, montana

[MrCritical]

Strange case indeed.

Let me start by saying you're the first case in my dealings with the "Quad 4" design engine that would even run on Bosch plugs at all. And I go back to the first year of production to the present. My '90 Grand Am GT wouldn't pull out of the driveway after I put a set in personally.

Just because you found a converter for $79 doesn't mean the one the tech was pricing for you cost $79. Converter prices vary a ton. A $79 converter may last a year or two, or a week or two.

Diagnostic charges cause more hard feelings at a shop than anything else. If you trust the tech, and he's doing work he's qualified for, he's probably not trying to rip you off. Ask him about his parts prices, parts warranty, ect.

Unfortunately (and I'm not trying to be a smart aleck) the price of the repairs and your economic situation are not related. And I've been there myself.

[tasunkawitko]

hi, MrC - thanks for the reply.

definitely no hard feelings on my part as i did take a couple of automotive courses back in college, and i know what mechanics go through when it comes to diagnosing a problem. i definitely agree with this:

>>>the price of the repairs and your economic situation are not related<<<

since i got the car a couple of months ago at no charge from the original owners (my parents) who took very good care of it, i am still coming out of the experience in good shape, and i definitely trust the mechanic. i'll sit down and discuss the options with him and see what we can do to get the best repairs that i can afford.

since i have no experience with the quad 4 design or with bosch platinums, i'm definitely not in a position to say that the mechanic is wrong; all i know is that my dad said the car didn't run "worth a d*mn" on the original delco plugs and that it ran really well for at least 60,000 miles with the boschs before this problem started. considering that the majority of people i talk to do not hold the boschs in high regard, i am inclined to believe that my dad's experience might be the exception, rather than the rule. hopefully this will be the end of the ignition problems and i can get the catalytic converter replaced as soon as possible.

question: my hypothesis is that all of these problems may have originated with the MAP sensor hose coming off. can you or anyone else tell me what the symptoms would have been with just this problem? i am guessing that the hose came off undetected long before i knew about it, leading to other things such as fouled plugs etc., which led to misfires, rough running etc., and it cascaded from there, leading to where we are now. is this a possibility?

in any case, i will be sure to provide updates on this as they happen.

thanks again, and look forward to future discussion on this and any other topic -

ron

[tasunkawitko]

another update -

i picked up the car last night when i got home from work, and it seems to run just as fine as it did before the troubles started. i am at a complete loss as to explain how sparkplugs that didn't work before, work now - and how spark plugs that did work before for several years, now don't. having said that, i am happy to have things back to normal.

either way, this is a great running car that that suits my commuting situation very well and i intend to keep it on the road and in top shape for quite a while. the next project will be the catalytic converter - i didn't notice any symptoms or problems while i was driving it last night, but my mechanic has informed me that it needs replaced because it is clogged, so it will be done as soon as i can.

if anyone still has any ideas or thoughts on the situation above, i would be most appreciative to learn them.

thanks again -

ron