97 sunfire rough idle mystery??

[=RM=PimP]

i have a 1997 sunfire with 2.4L DOHC (not a GT) (se coup) the car runs find down the road but idles rough, it very very rarely dies on me the check engine light comes on only if im driving it in town where it idles alot but when im going down the highway it goes off, took it to autozone with the light on and it says "Multipel cyl. misfire" (sorry for spelling) ive put new plugs and wires (whatever u wanna call them) and had my coils tested at AZ and was all good even replaced the housing for the coils (not sure what u call it but i was told it acts kinda like a distributer cap) and it still runs funny, throttle positon sensor has been changed and i had the catyllic converter checked and it was good, anyone got any ideas on the matter, thanks for your input

[manicmechanix]

It's probably dirty fuel injectors. I think the 2.4 also uses the Multecs 2's similar to the V6 (they don't directly interchange though), and they are really bad about clogging up. Try running a big bottle, that treats up to 20 gals, of Techron fuel system cleaner in the tank. That might help but if it's running that bad to set off misfires the injectors might need to be cleaned by the dealer on the car. That should get them working OK. A test for dirty injectors is the cylinder drop test, but sometimes they charge a diagnostic fee for this on top of the fee for cleaning. Which is stupid because a cylinder drop test is part of doing a proper cleaning job. If you have it done maybe ask for just having your injectors cleaned and skip the diagnosis.

When they get old and dirty though I don't think they can even get totally cleaned on the car and to get the running perfect they'd have to be cleaned off the car or rerplaced all together. Anyway, I think you can run two tanksfuls of Techron consecutively at first. See if that helps.

[=RM=PimP]

would it be possible to take them out and clean them myself, i am mechanically inclined and was considering replacing the o-rings on the injectors anyways

[manicmechanix]

It would be even harder to clean them off the car. you would need some equipment that hooks up and runs cleaner through them. It'd be easier to clean them on the car with a simpler cleaning equipment set up. Really all you can do without the equipment is run Techron through the gas tank.

[=RM=PimP]

ive seen places offering fuel injector cleaning like walmart tire and lube and also at several oil change places and tire shops, is this the same thing or is what the dealer does totally different and better? thanks for all of your input btw, im hoping to get this lined out, lol

[manicmechanix]

Originally Posted by =RM=PimP

ive seen places offering fuel injector cleaning like walmart tire and lube and also at several oil change places and tire shops, is this the same thing or is what the dealer does totally different and better? thanks for all of your input btw, im hoping to get this lined out, lol

Yeah it should be similar to what the dealer does, but ask if they're cleaning it directly at the fuel injector rail. Some other question you can ask is, If they can do an "injector cylinder drop test" and a "injector coil test", to verify the injectors just need cleaned and to verify they got cleaned out after the cleaning. It should be cheaper than at the dealer. The dealer probably has better equipment and know-how to clean and test the injectors, but that doesn't mean they necessarily will do the job any better.