multiple misfire in 97 monte carlo

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Hi , I have a 97 Monte carlo, 3.1L engine and have a problem with misfire and rough idle. When service engine light comes on it gives me 2 P0300 codes which reads multiple misfire on code reader. I have done a valve job, new lifters, new injectors, new wires and plugs,etc and after all this I still get 2 p0300 codes for misfire again. When I first started it after maintenance I got a p0305 code which is a nr 5 cylinder misfire. I pulled that plug today and it has black soot around ceramic tip, but all the other plugs look normal. I have checked and tested the ignition module and packs and they are firing normal. Anyone have any ideas as to what this could be ?????? Thanks Jimt

posted by  jimt

you might have a bad coil for cyl 2 & 5 or the module under the coils is failing
with coils most shops will replace all 3 and sometime the module just to be sure (because of mileage and age) you could just replace the one coil to try it

posted by  osborste

There is a difference between testing for spark and what the secondary ignition is doing on a running engine. it takes alot more energy to fire a sparkplug inside the combustion chamber than it does doing a spark test. What you really need is someone with a scan tool (code readers are crap) to look at the data stream who understands what they're looking at. Based on your shopping list you've spent a BUNCH of $$$ and haven't accomplished diddly.



What shop is that? I couldn't imagine trying to sell a customer three coils and a module "just in case". Proper diagnostic techniques will uncover the defect(s). Shotgunning parts is for amateurs and gives this profession a bad reputation.

I know, I know, you sell parts for a living so the more tha marrier. Gotta keep your numbers up.

posted by  vwhobo

so two weeks a month maybe lucky a year another one goes(coil)its only a suggestion
and no i don't sell parts i don't like come backs do it properly or take it somewhere else and have to go back to them and complain you didn't fix the problem
i agree thats why my last line said he/she could replace the one coil and try it

posted by  osborste

got to add more
hobo you and i both know there are crooked shop's/mechanics out there the bottom line is there are good mechanic's out there too they just have to pay bills(unemployment don't pay well)and what ever the shop owner say's get's done. no matter what the mechanic say's

posted by  osborste

I agree vwhobo, I've spent close to 600 dollars on this already, but believe me it did need a valve job, and new injectors. Two of the old ones had about 40% flow through them. I took it to dealer shop and they put it on scan tool and told me the nr 5 cylinder was not showing any combustion. He said it was probably the fuel injector, which is why I went ahead and replaced all of them anyway. What I still don't understand is why the only the nr 5
spark plug shows that the cylinder is running rich. The plug is completely black with soot. Others are fine.
I am taking it back to dealer again this week and let them put it back on scan tool and see if anything has changed. Appreciate you help vw. Jimt

posted by  jimt

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