misfire cylinder-4

[john67]

I am working on a 1999 Plymouth Neon DOHC automatic with 69k. The engine has a very rough idle. Code says misfire cylinder 4. I have replaced the spark plugs twice. First with platinums, then with OEM Champions. I have also replaced the plug wires, coil pack, and one fuel injector. I have tried fuel injector cleaners and different brands of premium gas. Disconnecting the battery seems to clear the problem for 1-3 days. The oil is clean with no signs of coolant and the engine runs fine at anything other than idle. The local dealer doesn't know what is wrong, but says it may be a bad valve spring or camshaft. I don't really buy that explanation given the problem goes away (temporarily) after disconnecting the battery. If the cam is bad, it would run bad all the time. Plus, I would tend to think a bad spring would make the engine run worse with higher rpms. This problem exists only at idle. Any thoughts?

[98NeonExprDOHC]

It is normal for DOHC neons to have a rough idle. I started to have misfires @ 15,000 miles new. The dealers flashed the PCM a new idle code in 1999. No change. Changed sparkplug wires. No Change. Using 93 octane gas has reduced the misfires. I have not misfired at idle in over 25,000 miles. The real fix for me I believe was when I changed the cam position sensor with the NEW Mopar part $60 installed at the local shop. go to the following site and read the post "A Big Purple Lemon!"

http://www.ripoffreport.com/reports/ripoff3140.htm

[john67]

Thanks for the info. I haven't heard much good about Chrysler quality from the people I've talked too. After reading the story you provided the link to, it appears the quality problem may be more than just some individual's bad luck. I'm not a Mopar fan, but I didn't want to come out and say bad things about them, given I'm in the Mopar section of the forum. I'll check into a new cam position sensor. I may also try a local shop where I know the mechanic, instead of going back to the dealer. The auto trans is going bad too. The trans doesn't want to go into overdrive until it has gotten up to normal operating temp. Hopefully I can talk my gf out of this car and into something higher up the quality ladder.