Manager Forum

Hello guys, we've got a Neon in here (1B3ES56C55D134616 if needed) This is the clients first time here so I don't have a full history on it, but he bought it at about 120,000 (its at 149,554 now) he was told timing service had just been done on it (We can confirm everything looks new under the cover) it has had a misfire code for awhile (not sure how long as the client isnt sure) He himself replaced the plugs the wires and the forward O2 sensor and the misfire is still present. We checked over all the work he did (naturally) first. Everything looks good, (The plugs are NGK I wouldn't have used them but they are all firing as they should during testing) It looks like it has a new injector on it so we checked everything in the fuel system and even did a fuel system service, still misfires. You can only feel a misfire at idle, under load the vehicle runs beautifully. We smoked it and found a large leak at the intake manifold when it is cold and we replaced the gasket. Still misfires, code still active. No other leaks found. Cat isn't plugged. Checked wave forms of both the cam and crank sensors everything good there. Leak down and compression test checked out good. We are going to do a timing tear down next make sure it isn't off but does anyone have any suggestions for us? We've exhausted everything suggested as a fix on identifix. Let me know if you need any other information.

Is it a random misfire or specific to a cylinder? Are the cam and crank sensors in synch on scanner? Maybe a camshaft lobe wiped? I have had spark plugs in the past that would jump a spark tester that would not fire under compression. What is the MAP and baro readings? Just a few tidbits to chew on.

Its a misfire on the number 1 cylinder and the sensors are in sync. I'll ask the technician about the rest: He states the MAP readings looked normal to him. He went to drive it I'll ask him about the rest when he gets back. Thanks Jeff!

This may or may not apply to this car but look at the wiring on the coil feed about 3 or 4 inches away from the coil. There is a vacuum hose I think that's what it is laying across it. I've seen a lot where the harness is worn just enough to cause a misfire. The coil will fire but the voltage isn't anywhere near enough to fire plug properly.

Did the timing belt brake? Or was it done preventatively?

Are the coils the same can they be rotated?

Definitely do a cylinder leak down test on that cylinder. I have had my share of neons with burnt valves that only show a misfire at idle. HTH Jerry

I see you did a compression test and a leak down test. Sometimes these do not show a volumetric efficiency problem. I'd suggest a running compression test. If the problem is mechanical, this will show it. If the results here are all even, the issue is fuel or electrical.

The coils can't be switched, and as far as the client knows it was done preventatively. It seems late to have done it preventatively since Dodge recommends the change at 102k. But it's not inconceivable that it went to 120k. Leak down and compression check all returned normal results.

OK...next step is to scope the injector and coil. I would compare spark kV to good cylinder. Another test we did at chrysler was an injector max voltage test. You could also run an injector ramp test. Compare those to a good cylinder. And for what it's worth I might buy a cheap coil just for a test. They were common failures when I worked for Chrysler.

I would try to change the coil with a known good one. Like someone said it might not spark under compression. At least then u know then that is not it. Have had a lot of them spark out side but not inside.