Been trying to diagnose a problem on a friend's 2003 Dodge Neon SRT-4. I'll keep this short since we haven't been able to figure much out on this. Basically, the spark plugs are dry and white along with a very erratic idle. It will rev up and down at idle, struggling to run. It will eventually die if left running long enough. With testers and dataloggers, the O2 sensors read between 12.5 and 14.7 AFR. The car has an aftermarket Zeitronix wideband O2 sensor that also reads the same thing as the factory sensor. Even though the sensors are reading rich, there is no smell of gas from the exhaust and like I mentioned, the spark plugs are indicating a lean combustion chamber. O2 voltages are consistent with specs. A local mechanic/tuner/genius couldn't figure this out.

So the basic question I'm asking is: How do you have a lean condition in the engine, but a rich condition in the exhaust?

Solution: Sell the neon, buy an Evo.

I'm gonna guess you gotta serious vacuum leak though.

Its a Neon - that there's yer problem.

>

BA-ZING!

Solution to your issue

This post has been edited by playr158: Apr 6, 2010 - 11:57 AM

Looks like the only thing I accomplished from this post was feeding the trolls. Thanks for some sort of answer Nartanian.

Yea man, I think it's a leak possibly. I would check for any loose fittings on the intercooler piping such as loose couplers or something. Also check what your vacuum pressure at idle if you have a boost gauge.

This post has been edited by Nartanian: Apr 6, 2010 - 1:09 PM

The way it's idling is pretty much the same as it would with a vacuum leak. The boost gauge bounces up and down between 11 and 8 inHg vacuum. We couldn't find a leak anywhere, and the datalogger didn't pick up anything that would suggest one. The mechanic is suspecting that one of the cam gears jumped a tooth. He did some trickery with the O2 sensor to fool the voltages to make the car run around 10.8 A/F ratio, and it was purring like a kitten then. At that point we considered that he might have somehow gotten a full tank of pure E85 (stoich at around 9.8:1), but I don't think that's likely since there's no stations here that carry pure E85. I know a truck driver who hauls gas, and he told me that some stations are premixed with E85 and others have to be manually mixed by the driver. So I guess there is a possibility of forgetting to add the gasoline... We drained the gas, and it definitely had an odd smell. I dunno though. Might rip the timing cover off and see if the marks are lining up. Looks like it'll be a PITA though

Oh well. Compared to the Celica, everything is hard to work on IMHO =)

you try spraying carb/throttle cleaner around the intake and what not. If there is a leak that will make the engine run normal when spraying it by the leak. Just a thought tho if its a tiny one.

possibly the throttle position sensor my honda use to do that.