Questions and Answers
Dodge Neon Code 51
Q. My wife has a 1997 Dodge Neon, and we recently had the head gasket replaced. Afterwards, we failed the local emissions testing in Kenosha, WI. Our CO and HC were way high. The emissions testers told us that the fourth cylinder was not firing and was causing a rich fuel/air ratio.
After that I replaced the plugs, and tightened the wires, hoping to eliminate the problem. Our SES light went off for a few days, after which it came back on. Following Haynes repair manual, I ran the OBD-II diagnostic test, and it gave me code 51 which means (according to Haynes), that we are running too lean a fuel/air ratio.
What in the world is wrong???? We have very limited funds, especially after these latest repairs. Also, we just had the EGR valve replaced.
Any help you could give me would be appreciated.
PhillipA. Apparently by replacing the plugs and repairing the wires you corrected the original problem.
This code is usually caused by a vacuum leak. Check for unmetered air between the Mass Air Flow (MAF) sensor and Idle Air Control (IAC) solenoid. Then check all engine vacuum hoses for damage, leaks, cracks, blockage and proper routing. Also check that the oil cap and dipstick are seated properly.
If the vacuum lines check out okay, then it's possible you have a bad MAF or injector(s). Now I see you changed the plugs and air filter, but did you replace the fuel filter? This could cause the same problem also.
Additional Information provided courtesy of ALLDATA
