Chrysler Repair: plymouth neon sohc 2.0l: misses when hot/codes 0351, 0390, crank sensor, plymouth neon

Question
Roland,
I recently change the headgasket on my nephews 95 neon sohc 2.0l because of oil leaks. all went well until the test drive. The car starts and runs great until it gets to operating temp. At that time it stumble and revs up to about 1500 rpm and then stumbles again and dies. It will not restart again until it is cool. If you try to restart it warm, it misses severly and backfires. I have checked the codes with my scanner and get p0351 and p1390. I have checked the plugs,wires, and coil and all are the same spec when cold or warm. I would appreciate any help that you can give. Thanks Dennis

Answer
Hi Dennis,
According to the diagnostic manual the 0351 is about the spark coil primary circuit not responding as expected as seen by the PCM. But also it says to deal with any codes related to cam/crank sensor first. The 1390 says there is an incorrect relationship between the cam/crank timing signals.
So my thought is that what you have going on there is a failing cam or crank sensor, but without a code to suggest which it is. If you got an 0320 that would say crank, an 0340 would say the cam was the problem. The breakdown with heat/recovery when cool, is exactly the sort of behavior one would expect from either of those sensors. One way to possibly find out which would be to get a can of circuit cooler (essentially refrigerant in a can) from an electronics supply store and then when it the breakdown mode try spraying each sensor individually and see if by cooling down one or the other you can clear the symptom. If so, then replace that sensor which responds positively to the refrigerant. Once that is sorted out I would believe the 0351 will disappear.
Roland
PS The other thing you might want to check is whether the timing of timing belt is as it should be as another interpretation of the 1390 could be the result of a misalignment.