Hey guys! Sorry to turn up a common issue but looking for a bit of insight. Just recently got done with an extensive top end rebuild(new Clearwater head, all new sensors, ignition…..the works) on my 96 4.0. Been throwing a p1391 and have a pending p0420. I’m not really showing any symptoms of either of these codes other than a buck when I let off the gas at maybe 40+mph, no stalling, misfires, rough idle. Grant it I’ve put less than 100 miles since the rebuild, I haven’t really noticed any “hard start” per say, kinda a sluggish start on occasion but no more than that. NTK EH0245 for Cps, both o2 sensors are also new NTK’s, cardone 844694 (84-4694) for the distributor. New wires, plugs, 12 hole injectors, fuel rail, ignition coil, exhaust all the way back other than a new cat. I have noticed that’ll only happen once per time I drive it, I’ll get a strong whiff of gas for a moment then itll go away for the rest of the trip. Lemme know if you need more info, I can provide part numbers and parts that I used for the whole rebuild but as far as symptoms, that’s all I got, same goes for codes. Thank you!

 

Did you have either of these CODES before you did the extensive work? If these codes only appeared are after the rebuild and not before it..... you may have unknowingly introduced at least one of the codes with one of the replacement sensors that were installed.

P1391 can be related to both the crankshaft position sensor OR the camshaft position sensor and of course their associated circuits/wiring/connectors so keep that in mind. From my experience, it's more often the crank sensor circuit with just the P1391, but don't get tunnel vision. The P0420 is for catalytic converter efficiency. So the cat was not replaced? How many miles on the cat? Could be the cat itself but may want to drive it a bit and see if the code sticks around.

As for that gas smell, smells are kind of tough for us to help you with. Try to isolate it with your sniffer. Or your neighbor's sniffer!

Good luck and keep us updated!

 

Before the work, no CEL’s and no major issues, it did have a faint gas smell but not as strong as it is now and again….the gas smell now is really potent and then goes away after like a second or two. I’m starting to think that the distributor may be a possible culprit due to the ears not perfectly lining up. The two whole you’re supposed to line up are maybe 1/2-3/4 lined up. But I’m still open to option as far as the 1391. I’ve been looking at mopar 56026921 as I have round connectors and pre OBDll. As far as the 0420 I’m not too worried about, more or less just curious as to what everyone had to say.