98 Neon SOHC 150K mi. hit a deer lost the radiator, replaced that, while in garage cleaned and washed down engine compartment real good now car runs like crap. Idle is good as well as reving up engine while in park but engine lacks power and stumbles while driving, plugs 1 and 2 are burning fairly clean 3 and 4 are fouling with carbon - real fast as well. have checked coil and it tests fine ok out of the car, have new spark plug wires, MAP sensor shows 4.5v in and 1.1v out, TPS reads good and linear, fuel rail shows 45psi static and 45-55psi running but leaks down in 1-2 minutes after shutoff, compression is 150psi cold all four cyc. with nominal leakdown, new pc valve also, throwing a P300, 303,304 code - ignition, I am at a loss at this point remaining parts cost big dollars.... Help... please...

:i con_hyper:

 

The misfire is on #3 & # 4 I’m guessing it’s not coil problem as it works in pairs of #1 & #4 and #2 & #3. It could be an injector issue but, if you washed under the hood I would check the main connector between the body harness and the engine harness. This happened to my 95 and the “O” rings that seal the connector were cracked and the connector full of water.

 

Me thinking that at this point also, will give it a try for what its worth.

TX