2000 5.0 l P0340 runnin rough

[Macgiobuin]

I have a 2000 Mercury Mountaineer 5.0 l V8 110k miles.The car started running very rough, at all times and temperatures, but not if you stepped on the pedal and really floored it. Ck engine light was illuminated, my code reader said p0340 (camshaft position sunsor). I checked it on an ohmmeter, seemed good, reacted to ferrous metal that passed in front of it; actually soldered the wires to the spade connectors; still got the problem. Replaced the sensor, still the same; continuity check of wires to PCM, good; rewired the signal wires to the PCM plug, still the same. Looked at the engine while it was running rough when it was very dark (not even a full moon)--no voltage leaks from the secondary ignition wires. Took out the plugs, and the 4 plugs on the passenger side were gas-wet, while the 4 on the drivers side were perfect. Replaced all 8 with new Motorcraft platinums. I did a compression while I was at it and I got between 162 and 171 on all 8 cyls. This has 2 coil packs of 4 plugs each, and each plug pack services 2 plugs on one bank and 2 plugs on the other. There is only one fuel pressure regulator on this engine. I suspect oxygen sensors on one side (?) maybe. I'm lookin for ideas. The timing chain jumped a tooth? Problem remains. Help.

[exploded99]

Timing chains are not often a problem on the V8's, and if you are able to get good full throttle acceleration up to redline, your timing chain is most certainly ok. Also, your compression test was ok.

I think your reasoning on the fuel pressure regulator and the coil packs is good - you have a problem with all the cylinders on the passenger bank, and the FPR would affect both banks. Also, you would have to have 2 bad coil packs to get problems on those 4 cylinders - most likely problems would appear on the other bank as well.

Could be a bad O2 sensor, except that the appearance of the p0340 and the wet plug problem at the same time would indicate they are somehow related. You could try a new O2 sensor - I would guess that won't fix it cause it won't fix the p0340 issue. It would rule it out, however.

Just a guess, I think your PCM may be the culprit. If you really want to beat up the testing, go to alldatadiy.com, subscribe for your vehicle, and there is a pinpoint test chart by symptom (including p0340) that will help you do a bunch of pinpoint tests that Ford specs for this problem.
You follow the flow of tests, and at the end it tells you what part is bad.

You can probably find a used pcm - new ones are $$$$.

Good Luck!