This morning the truck drove great on the way into work. On my way out to lunch this afternoon, the truck started bucking and vibrating badly while acclerating. At first I thought it was the transmission, and checked it. Fluid was fine. After that the truck drove fine for another 10 min. Got back in it to go back to work and its back to running on 4 or 5 cylinders. At a stop light it shakes and stutters like its got a huge cam in it. While acclerating it feels like I have one square tire. And when I back off the throttle is runs smooth.

When I got back here to work, I put it in Park and walked around the truck. It was stuttering and sounded pretty bad, like it was going to stall. But the smell of rotten eggs was most noticable.

Anyone have any ideas? My SES light came on on the way back, so I will attempt to get the truck to Autozone tonight and get the codes read. Anybody have this happen?

 

That is exactly how mine acted when I had a plug misfire. Sometimes the plugs will only misfire under load. When you have the code read I bet that’s it. Is the Check engine light blinking? That is what mine did. Mine is a 97.

If you have plug wires on the 4.2? If so then press on each one to see if one backed off the plug.
If you have coil on plugs you will have to find out which one it is. Be careful, this is the same symptom some have had just before launching a plug but that was mostly on the v8's.

 

Thanks WLF,

My engine is the 4.2L V-6. Regular plugs and wires. Maybe I'll give them a look when I leave tonight. As far as I know, there aren't any 4.2's that have launched plugs, but its good to know. No, my SES light is not blinking, just on.

I was thinking that its got to do with either the IAC valve or the throttle position sensor. Never thought it could be a loose wire or condensation or something. It been really wet here with the recent snowstorm, so it could be moisture in the plug wires. Hmmm...

 

These are not symtoms of a bad IAC or TPS. Those have to do with idle speed (IDLE air control). Your problem is probably what has already been said, a bad plug/wire/coil. Another possibility would be a plugged cat. You said it smelled like sulfur, the cat makes a smell like that. Also, could very likely be a bad O2 sensor. One thing for sure is that you can find out with a simple code read.

 

Well I got the codes read after work tonight. P303 - Cylinder #3 misfire. I haven't checked the plugs/wires yet but will tomorrow night. Hopefully its only that.

 

OK - Changed plugs and wires today. Nothing changed. The truck idles fine in park or neutral, under any load it was stumbling and missing.

I measured the resistance across the signal wires on the coil pack and the resistance across plug terminals 1-5, 2-6 and 3-4. The 1-5 and 2-6 measured 9.6K ohms but 3-4 would not measure anything. Looks like a broken coil.

SO - my big problem. I started the truck to move it into my driveway, and after it stumbled a bit it smoothed out and ran at high idle. Then the oil pressure light came on. And stayed on. I shut the truck down as quick as I could. I restarted thinking it was a fluke. Oil light stayed on. I shut it down, and now it sits in front of my apartment on the street.

I'm not sure what to do. Please help! Any advice would be greatly appreciated!

 

Would a misfire set off a CEL light?

 

The P300 codes are missfire (by cylinder) codes. I reset them yesterday when I changed the plugs and wires.

What do you guys think about the low oil pressure?

 

its possible that you could have a bad oil pump but i dont know if that could cause it to run roughly. I wonder if resetting the computer could help any?
Good luck with your problem--someone will have an answer.

 

crashz,
The oil sending units are simple on-off switches. I bet you somehow knocked the oil sending wire loose while doing the plugs. I don't know what is causing the high speed reving, not much with a change of plugs wires that would do that. One thing for sure. If you chase down the oil sending wire and it appears to be making good contact and you still have a light on then it is time for a tow to the dealer. A new short block is serious money.
Good luck.

 

Thanks WLF,

I started it yesterday to move it into my driveway again and viola! It started up and ran good, plenty of oil pressure. Of course as soon as I put it into gear, it went back to running on 5 cylinders. I pulled the igntion module off, and it is cracked with a little rust seeping out. Along with the the secondary resistance being off on the 3-4 terminals, I think I found the culprit. Thanks!

 

Ok- got the new coil pack on and it runs great. This morning the oil light went on and the gauge read zero and fluctated on /off for a few minues. But it seems eletrical, because when I stepped on the brakes the oil pressure would read fine, and when I let off the pedal, it would drop to zero. I wiggle the wire a little and it stopped fluctuating and read normal. Thanks again for all your help!

 

I'm glad things work out for you. I kinda thought that was the problem with the oil sender.

 

The best thing I can recommend is stick with OEM parts. These computerized engines seem to have a hard time dealing with non-Motorcraft components. Read my story below, I hope it helps someone. I drive a 1998 F-150 4.2 5-speed 2WD with 76000 miles on it.

Hi, I had the same problem as everyone it seems, cold weather, blinking / flashing CEL, rough running, no power, an obvious engine miss. Autozone had PO302 cylinder #2 misfire. By reading all these posts, it could have been plugs, wires, coil assembly, a fuel injector, MAF mass airflow sensor, 02 sensor (one of four), upper intake, lower intake, or water, ice, possibly antifreeze in the fuel. My plugs and wires were only about 18 months old, so at first I did not figure this to be the issue.

My engine was only misfiring intermittently, mostly when cold. The first night it happened, by the time I got home my truck was running fine. Same thing the day I took it in, misfiring at startup, drove like a champ all the way to the shop. I would have dealt with it, were it not for the backfiring and possible damage to the catalytic converter. We don't have emissions testing in Michigan.

I started with dri-gas, no luck. Checked all the connections on the plugs and coil, no change. Swapped out the #2 cylinder wire, same result. I broke down and took it in, and discovered that when my cousin tuned up my truck, he put Champion plugs and wires on the motor. High end stuff, but with today's vehicles it was only a matter of time before there would be trouble. My mechanic (NOT a Ford dealer, by the way) replaced the plugs, wires, and PCV valve with OEM Motorcraft parts, and my engine was cured. This would have been the last thing I would have done on my own, since those parts were relatively new. Coil, injectors, and sensors all fine. As luck would have it, the main reason I took it in to a shop is that we have had single digit temperatures all week. Actually saved me money, a new coil at NAPA is $111.

My mechanic told me he sees a lot of 4.2 engines with problems, and most have some non-spec equipment, plugs, wires, exhaust, ignition. The 4.2 has a pretty hot ignition, and needs the double platinum plugs and comparable wires. At the time, I also had the fuel filter replaced, and the injectors serviced, in a cold wehe time I got home my truck was running fine. Same thing the day I took it in, misfiring at startup, drove like a champ all the way to the shop. I would have dealt with it, were it not for the backfiring and possible damage to the catalytic converter. We don't have emissions testing in Michigan.

I started with dri-gas, no luck. Checked all the connections on the plugs and coil, no change. Swapped out the #2 cylinder wire, same result. I broke down and took it in, and discovered that when my cousin tuned up my truck, he put Champion plugs and wires on the motor. High end stuff, but with today's vehicles it was only a matter of time before there would be trouble. My mechanic (NOT a Ford dealer, by the way) replaced the plugs, wires, and PCV valve with OEM Motorcraft parts, and my engine was cured. This would have been the last thing I would have done on my own, since those parts were relatively new. Coil, injectors, and sensors all fine. As luck would have it, the main reason I took it in to a shop is that we have had single digit temperatures all week. Actually saved me money, a new coil at NAPA is $111.

My mechanic told me he sees a lot of 4.2 engines with problems, and most have some non-spec equipment, plugs, wires, exhaust, ignition. The 4.2 has a pretty hot ignition, and needs the double platinum plugs and comparable wires. At the time, I also had the fuel filter replaced, and the injectors serviced, in a cold weather climate it makes sense.

I don't think my mechanic is BS'ing me. He said an inept or crooked mechanic could easily have used $3000 worth of parts chasing down a cylinder miss. I believe him, mainly because that same cousin that tuned my truck "as a favor" told me it was my coil for sure. He had just spent $2300 in parts at his Chrysler DEALER for his 2001 Wrangler figuring out a cylinder misfire. He had the MAF sensor, 02 sensors, injectors, and plugs and wires (twice) replaced. Intakes serviced, fuel filter, you name it. Turns out it was the coil. The whole reason I am now a believer in OEM equipment is that he is always putting some high end high cost performance part on his Jeep. Since he bought it he has put all high performance parts, ignition, plugs, wires, exhaust, K&N, you name it. And his check engine light has come back on, even though it seems to run fine. $2300 to figure out a $60 coil.

 

Ditto OEM parts. Not just ignition. I go to Ford for all my parts, except after noon on Saturday and on Sunday. Then it's to Napa.

One thing that caught my eye in the original post was the rotten egg smell. There are two places you get rotten egg smell, the cat with a rich exhaust and an overcharging alternator boiling the battery. Rotten egg cats are pretty much gone, I'd bet on the alternator overcharging. It might not be a coincidence that you had other problems. The alternator might (long shot, thin ice, etc.) be the original culprit. You can watch it with a scan tool (IGN1 voltage) or have it tested. I'd watch it if it were me, just in case.

Good luck.