2000 Ford F-150 - P0302

2000 Ford F-150 Lariat
Automatic Transmission
5.4 L Triton V8 engine
98,000 miles

Ok, Here is my problem.

My truck was running rough and the RPM gage would fluctuate up and down and I knew that it wasn't running right. So i took my truck to the mechanic and he hooked it up to a computer and he said that there was a cylinder 2 miss. I asked him what needed to be done to fix the problem. He replied with a tune up (changing fuel filter, and the spark plugs). I said ok and he did it. The next day I notice that the truck is still running funny. Whenever i would slow down to stop at a stop sign the RPM gage would drop to about 400 rpms and then shoot back up to 1000 and bounced up and down until i accelerated. I called him back and he said that it might need a new coil for the spark plug. I said ok put it on there. He called me and said he took in on test drive and it ran fine. On my way home from the shop it started to act up again. Well needless to say he has put 3 sets of spark plugs in it because he said sometimes u can get a bad batch, he has put a coil in it, and also said i might have bad gas (so i filled the truck up with new gas). I am about to go back to him for the fourth time.

Does anyone have any idea of what might be wrong with my truck? because the mechanic is set on the fact its just the spark plugs. I have been patient, paid him $312, and took the truck back to him 3 times and the problem is not fixed.

After so many changs of spark plugs and ignition coils and if the DTC code is consistently P0302, the next item to check would be the fuel injectors. If it is bad bath of spark plugs or ignitions coils, the chances of getting the same code is very unlikely. alternatively you can try swapping the position of ignition coils and spark plugs, if DTC same, then you can eleimnate them as the cause.

now its sayin random miss

Assuming he put the truck back together correctly, you probably have a bad coil, I would think he has a scan tool and knows how to use it to determine which cylinder is causing the problem. The random misfire is not good information. A coil will work good then stop then be ok and so forth. If he is not able to determine what cylinder it is and does not know about mode 6 on a scan tool find out what scan tool he is using and I will help you and him.

For random misfire the normal cause would be fuel rather than igniton.

Check the fuel pressure and delivery or supply lines.

For your FYI random misfire does not mean fuel related misfire only, it could be and very well be ignition. It means the PCM cannot detect what cylinder it is doing the misfire hint the word "RANDOM".

If it is ignition, the PCM would be able to identify which is misfiring.
Anyway I mentioned quite often and not definitely. The guy has been fiddling with the ignition coils and sparks plugs so the next option would be to check the fuel.

LOOK PAL I understand very well how a PCM works and just so YOU know if the miss was ignition, fuel, clogged converter, egr ports, or mechanical related if the pcm is able to ID what cylinder it is it will flag a cylinder or cylinder(s). It's RANDOM because it has a misfire but it is not severe or frequent enough for the pcm to ID what cylinder it is. It very well could be gas, doubt it, but you said it yourself he was messing with the coils and coil boots. If the truck has alot of miles over 100k the coil boots should of been done with the plugs anyway. If he has a scan tool all he needs to do is look mode 6 data and test ID#53 and it will tell him or you or whoever what cylinder is missing on a ford if they have a misfire with no light or a random misfire issue.

I'd agree with a likely ignition problem, but also has a check on fuel pressure been done? Fuel pump/ regulator could be at fault. I take it MC or Autolite plugs were installed, especially if this engine has EDIS ignition system?

the tune up included a change in spark plugs and new fuel filter.
when he first put the computer on it it said miss in cylinder 2. now when check engine on it says random miss.
so i should tell the guy about ignition problems?

i already tried the new gas, didnt work. he said he put a new set of spark plugs in it but he didnt say anything about a "boot". he changed the coil on number 2 and it also didnt work.