I've got a 2002 ranger edge 3.0L. I've been getting random misfire, misfire in cylinders 1,3,5, and a p0171 which i think is a running lean on bank 1 code. has spark and compression on all cylinders, i'm fairly confident there isn't a fuel pressure problem. When the engine is at idle it is fairly smooth, but when i hit the gas it immediately backfires in the intake. It will also ping throughout the driving range, which i think might be more smaller backfires. I checked the vacuum pressure and it was steady at 16 pounds at idle and all the tests i could do with the vacuum pressure tester came up normal. I took the o2 sensors out and ran it to see if it was a backpressure problem but that did nothing. Anyone have any idea what could be wrong? I'm thinking a o2 sensor could be bad, don't really know what else to consider.

 

oh, and the truck has 137,000 miles on it and has had all its regularly scheduled maintanance

 

I had a similar problem wiht my 99 a few months ago, it turned out 1 of my plugs had a small crack in the ceramics. I still got spark from it, but it would give me random misfires and dead starts.

 

I've put new plugs and wires in the engine but it did not fix the porblem

 

I did too, and one of my replacement plugs had a faulty post.
then the one I got to replace that one was cracked as well...
3rd times the charm as they say
I would double check just to make absolutely sure.

also, take a look and see if there is spark from the wire onto the exhaust manifold, even after doing the changing of these things on my truck (new plugs/wires) I can still see some spark occasionally between the plug cap and manifold.

 

Fixed the problem. Somehow my coil pack had to wires in the wrong place. Which blows my mind because that was the same configuration its been in for at least 2 years and it just now started causing a lot of trouble. But now she is running better than ever!

 

heh
same thing happened to me except I got 1 wire wrong. and the same after effects too, ran better than it had in several yrs