Our 95 351 truck is missing on a single cylinder it seems. We just got the truck with 109K miles on it. I replaced the fuel filter, a bad gas tank, and some other odds and ends before we put it to work. I was going to change other things when I had time, well with the miss I guess I have time now. I changed plugs, wires, cap, rotor, and just finished changing injectors and it has the same miss.

While driving under throttle you can hear popping in the catalytic converter and backfiring slightly out the exhaust. I figure the popping is the fuel from the dead cylinder being burnt. When the torque converter locks up the trucks shakes from the miss.

The symptoms are much like an injector stuck open which is the reason I just went ahead and changed them.

No check engine light, no codes. I'd assume it might throw a rich code after driving long enough.

After running for 30-40 seconds all the drivers side exhaust runners were hot, just the rear two on the passenger side were hot. The second cylinder back was a little warm and the front cylinder was pretty much cold dead.

Whacha guys think? We need this truck so I need to get something figured out soon.

I don't want to mention what I think it is yet till we see some ideas. I don't want to sway thought right off the bat.

 

Ah yes, after driving and getting out of the truck you can smell rich exhaust smell and the cat is hot.

The miss is at all throttles, all RPMs, all gears. and whatnots.

 

Wonder if you can check to see if you have a signal getting to the injectors in question. But you mentioned a rich smell.

Double check wires to see if there might be a break or bad connection inside them from manufacturing.


Dead rat in the intake runner for that cylinder?

 

I'm thinking that you need to pull the passenger side valve cover, and rotate the engine, checking the valves. Look for bent pushrods and up and down movement for #1. Might do a compression test 1st, since its quicker idea if that cylinder is dead. It's a lengthy process pulling the plenum, etc, but nonetheless, you'll probably end up doing that to check pushrods and up/down for the rocker arms.

 

Do a compression check. You may have a burnt valve or a stuck one. Make sure and give it a little squirt of oil first as I'm sure the cylinder wall is washed down from raw fuel and not firing.

 

That stuff too. But if you have bent push rods wouldn't you hear it?

 

Lots of times they make no noise.

 

I also forgot to add. Earlier in the year when it first started getting colder the truck would miss at first start up for awhile and then get better and be good all day after that. This continued to get worse and now it misses all the time.

I will be checking spark, compression, and injector trigger tomorrow. I just had the plenum off for injectors and really don't want to do it again but will if our suspect of valve train continues. I have a sneaking suspicion that a lifter is at fault. As in as it was wearing out it would take longer and longer to pump up till now nothing. But never any noises.

 

Do the dollar bill test on the exhaust pipe. That's the redneck way to check for a burnt valve!

 

Was that before you did the injectors?

 

Double check the plug wire arrangement also, I have crossed em a couple of times and got this. Checked everything I could think of and a buddy will come up and say "Well here's your problem"! Makes me feel like a royal idiot!

 

Yes, I only did the injectors because of the miss after doing plugs, wires, cap, and rotor.

 

I am going to check the new ones to make sure but the miss started with the old plug wire/cap/rotor setup. I did one plug and wire at a time when I switched to the new stuff to keep everything strait.

However! After looking up firing orders just to see I see every one shows the number 1 plug wire to be at the back of the disty. I remember when trying a different plug wire today on the number 1 cylinder it was at the front passenger side of the distributor I believe. I will have to check this out tomorrow.

All diagrams show like this, is this right even for the newer 351's?

 

If you have the old cap put it back on. I have got a bad new one before that will cause crossfire inside.

 

After hearing that, I'm leaning toward valve/valvetrain problem.