Hello all! New Member here!! I have been reviewing all of the previous posts regarding misfires with these 5.4's and it sounds like the common consensus is the plugs.

I just replaced the plugs with Motorcraft ones and put all new COP's in and problem still exists! Might be even worse now.. (I did buy cheap Ebay COP's but read they should be fine..) The plugs I took out were surprisingly clean and no carbon stains or fuel on them..

I also put new air filter in and cleaned MAF sensor. Fuel filter was replaced few thousand miles ago..

I was getting P0303 for misfire in cylinder 3 before putting new plugs in but has not returned since the plug change..

I do not know what else I should be looking for.. Fuel injector? Phasers? Transmission?

Any ideas? Thanks!

 

The overdrive band in the transmission may be slipping. How many miles do you have?

 

I have 146,000. but I just got code P0303 back for cylinder 3 misfire which from what I have read could be the reason of the shakes at low RPM's in overdrive. I never thought of the overdrive band. I am still trying to figure out this misfire for the moment. I am throwing a new fuel injector in tmw and see if that helps. If not, then I may have to start looking at transmission faults..

Thank you for the help so far!

 

No problem. I had a bad shake and it ended up being plugs and COPs. A quick test is to move the #3 COP to another cylinder and see if the misfire moves. That'll tell you if it's a COP or Spark plug.

 

Yeah I tried that already and misfire stayed on cylinder 3. So not the COP and I replaced all plugs. Still on 3 so I am trying fuel injector. I am also going to do compression test tmw. I hope the injector clears it up. It does have a sort of rough idle and I unplugged cylinder 3 fuel injector and idle didn't change much so that may be the problem.

I am determined to figure this out as the non stop shaking is driving me crazy!

 

Sounds like a good plan. I haven't had to mess with my injectors yet, hope that fixes it.

 

Swapped the fuel injector out this morning but still has the shakes in low RPM's coming into overdrive. I am going to do compression test on cylinder 3 later today but if it checks out okay, may have to start looking into transmission problems. Does anyone think that torque converter could cause this? Thanks!

 

no. check to see if its getting power to the injector. and the coil.

 

brokenleg- Do you mean check resistance on COP and injector with an Ohmmeter? Or is there a way to check the electrical connections?

Thank you for the help.

 

You can look into the trans and torque converter, but if you want to fix this look at the engine. That's where the shake is coming from. There is nothing wrong with the transmission or torque converter.

 

Thank you for the help on this one. I am still having a problem somewhere with a misfire and code P0303 popped up as well as P0172 for bank 1 too rich. These have both popped up before. With the new MC plugs, new coils, and new injector on cylinder 3 I can not figure out why I am having a misfire in cylinder 3. I checked coil and it is getting power.
I guess next thing to do is check compression in the cylinder..

 

I had new plugs put in and months later developed a miss,shutter. Found out what cylinder. Replaced everything but the plug and still there. Replaced new plug, problem solved. Try swaping that plug.

 

Soooo.. I have been MIA for the last few months (busy with work and family). I am still having the miss fire on #3 (P0303) and codes P0172 and P0174 (trying not to drive truck much). I have the occasional P0300 random misfire pop up. I finally broke down and took my truck to a trusted local shop to diagnose what is going on.

They swapped plugs and COP's around and miss stayed on #3. They ran compression test and it was good. They checked for back pressure near CAT and tested fine. They then started running live data test and they claim my PCM fried out and shut truck down (hard to believe, but what can you do..). Had to have them put in a new PCM and have truck re-programmed. Didn't solve anything!! Same codes still popping up and problems still exist.

They said it appears I have a newer head on bank 1 and that timing cover has been off in past (they found silicone sealant around it instead of gasket!!) Damn it!

They recommend replacing the engine..

Does ANYONE have any recommendations on what to do?? I AM DESPERATE!!

My gut is saying this is a timing problem or I have damaged internals..

 

Any updates? I have the same issues only mine is a p0308 code with a p0174 code. I have replaced everything concerning that cylinder and it stays on the same cyl. I don't have plugged exhaust. If I step on it it just really shakes. Gutless. I can hear the miss at low rpm about 2000 and it isn't a steady miss making me think it isn't mechanical i.e. a burnt valve. I'm at a complete loss. Don't know what else to do.

 

If it isn't ignition and compression is fine it probably is a bad injector.