1999 3.0 misfire

[KSnake]

I’m new here. Bought a 1999 B3000 Troy Lee edition a couple weeks ago. 141,000 miles. Third owner. Yesterday it suddenly started shaking very rough after I pulled out of driveway. Two weeks ago I changed transmission fluid and filter. Put a can of sea foam in the fuel tank. Had a small coolant leak which I pressure tested and turned out to be radiator cap. So replaced the cap and no sign of leak.

After the sudden shaking it threw a P0306 code - misfire on 6. I replaced fuel filter and today pulled the plugs and checked compression which is between 152 and 138 across all cylinders. #6 specifically was 150, so all within good range.

Next, I’ll clean intake. But beyond that, where do I look for the cause of misfire. I’m thinking either fuel or air at this point. Injector? Would another can of sea foam help? Air intake? Cam position sensor? Timing chain? Thanks in advance for replies!

 

[KSnake]

I should add this is 2-wheel drive, 3.0 flex fuel.

 

[renton]

If it was something major it would most likely missfire on multiple cylinders. I would replace the spark plugs and see if the spark plug wires are good. That solved my missfire issue.

 

[renton]

also if its sat for awhile before you bought it the fuel system could be gunked up. When I got mine I replaced fuel filter and used royal purple fuel cleaner.

 

[ProTouringRanger]

Sir, What did you figure out on the misfire. My 05 has been doing this for 4 years now and I think I'm down to changing heads.

 

[Lefty]

The same thing happened to me. I wasn't exactly sure what the problem was, so I went ahead and replaced the plugs, the coil, and the wires. Along the way, I found that the wires were getting old and cracked right where those little plastic looms had held them.

There is also a coolant hose that crosses over the top of the coil. I found a small leak there. I replaced the hose and kept the new coil just to be sure.

 

[ProTouringRanger]

I have replaced the coil pack, injectors on 4,5,6 , wires, plugs, ICA but not the MAF of the Timing sensor. Big problem is every time i get gas its like it goes in to limp mode which misfires on cylinder 4,5. This is a 4 year problem I've been working on. and yes it has a lot of miles on it but it never misfires going down the road only at idle.

 

[2014 Z51]

I'm New here. I've been chasing this same issue (Misfire of # 4 Cylinder P0304 code) for a couple of years now. I have changed the plugs, plug wires, coil pack (twice) fuel injector (twice). MAF Sensor, Cam Sensor, and checked the compression, and it good. This Misfire happens intermittently, at idle and or driving.
I'm so frustrated, I've never had and issue like this, that I couldn't fix.

I forgot to mention that, I also replace the EUC.

Any advice would be Greatly appreciated.

 

[ProTouringRanger]

Z51 i think it might be a valve seat issue. And i dread that. mine only happens at idle. never going down the road. And i have 3 exhaust bolts broke on each head. Well at 290K its been a good truck. I wish i could tell you more.

 

[2014 Z51]

Z51 i think it might be a valve seat issue. And i dread that. mine only happens at idle. never going down the road. And i have 3 exhaust bolts broke on each head. Well at 290K its been a good truck. I wish i could tell you more.

Thank you, I think that is probably the issue too but, I have never seen this with all the years I have been working on Vehicles.

What is the "ICA"?

 

[ProTouringRanger]

My bad AIC Air idle control valve.

 

[ProTouringRanger]

If any one could tell me if 1991 heads will fit a 2005 it would be nice because i have a rebuilt set read to go. Both 3.0's