So I've had a misfire for quite awhile.

I have:

New plugs, wires, cap and rotor (twice)
New o2 sensors (both upstream and downstream
Replaced ground strap
Checked and needed to tighten a few manifold bolts.
Fuel injectors were replaced with 703s and have been moved around and confirmed that's not the problem.


A few years ago I overheated and warped the head. When the head was machined they checked all the valves and said they were good.

Any other ideas on what it could be?

 

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Is your Check Engine light on? Have you used a code reader to see if any diagnostic trouble codes have been stored?

 

Yes. CEL is on. It had both o2 sensors on there (not anymore since they've been replaced)

Now the only code is for cylinder 6 misfire
- P0306 - cylinder 6 misfire detected.

 

Ever done this?

Pretty easy.

Get a cup of water, preferably something like a 24 to 32 oz. cup.
With the air cleaner off, hold the engine RPM at 2000 RPM or higher and dribble the water from the cup, which you've pinched to look like a spout on top, into the carb or throttle body. Go slowly and the engine will bog a bit. Stop and let it recover. Repeat until the cup is empty.

 

I've ran cleaner through it before, but have not tried that. I've read about it before however.


Wouldn't seafoam produce the same effect? I have two spray cans of that stuff somewhere.

 

Seafoam doesn't work on the same principle.

 

Got it. Will try this later then.

 

If you use seafoam, get the non aerosol version. Unplug the vacuum line from the brake booster and stick it in the can of seafoam. You'll have to hold rpm up or it's likely to stall and die. When the can is empty, kill the engine, reconnect the brake booster line, and wait 15 minutes or so before starting the engine again. Then go drive on the highway until the exhaust stops looking like you've got an old diesel.

 

I think I have the aerosol kind. I'll have to look again.

 

Skip that snake oil. If there's carbon under an exhaust valve, the chemicals will not remove it.

Do the water.

 

Should i warm the jeep up before i do it?

 

Yes.

 

Okay. I gotta drop a trailer off at my parents house. So i'll let the Jeep work a little bit before i waterboard it.

 

Just replied in the other thread, but didn't help. Going to replace ignition coil today.

 

A coil won't cause a single cylinder misfire. Save your money