Hello. My 5.4 shows misfires on cylinder 2-3-4. It has 150k on it. I bought it with 35k on it. It was running fine at 75 mph and started to miss. No noises. Nothing. A little history At 139k a chain guide broke. Replaced chains etc. plugs at 110. 7 of the 8 broke. Oil changed no more than 5k miles. Fluids clean and fresh. First problems ever was the chain guide. The scanner showed bad coils today. Odd to have 3 fail at once. But ok. Replaced. Still same cylinders showing misfire. Even took one coil and moved it to cyl 1 and scanner showed miss on 1. Any ideas? Other tests?

 

What brand are the plugs?

 

They are motorcraft

 

Take a good close look at the connectors for the coils and see if the latches are broken and/or the the contacts are corroded. Has there been ANY recent work done on the truck? It's not uncommon for mechanics to damage the wiring leading to the coils. They could have left the wiring loose the last time that they worked on it and they got against an exhaust pipe or other hot spot and are just now melting and shorting out.

 

I will recheck connectors again. I did a bg air and fuel induction service around 10k ago with a bg oil restoration 109 serice. Picked up 2 mpg. Also changed oil about 3k ago.

 

After 13 years and 150k, it's not inconceivable that you are having multiple coil failures, especially if the spark plug change was put off till it was running bad. Worn plugs put a lot of strain on the coils.

You may want to pull the plugs and look at them - the misfiring may have fouled them.

 

Thanks. When I replaced the spark plugs it was running fine. Roughly 15k miles ago. I guess 3 coils could fail at once. But after I replaced them. It still misses in the same cylinders. I did check the plugs yesterday and looked fine. Even did a compression test. All within spec.

 

The 05 5.4 3v had a bad batch of fuel injectors - you might want to start looking at those. However, they usually stuck open, flooding the cylinders.

 

Found loose connector. Runs better. But still missing. Getting right side timing code and fuel trim lean and rich? Will back pressure cause the timing code? Exhaust flow at tailpipe is weak. I assume I damaged the right side cat driving with a misfire.

 

I would go to a good muffler shop and have the whole exhaust system tested for backpressure. Replace what's necessary.

Please post the exact codes.

 

Thanks. So I guess it is possible?

 

Another revelation. When blocking off Gail pipe when engine is running. It makes little difference on the way it runs. I would think it would choke the engine down. No cat codes. Muffler had a rattle in it for a couple weeks off and on. Could a baffle in the muffler cause this?

 

Just an outside the box idea (because I just replaced mine) - have you thought about testing the vapor canister purge valve? I had a lot of the same problems you have: lean codes, random misfires, I had an O2 code, and when the valve breaks it can also cause rich codes.

Replaced mine for $60, running like a champ now.

Video shows a way to test it at the end. Not exactly our truck, but close enough for reference. Valve is located on the firewall on driver's side.

 

Thanks. I am on it in the morning!

 

You bet. That's why you have to have it inspected by a muffler shop that has the equipment to determine where the blockage is. It could be a cat blew out its guts which got stuck in the muffler.

Again, please post the exact codes. "Getting right side timing code and fuel trim lean and rich?" doesn't tell us anything.