Good afternoon,
I am looking for additional things to check on my 98 E350 van with a 5.4 engine, 120k miles. It was missing badly, but no CEL. Miss started earlier this winter, thought it was bad gas, but 1/2 dozen tanks with injector cleaner have not helped. Should have scanned before I started working, but I didn't, so I am not sure if anything has changed.

So far I have replaced all the coils & the plugs. I have exchanged the 5 & 6 coils & injectors, but after driving for 3-4 miles the pending P0306 code returns, still no CEL. It is missing on one cylinder all the time, from idle to freeway speed. Plugs all look the same. Replaced the plug again on 6 no change.

So any suggestions on where to go from here would be appreciated. After reading thru other posts on similar problems, I am very reluctant to take it to the $tealer for a big investment & no solution.

 

Have you checked the compression on #6? Perhaps a cam follower fell off.

Could also be a bad ecm or wiring.

 

After checking everything everything suggested on this site & everything appearing to be fine, I went back & started looking at the wiring again.

This 5.4 is in a van, which makes checking anything tough because it is hard to reach & even harder to see, but after removing the fuel headers, vacuum lines I was able to look at the wiring harness. After close examination I noticed a few strands of copper wire poking out of the black tape wrapped wires heading to the #6 injector. After disconnecting all the other connections I was able to pull the harness back into the cab & see that one of the wires to the injector had broken right where it came out of the harness. Apparently it had been rubbing on the plastic holder on the top of the engine. Looking at the shape of the wire, it had been compromised for a very long time. Ended cutting open the harness & cutting out all of the damaged wire & spliced in a few inches of new wire.

4 hours of putting everything back together & everything is running great. Turns out I had a $3 problem that I spent about $300 to fix, but I have a lot of new parts that I hope I don't need to worry about for a long time.

Hope this little saga give some hope to others that have similar problems.

 

Good Job Bob!

 

You wouldn't be the first to throw money at a problem only to find the cure was something far far less expensive. Of course its never simple even though its not pricey!

Had a similar situation with a misfire---orginally had Cyl #3 COP fail which was easily cured by replacing it. About 4 months later the misfire returns and codes now say Cyl #7----WTH?? Were my new Granatelli COP's failing one after another?

Assuming it just had to be the COP replaced it (under warranty) and misfire still there---Drats! Started the engine and fumbled around trying to assure my connections to injectors and COP's were tight. Discovered that Cyl #7's harness connector wasn't latching as designed, would run perfectly if I held it inwards.

Got NAPA's part number EC259 and took quite a while to replace the defective connection------not a bit of problem since then.

At least you know the work you've done already won't need attention any time soon again. Good going indeed!