2003 Ford Expedition - 4.6L Misfires

[Jeff @ Able Auto]

OK gettin kicked around by this one! 2003 Expedition, 4.6 V-8.

Not setting any codes. Misfiring on cylinders 1-2-4. Good spark and injector pulse. Compression good, leak down test at 10% or less. Fuel pressure at spec 55 running. Volume is over a pint in 10-15 sec. Removed O2 sensor to check for plugged cat, passes. Customer (used car lot) had me install new right side injectors, didnt help. O2 sensors both banks show lean. Engine will hardly idle and has no power at all. I thought timing chain on right bank may have jumped, but also thought that should show on compression test and cylinder 3 would be misfiring (or I would think). Engine is pulling 12" vacuum and is steady.

Any input would be greatly appreciated!

[steven kiser]

Bad intake is the first that pops to mind.

[Tim Martin]

What is compression? The 12 inches of vacuum is a sign of a very poor running engine either caused by incorrect timing, or major vacuum leak. However, a major vacuum leak would not exactly result in a low power situation.

[Jeff @ Able Auto]

Well I came in this morning to get back into this beast. Wanted to post an accurate compression number (couldnt remember the exact psi). Pulled #2 plug and low and behold it was dripping with coolant. One of the first things I did was a "blue juice" test on the cooling system for exhaust...nuttin showed up! Compression on that cylinder is 175 psi. Possible cracked head ? Knowing this customer he will probably buy a total at salvage auction and swap engines. Thanks for the help folks. Will keep ya updated!

[Tim Martin]

Ouch!

Houston, we have us a problem!

[Jeff @ Able Auto]

This is a used car from the lot next door. The fella buys crashes and repairs and resells. When I first moved in here I thought it was just another "chop" shop. After a few months of watching I saw that it wasn't. This ol boy does em right. Repairs all the issues and stands behind them. Cuts frames and rewelds at factory weld points as much as possible. Uses quality sheet metal. Repairs all air bag, abs, check engine light, etc. issues. Like I said he will probably buy another low mileage total and swap engines, pull off any usable parts and resell the shell for scrap! He pays me without question. I do give him a break on labor and in return he sends in the buyers when they come back in asking about maint and repairs. Thanks again for the input!

[jbadenoch]

Lots of times on fords with lean on both banks, either vac leak in pcv hose on rear of eng or maf sensor faulty, although coolant on plug hurts

[Jeff @ Able Auto]

yea I checked all of those. The no misfire on cylinder 3 was throwing me off. Once I found the coolant that sealed it! Thanks!

[brianp87]

Sometimes it takes the vehicle to be really hot to show up as a combustion leak. Looks like it will require some tear down to find the issue

[Jeff @ Able Auto]

160k +...gonna swing an engine.

[ricmorin]

I have a V10 with a plastic intake. Twice the manifold leaked coolant into the cylinder. Both times it hydro-locked the engine. The first time it bent a rod. Second time I got lucky.

These plastic intakes are known for leaking coolant into the combustion chamber. I've seen many. Of course, with 160k, well you know.

I still have the rod. Not sure why.

[steven kiser]

I still have the rod. Not sure why.

I'm sitting at the counter looking at a piston that we took out of a dune buggy. Shop in California that specializes in these things rebuilt the engine before sending it east and when the customer got it there was a smoke screen the Navy could use when it was started. We yanked the head that the oil was burning from and both pistons looked like that had been in a vice or something. There were little dimples left on them where it was gripped. The upper compression ring was frozen and the oil ring and slings were lined up so there was a 1/4 inch gap and the oil flowed right through and burned. Everything else was perfect. We replaced pistons and rings and kept the ruined ones. They looked like they just came out of the box. I still have my first brake rotor that the braking surface had been ground away and the piston was ripped apart by the cooling fins. I have all sorts of "trophies" laying around the shop.

[Jeff @ Able Auto]

I have a V10 with a plastic intake. Twice the manifold leaked coolant into the cylinder. Both times it hydro-locked the engine. The first time it bent a rod. Second time I got lucky.

This engine has an aluminum intake. Did check it in the beginning for failed gaskets due to the lean conditions. It was bought at auction for resale. There is evidence it has been worked on elsewhere. Fuel tank has been out, coils swapped around, etc. Gotta say it really ran me around in circles.

[ricmorin]

Oh, aluminum? Hmmmm.

I guess it's still possible, but less likely.

Anybody want a slightly bent piston?