Another freebie: 99 with misfire

[Roont]

The curse of the profession is aquiring free vehicles. The curse of being a hoarder, is sometimes I don't flip them haha. This one came to me with a bad #4. Compression is a bit lower in it than the others, but it also doesn't misfire after warmed up. Also has fault for tank vent. I'm in NJ where we only do emissions now, so hoping will find the time to tear into this and give it another chance. For my area it actually has minimal rust for a 99.

 

[leoJr]

Our '99 5.0 seems to be hard on spark plugs. First is develops a slight miss when cold. Then it has a miss all of the time. Later it throws the check engine light. Changing the spark plugs and all is good for awhile. They are silly easy to change on our 5.0; just remove the inner fender skirt and the plugs are right there. Good luck!

 

[koda2000]

OP - Is it a 4.0 OHV engine?

 

[Roont]

This is a 4.0 SOHC engine.

So far have changed injector o rings, and while I was in there, swapped injector #4 with #6.

I also swapped plugs around as well as wires, misfire remaining in #4.

That's as far as I got when they called off the diagnosis.

Waiting for title in hand before I dive in

 

[koda2000]

Has the engine ever been overheated? If so you may have a small head gasket leak, which will only get worse over time. As the engine cools if may leak/squirt a bit of antifreeze into cyl 4 and cause a misfire. This is a big deal on a SOHC engine because pulling a head off is a major PITA due to the timing chains. Cly 4 is on the driver's side, so that head can be removed with the engine still in the truck (still a lot of work). You have to pull the engine to remove the passenger side head, because the passenger side cam chain is accessed from the rear of the engine.

I'd think long hard about trying to fix a SOHC engine. Trust me I know exactly how much work is involved, not to mention special tools and knowledge. I've got a SOHC engine ready to be pulled out of my ST with just 3 transmission bolts remaining, but I have to wait until this never ending summer of daily near 100 degree temps subsides before I can continue. Then I figure I'm looking at around $2000 min to repair it (assuming it's salvageable). I'm beginning to think I'm wasting my time and effort. If you love doing this type pf work dive in, but consider what you may be up against.