2.7l Cylinder 3 misfire

Is there any chance old belt residue on the pulleys? No way an expert but could it be the pulley bearings?

 

I appreciate the follow up and reporting of the fix… most peeps just drop off the forum when their specific problem is fixed with no follow up.

 

Thats possible but I just reused the same belts that I had before I had the motor rebuilt, I’ll check to make sure. It could be the bearing on the pulleys too it’s so loud when you are trying to find which pulley it is coming from it gets confusing. Either way a lot minor than all the crap I had to go through with this damn truck.

 

Final summary/timeline for those that might have a tricky misfire (which mine ended up not being):

1. Initially I had a p303 code (cyl. 3 misfire) with the engine audibly misfiring. New coil, new spark plug installed same issue.

2. Took fuel injectors to get cleaned and tested at a shop. I received them back with a clean bill of health from the shop, who said they had been pretty dirty however still worked good. Reinstalled and still had same code with an obvious misfire coming from engine.

3. Began testing,

Compression tests results:
Cyl.1: 170psi
Cyl.2: 180psi
Cyl.3: 195psi
Cyl.4: 185psi
These appeared good to me

Fuel pressure test was 46psi

Noid test for all injector wires were strobing properly

I checked for spark on all 4 cylinders and there was proper spark on all.

Finally I replaced the MAF sensor.
Still same code

4. I thought it was a valve issue at this point so I pulled the head and sent it to a shop to get cleaned and checked. Head came back with a clean bill of health so at this point I said F-it, I’m already this far into it, and pulled the lower end to get sent in for the same thing. When I got it back they said the rings were toast but had replaced everything and shaved a little on the cylinder walls. The motor was ready to get put back together.

5. I put the truck back together and still had same code and obvious misfire happening to the engine!! At this point I began to continuity test everything. I tested the coils, the coil wiring, the injector wiring and the injectors themselves. I finally found the issue when the cyl. 3 injector had no continuity whatsoever. Purchased new oem injector (very expensive ~$300) and it fixed the p303 code and misfire!

In summary:
I went into this project with not a whole lot of mechanical experience and thought throwing parts at a problem was a way to solve an issue. I learned that a good multimeter was one of the most invaluable tools to properly diagnose an issue. Simple continuity tests can help guide you in the right direction. Dm93 helped me a lot through this project and I love the quote in his bio, it says, “test don’t guess”. Which is seriously the most important thing to do in a situation like this and don’t take a shop at its word! Test the parts you get back from them to make sure they actually work (continuity testing)!
I learned the hardest way possible so I just want to make this final post for those in the future who see this thread. Test everything before you start buying parts, it would have saved me a bunch of money. However I do have a damn near brand spanking new motor out of the deal. Thanks again to everyone who commented.

 

Well said and thank you for posting everything and following up. A lot of times people come on here and ask for advice but there is no follow up. If you plan on keeping the truck forever, at least you know the engine is in excellent working order now.

 

Not that it matters since the motor got rebuilt, but the cylinder 1 compression would of concerned me. I believe the max variance in compression is 15 psi, which cylinder 4 was at and cylinder 3 was beyond.

Not that I would have rebuilt the engine anyway, 170 psi isn't bad, but it peculiar that cylinder 1 was such an outlier.

 

Lukegoes
Thanks so much for the follow up summary
Appreciated.