Misfire on #3

[dogdammit]

I have a 2003 3.0 RWD XLT Extended cab. The code is, as you probably know, P0303. I took it to a shop and I think there must have been some miscommunication because they said it needed plugs and wires. It didn't really sound like that was a problem to me, especially the way they said it but I pulled it out and did it myself. No change. I made sure to do it as proper as possible, took the clips in the house and washed them with dish soap, kept the old plug wires in a sort of layout so I could reference where the new ones should go, also replaced one at a time to be absolutely sure I had it all correct. I am thinking about going back, unfortunately I have to pay another diag... kinda wish I would've let him have it. Anyway I want some y'all's opinions before I do anything more here.

I have power to the injector just like the others, the old spark plug and wire looked okay, like the shop said just worn out and it was about time. I have not checked compression or injector pulse, I think I can put a test light or wire up a light bulb and that'd show me injector pulse?

 

[SenorNoob]

AFAIK a 12v led with a connector is all a NOID light is...

If you can check compression, you can figure this out at home.

 

[dogdammit]

AFAIK a 12v led with a connector is all a NOID light is...

If you can check compression, you can figure this out at home.

Cool I'll try it tomorrow.

I was hesitant to take it back because as soon as he said it needed plugs and wires I was like dude I should've just looked at it myself it's super simple. That and I'm not sure why they didn't know the problem.

 

[SenorNoob]

Most times finding the problem involves taking more stuff apart than a shop can reasonably do in an hour of diagnostic time.

Nobody wants to pay for 8 hours of diag to find out they need an engine...

 

[dogdammit]

Ok well I didnt get around to checking compression, I had to go buy a tester but I barely made it a quarter mile and it's now for sure a dead misfire and i'm not comfortable driving it anymore. I'm thinking to order a fuel injector since it got worse. Also when I tried to restart it, it sounded like was getting stuck on one cylinder for a moment, but I can't really smell any gas. This is very confusing now.

Also should I do all 6 injectors at once? I feel like that's one of those things that needs to be done in pairs. In that case, do you guys trust the remans on those from RockAuto?

 

[bjkeeling]

Check compression for sure. The '05 Vulcan, and I think a lot of Ford motors of the era have recessed spark plug ports; I had to buy the expensive compression tester with the longer bushing. You're in the US so you get better stuff, and O'Reilley's will loan a tool you one that should work.

If you have tubing or a long screwdriver to use as a stethoscope you can check if that injector is making a different noise than the rest. On the '05, #1,2,3 are all easily accessible, drivers side 4,5,6 are under the upper air intake. Compression, ignition, timing, air/fuel mixture. If you have fuel in the rail at the correct pressure and it's only one cylinder then yeah a plug, wire, or injector would be my guess. Always unplug the MAF (PCM will run off assumed tables if it doesn't get a signal) and rule it out if you're chasing air/fuel issues - easy to do, wise to rule out - don't leave it to last like me.

Hard to say what the truck is worth to you, and what the current engine's mileage is - if you want to limp it along or keep it forever. If all injectors are factory, they all have the same number of cycles on them, but if you're up to accessing them and replacing them if they fail down the road there's no need to rush. If the compression is all around 150-160psi and you're willing to keep working on it as issues arise, do it right.