Came here hoping the guru's may help. 2000 1/2 ton 5.2 liter. As said Cylinder 7 misfire. It's the only code I get. I can consistently watch it thru live data on the scanner as well as hear the mis. New cap, plugs, wires and rotor. Swapped injectors 1 & 7. Seafoam treatment through booster vacumn line and fuel tank. Fuel pressure is good. Idles good. Misfire comes on about 1800 RPM under a load, not in park or neutral. And only when reaching operating temperature. Vacumn is consistent 17 in. at idle. Inline plug tester shows consistent spark. And test light from + battery to injector ground shows consistent fireing of the injector. The plenum is dirty but not wet with oil. Compression is 130-140 with #7 being at 135. What am I over looking? Not looking to just start swapping parts, in hopes of fixing it.

 

I have a similar problem in #8, about the same compression. So far mechanics have guessed bad or burnt valve and, or a cracked head. Will be curious to the feed back you get. Have yet to do cylinder leakdown test. Do you get CEL all the time. Possible bad plug wire out of the box?

 

Thanks for the reply, I have swapped the new wires as well under the "new does not mean good" Theory. Curious if the plenum issue I see so much of here should show in the vacumn guage?

 

Are your plug wires routed the way the the tsb states?

 

It would show lot lower than 17 in with plenum leak, I believe. Also get #5 as far away from #7 wire down by the boot. http://www.secondchancegarage.com/public/186.cfm

 

Compression is good, so, I doubt that it is a head, or valve problem. The electrical end of things seems to be doing what it's supposed to.... so, that leaves that out. The miss didn't move when you swapped the injectors, so, injectors are good..... Check the connection at the injector though. If the little clip that hold the connector in place is missing, that could be your problem. They really don't get that good of a connection.... Routing the plug wires per the TSB can't hurt you either.

What does the plug on number 7 look like, as compared to 5?

 

Plugs look good and wires are per TSB.

 

Swap the plug and wire (both ends of the wire please....) with cylinder 5. See what happens. (or, just try the plug first, and if nothing changes, swap the wires.)

 

I have swapped plugs, wires, and injectors between 5&7 with no results. Starting to think valve train but have no ticking sound.

 

Pull the valve cover on the drivers side, and check valvetrain on number 7.