Hey everyone got a quick question for ya. I have been having a noticeable miss at the #6 cyl and the CEL proved it. The engine will smooth out after it has been running however on cold starts or even if I'm going in reverse you can really feel it. Now outside of fuel injector, spark plug ( brand new ), wires ( brand new ), coil ( brand new ), cap and rotor ( relatively new ), pickup coil ( brand new ), crank position sensor ( brand new ), and compression. is there any where else I should be looking. I will be pulling injectors this weekend and fuel rail. Thanks!
It feels as though there's a mild cam in it but basically disappears once the engine is warmed up and I've driven it.

 

Sorry I can't be of help. I have done all of that as well (with the exception of the coil and CPS) and have yet to solve my mystery misfire either. If you get yours solved before me please share and I will do the same. I have been told that the cat. converter can cause this as well as the cam position sensor (in distributer). I have checked my cat but not the cam sensor yet. Good Luck.

 

The cam sensor is supposedly fairly easy to replace if that ends up being the issue. Look it up in the service manual (look at the DIY thread).

To do an initial check on the injector, you don't need to pull the rail or the injector itself. Remove the wiring harness from the injector on #6, and take a multimeter, set it to ohms, put one probe to the left terminal, the other probe to the right terminal, and see what it shows. If cold, it should be in the 12.0 to 13.0 ohm range. Anything less than 12.0 or more than 13.0, it probably should be replaced.

If it was a cat issue, I doubt it'd disappear after warm-up. Have you routed the wires properly?

 

Yeah Jason I did and the truck ran fine for some months. This occurred after the tank got REAL low a couple of times. Now I'm starting to smell unburnt fuel out of the tilpipes. My buddy says it might be the MAP sensor not working right. The computer might be reading WOT even though it's at idle. I will check the ohms though at lunch. Thanks.

 

ok Jason I checked all of my fuel injectors and they were all 12.5 on the Ohm meter. Now how do I check th MAP sensor?

 

deflated lifter maybe?

 

yeah??

 

Mysterious misses are the B*tch aren't they? I got one as well on rebuilt motor with new heads. Ugg! I just did a compression test today have no compression in one clyinder though. Did you check injector pulse? How about fuel pressure at the rail? I would do that before i just started pulling stuff out. Check the pulse make sure that the injector is being told to fire ( a Noid light will do this) if it is being told to fire switch it with another and see if the miss fallows the injector. I have also heard of some guys having problems with IAC, and intake gaskets doing this especially since you said the problem goes away after the truck is warm. You also might want to pull the valve cover and watch them work. I had a broken valve spring that caused this to happen once. Also not to be the bear of bad news but... on 98 to 03 5.2 and 5.9 engines the heads are known for cracking between every exaust and intake valve on every cylinder and eventually one just gets bad enough it causes a misfire (trust me been here with this problem) you wont get an oil coolant mixture with a problem like this too BTW. I had to buy new heads. Just some thoughts. Myself and Auram have been having this problem as well........

 

Thanks DodgeCrazy, everything you just said I was afraid of. I had this exact problem with the #5 cyclinder on/off for about 1 yr. I was told that the spring can break and when it's wound down there's a miss fire but it could wind back around and it will level out. I have been toying around with the idea of getting new heads for a while now and even had the website of a company that was given to me by one of the members and they weren't expensive so I'm going to try and dig it out. Last night the truck started and the miss was gone but I'm not falling for that again I'll try everything you suggested again. I did all of this with the #5 then it turned into multiple/random missfires. I replacd the pickup and crank sensor, plugs, wires ( routed properly ) and it went away. The fuel pump is only about 8 months old but I'll check it anyway and get back ith you.

 

what's a deflated lifter?