whats up everyone.. first real post asking for help here. ive searched all over the forum and read so many threads, been a HUGE help. but im still at a dead end here.

my we have 02 Tahoe, z code in the vin. 5.3L. its been having a random misfire. no real rhyme or reason to it. sometimes hot, sometimes cold sometimes not at all for a day, then at the light you may feel a bump,bump,bump mis and maybe a quick bump in the power when you take off . only got I ever got out of it in the beginning was random misfires on the advanced auto part scanner. I got a different hand held from a friend and got it to show a consistent mis in #6 . now, in the mix of this small mis I feel , it will catch a real bad mis session, and run like total crap, maybe even toss out a small backfire and pop if you try to pedel through it. then it will just go away. in the man time did all plugs and wires, I figured it could use them anyway. did iridium plugs gapped at .040 , a fuel filter, and sprayed all around the intake looking for any leaks or change in the way it ran with no luck. and cleaned the mas air and throttle body.

playing with the mis in #6 code.. I was told by a parts changer type mechanic it definitely needed all coil packs done, wasn't buying that or spending $400 on a guess. so I just got 1 pack to play with. 1st thig I did was put the new pack on #6 and then put #6 pack in place of #1 . cleared it and the code came back up as #6. so I pulled the injectors and swapped #2 and #6 and also tossed a fuel filter on it and in the mean time checked the fuel pressure. pressure was around 55psi( which should be good for the Z vin?) . also the regulator doesn't leak on prime, or at all. .. but after swapping these parts and injectors around I drove it for a while with the mis still there but no code, I had to drive it for about 70 miles to get any code to pop back up and that was a new code for this truck. the 0430, so I started messing around with 02 sensors. I swapped the top ones, but now im thinking I should have swapped the rear sensors? I had the truck on a snap on machine last night and it "looks" like the right side of the engine is backing up, become rich, then drops to lean real fast . only misfires are on the passenger side of the engine, and those plugs where darker than the driver side plugs when I changed them, the driver side actually looked a little lean. and when it really started missing good and running way bad it showed pretty rich on the passenger side then too.

next step is to see about having the cat checked out. guess that's really what im asking , where to next. does this seam right? I just don't really trust mechanics and ton and feel like they will definitely want to sell me on a $250 cat job. I don't think ive left anything out, any guidance is definitely appreciated .

 

also, I did say my scanner wouldn't pull the #6 mis up any more. but on the snap on machine I could see it was there a swell as others only on the passenger side associated with that 02 bank

 

Change your Intake gaskets. I bet it will fix your problem. I sell auto parts and had customers with same problem. Wanting injectors and coils. I told him to change Intake gaskets and fixed it. Spraying around them don't seem to work like older engines for some reason. Good luck.

 

Seen this happen to a few trucks I've worked on.

 

I almost don't want to say anything since you don't like Mechanics, but when you spray down the intake with carb cleaner. You should be watching O2 sensor readings, preferably in a graphing mode and watch for any significant change in readings. Usually you will see a spike and then stay high or low until all the extra "fuel" is burned. Spray again and verify the spike comes back and you know it's gaskets.

 

Just wondering what did you find was the problem?