Hello Everyone

I'm in need of some help. I have a 2005 Chevy Express 2500 LWB Van with a 6.0 and a 4L80E and 64,00 miles. I'm having a problem with a rough Idle and a misfire intermittently.

What Ive done to it:
Cat-back magnaflow exhaust

Made my own K+N intake (now back to stock as per dealer tech recommendation)

and a hypertech programmer. (tried going back to stock many times thinking maybe its the program giving me the problem)

had many codes p0174, p0171, p0137, p0157, p0133, p1133, p1134..

her is what I did to it:
new intake manifold and fel pro perma-seal gasket
thoroughly cleaned TB including the IAC valve
new MSD wires
New E3 spark plugs ( they were on of the first things I did thinking it was in need of a tuneup)
Had GM do an Injector cleaning service on it

Had many mechanics look at it and suggest things but very few actually new what to look for except for the last guy who was recommended by Billy thanks bill great guy over there at Parkway Friendly service on Broadway in Fair lawn NJ. He found the most significant problem and he is truly a great guy to deal with.

But Im still having a problem of a rough Idle problem and also the entire time the fuel trims have been erratic. and now im starting to get o2 codes again for slow response, insufficient activity and voltage, Its perplexed everyone. any help would be greatly appreciated.

Thanks

Don

 

You need to hook a scanner up to it and log it to see which cylinder(s) are misfiring.

 

Its very hard to diagnose something like this over the internet but based on your codes i would look for a vacuum leak, i see u have already done the intake gaskets but thats probably the most common issue...also what about plug wires? look there and holler back
edit, I see you've already done plug wires but go back and look at this stuff, if I had a $20 for everytime somebody replaced a part and assumed it was good I would'nt have to work anymore, spray some carb cleaner or brake clean(the flammable type) around the intake with the engine running and see what happens.

 

Have you actually changed the O2's??

 

Im sorry man but get rid of those E3 plugs and change back to stock type plugs. Those E3s are Junk

 

hey guys
I did change all the O2 sensors and I changed bank1 sensor 1 a second time and now Im onto my 3 ill be doing that tomorrow. getting P1134. Ive had it put on a scanner a few times the only one to find anything was that I had cylinders 5,6,8 misfiring changed the wires and it got a lot better then took it to the dealer they put it on a scanner for an hour. the only thing they said was the K+N was moving to much air at idle, it was calling for 15 -20 on the long fuel trim took the filter off left the maf open and it dropped to below 10. the other thing I noticed today if if you idel up to 940 rpm you can feel a drop in rmp and its missing. Also forgot to mention that It was put on a smoke machine for 2 hrs and no leaks any where! I will see whats up with the misfire with a scanner again. I was wondering if the maf was not working properly could it cause these issues?

Thanks for all the responses

 

2007 chevy 5.3

I would but the rough idle and codes p0174 and p0171 where there before the plugs and no change after. did I mention it pulls great on the highway of from 15 up if I give it gas just below that or at Idle it mises.

 

Also 1 More thing the codes don't all come at the same time and they are pending codes or soft codes. the only hard codes are p0174 gone now, p0171 gone the only one now is p1134 changing that o2 tomorrow.

 

Hey Don, glad that Les (or his son possibly?) was able to help you out...somewhat at least. I don't buy the K&N flowing too much air, but I wouldn't doubt that it may have oiled the MAF sensor. A faulty MAF reading to the PCM will cause a slew of problems...I've seen false lean codes multiple times on different manufacturers due to faulty MAF sensors in the past. Also, as mentioned above, I'd swap out the E3 plugs for either some AC Delco's or NGK's as the E3's have proven themselves to cause more misfires than they cure, straight out of the box

 

Yup x1224455 lol change the spark plugs and it's pretty common we get it a lot .. Oiled up mass air flow sensor or Meter whatever u wanna call it...