Heavrolet98

iTrader: (1)

I just bought a 03 2500HD for dirt cheap. The kid that had ut blew the 6.0 and stuck a 5.3 in it just to sell it. I plan on putting a 6.0 back in itin a couple months but im driving it the way it is for now and im getting 1mpg. It still has the 4L80e and the np263HD transfer case and stock 4.10 gears with 10" of lift and 35" tires. I keep getting a bank 1 lean code and a maf code but Ive tried 3 different mafs I know 2 are good for sure but I still get the code. My stft bank 1 is 55.3% all the time and bank 2 is -3 to 6 which is more in the normal range that I know of. The kid did tell me that he changed the computer because the original got damaged but I don't know if it was programmed or not. Where do I start? I need some ideas.

nonnieselman

iTrader: (10)

First id start by getting a tune for it.. that would be an easy tune to do for any tuner out there.. That would get you in the ball park of what your dealing with. Then see how everything does.

1dirtybird

iTrader: (7)

Check for vacumme leaks on the intake-head. He may have reused the old style orange gaskets or pinched the knock sensor harness between the intake and head.

oakley6575

iTrader: (5)

This ^^

My dads truck started running like **** one morning. On the way to his office, the truck used over a quarter tank in a 8 mile trip. His intake tube had come loose and the truck just dumped a **** load of fuel to compensate. Check vacuum leaks from the air box after the MAF to the motor, around the intake, ect. Something has to be going on for it to only get 1mpg. Have you looked at the plugs?

Ferocity02

iTrader: (59)

I'm surprised it even runs at 1mpg.

Gadgetized

iTrader: (9)

Try swapping O2 sensors from bank 1 and 2. If the problem follows you could have a bad O2 sensor.

nonnieselman

iTrader: (10)

1mpg is just a calculation... i dont think its possible to get 1mpg in something like that.. unless he was trying to tow a 128,000# load and not moving but 40mph and had it to the floor at 6000

b4z

Are you getting a sulphur or rotten egg smell from the exhaust pipe.
I used to have camaro that would go full rich because the ECM(pcm) had failed.
it happened 3 times over the years I owned the car and would never throw a code. Gas mileage would drop to around 8-9mpg and wouldnt hold an idle.

Heavrolet98

iTrader: (1)

The truck runs great until I hit around 40mph and try to just crusie, if I floor it it will smooth out and take off but when Im just crusin it spits and sputters like crazy. If I let it sit and idle for longer than 1 min it will start to miss and kick a random miss fire code. I changed the intake about 2 weeks ago to a 6.0 intake so it wouldn't have the open vacuum line for the brake booster since the truck has hydroboost. I used brand new felpro gaskets with the blue rubbers. I know I didn't pinch the knock sensor harness, I'll check for vacuum leaks when I get home tonight, the intake tube is on tight with no rips or tears that I can see. I was thinking about swapping the bank 1 & 2 O2 sensors but wasn't sure if they were the same. I will definetly be doing this before I leave work I can monitor it on the ride home. I'm thinking the O2 is bad but the fact that I'm not getting any codes for it was trippin me up.

Heavrolet98

iTrader: (1)

Also, when the truck is in park and I rev it up the speedo will jump up like its connected to the tach. Holding the rpms at 4,000 the speedo is reading 100mph. Has anyone had a similar issue? I've tryed 3 different speed sensor out of tcases my brother has. I'm wondering if the computer could be for a totally different setup and not reading the signal correctly for the sensor? I definetly need to get Wheatley to send me a tuned pcm for the truck and see if that helps.