hey everyone i was hoping one of you more experienced guys could help me out with this problem iv been having with my truck, ill do my best to make it short. The truck seems to studder/ hesitate and backfire when i try to accelorate from a dead stop. It will keep on backfireing and studdering for about 15-40 seconds of driving and will eventually pick up and drive normally. Even if it stops after driving once i stop at a light or let it idle to low for any amount of time it begins to backfire again (The engine/truck also vibrates when it is idleing at a stop in DRIVE but not in NEUTRAL ???). Another thing is that this USUALLY only happens when it is a hot day, not so much when it is cold. Oh yeah and gas milage sucks really bad im spending like 20$ every 2-3 days of just driving to school and work (about 30 minutes of driving in total a day).

The Things that my mechanic and I have tried already:
-Put in a new timing chain set (chain, guides etc)
-Put in a new TPS or throttle positioning sensor
-Put in a new Mass air flow sensor box

After all of this the problem still persists although not as bad as before. I dont no what else it could be and these parts are really costing me a lot. The only other thing i can think of is the catalyic converter being clogged but i dunno how that is possible because it is only 5 months old (its a big turbo performance cat). Hopefully someone will have some ideas, thank you for reading

 

bumpp

 

http://personal.utulsa.edu/~nathan-b.../3troubles.pdf

Try running it down through the troubleshooting guide. It could be a number of things. Start testing things with meters and such before you spend a lot of money on unneccessary parts.

 

You replaced the timing chain, are you sure it is timed correctly? 5* TDC compression with the test connector jumpered. Have you tried to advance the timming a little at all?
New TPS, was it setup within spec?
Any holes in the intake lines? How about vacum leaks? Take a can of carb cleaner and spray around all of the vacum lines and see if the rpm's increase.
Ignition parts in good shape? plugs, wires, cap, rotor.
Just some things to check out.

 

yes the timing and tps was set correctly, my mechanic tried looking for vacum leaks but couldnt find any. Im gona get some carb cleaner tho to see if that works at all. The truck recieved a tune up about 6k ago including plugs wires cap etc. Im going broke over this stupid problem and its getting me pissed! lol

 

Run the FSM checks on the AFM.

 

I had similar symptoms when mine had a small crack in one of the rubber connectors for the air intake so the MAF was reading one air flow and sending it to the computer but the engine was getting a different air flow and not liking it. It would all even out at higher rpm, but idle and accelerate like crap. Also didn't match your description in that it didn't matter about drive/neutral or warm/cold. Just another idea. Also the leak wasn't easy to see or hear.

 

yeah il check for leaks thanks for the advice!

 

Sounds like you need to find a new mechanic, he is gambling with your money doing repairs that are leading to no solution.

 

yeah im really pissed off im not even gona mention how much he has charged me so far. Actually i will, so far he has replaced the TPS, Timing chain (parts under warranty cus the part was faulty he said), put in a used MAF box and fixed a warped U joint (i had it fixed but is not related to the hesitation obviously) and so far he has charged me near $1500. This is killing me and i dont want to have to sell my truck over something stupid like this!

 

$1500?

well, i suppose that is canadian so its about $20 american lol.

But really, thats ridiculous. Find a new mechanic. YOu are getting farked. You should never pay a mechanic for his faulty "guess work"

 

where in toronto are you?
shoot me a pm, and i can come over and take a look at the truck for ya.

 

ok cool thanks man

 

the mechanic is now saying that it is the MAF box that he replaced with a used part. Another used one is coming in under warranty i hope it fixes the problem this time

 

sounds like you have a guesser doing your work...PULL that TRUCK!! He's just going to cost you money. Mechanics who do that with parts, are what we call "parts swappers" here in the wrecking industry. They will keep swapping out parts until they find the problem...if ever.