99 7.4 running lean

[sigpros]

I have a 99 with the 7.4. The check engine light keeps going on and off. when it's on the mpg goes down. When i check it says "running lean on the left bank" I have had it to the dealer twice. New fuel filter,pump, intake gaskets and a tune up. Still same problem. Also when I drive it stop and turn it off then start it again it doesn't want to run you can stand on the gas and it won't go over 15mph. after about a minute it will just take off and run fine. I also think it is doggy compared to the chevy 350's I have owned. first bb. Thanks for any help

[76silverado]

It could be an O2 sensor or bad cat. Welcome to the forum you will find us nice and helpful.

[JOHN JAY]

tell the dealer they failed to correct the problem. the sensors are putting into limp mode. I would clean them ,the cat wouldnt be the first thing I would suspect intermitant. I hate it when the dealer tip toe around with your money...

[sigpros]

By sensors do you mean the O2 sensors?

[Case 7230]

Could be gummed injector/s. Have you tried running a can or two of fuel injector cleaner thru it? I have had good results with both Lucas and Cyclo.

[leolkfrm]

you paid someone good money to fix it! take it back and make them do it right, and don't give them anymore money they quoted you a price to fix it and for what you paid it should be right

[sigpros]

I was going to fix it myself. I will try the fuel injector cleaner. the dealr said it wasn't getting fuel to the injectors. Also I read on a diffenent post that after market O2 sensors are junk. What do you guys think about that?

[leolkfrm]

If the dealer said it wasn't getting fuel to the injectors and the problem is still there ask why he charged you for all the wrong work! I'm sorry but if it was charged I'd be putting a hold on the credit card for unsatisfactory work

[stumpuller454]

Which codes are comming up, just the p0171?

IF so inspect
-exhaust leaks
-fuel filter restriction
-vacuum leaks after the MAF sensor (hoses, connections, throttle body, intake, and EGR)
-is your idle high or unsteady? > inpect IAC operation
-check PCV operation
-If you have the california AIR system, it could be stuck OPEN
-contaminates in fuel
-VCM connections ( make sure are tight and connected, grounds good)

seing that you are also experiencing power loss, and that it appears the dealer went over the fuel and ignition side of things....and they must have done the intake stuff to try and get rid of a vacuum leak, but you could varify your intake vacuum at an idle, should be around 17-19"hg (inches of mercury) maybe check your air filter, maybe they missed it? and get the exhaust checked for restriction or a leak. you should ask the dealer if they did an injector balence check aswell...>stump

[sigpros]

The intake gaskets were shot. they were leaking antifreeze out. I can hear an exhaust leak. I will climb under there and try to track it down. I did the fuel pump myself because they wanted $700.00 to do it.