help with hard starting

hi all, newby here. i'm trying to help my son with his 99 tahoe 4wd. the truck sat for about 6 months, ran ok before this. however now when you start it the first time of the day it rans and drives perfect for however long its running, could be 5 mins. or 2 hrs. runs great! but if it is shut off it will not start unless the gas peddle is held right to the floor, it starts and runs real bad, has allmost no throttle response,and stalls at will, putting it in gear stalls it out. took it to autozone had codes scanned had just every code it could have! anyone have any ideas? thanks, steve.

Do you have the list of codes that were stored?

if it just sat for 6 months, i would drain and replace literally EVERY fluid. also get a new bat and plugs. if that doesnt work, at least you know the fluids are good.

i'd check the fuel filter

thanks for replys. had codes for all sensors being out of range or low output, so many codes can't remember them all.has new battery, dist. cap and rotor, wires, coil, plugs, oil and filter, pulled tb off and cleaned, checked fuel presure and injectors for leaking. runs perfect first time started no mater how long, i can start it and run it for 30 seconds and won't restart without holding gas to the floor,checked grounds but will check again. thanks for any ideas. steve

hard starting

whats up dude ,it sounds like u might have some kind of clog in the tank , or maybe in the filter,fuel pump is also a possibility . try to trouble shoot in this order.1)fuel filter,2) gas tank ,3) fuel pump its in order from least expensive to most . hope it works out :yesnod:

If it runs great the first time at the beginning of each day, but does not restart again until cold, then a dirty/clogged fuel line or filter would show the same symptoms whether engine is hot or cold. A weak fuel pump could be a possibilty, but usually a weak pump would gradually start to cause fuel starving issues after running for a while, not all of a sudden once you stop the engine and then try to start again.
With the codes showing bad sensors everywhere, I'm leaning more towards a bad ground connection somewhere or PCM.

I had the exact same thing happen to my 99 Tahoe 4 door, 4x4.

I changed the fuel filter, this seemed like it helped, but the truck still had the problem. I asked around here, someone said, dump several bottles of fuel injector cleaner in the tank.

I tried using a bottle here and there, again, that helped, but I still had the problem.

Finally, I decided to listen to them and dumped in 4-6 bottles of injector cleaner. Low and behold, I don't have the problem anymore.

Will this work for your vehicle? Maybe. Did it work for mine? Yup.

When I was using the single bottles here and there, it was STP. When I dumped a lot in there, I used the generic WalMart brand injector cleaner. Why use generic? For me, price and the fact that WalMart does not own their own petroleum distillery. Heck, I've been considering using their full synthetic oil instead of Mobile One. I don't picture WalMart having a chem lab to make this, they outsoure it and brand name it. I wonder who actually makes it for them.

Hope this helps
Hardwarz

I'm having this problem, as well. I also keep popping an ECT sensor code for some reason. It has a brand new ECT sensor. I guess I can try to flood the tank with the cleaner like the last poster. This is on a brand new 0-mile longblock. My Tahoe sat for 6 months as well... I'm hoping bad fuel. Will post back with any solution I come up with.

well seeing that you just swapped the motor out and that the sensors are reading low I would agree with JKmotor. This is a wiring problem like whoever did the work installing it forgot a ground. I would check all the wiring under the hood.

its either the fuel filter or pump mine did that two one or the other