Runs and idles until try to drive it then it misses pretty bad.

[Richard1234]

I took my sons 1999 5.7 Tahoe to express oil to try and get the problem fixed.They are telling me they want to "start" by replacing the computer, crank sensor, cam sensor and some valve that I have forgotten the name of.with no guarantee it will fix it.It seems like they are just trying to throw parts at it to me.
It cranks and runs but will try to shut off randomly and if you try to drive it it misses pretty bad. If you keep it at very low rims it will drive.I have no idea what to do.If possible please help me.

 

[Hoesgottaeat2]

I took my sons 1999 5.7 Tahoe to express oil to try and get the problem fixed.They are telling me they want to "start" by replacing the computer, crank sensor, cam sensor and some valve that I have forgotten the name of.with no guarantee it will fix it.It seems like they are just trying to throw parts at it to me.
It cranks and runs but will try to shut off randomly and if you try to drive it it misses pretty bad. If you keep it at very low rims it will drive.I have no idea what to do.If possible please help me.

Sounds like they pulled out the parts canon on it. Is the SES light on? If so, what code(s) is it showing? Have you done any repairs at all to it yet to try to remedy this? My first thought, and one of the least expensive, is distributor cap and rotor. Known culprit and will produce said symptoms. In particular the distributor cap(might as well replace the few dollar rotor while in there IMO). Give us more info (and history if you know it) so we can try to help.

And greetings, welcome to TYF from NY!

 

[B-train]

Check distributor cap and rotor for corrosion. There is a know issue with newer parts that are prone to tracking and then they run weird. The other thought is the spider injector assembly

 

[OR VietVet]

Throwing an ECM at it is mind blowing. Very rare for an ECM to fail, but it can. Sounds like you need to see what fuel pressure you have at idle and when throttle in gear. I agree with the spider gear scenario that @B-train brought up about the spider set up. If you can get a fuel pressure gauge attached and get long enough hose to allow for bringing gauge out back of hood and tape to w/s and drive it.

 

[Marky Dissod]

I took my sons 1999 5.7L Tahoe to express oil to try and get the problem fixed.
They are telling me they want to "start" by replacing
the computer, the crank sensor, the cam sensor, and some valve that I have forgotten the name of,
with no guarantee it will fix it.
It seems like they are just trying to throw parts at it to me.
It cranks and runs but will try to shut off randomly and if you try to drive it it misses pretty bad.
If you keep it at very low rims it will drive. I have no idea what to do. If possible please help me.

The moment they said 'the computer', before anything else, they disqualified themselves as a competent diagnostic shop.
They did it again, in the same sentence, when they said 'no guarantee it'll fix it'.
Don't EVER go back there again, even if just to pee.

The ECM is nearly always THE LAST thing to get replaced.
Whenever one loads the parts cannon, always start with the smallest / cheapest / easiest stuff to replace FIRST.

Cap & rotor sounds WAY more likely.

 

[Hoesgottaeat2]

Don't EVER go back there again, even if just to pee....

 

[iamdub]

I took my sons 1999 5.7 Tahoe to express oil to try and get the problem fixed.They are telling me they want to "start" by replacing the computer, crank sensor, cam sensor and some valve that I have forgotten the name of.with no guarantee it will fix it.It seems like they are just trying to throw parts at it to me.
It cranks and runs but will try to shut off randomly and if you try to drive it it misses pretty bad. If you keep it at very low rims it will drive.I have no idea what to do.If possible please help me.

Lawd. I'd check fuel pressure first, then check distributor cap and rotor. Don't start throwing parts at it- CHECK the items first. If it has been a while for the distributor stuff, you might wanna go ahead and get new parts to install just because the screws for the cap can be a pain to access. With any decent mileage, the terminals will have some corrosion, anyway. Use ACDelco or maybe Borg Warner parts only.

I'm currently leaning towards weak fuel pressure, though. A clogged cat presents the same symptoms.

Questions (yes, others have asked already) :

Did these issues start suddenly or did it progress to this point?

Is the SES light on?

Excessively smelly or even visibly sooty exhaust?

Do you have access to a scan tool that shows live data?