I need some help….Auto help! 
My 99 GMC has a hesitating problem. I’ll step on the gas and it’ll try to go and does,but the acceleration isn’t there. If you keep your foot in it,after about 15 seconds,you can feel it kick in and accelerate…….. Fuel pump? Fuel pressure sensor? 
Any help would be greatly appreciated!
When was the last time you changed your fuel filter?
Cheap and easy route first.
About a month ago….I’ve run seafoam thru it a couple of times also.
Sounds like that new boat is to big, you might want to give it away (I happen to know someone). Then your truck will go just fine. 
Chappy, the way my luck runs, the process of elimination gets pretty expensive. I’d have to take it to a good shop.
I know,………..That’s the way my luck is too! That’s why I thought I’d check on here first.
Crappie….Nice try,but it does it when I’m not towing anything too. 
Probably nothing that half a dozen injectors and $450 won’t fix.
Shut up!!!!!Guess I’d now where the plow money was going!
You haven’t mentioned what motor. I have heard different things about GMC and Chevy concerning 1999, some say GMC used 350’s until the 2000’s came out and Chevy used the newer 5.3 and 4.8 for the entire 1999 MY.
No matter what motor it has, check the fuel pressure, on the 5.7, the shrader valve is just behind and on the drivers side of the throttle body. The pressure should be 59-66psi with key on engine off, and the pressure should not drop after the fuel pump quits, if it does drop you will probably need a new fuel pressure regulator which is easier to replace on the 5.3. On the 5.7 the regulator is in the upper intake manifold, mounted to the side of the injector metering body, takes about 2 hours to replace. The 5.3 regulator is external and shouldn’t take an hour. If this problem only happens after letting it set a while, its probably the regulator leaking fuel into the intake(or with a 5.3-leaking fuel into the vacuum line)
Sorry….454 7.4 liter…..104,000 miles.
Would that also cause it to run lean???
Go to http://www.dieselplace.com and get signed up. Go down the list of forums and you will find “GM Gassers” and click on that and type your questions. This is primarily a GM site.
If the fuel pressure regulator is weak, it could allow more fuel to return to the tank than it should. I’m not real sure on the 454 as to the exact fuel system(whether it is a true multiport setup or the csfi spider)
Fuel Presure regulator would be my first guess.
Gonna get it checked after work. Thanks
Also try http://www.chevytalk.org
Sorry Chappy, but in order to get this “fixed”, you are going to have to put it on a computer and read it.
That is low miles for that motor, and as long as the basic fuel filter, airfilter, plugs are fresh, there isn’t much more you can do.
$100 on a scanner for diagnostics will save you $300 of “trial-error” and a lot of headaches and wasted time……wasted time where you could be on the water!
Thanks all……I think I might have it pinned down. I have a K&N air filter on it and I’ve just blown the crap out of it……I did’nt know there was a cleaner for it also…..Cleaned it yesterday and it seemed to work alright this AM. Now I need to get the Guest room done in the basement! Oh goody! Thanks again guy’s for the responses! 
You didn’t mention any Diagnostic Trouble codes “check engine light on” being set.
If so you definitely want to get the codes read.
I have a K&N air filter on it and I’ve just blown the crap out of it
If it still feels sluggish your mass air flow sensor could be dirty. Its very common more so with K&N filters because they have oil on them and it can coat the sensor and collect dust.
You can clean the M.A.F. sensor with brake cleaner It is located in the air duct after the air cleaner. take it apart and look at the two wires they will have a dirt buildup on them clean it with some brake or carb cleaner.
Don’t scape them with anything.
It makes a big differance if they are dirty the computer doesn’t think you are getting enough air and reduces the amount of fuel it delivers. I check them with every tune-up I do and i would say 50% need to be cleaned on average for me.
That is exactly what we did.Checked the MAP sensor and cleaned it and cleaned the air filter. hopefully it’ll take care of the problem.
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