It's 2003 sierra with a vortec 4.8l. Went to AZ to get code for light. Code read MAF,map,or pressure. Cleand maf,pressure switch,ran fine but still a code. Pulled off intake ...

It's 2003 sierra with a vortec 4.8l.
Went to AZ to get code for light. Code read MAF,map,or pressure.
Cleand maf,pressure switch,ran fine but still a code.
Pulled off intake hose from maf to throttle body and cleand trottle body. Now it surges up and down and when you hit eccl pedal it dies.Cleared codes and it will idle fine intill you hit eccl,then starts to lope.
No vac leaks.
Fuel presure 55
go up to 65 when vac hose removed from fuel reg.
New pump 3month ago.
Has the fly by wire throttle body, all I did was clean it. Now it won't run......

what the hell did I do??????

Did fuel come out of the vacuum port when you removed the vacuum hose from the pressure regulator?

No fuel leaking from pressure regulator.
I found the problm,it was the map senser. I had cleaned it and blew it off with an air hose(a BIG no no) I guess it ruptured the little dighfram in it. I now know what not to do...
Also when cleaning the MAF use 3m brake cleaner,it leaves less of a film.
The truck now runs better than it had in years.

Thanks for the input
peace
DanD.

lzn197 wrote:Did fuel come out of the vacuum port when you removed the vacuum hose from the pressure regulator?

I love a happy ending!

Chebby

DanD wrote:Also when cleaning the MAF use 3m brake cleaner,it leaves less of a film.

Not sure that I would support using brake cleaner on the MAF, but I am glad it worked for you. I'd stick with MAF cleaner, since it's such a fragile part.