1994 possible fuel system probs

[tattedcutie216]

i have a 1994 gmc sierra extended cab with 152,000 miles on it. about a week after buying it i started having problems. it would idle fine then when trying to accelerate it would bogg down and try to stall. at first it would only do it after running for a while. it progressively got worse and eventually was actually stalling. (all happened in about a week) we replaced the fuel filter and the egr valve. tested the injectors on the throttle body and they tested fine. all spark plugs are brand new, filters are all brand new. the mechanics where i bought it are lazy as can be and only fix what i say i think it is. someone please give me an idea. the fuel pump is only 3 months old so i don't think it would be that. any ideas?

Confused in ZHills

[duke350]

have you checked the cat for backpresure? it may be clogging up. Also, get the fuel pressure with a gauge, do not assume its correct just because it is there. When it stalls does it seem like its losing spark? Or fuel? When it looses spark its more of an immediate stop, when it looses fuel it will kind of sputter and chug. You can check the cat with a pressure gauge in the exhaust before and after the cat or with a vacuum gauge at idle and and about 2000 rpms.

[Crab Spirits]

I have had this happen on a 94'. It was the cat. The catalyst somehow shattered inside and it would flip 90* and totally block off the flow. When this happens, you accelerate and the truck falls on it's face. Go under there with the engine idling and you can hear it rattling around in there. You can also pound on it with your fist to see if you hear anything.

[smaurno]

I had similar problems with a 93. I kept getting code 32, which is supposed to be EGR, but got no better after changing the valve and the EGR solenoid. I changed sparks, wires, rotor, cap, coil with no improvement. It turned out to be the fuel pump. Even though your fuel pump is new, it may be defective.

[mwid73]

I had a very similar problem with my '93 Silverado. I tested everything I could think of and thought there's no way it could be the fuel pump because I just replaced it like 10,000 miles prior. So I pulled out the sending unit and pump and the short 1 1/4" rubber gas line connecting the pump to the sending unit had a cut in it. Was probably pumping half the fuel right back into the tank. I guess my point is even if the pump is new you should definately check your fuel pressure anyway....