ChevyBum

Hi there i have a 1989 single cab, step side, c1500, 5.0. i have had he tranny rebuilt, plugs, cables, coil, cap, rotor, distributor, harmonic ballancer, rear main and front main seal replaced. i rebuilt the fuel pressure regulator replaced one of the injectors and a new ignition switch and ignition module. It was miss firing really bad, the mechanic i took it to said it was a short and that he fixed it( didnt tell me exactly where). ive also replaced egr valve, o2 sensor and map sensor. somewhere in the midst of all this the truck now boggs down when giving it gas at a low rpm. truck runs fine in park and nuetral ( a little miss, mechanic i just got it back from said its not causing the bog). when i put it in drive it idles a little low but runs fine just sitting there, but when you give it gas it boggs down and doesnt want to go anywhere. you can gas out of it but it bucks around for a second then when it shifts and hits low rpm it starts bogging down again. ive replaced the fuel filter as well ( black gas and chuncks came out when i blew air through it). check engine light is on but the mechanic said its only a miss fire code....im at a loss and need help...i was going to replace the fuel pump and internal screen but my buddy said i need to replace the whole sending unit too if i was going to do that, is that necessary? PLEASE any help will do!! thanks

BAGnDRAG-K5

You Sir, most likely have a clogged catalytic converter or a stopped up muffler. I would either disconnect the pipes to the manifolds or drill/blow a hole in the exhaust pipe just in front of the foremost catalytic converter(closest to the engine). This will free up the engine from the excess back pressure and it will run much better under a load (in gear). If this is in fact the cause I would take the opportunity to replace the exhaust with nice pipes and mufflers. LOL

Hope it helps.

ChevyBum

Thanks man ill try to clear it but when I bought it the cat was replaced with a piece of flex pipe....any other ideas ill try as well.... Thanks again.

BAGnDRAG-K5

hummmm??? Is the muffler new also?

ChevyBum

No its not but that flex pipe is almost broke off.....I know its not helping the problem...I was going to put a new distributor and cables...and replace the fuel pump but I don't know if I should replace sending unit too cause my fuel gauge works

BAGnDRAG-K5

OK. You need to go and ask this mechanic what he did. I think you are tossing money into a bottomless pit and running in circles with it. You need to know what he did EXACTLY to fix this wiring issue. He may or may not have fixed and created a new or caused the old issue to resurface.

ChevyBum

Ok thanks....do you think it could be a tranny or fuel pump issue.......imma call him right now

BAGnDRAG-K5

What is your fuel pressure at right now? If you don't have between 10-14 PSI it is too low and the pump might be out.

Does your motor shake and hesitate when this is happening or does it just feel like the brakes are being applied like you are power braking it? No hesitation and a steady uniform RPM range?

ChevyBum

It it hesitates a little bit but it also feels like the brakes are being applied

Diestec

Try scoping your throttle postion sensor if you cant have a mechanic do it when we were in class our proffessor messed with it to gives a bug to scope out and it cuased the exact same symptoms that your having