Ccemerson23

I have a 1989 1500 5.0/305 4x4. Its wanting to bog down as soon as I hit the throttle and slowing down its wanting to cut off. I have rebuilt the throttle body, new plugs and cap and button, new fuel filter, checked all the vaccums, checked injectors, fuel pump sounds like it comes on good and strong. It runs like a clock as soon as it gets some RPMs up. Just getting there is the problem. Let me know if anyone has and suggestions.

SWHouston

Timing/Advance maybe ?

Ccemerson23

I thought the same thing, but it has computer timing its not a vaccum or mechanical. So if it was timing it would have to do with the computer right?

SWHouston

That right. You might try disconnecting the Battery for a few minutes. Sort of a re-boot. But on some systems, it takes a few miles for everything to load, but, that shouldn't effect your problem. I just thought I'd mention that.
Your next logical step is to have diagnostics run on it, find any problem codes.

graydog

I cannot find a way to start a new thread on this forum, so here goes......I have a 1989 w/350 w/4speed trans. that is acting like Ccemerson23's. It barely runs. If I accelerate it belches and misses. If I take it out of gear and push pedal all the way down, It cleans up somewhat and will keep running and I can speed up to 20 0r 25 mph. So far I have replaced fuel filter, gas in tank seems clean. Air cleaner is clean. I had cat.converter removed & new muffler and tailpipe installed yesterday, but that didn't help. Does not seem to have any vacuum leaks. I am going to TRY to get it back to my mechanic today. He is 2 miles away on highway. Because of starts & stops at stoplights, it is impossible to drive on city streets. Any suggestions will be greatly appreciated.

cleveland63b

EGR valves have a lot of problems on the TBI models the easiest quick check is to unhook the vacuum line from the egr valve and see if it improves when driven, although that test isn't 100% effective as the exhaust gases and still push the valve open sometimes.

evans906

The problem could be the catalytic converter is plugged. Use a exhaust backpressure guage and connect it to the front o2 sensor port, start the engine, run it till normal temp. is reached. Watch the guage and rev the engine to about 2000 RPM the guage should not move from zero maybe just alittle. Next snap the throttle, the guage should read zero. If not replace the catalytic converter. Good luck.

Gundog

The timing on these trucks is still done the old fasion way. There is a bolt on the intake manifold directly below the distributor, it holds down a v shaped clamp. Loosen the bolt, start the engine and turn the distributor about a 1/2 inch to the left then back past the origional setting and see which way the engine speeds up a little and smooths out. Once you are going in the right direction, snug the bolt beck down and take the truck for a ride. If all is good if not, try turning the distributon a little more. Sometimes these old trucks wear the timing chain enough that a timing light is useless. Been there.

graydog

Thanks Gundog, evans906, & cleveland63b. I removed the catalytic converter about 3 days ago. My mechanic was out of town over weekend. We will try your other suggestions tomorrow, I hope. Your response and help is greatly appreciated.

graydog

My mechanic got my GMC TBI 350 pickup fixed this afternoon. It is back on the road and running fine.

Maybe Ccemerson23 is having the same problem. The in-tank fuel pump was not putting out enough pressure. It was putting out about 5 psi and the TBI needs about 10 to 15 psi. If you replace the pump, replace the electric pigtail connection also, I was told. Looking back, the pump has been going bad and getting worse for a long time.

Thanks again for everyone's help.