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1990 Chevrolet Silverado 1500 bogs down on acceleration

Lack of power on slow highway acceleration, it bogs down a seems to have a misfire like feeling. All plugs, wires, cap and rotor replaced, new egr, map, temp sensor (another subject) all replaced…

Reading out the diagnostic codes is where to start. In my experience bogs are often due to a fuel problem (e.g. fuel pump) or clogged cat. If no codes, measure the fuel pressure, see if it is ok at idle or it drops when this happens, and if that’s ok try temporarily disconnecting or bypassing the cat.

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Thank you, I will look into the fuel issue first. I have measured the exhaust pressure by removing the O2 sensor and plugging in my vac/pressure gauge with very little if any movement on the needle at all even when at high RPMs. So, I think you are on the right track with it being fuel related…now to find that fuel pump….

I’ve had several of those trucks with the 350. Does the check engine light come on, and do you know how to retrieve the codes stored in the computer? Really easy to get the codes on an OBD1 system GM with a paper clip.

As for your exact problem, could be several things. Change the fuel filter if you haven’t recently because it’s external to the tank and routine maintenance anyway. If that’s no help, and assuming there isn’t a code set pointing to a particular problem, you might have the fuel pressure checked to see if all is well with the fuel delivery. You can also remove the air filter and breather assembly and have a look at the fuel spray pattern in the throttle body. Compare your spray pattern to pictures of proper spray patterns online. I’ve seen example pics years ago, but would have to search to find them now. Good luck. I’ve got a soft spot in my heart for the TBI 350’s and probably always will.

George pretty well beat me to the punch. Change the fuel filter before replacing the pump though. It’s cheap and easy, maybe you’ll get lucky.

Thanks and will do.