i have a 98 4.3 vortec that i just bought. if you open the throttle slowly, its o.k., but, at regular acceleration or fast open it just bogs out. i changed the throttle position sensor, but it made no difference at all. when the motor is cold it seems to be a little worse.any ideas? thanks, mike.
I think this engine also has a Mass AirFlow sensor. So if this has not been cleaned in a while a cleaning might cure the problem. Also connecting a scanner to the ECM might highlight a problem with the TPS, its wiring, or the MAF sensor and its wiring.
Hope this helps.
You might want to check the fuel pressure. Your engine has the Central Multiport Fuel Injection system. This fuel injection system has what is called a spider assembly. This spider assembly http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800bfe44 has poppet valves that are blown open by the fuel pressure. If the fuel pump pressure is low, these poppet valves can’t open fast or far enough to allow fuel into the engine under acceleration. When the motor is cold, this is when the demand for more fuel is the greatest so the problem will be worse under this condition.
Tester
thanks! this is more info than i can find anywhere else. ill check fuel pressure next. thanks again -m
i was told that you can check the maf simply by unpluging it. is this true? should it run worse or at least change how the motor is running? im not sure what im looking for with an “unpluged” maf. thank you. -m