Hi.. i'm new to this board but a long time member of v8s10.org. I have a 91 2wd 2 door blazer with a 4.3 TBI engine. At certain throttle positions it cuts out completely, and the truck will buck and act up until I either leave off the throttle or dump fuel to it. 2 years ago I put a new fuel pump and tank in it, and I rebuilt the entire distributor in August thinking it was a pickup module causing the problem. Timing is dead on.

It has a new cap/rotor, new wires and relatively new platinum plugs. I keep thinking the TPS but have yet to check it out and have been looking for info on this board for the procedure on this.

Any ideas on this.. as it is a real pain in the A$$.

Thanks
Chris

 

is the check engine light on?

 

No check engine light.. idles fine, and only does this at a certain rpm/throttle position it seems. I am going to clean the EGR and see if that helps and use the paperclip method to check for any codes.

Chris

 

The TPS is not hard to change. I would also try some fuel injector cleaner as well as a fuel filter just in case that it is a fuel problem and not electrical. If you have access to a scan tool you can read the TPS Voltages from closed to full throttle.

 

I am going to check the voltage of the TPS this evening, and clean the EGR. I may throw another fuel filter in it, even though I just changed it 2 years ago when i put the new tank/pump in.

Going to check the injectors and see how they are firing using the timing light and see if that is an issue. This is driving me nuts and has been all summer and I can't get to the bottom of it.

Chris

 

Well i cleaned the EGR, the PVC was dirty and i took the TBI off and fully cleaned all the ports. Injectors are firing nice, and timing is fine. TPS voltage is dead on. 0.54 volts closed then up to 4.5 then back down to .54... no hickups or wavering. All vacuum lines were fine.

I am going to replace the fuel filter, but as of now I am out of ideas. It still cuts out, especially going up a hill with a steady throttle pressure.

Any other ideas?

 

Are your plug wires all in good condition? You can run the engine in the dark with the hood open and look for any arcing to ground. Is the temp sensor for the computer reading accurate. (the one by the water inlet). Is the O2 sensor reading accurate? Could the cat be partially clogged and at high flow rates be causing an inaccurate reading by the O2 Sensor which the computer uses to control the air fuel ratio? The other input is the knock sensor, if it detects any engine knock it will cause the timing to retard.

 

Wires appear to be ok.. i did the dark thing and didn't see any sparking or other issues. I still may get a new set just in case. I haven't done anything with the o2 sensor. I emptied my cat out 5 years ago, long before this issue appeared.. so I know that isn't the problem. Didn't know this engine has a knock sensor.. worth a look.

I need to hookup my aftermarket tach and see what the rpms do when this happens. Just seems to be electrical.. but I can't pinpoint it. Need to pull the plugs and see what they tell me.

 

The knock sensor is located to the right and below the distributer at the back of the engine. It is tough to find.

 

One thing I have discovered while driving that I didn't mention was this usually only happens under LOAD. Meaning.. while going up a hill or on ramp. And most frequently in overdrive. If it is missing, and I drop it into 3rd gear, it goes away.

Transmission issue? Converter? I do need to pull the plugs and check them, just been too hot to mess with it the last few days. They are 4 years old, bosch platinums, with maybe 30k on them. The wires are probably 2 years old, just napa replacement.. but i did have to rewire a boot end due to it pulling off when I was checking the timing.

Chris