Hi Everyone,

I have a 1992 chevy v6 4.3 2WD. Over the past month I have replaced the fuel pump and filter, complete tune up with distributor cap, rotor button, plugs, wires, new fuel pressure regulator,and new map sensor. The truck runs great when it is cold. Starts up fine with no problems and runs fine until it gets warmed up. Once it get warmed up it runs horrible loses all power won't even get out of its own way and the valves start tapping. Even when I tow a trailer loaded it runs perfect when its cold and then once it warms up it just dies. It has been sucking gas down like crazy just driving about 25 miles burns a 1/4 tank or more. But its weird it will run fine one minute and the next run like ****. I can let it run in the driveway for 2 hours and it will never act up even after its good and warm. It has a mind of its own sometimes it runs fine warmed up and others it won't even move. It has never had any codes the whole time. No vacuum leaks, temp sensor reading properly, O2 sensor reading good, and throttle position sensor good. Any help would be appreciated.

 

You're absolutely sure the coolant temperature sensor is good? That's the first thing I thought of. Is the exhaust black when it's warmed up and running crappy?

 

Welcome to Truck Forums

When you did the cap plugs, wires, cap and rotor... Did you distributor happen to come loose? Sounds like a timing issue.

 

Ok, sounds interesting.
Almost sounds like two seperate issues. Runs good cold then bad warm with valves tapping? That sounds like a mechanical/oil pressure issue.

High fuel consumption and low power warm sounds electrical.
Do you have a scanner? Not a code reader.

With that kind of fuel consumption your fuel trims should be all whacked out.

You also stated it just dies, so does it also have a stalling condition? If so does it loose spark or injector pulse?

How old is the O2 sensor and if you replaced it was it a cheap aftermarket one?

Mileage on truck, stock or modifed is useful data as well.

 

Also check for the catalytic converter plugging up.
Do you have access to a back pressure gauge?
If not remove the O2 sensor when it is acting up and see if that helps.

 

Something is telling the truck to turn up the fuel supply. I would bet the catalytic converter is showing signs of clogging from this condition.

 

Do those trucks have one of the spring operated chokes on it? My old Ford did this, and I just disabled the choke, and ran a old bicycle shift cable to it, and then into the cab. Worked like a charm, went back to getting good fuel mileage, and ran fine, once it warmed up and you turned the choke off with the cable.

 

LOL I use to do that with my ol 318 Dodge back in the 80s
Yeah it worked great

 

For awhile, after I started it, I popped the hood, and just jammed my pocket knife in the choke, but I got tired of that after awhile.