Fuel Issues

93' GMC K1500 w/ 5.7. Automatic w/3.42 gears. This truck is getting 8 mpg!! It is dumping alot of fuel in the Throttle Body and I cant figure out why. Just about every sensor is new and Im not reading any codes. I need some help of the fuel system. Any ideas??

What was the mileage when you first got it?

You may want to get it on a good engine capable sanner and read out all sensors and engine running data.

Is both injectors have the same spray pattern?

Engine coolant temp sensor could be bad. Colder engine needs more fuel. The other area to check is the MAP sensor and the vacuum hose to the sensor. Low vacuum at the MAP tells the ECM that the engine is under load so if the MAP sensor or the hose does not hold vacuum, it will use more fuel. Also, the port on the TBI is restricted, this will also fool the MAP to think that the engine is under load.

On my 90 K1500, the end of the hose at the MAP was leaking and I had to replace it. The rubber end is glued on and the glue no longer was working.

Injectors could also be bad but like MT-2500 said, a scan will show you if the MAP sees the engine is under load or if the ECT sensor is off.

//2000CAYukon

I have scanned for codes and get none. All the sensors are new and I have changed most of the vacuum lines. Im at wits end! This truck is dumping alot of fuel to me. Could it be in the distrubutor or a timming issue? I am running out of things to check. I have been through the truck several times.

Are you sure that the vacuum port that the MAP sensor is connected to is not restricted? What did the fuel trims look like when you had it scanned?

//2000CAYukon

It runs like a champ until the engine temp gets to operating temp. I changed the ECT sensor and tested it. What else could it be?