I was looking under my truck yesterday and noticed a line running down and hanging on the ground. I am pretty sure it is a vacuum line. It runs from on top of the tranny and looks like it was the one that is zip tied to the tranny dipstick under the hood.

Any way the question is, it was pcapped and when i went to move it i noticed it had melted on the ehaust pipe. I havent had a chance to cap it yet. Could this cause bad gas mileage? Do i need to add more hose to it and run it back under the hood or just cap it and leave it where it is?

Thanks for the help.

 

You really need to determine where it comes from and where it goes to. You have a few options. If it really is the one that is zip tied to the dipstick tube under the hood, then it runs back to the transfer case vent. In this case, it is not a vacuum line and only a vent line and will cause no problems with your engine.

Is your 4wd working properly? If your front axle is not engaging, then it is possible that the line in question is the vacuum line either to or from the vacuum switch on the transfer case (if you have the 3-button switch on your dash). If this is the case, then it could cause a vacuum leak, affecting engine operation.

Is gas mileage your only symptom? How bad is it? What have you done to remedy the condition?

 

I did look and it does head to the transfer case which you stated above. the 4wd still works just fine. I have noticed about a 70-80 mph drop in a full tank of gas? I am going to clean my EGR and MAS this weekend to see if it helps. Also just replaced the air filter. Had a tune up about 20 k ago so it probably wouldnt hurt to freshen that up as well.

 

I have fille up and been keeping track of my temp. I believe i have a bad T stat that is sticking open all the time. My truck is only run ning at 150 degrees. I believ i read before that running to cold causes the com puter to run more gas trying to heat the engine to 185 for proper mixture. Is this correct?

 

Having the thermostat stuck open can definitely diminish your fuel mileage. The gist of the situation is basically as you have stated. The PCM is looking for a certain engine temperature and will adjust the fuel/spark in attempts to bring the temperature into check. This will cause the engine to use more fuel.

 

Thanks this is what i thought. Gonna change it tonight and will keep you posted. Thanks for the help much appreciated.