Okay, I know i have a vacuum leak. My father who is a professional mechanic has a code reader and we keep getting the same code and he knows there is a vacuum leak. When I start the truck it starts fine. Then after running for about 20 seconds. It starts acting like it wants to cut out. It starts jumping. It wants to do that for about 15 seconds then it's all fine. Runs fine and drives fine. What could it be? We replaced a vacuum hose a while back and the light still came on so we still have another one somewhere.
Thanks,
Robert.

 

What was the codes he was getting? P0171 and P0174? Others? Each one give us a different area to look. Without them, we can give you 10000 different ideas, and we could be wrong on most of them.

 

I didn't write them down. He didn't say either. I was just told that I have a vacuum leak. It's not that big of a deal at the moment. I know after Christmas we are going to try to find it. If we don't, I'll get the codes for you guys and let you know.

 

It's the p0171 and p0174 codes. I just got this fixed on my truck. Intake isolator bolts wore down causing a vac leak under the plenum. Bought new bolts and gaskets off rock auto for $50. Fixed, no codes, no more surging rpms.

 

Assuming its a 4.2 v6

 

It's actually 4.6 v8

 

Are you getting better gas mileage?? Theres a benefit from the leak :/.. I had a leak for a year before I took it in to the shop, turned out to be a 2" elbow hose in the back of the engine had a tiny hole in it... They had to use a smoke machine to find it. Cost me $3 in parts and $150 in labor...

Oh and I was getting the O2 sensor error codes, it would almost stall at idle