I had my IP replaced about a month ago and it runs great but at about 1200 rpm's it has a miss to it. It seems to only do it when it has warmed up good and only does it under light load. When the IP was replaced the LP was checked and the mechanic said it was good. I have since put a gauge on it and it runs about 4 1/2 at WOT and 11 at idle. When the miss occurs there is no surge in pressure and it maintains about 9 psi. Has anybody had this problem or one like it? Before the IP went out it was doing the exact same thing so I am worried and of course, the mechanic says it is not the IP. Any suggestions or help would be greatly appreciated as I can't get any help from the mechanic other than to wait for it to break down.

 

First off, your LP is dead. Take your truck to Autozone and see if they can pull any codes. If p0216 comes up, then it's time for a new IP.

 

....and I say the lift pump is not dead. 11 at idle is fine and 4.5 wot is ok too. With psi like that you would pass the volume test no problem. I do agree on the "get it scanned" suggestion though, but I would probably use a better source than an autozone. Being your VP is fairly new if there was a code I would want to see how many starts it has. If there are quite a few I would clear all the codes and drive the truck until I felt the "miss" and then get it scanned again to see if a dtc set. Most generic scanners, or doing the key on/off thing will tell you there is a code, but gives you no clue on how long it's been there.