I have a 2001 4.2 w/ 118k miles on it. I bought a new PCV valve hoping it would fix my P0171 & P0174 codes I get everytime there is more than a 10-13* air temp change. So the only thing I can think else to check would be the 90* elbow everyone talks about replacing.

Also, I have a temporary power loss between about 1700-2000 RPM. When accelerating it is noticable, and when drving is felt slightly. But as soon as it hits 2050 RPM, it just rockets off! Could a bad elbow possibly be causing this too?

Thanks guys!

 

nobody has anything??

 

Did you check the elbow near the firewall behind/under the intake manifold. It can go bad as well, if you can reach it and you can squeeze the sides together easily then replace it. Just follow the hose from the valve cover to up under the intake manifold.

 

i thought that was the PCV elbow...

i will do that too then.

*bump*
how much did your UD pullies help with power and mileage?

 

Well if your setup is the same as mine, there is one 90 degree elbow near the pass. side valve cover but there is another tucked up behind the intake near the firewall.


well I put my UDP and CAI on at the same time so not sure which helped the most. But I did notice I got about 1/8th of a tank better mileage and it had better accel and passing power. I don't have any concrete numbers to give you just my impressions of how it drove after the install. Unfortunately you can't get UDP pullies(plural). Seems they only make a 25% UDP crank pulley for our motors. For other trucks they have a set for the crank, alt. and water pump ( I think or it may be the PS pump)

 

I think we can all agree that you have a vacuum leak. So I would spend a little money and go get a vacuum leak check. Thats what I did and fixed ALL of the leaks.

 

where would I go to do that though?? and how much am I looking at spending?

 

I had same problem, at about 133K, bad power, bad gas mileage, CEL codes all over the damn place. For me it was two elbows, the one in front underneath upper plenum that mounts to EGR from the bottom side, and the one off the PCV that connects to a plastic line that connects to the one on the egr valve. I replaced all vacuum lines and rubber elbows for about $20, partly because I dont let the stealership touch my **** at $70/hr shop time, and partly because this repair is EASY. Their estimate was $700 to do the same thing. Oh yeah, I also replaced upper plenum gasket, about $15.00 for the felpro IN STOCK surprisingly at a small town autoZONE. Gas mileage back up to 20, able to bark the tires from 2nd to 3rd again, just like new! So, I am thinking I had this problem for thousands of miles but it didn't throw codes until things were really rotted out. when you take yours off you will know what I am talking about.

 

Well, I dont remember if the other one connects to pcv, but it is on the intake, on the passenger side, behind the intake rather, on the top back passenger corner,so you cant see it, but you can reach back and feel it, and I bet good money you will feel the rot, and maybe even holes. DO you hear a hiss or sucking sound while your engine idles rough at startup?

 

not really...at least not that I can tell....

but im going to get that checked out, eventually....

 

Just recently I changed out my air filter.The MAF sensor wire grommet that fits into the filter housing was left out.My engine showed codes PO171 and PO174! It ran kind of rough,and after re-installing the grommet and clearing the codes everything was ok!

 

well im pretty sure that my grommet is there, because i put my intake in, and made sure i had everything right.

i do also have a possible exhaust leak. can someone describe what kind of sound i would be hearing if i did?