dmbfan128

Apparently 100,000 miles and the truck wants a new everything... I recently pulled a the code which said bank 1 lean. I checked the injectors and they seem to be working properly, i also checked the fuses, as well as the fuel pressure. The truck has noticeably lost power and it makes a funny noise when accelerating. Any ideas?

Good old Bill

There is a TSB for the 02 4.2L engines with the black plastic plenium chamber. Thats the thingy between the throttle body and the aluminum intake manifold. A code of PO171 and PO174 will be generated due to faulty material composition of the isolator bolts.

When the plenium chamber is removed to replace the isolator bolts, take a closer look at the two intake runner valves. These valves become disconnected and can make noise. I really have no clue as to the purpose of these valves, but intake manifold (plastic plenium) has to be removed for access both physically and visually.

dmbfan128

I have already replaced the isolator bolts, i just finished replacing the imrc bushings and rods and it is still doing the same thing... Im lost as to what else it could be.

Good old Bill

Too bad my attempts have failed, have you done the choke spray thing to check for leakage. Its still probably a leak somewhere. I've heard of MAF remedies and other guesses, cures have always come from leakage somewhere. Good luck. Get back to us with results and findings.

Question, were the isolator bolts of the green color?

dmbfan128

The new isolator bolts were a dark greenish yes. I'm gonna try a new MAF today and see if that helps and I'm gonna check the injectors again.

SuzukiRider

Youve more than likely have a vacuum leak somewhere.

dmbfan128

So turns out I accidentally broke one of the IMRC bushings last time and didn't notice it. The rod was dangling. However I fixed that and now it's still doing it? How would I go about checking for vacuum leaks and where would be the most obvious areas it could happen?

SuzukiRider

Spray bottle of water works well. Check all the vacuum lines especially the undersides. When you find the leak the engine will bog down when hit with the water.

dmbfan128

No vac leaks I'm gettin angry at this thing now...

dmbfan128

Ok, so for future reference idk about other years but this is what I found out after some research and after a few smog vapor tests. If you have redone the IMRC bushings and those butterfly valves still work, and you have redone the isolator bolts as well as the plenum gaskets, and still get a P0171 and/or P0174 the plenum itself could be the culprit. After awhile they begin to warp and can cause these codes. I just replaced mine and it has made all the difference. Just an FYI.