Car is 2002 x-type 3.0 I am still getting 171 and 174 codes. Found bad PVC Breather hose and replaced it but the Brake booster hose still looks good, like it was replaced before I bought the car. On the dash The Cruise is not avail. at times comes on and the Brakes still feel like they have no vac. assist. The booster doesn't seem to be leaking. Car is running smooth, except when the Cruise warn. is on I have to accelerate slowly or car misses bad. Any other ideas..

 

jasper, have you replaced the o-rings on the IMT valves yet. That would be the next place I would look. Did you replace the spark plugs recently? It may be that you have a leak between the upper and lower intake manifold. I would also look at your bellows piece between your MAF and the throttlebody to make sure you don't have a rip there. That would also cause what you are seeing.

 

I"ll give the O rings a try, the other things look ok. I had a tuneup about 1 1/2 year ago. Had been running good till a couple of weeks ago. The mech had replaced the gaskets then. I can clear the codes and it will run about 25 miles before things come back. I"ll give them a try.

 

I just went through this with my car. After searching the forums I found a couple of ideas that I had not tried yet. One was cleaning/replacing the MAF sensor, I choose to replace it. Also replacing the fuel filter since my car has 170k miles and I had never done this (yikes! Is fuel supposed to be brown?). No problems since I did both.
If I was going to do it again I would start with the fuel filter, it's the cheapest then work from there.
FYI - all this was done after inspecting the vacuum system first.

 

Jasper, I would also recommend cleaning the MAF sensor. That can cause what you are seeing as the MAf is not registering all the air that it should, leading to erroneous calculations in the computer.

 

If the o-rings do not work yook at the plenum gaskets, upper lower fuel rail, I had a miss on all 6 cylinders, replaced those and the injector o-rings, also the battery was replaced, the miss and all codes including catalytic converter running hot code went away, runs like new now.

Hope this helps