Arrgggg , I thought I had this fixed but I have now pulled the code 4 times since my last "fix". Here is the strange part (at least to me), every time it has been at speeds in excess (we will just leave it at that) of 80MPH. Here is what I have done so far in order over the last year.

- replaced brake booster vacuum hose
- replaced breather hose to new style
- replaced MAF sensor
- replaced fuel filter

The last 2 were done just a few weeks ago and seemed to make the biggest improvement over how frequent I was pulling the code (it was actually happening so much I parked the car and drove my truck that gets a wonderful 11 mpg's). Not fun when commuting 100 miles per day!

I have checked all/most of the other vacuum lines and have found no problems.
When searching the forum I saw several people have replaced the IMT O' rings. Other then this whats next?

 

IMT o-rings and intake manifold o-rings are next in line!

 

I ordered up the IMT O'rings today, I had a feeling I would here the intake manifold gaskets were next. I'll have the new parts tomorrow and get the put in. Hopefully that will be the fix, if not then I planned on doing a spark plug and coil replacement next month. I'll replace the manifold gaskets then.

 

waterfowlhntr, your problem is the upper intake valve. Because you are getting only the P0171 code, that is specific to a bank, not a complete intake system problem. Granted, since you are at it, might as well change out both of them. THat should fix your issue.

 

Crossing my fingers, thanks! I'll update when the job is complete and if it truly is fixed.

 

Lookin' forward to hearin' good news

 

OK, new o'rings in last night. Let me tell you, I wish all repairs were that easy!
Drove into work this morning and tried to keep it above 80 MPH as long as possible and so far no problems! I'm not going to call it fixed yet until 1 full week of driving , I will update then.

 

OK, this is NOT FIXED!!! I popped the code again tonight at 78mph.
Whats next? H.E.L.P!!!

 

PCV Hose might be culprit but generally it should be associated with 0174 code . We did replace EGR Valve and PCV Hose in our case , these solved the problem

 

waterfowlhntr, since you have replaced the "big 3" (PCV hose, brake booster hose, and the IMT o-rings), then that only leaves but a few things. It is looking like your next step is going to be replacing the o-rings on the intake. You have 2 choices here. You have an upper set and a lower set of o-rings. Most of the problems are with the upper set, it is also just a little bit more work to replace the lower o-rings. So, it is a question of whether you want to spend a little bit extra now to replace the lowers when you replace the uppers or take a gamble, hoping that it is only the uppers that are the issue. The down side to just replacing the uppers is you may have to go in a second tome to go after the lowers.

I would also do a good inspection of the plastic portions of the intake when you are there. I would also do a detailed inspection of the bellows piece that is between the air box and the throttlebody. If you got a small rip in that, it can lead to some confusing things. Granted, I would expect it to cause both P0171 and P0174 codes. But, it sounds like you are on the edge of a problem and it may be that the computer is simply a little more sensitive to the one side.

 

+1 with thermo!

BTW Fel-Pro makes aftermarket gaskets kits at great prices (upper and lower intake gaskets that is).

Make sure to check the valve cover seals (gaskets) they are prone to leaking into the sparkplug wells as well.

 

You need to replace the upper and lower intake gaskets. The lower are not hard. You just take out the 4 bolts and lift the fuel injector manifold up enough to pic out the old ones and feed in the new ones with your finger and wiper the mating surfaces clean. Cause past that the next most common is the brake booster itself.

 

RegentV12/Thermo, I had planned on doing a plug replacement next month and at that time was going to replace the upper o'rings and PCV valve. I had not planned on doing the EGR but if it is not difficult then I will do it also. Question when doing this that is unrelated to the code issue I'm experiencing here. Should I also change all coils as precautionary maintenance while doing this job? Car has 175k on her.

Thermo, I did inspect the bellows very thoroughly just last week (again) and there were no signs of cracks. All fittings going into it all have zip ties on them. I'll research doing the lower manifold gaskets before taking on the plug change. I'm with you on this, I would like to only do the repair once.

I guess I will keep her under the 75MPH until I can do the plug/manifould gasket change. Damn, she sure is fun to drive faster then that!

 

@175k I WOULD AT LEAST REPLACE THE COILS ON THE BACK. YOU DONT HAVE A EGR VALVE(OOPPS YOURE IN CALI MAYBE YOU DO ) YOU HAVE CARS BUILT TO DIFFERENT SPECS DESTINED FOR CALI, JUST LIKE LAWN MOWERS

 

Thanks Brutal. Since you suggest changing the rear as might as well change them all? Not sure on the EGR, where is it located?

 

Heres a picture of what Brutal said in post #12

 

This problem has slowly worsened over the last week. I took it to my local shop today to have a smoke test done and they discovered 3 vacuum leaks. #1 is at the throttle position sensor O ring, #2 brake boost hose fitting going into the intake manifold, #3 vacuum to purge hose fitting into the intake manifold. The positive side is it is quite cheap to fix. Parts will be in Monday so will update again once they are in.

 

Reading the thread, I was thinking what you just posted as #2 and #3. I started adding them to the "X-type enhancement package", I even did and ECM update and TCM update while I was at the dealer. At your mileage though, I don't think a TCM update would be necessary. Good luck, those codes can be tricky if you hit all the big points and it still comes back.

 

Geez i guess it takes pictures now to get thankyous!!!

 

Brytal, a picture is worth a thousand words.

Had my shop replace the 2 vacuum line o rings (#2 and #3 from my previous post) yesterday. They were not able to take care of the throttle position sensor o'ring due to the one piece design.
So far so good. I think my cat is back!! I'm going to call this fixed!