Hi guys,
Yes, those damn codes are still haunting me. Months ago, my first mechanic replaced my Radiator Overflow Tank due to a faulty Antifreeze Sensor.

That turned into a Coolant Leak that he couldn't find, so the 2 hoses under the Intake Manifold were replaced, as everything else was ruled out. While it was thus torn apart, I had him replace all the other hard to reach hoses. (Thanks for the tip Brutal) That little adventure was 33 days in the Shop.............

That immediately morphed into the 171, 174 codes that are now on constantly. He rechecked EVERYTHING. He replaced the MAF Sensor as I had a new spare anyway. The Upper O2 Sensor were both replaced less than a year ago. He replaced the MAP Sensor. He did a Smoke Test and verified that everything was good and tight, no vacuum leaks. After many fruitless hours of looking for the problem and not charging me for these latest ongoing efforts, he turned me over to another shop with better diagnostic tools.

They did another Smoke Test, and rechecked the hose fittings etc. After their first day of searching, no joy.

Brutal, it does have the new MAF Sensor, and they did verify that it is working properly. He had a funny acronym when I told him that it was brand new. He said that to him, "new" means "Never Ever Worked", so I think that he is being pretty thorough in his methodology. They were closed for the holiday, so I hope to hear good news today or tomorrow. Overly optimistic? Maybe!

Any knowledgeable suggestions are much appreciated, as I can pass them on to this newest shop.
Thanks!
Brian

 

Can you also 'summarize' your timeline. Was your 02 sensors done before or after the big manifold hose replacement project. I'd like to see the progression of the work, and when the codes actually popped up.

sorry, didn't read your thread before putting brutal's quote up there.

 

Link to another thread. For ideas.

 

Clear out long term fuel trim corrections with a battery hard reset.. The next thing to do is to pull up short term fuel trims with a scanner and with the engine running, spray brake clean around the intake gaskets at least as close as you can get. Around the intercooler bellow ducts( theyre 2 piece and slide in/out and are leak sources alot) the throttle body adapter etc...what theyre looking for is a reduction in fueling on short term fuel trim. This indicates a vacuum leak. Forget the smoke test and use the cars electronics. Leaks can be so small and under areas youll never see smoke. But you can get the spray in areas you cant see or get to and then by monitoring short term fuel trims you can see when it picks of the spray without ever hearing a idle speed change

 

Obviously, if the codes came up right after the manifold was put back, there is an intake leak somewhere. With the SC, there are a lot of possibilities. I would pull it apart carefully, one piece at a time and find the part that is leaking. There are some other posibilities but it would be logical to think the manifold removal did it. Also consider a dirty fuel filter, a dirty or dragging injector, a bad MAF, or an exhaust leak before the catalyst.

 

Hi guys,
Thank you so much for the good advice, I truly appreciate it! I'll copy these notes and take them by the mechanic tomorrow for him to try them out.

My Upstream O2 Sensors were replaced in Aug of '09. The 171,174 codes reared their ugly heads immediately after the manifold was removed about 2 months ago. Seems to be pretty clear that something went awry from that job, as they popped up as I drove the car away from the shop.
Thanks again, I'll let you know what they find!
Brian

 

I think you're on the right path now Brian, I feel good about this.

I asked for the OP from that first thread to summarize his repairs also, in case there's another clue in there.

Check the part and full load breather stubs, possibly cracked during removal and reinstall? I hear they're brittle on those 4.0s.

 

Hi all,
It seems that my nightmare has finally ended. After $1400.00 in follow-up work, and spending a month in this newest mechanics garage, the codes are now gone, and the Jag seems to be finally back in good health. We never found a "Smoking Gun", but rather, found many possible suspects such as:

Vacuum Hose off MAP Sensor was short.
EGR Bolts were only finger tight.
Lower Intake Gaskets showed signs of minor leaks.
Supercharger gasket showed signs of minor leaks.
More bolts on these two components were only finger tight.

After tightening everything back and replacing a slew of gaskets and O-ring Seals, the codes are now gone. As much as I personally like my first mechanic, he really did me a disservice with his shoddy work, and I'll not be using him again.

Thanks to all who offered information and advice on this issue, it was greatly appreciated.
Brian

 

nice, now enjoy it for a while its like getting a new car all over again, right?

 

Brian, I am so pleased to got it fixed. Kudos to you for not giving up!

 

Thanks guys, it's SO good to have her home again! Matt you are 100% correct, after a month's absence, it is almost like getting a new car! As they say, "Absence makes the heart grow fonder), and I think that works double for a Jag! Hopefully, my luck will hold up longer this time............
Regards,
Brian