This might help http://www.gusglikas.com/images/Auto...otos/P0171.pdf

 

Stop calling it a "stupid check engine light". Understand it means there is a FAULT.

 

If there was a serious fault it would be evident(i.e: fuel consumption would have gotten worse, misfire, loss of performance, etc..). Only reason i called it a stupid check engine light is because the car is running fine and i have to do a California smog check on it by February. So if this fault doesn't get fixed soon im gonna have to put the car away. So call me old fashioned or what not but im used to there being a problem when there's a problem. On top of that i already took it to 3 mechanics in town and non of them will even touch the car "because its a JAGUAR" . Now with that being said I really truly appreciate all your help guys, especially Jagv8. To this day it amazes me that you guys take the time out of your busy lives help out so many people on these forums. Sorry if im a bit frustrated but im sure you all know how much we all love our S-types and how much id suck to have to put it away especially for something as minor as this.

 

It's NOT running fine. It's running lean and you have codes to prove it. At most, you just THINK it's running fine.

You do have a problem, possibly more than one. It probably SHOULD fail the "smog" (I rather hope it's not genuinely just a smog test).

I know it's annoying to have faults that aren't glaringly obvious but if ignored not only is it causing pollution (which kills, let's not kid ourselves) but also can be burning up your catalysts.

I'd be looking at fuel trims at idle and at fast idle (say 2500rpm) if I'd carefully checked for the common causes and they were not the problem. I'd make sure it runs CL (closed loop) on both banks and so on. Nothing new, I've said this before for those codes.

 

Yes, keep checking things...

What JagV8 is trying to convey is dead on.

My car was running fine..Then I started noticing it feeling "a little slugish"... Then when stretching out a gear, hitting high rpm, it triggered the light.. I wouldn't stay lit, and the car kept driving OK otherwise.. Ended up being a failed cat..That I think I caused by running cheap premium fuel with ethanol in it...

Just saying.. As annoying as it is, the car is sensing something wrong. With some patience and going through things one at a time, I'm sure you'll find it. Do the tests that JagV8 suggested and post up the results. My guess is someone will see something that may point you in the right direction..

Oh, if you didn't do the "dish" soap test in Gus's article, I would. You would be amazed at what leaks you can find that you didn't see. I've done it with carb cleaner in the past as well.. Listen for a change in engine rpm or a stutter.. But Gus's way sounds safer than spraying flammable liquid around a running engine..LOL..And gives you the same result.

 

The good news is, that with both P0171 and P0174 it's unlikely both cats died at the same instant
An air leak or some other common-to-both-banks cause is far more likely.

 

When I was tracking down my problem with my car recently I used TB cleaner. I had 2 cans in hand and I began spraying liberally and with direction, when the car began shacking I hit the spot. Made the repairs and all was good.

SRJag, all indication leads to a vacuum leak, you can spend much time looking for someone to tell you differently but the people on this page are truly trying to help and not mislead you. We are trying to help.

 

Hey Guys, Sorry if i came off wrong..I never meant to say/mean that you were trying to miss lead me. I meant that I hate the way these things are hard to spot. So im truly sorry if i offended anyone.

Anyways Tomorrow after work ima look for that vacuum leak. Any suggestions on what to spray the tb cleaner/ soapy water?

Oh and something interesting happened today. I started the car before work this morning: NO CHECK ENGINE LIGHT!! idk what happened but it was off. After work it was off and just now as i drove to the grocery store it was still off. I didnt reset it or anything.. it just went away..any thoughts?

 

Using either one will work. Using the TB cleaner will cost you a few dollars and has a directional straw the soap spray will cost less and do the same thing. In either case both are non flammable. Both the procedure be Brian and my procedure with the TB cleaner are on my page and I would not recommend anything I would not do myself.

 

Actually we're (usually) quite thick-skinned, and besides some of us have had pretty much your reaction in the past (blush). Not quite the same, but the frustration (along the lines of "why can't I fix this sucker" - different car, not the jag).

There are DTC PDFs in the workshop manual and some in the FAQs here. They detail when codes turn the light on & when it goes off. What you see now is what happens when a fault is not solidly there. Possibly a good time for the smog test but ONLY if you check the "OBD monitors" (google for info) are set, as I guess they'll allow at most 1 or 2 that aren't.

If the monitors aren't set, codes often cannot be flagged as the PCM just can't figure out what data to trust and what not.

The intermittent codes you have could be a leak that's now sealed. Maybe the weather is the reason. If the codes stay away, TB spray is not going to find a leak if it's no longer there

 

srjag, not to get off topic here but I have a comment for Gus on this piece:






Gus, the above piece that is pictured is the fuel rail inlet bracket located at the rear of the intake manifold correct? The bracket is there for the protection of the fuel delivery system incase of a major front end accident. Brutal has indeed stated the importance of putting the bracket back in place. I know its a pain to remove and install but it is there for a good reason.

 

Whoa! Nice catch Rick.. I missed that!

Yea, Gus (and any others doing that)... It was all the rage a while back to remove it until Brutal cleared up the actual use and potential hazard if left off... Think lots of flames....

 

Yes I know! I have it in my bag to reinstall and I plan to remove it from the procedure. Yes I know!