Hi all,
I have had this problem for the last 5 weeks- i get fault code POP174 and PO171 (system too lead) which pops up with restricted performance for about 10 mins about 2 times every 200miles.
Then it happens as soon as i get home i plug in the laptop and do a diagnosis/look at live data and the fuel trims are always very low and its not running lean.

I've checked all the pipes for air leaks and its fine!

I know (i think) its got to be a air leak for it to fine with low fuel trims and the next thing its running lean, but not once in the last 5 weeks has the restricted performance been on then i plug in my laptop. I also drove for a hour with my laptop on the seat but still no fault, but next day within 30 mins driving i had restricted performance again for about 5 mins.

Any ideas?

Thanks Simon.

 

Check the IMT O rings for any signs of leaks.

https://www.jaguarforums.com/forum/s...ck-pics-49214/ thanks Rick!

 

Just checked them and no sign of them leaking.

Thanks.

 

I chased that one for quite a while. First, of course, check all vacuum lines and connections for leaks (thanks to Rick there are pics). I couldn't produce a leak but by virtue of having 2 3.0L S-types on-hand, swapped MAFs and isolated the problem to the MAF. I wouldn't necessarily fork over ~$100 for a new MAF as a shot in the dark..but if you've elminated everything else.....oh...wait! just noticed you have MY2002 - but "late 2002" and in the UK....if it is not a facelift car, it is probably the vacuum elbow under the intake manifold...but I'm guessing you have a face-lift model...

 

Cheers, yes its a facelift model. As you find out it was the MAF, was it leaking or was it giving out wrong info to the ECU?

 

More than likely the MAF is shot, you could try MAF cleaner and see what happens:

https://www.jaguarforums.com/forum/s...ics-faq-52720/

 

I agree. Try cleaning out the MAF with some MAF cleaner. If that doesn't work, then I would say replace it.

I actually had the same codes a few months ago and replacing the MAF did the trick.

 

Neither, per se. I ran real-time data from the OBDII port and found it was reporting greater airflow at the same conditions than its twin in the 03 car. Swapped 'em and the difference was lesser but still there. No codes either car after the swap. Swapped back and codes returned on the 05. So put the "bad" MAF in my daughter's car and sent her off to college. Both were good for a year, and she got P0171/174 and RP about 30 mins from home at the end of a 6 hr drive after about a year later. Swapped the "bad" one back to the 05 and sent my daugher back to school with the good one. Ordered a replacement and got 'round to fitting it about 3 weeks later. No codes in the period while it was on the 05 at the end.

 

I would be looking for a vacuum leak. See if you could have a smoke test done on your engine it will locate a leak from front to the back. I have three links that could help one to locate the problem if you do it yourself and the other is about my leak that caused the same codes. The one posted by Rick is related to your model year. I hope this helps.

Link http://www.jagrepair.com/images/Auto...otos/P0171.pdf
Link JagRepair.com - Jaguar Repair Information Resource

 

Hi all,

Thanks for all the replys, this is the place to come to for help. I posted the same question on the UK Jaguar forum and not 1 reply.

aholbro1, i love the bit in your post- So put the "bad" MAF in my daughter's car and sent her off to college'

So im going to take so live readings from the MAF and vacuum and then wait until i get 'restricted performance' and recheck readings.

I will post my findings.

Thanks again for all the help, Simon.

 

Hehe, Simon - I really wrestled with that decision because daughter's school is 6 hrs distant - but both Motorcarman and a friend at work who has an 01 S-type and is a forum member and also a car-guy kept advising me, "It causes codes in one car, but not the other...put it in the one that makes it happy and roll-on!"

Not quite so bad this year as little brother and is F-150 is also on-station there and in reality, neither of them NEED a car for school as they live on-campus, so they should surely be able to get by on 1 if necessary - infact, I hauled daughter's home last weekend for a coolant leak...learnt this afternoon the rad is unrepairable so I've gotta find one and install it before end of next week when they get home for "fall break."

I made several posts on P0171/174 and snagged a great tutorial on fuel trims from (XJRGuy) I think it was...I'll see if I can dig them out and post links back in an edit. Neither MAF was out of range or anything, just significantly different at idle, and at various rpm's/loads. Fuel trims were not perfect but not terrible either. IIRC, the "bad" MAF was reporting higher airflow, which should have caused Rich, not Lean codes if it was lying....but there you have it.

 

Well i changed the IMT o rings today as i found the bottom one leaking, but its still going lean. Next i think is the air flow meter.

 

Simon here's the thing, it could be the MAF, sometimes a cleaning works and sometimes not its a difficult call.

Also you having a late UK MY 2002, I don't believe that your engine has the elbow located under the lower intake manifold. Here in North America our MY 2002 did and that is also a very well known problem here that throws the same codes.

 

Thanks joycesjag, mines the later engine, so no elbow located under the lower intake manifold.

How do you clean the MAF?

 

Get a spray can of MAF sensor cleaner at any auto parts store. Remove the two screws (usually Torx, but sometimes Phillips) that hold the MAF sensor in place just after the air filter housing. Unplug the MAF sensor electrical connector. Spray the MAF sensor with three or four good shots of MAF sensor cleaner. Do not touch the element with your finger or with the spray can's nozzle. Allow the MAF sensor to dry for ten to fifteen minutes. Repeat the cleaning process. After the MAF sensor is thoroughly dry, re-install it....

Crank up your engine, take the car for a test drive, and if you're lucky you will have fixed your problem....

Let us know....

 

I would replace the upper and lower intake gaskets before the mafs. Less expensive and known issue too.

 

Worth an OBD tool for live data and look at LTFTs so you at least know if it's an air leak and roughly where.

 

Thanks, but both upper and lower have been changed.

There is no MAF cleaner for sell in the U.K.

I have watched live data and theres no signs of a air leak. Then looking at live data both vaccum and fuel trims are normal.
The engine just goes lead for about 5 mins in a hours driving and out of all the times ive been in the car watching data it does not happen.

 

well then just leave the live data up. itll never happen again. that was easy

 

I had this on my R, turned out I'd just forgotten to refit the plastic hose that connects the intake tube to the top of the crank case. It has to be an air leak somewhere or MAF so you just have to work your way around the intake and replace or check everything that seals it.