A bad PCV Valve also caused PCM 174 (System Too Lean ) along with the poor fuel economy . I am not an expert and since you're talking about about this code I thought I should pop in .
My dad's car throws this code and it was in the service yesterday and they called they will replace PCV , it was a smoking gun in our case .

 

I just need to replace the O-rings on the breather hose to solve my P0171/P0174 vacuum leak problem. Does anyone know the OD/ID size in mm for the two O-rings. I really don't need to replace the entire breather hose. I've cleaned the TB an MAS sensor. The O2 sensors are good. A/F ratios are super lean.

 

Your cats will be next so a proper fix that gets trims to within a few per cent of zero is needed and fast.

 

You're correct. The design for the breather pipe to the PVC is "el cheap." o-ring seals in a high vibration area are sub standard. I'm thinking of inserting a nipple in each end and using a proper vacuum hose.

 

Since my gas mileage is still up where it normally is the o-rings and about 100 miles will tell me the story.

 

No it won't unless it's wildly bad. LTFTs will tell you.

 

Replaced both o-rings on the breather hose and all readings are spot on again. Of course the dealer wanted to sell me the entire breather hose. I'll get some miles on it and report back again.

 

Hi , the same problem I have on my str.Please advise !
I have checked shake test for any leak , replaced maf , replace breather valve, checked throttle body done almost everything, eml light did not came until a petrol fill up, after that again !!!!!! What to do guys this jag is a painnnnnnnnnnn

 

Need car details and get an OBD tool with live data then post LTFTs. Plenty of threads about what/how/when.

 

Stop throwing parts at it!! Why were all those things changed?

You must work with the codes or you are just shooting in the dark.

Have you checked for codes? Have you cleared any codes you found and did any codes come back after you did this?

What's a shake test?
.
.
.

 

Yes what is a shake test?

 

The O-rings on the breather hose that runs from the TB to the PCV, has an o-ring on each end that literally wears flat and get hard over time. Don't buy a new hose assembly. Just find a garage mechanic that will match them. Vacuum leaks aren't rocket science.

 

k&N filters are great; but, you must remember that they are less restrictive and normally the MAF should compensate to get you to the correct A/F ratio.

 

My 2003 3.0 v6 has now travelled several hundred k's without fault...

I was forced to replace the battery when the old (original) one failed and used that as the catalyst for a real good check... There were no vacuum leaks... Air filter was filthy so was replaced.

OBDII monitor showed MAF flatlining... A clean with special spray only delayed the fault.... A new MAF has fixed the problem...

Cheers,

 

Back to the drawing board. MAF sensor cleaned, new clamps on TB boots and air breather hose has new O-rings. Took a 60 mile drive and the P0171/174 codes are back with the ECL. Can't find a vacuum leak anywhere else. This series of codes started showing up after a 80k check on the car. Any thoughts?

Also, have these scans:

 

See #49

 

Do you need to see idle and 2500 revs?

 

Best way to get ideas.

 

I had these recurring on the 05, no joy finding vac leak. Live data didn't really reveal anything until I started to compare it to the 03 at similar rpm/load. Then noticed the MAF on the 05 was consistently reporting higher airflow than the 03 for similar rpm/load. Swapped MAF's between the cars and the codes went away for about a year, but eventually surfaced on the 03 which was now running the 05 MAF. Swapped 'em back to cure the 03 and ordered a new MAF for the 05. No codes in the 3 wks I shifted the original 05 MAF back to the 05 car until new one arrived and I found time to fit it. Everything fine for awhile, now the 05 periodically sports a "MAF invalid or out-of-range code" don't remember the number. May put the original MAF back on now that it's had a year or two's rest......

Of course...that was all backwards because if the MAF was truly over-reporting, the O2 sensors should have been seeing "Rich" vice lean, but I didn't try to reason it beyond "Swap the MAF's and both cars are happy happy"

 

I see some el cheapo MAF sensors on ebay. Any thoughts on which aftermarket ones are junk?