P0171 & P0174 Both Banks Lean
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From: Dallas TX
I started checking out this thread due to the fact that I have been fighting 0171 and 0174 for at least 3 years on my 05 s type with the help of members over in the s type section. I can completely relate to your frustration with these codes. I have to say that jagv8 has participated a great deal in trying to help me but alas, I still have not won that battle. To the point that I have surrendered and bought another car this weekend (the 09 xf) because I just cant do it anymore. I have done everything suggested by jagv8 and too many others to list, but I lost the battle. I smoke tested engine twice, changed too any parts to list, done the propane and carb cleaner tests, monitored fuel trims like crazy and on and on and on. I believe that the problem, at least in my case, is fixable if I were to turn the car over to a jaguar dealer with an open checkbook. I do believe there are hundreds of archived threads about 0171 and 0174, which indicates to me that even though this subject is documented in all other car forums on the internet, it seems to be a particular nuissance to our Jags, but I bet there will be rebuttal to that statement. But....my wife loves her Jaguars and consequently, I bought one with less than 1/2 the miles as on my old s type and I am praying I don't have to battle the lean codes on this car for at least a while.
Some of the responses trying to help those of us asking for help do come across a little short sometimes but probably not intentionally. I found I had to suck it up and appreciate the vast majority of people who really are well intentioned. If you find that freaking cause of your lean codes, please post it so I can see if its something I have not yet checked on my s type.
Some of the responses trying to help those of us asking for help do come across a little short sometimes but probably not intentionally. I found I had to suck it up and appreciate the vast majority of people who really are well intentioned. If you find that freaking cause of your lean codes, please post it so I can see if its something I have not yet checked on my s type.
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From: Dallas TX
After A LOT of diagnoses, turns out the rubber seals on my plenum were the culprit. Instead of replacing all the rubber seals I decided to try and fix what I had. I pulled all the seals out, cleaned them and the mating surfaces then coated all with petroleum jelly. Prior to putting everything back together the LTFT’s were pegged at 20%, now they hover around 5%, I’m happy with that.
I’ll keep an eye on the trims for a while, if they do start going up again I’ll spring for the new seals then, but I have a feeling this will last for a good while.
I’ll keep an eye on the trims for a while, if they do start going up again I’ll spring for the new seals then, but I have a feeling this will last for a good while.
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Joined: Nov 2014
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From: murrieta, calif
After A LOT of diagnoses, turns out the rubber seals on my plenum were the culprit. Instead of replacing all the rubber seals I decided to try and fix what I had. I pulled all the seals out, cleaned them and the mating surfaces then coated all with petroleum jelly. Prior to putting everything back together the LTFT’s were pegged at 20%, now they hover around 5%, I’m happy with that.
I’ll keep an eye on the trims for a while, if they do start going up again I’ll spring for the new seals then, but I have a feeling this will last for a good while.
I’ll keep an eye on the trims for a while, if they do start going up again I’ll spring for the new seals then, but I have a feeling this will last for a good while.
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From: Dallas TX
Waedo, which seals are you referring to? Again, I am still fighting problem with exact same symptoms as yours, but I have replaced all the plenum gaskets with no effect. Again, my issue is on a 3.0 s type though. What I don't get on mine is that the cel comes on and stays on even though my 0171 and 0174 are only "pending", not hard fault sets. I don't get it.
Jake, one way I found to narrow down that leak, disconnect all of your vacuum hoses and plug the ports then watch your fuel trims, if they don’t go down and you have good fuel pressure you have a leak between your MAF sensor and heads (assuming the engine is in good shape). With all of your hoses disconnected spray some carb cleaner directly on the joints and watch your trims, when they start restricting fuel you’ve found your leak, or in my case leaks.
In your case, I would disconnect all of the hoses and plug the ports, check the manifold joints with carb cleaner. If all the new gaskets are doing their job then start re-connecting the vacuum hoses one by one, watch your fuel trims to pin point which one is leaking. If you have good fuel pressure and good compression, then you have a leak somewhere.
If all of this fails, either take it to someone to have it smoked or buy the smoke machine yourself, they have some on Amazon for around $100.
Last edited by wardo5757; May 28, 2018 at 10:25 AM.
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From: Yorkshire, England
Waedo, which seals are you referring to? Again, I am still fighting problem with exact same symptoms as yours, but I have replaced all the plenum gaskets with no effect. Again, my issue is on a 3.0 s type though. What I don't get on mine is that the cel comes on and stays on even though my 0171 and 0174 are only "pending", not hard fault sets. I don't get it.
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Senior Member
Joined: Aug 2012
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From: Dallas TX
Waedo, which seals are you referring to? Again, I am still fighting problem with exact same symptoms as yours, but I have replaced all the plenum gaskets with no effect. Again, my issue is on a 3.0 s type though. What I don't get on mine is that the cel comes on and stays on even though my 0171 and 0174 are only "pending", not hard fault sets. I don't get it.
I have to say, of the many nationwide rides we’ve had over the years, southern Cali was by far the most astonishing. I can see the lure to that area, the beauty may just outweigh the government…
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Joined: Nov 2014
Posts: 293
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From: murrieta, calif
Totally off the subject Jake, I was just in your area last week. Me and some buddy’s road our bikes to Vegas then Southern California, up the PCH from Oceanside to Malibu, then the mountain ridges and valleys of Glendora and Mulholland and the obligatory Hollywood touristy things.
I have to say, of the many nationwide rides we’ve had over the years, southern Cali was by far the most astonishing. I can see the lure to that area, the beauty may just outweigh the government…
I have to say, of the many nationwide rides we’ve had over the years, southern Cali was by far the most astonishing. I can see the lure to that area, the beauty may just outweigh the government…
as to my s type fuel trims......they seem to be classic vac leak indicators. The ltfts are pegged at +19.5. With throttle they drop. The peculiar thing is that if I put the car in park and let it idle for about 20 minutes the stfts drop to below 0 and then the ltfts also slowly drop while car is still in idle . Then if I drive the car, the ltfts will start to climb again each time I come to a stop.
EVAP monitor NEVER completes
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Senior Member
Joined: Aug 2012
Posts: 160
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From: Dallas TX
ok, Wardo....that comment on the govt got a good chuckle out of me.....no, im not sure ANYTHING could outweigh the knucklehead govt we have. Its embarrassing and infuriating at same time.
as to my s type fuel trims......they seem to be classic vac leak indicators. The ltfts are pegged at +19.5. With throttle they drop. The peculiar thing is that if I put the car in park and let it idle for about 20 minutes the stfts drop to below 0 and then the ltfts also slowly drop while car is still in idle . Then if I drive the car, the ltfts will start to climb again each time I come to a stop.
EVAP monitor NEVER completes
as to my s type fuel trims......they seem to be classic vac leak indicators. The ltfts are pegged at +19.5. With throttle they drop. The peculiar thing is that if I put the car in park and let it idle for about 20 minutes the stfts drop to below 0 and then the ltfts also slowly drop while car is still in idle . Then if I drive the car, the ltfts will start to climb again each time I come to a stop.
EVAP monitor NEVER completes
The LTFT should go down when you're on the throttle because there is less and less vacuum the harder you're on it. That being said, given your EVAP PID never completes, have you tried unplugging ALL of your vacuum lines and plugging all the ports to see what that does to your trims? For me it only knocked my trims down 2-3%, fuel pressure was good so I knew it was either manifold gaskets or a cracked manifold at the areas I was spraying with the carb cleaner (and getting a trim response).
Last edited by wardo5757; May 28, 2018 at 09:11 PM.
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