I have had an intermittent and annoyingly persistent problem for 3 months or so with my 2004 Jaguar X type 2.5 petrol ; running out of ideas and the will to fix it.
Car performs excellently for a while (well a few miles) and then all of sudden it is not possible to accelerate beyond 3000 rpm (engine shudders). If the engine is already revving higher than 3000 rpm (e.g. doing 80 mph or so) then it cuts out and only kicks back in when revs drop below the 3000 rpm threshold. Try to accelerate over 3000 rpm and the engine shudders again.
However, If you pull over and let the engine idle for about 45 secs then the problem clears itself, driving is as normal, full acceleration, performance etc, until it re-occurs some miles later.
MIL on, error codes P0171, P0174 diagnosed
Erratic performing 02 sensors diagnosed for Bank 1 sensor 2, and Bank 2 sensor 1, thus new sensors installed. All 02 sensors operating correctly on subsequent diagnosis. Spark plugs changed at same time. No difference to problem though: still there, still being infuriating.
Checks done for vacuum leaks, none found, but PCV hose changed anyway. Also changed PCV valve (old one rattled, new one rattles as well!!). New MAF sensor. Again no difference in performance, car does it's thing at 3000 rpm at intermittent yet fairly regular intervals.
New IMT rings installed. New fuel filter and injection cleaner added to fuel. Fuel lines cleaned. No difference.
We are running out of ideas. What makes this apparently difficult is the intermittent nature of the fault. When it runs right it runs perfectly, and when it runs badly, it is a shocker.
Why does the fault appear to clear itself when the engine is idled?
Is this a mechanical fault, an electronic fault, or just a really temperamental car!
The local Jaguar dealers suggest that the injectors might need cleaning. However, if the problem was with the injectors surely the problem would occur all the time, rather than intermittently?
Thank you.
Have exactly the same issue on 04 jag x type 2.5. So far have replaced fuel filter, air filter k&n, plugs ngk. Codes cleared, same issue. Seems to appear when air temp is cold and eng is warm.
Am replacing upstream O2 sensors and cleaning MAF next. Will keep you posted if it clears up. Did you ever find the cause?
Only suggestion I have right now, would be to either borrow, or purchase a fuel pressure tester, route is as such that it is visible at base of windshield & tape it to the windshield while driving and observe fuel pressure during different conditions that your experiencing. When it decides it doesn't want to go past 3000 rpm's, that's when I'd pay special attention to it. Any reduction in pressure would give me reason to change fuel pump. If nothing else, you can rule that out if all is well. I'm thinking that maybe stopping to idle, gives it time to play catch-up.
Testimonial: "Thank you for your reply. That is sort of what I was thinking, only I do not want to really due to cost potential? Thank you for your thoughts."
Tell me this, does it happen more on a hot day, than on a cold or cooler day? Does it happen more when tank is over half full, or under half full? Have you taken notice to any of these?
Observed temperature gauge?
Can't help but think fuel starvation, with both codes indicating lean. Try one other thing, add a couple of bottles of gasline antifreeze to the tank, mix it a bit with a few gallons of gas and see if that makes a difference at all.
Methyl alcohol, used to prevent fuel lines from freezing in winter. I found on one vehicle I had with failing fuel pump, that if this was added to tank, it was less likely to quit on me, as well as one incident when plug wires & plugs were due to be changed, it eliminated stumble & poor acceleration as well, but as soon as I added just gas from pumps, it started to spit & sputter again.
Hi,What does it mean if it happens more when the tank is less than half and on cold days?
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I have exactly the same problem P0171 P0174 on my X-TYPE 2004 2.5, I changed the fuel pump, cleaned injectors, changed fuel filter, clean the tank and the car seems to be fixed, but 2 months later started with the same problem. One thing I note is that it begun check engine light turns on when the tank was lower than 1/2 and it turns off when the tank is more than a half. But now the problem persists in any way. Please any sugguestions!
This is the self same problem really that I posted about. Whatever you do never seems to resolve the problem because it is a cumulative problem, at least in my experience, and it seems to reoccur every 8 weeks or so. What seems to happen is that the ecu registers a fault somewhere in the air/fuel mix and once the accumulation of this fault data reaches a critical level it triggers the MIL. Our solution now after much anxiety and frustration has been to buy a OBD11 meter, turn off the MIL, disconnect the battery, connect the cable terminals together and leave it like this for a few minutes. Then reconnect battery, start car, reset radio etc and normally fault will not occur again for 8 or so weeks. You need an OBD11 meter to turn off MIL because just disconnecting the battery will not do this. Using cheaper grades of fuel also seems to be an aggravating factor, we only use premium grades now (e.g. Shell Vpower). It seems to be an annoying and persistent problem and is also experienced by some other jag owners locally. The root cause is probably a tiny air leak somewhere that is not enough to be identified but is enough to register on the ecu and accumulate over a period until the crtical threshold to trip the MIL is reached. Hope this helps
Hi again, thanks for your advice, I tried following the steps but the problem persist. But I think my problem is that I cannot reset the ECU, I connect the cable terminals together and leave it for minutes even a day and when I reconnect them the radio doesn´t lock, thats what I guess I´m not doing a good reset. Is there a special steps to reset the computer or just as you said?
I am not sure why you are having this problem. When I disconnect the battery and touch the terminals it clears the ECU memory, at least for these fault codes, do you have a secondary power source that maintains sufficient power to keep the ECU memory and the radio memory in tact? Alternatively is your radio code deactivated, which would account for why it is not resetting on power down. Remember that you do need to clear the fault codes and turn off the MIL with an OBD11 meter before you disconnect the battery, if you are not doing this the ECU will retain this information. Sorry I can be of no real help here.
¡Eureka! After seven months of frustration and spending a lot of money and doing a lot of things(described right here) I decided to replace one O2 sensor for testing in bank 1 so inmediatly one code was cleared, I replaced the other one and know my Jaguar have no codes. I replace the sensor 2 in bank1 and sensor 2 bank2 (both black connectors). I used NTK universal o2 sensors($40 dlls each).
I know this may not be the only problem causing these codes codes but it worked for me.
Previous to this, I tried with these:
1.-Change fuel filter
2.-Check for vacuum leaks(not found)
3.-Change the air filter
4.-Change the fuel pump
5.-Clean the fuel tank
6.-I used Luccas injection cleaner added to fuel
7.-Reset the ECU(I bought an OBDII scanner)
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It will likely be a vacuum hose split or broken somewhere around the throttle body
I have 2002 x type the gear box code came on and I was barely able to make it home. It was running great last night, but it is cold outside
SOURCE: p0171 and p0174 codes
P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)
If a car has a check engine light on and has P0171 and P0174 codes stored, the most likely cause is a vacuum leak. These codes are set by the car’s computer when it sees too much oxygen in the exhaust. Excessive oxygen readings in the exhaust will set lean codes. This does not mean that the oxygen sensors are defective. It is a common mistake for people to replace oxygen sensors when lean codes are present. Just because the code is related to oxygen sensor readings, it doesn’t mean that the oxygen sensors are bad. If both of these codes are stored this means that both banks of the engine have excessive oxygen in the exhaust. If the oxygen sensors are replaced it’s most likely that the same codes will reappear. It is very uncommon for two oxygen sensors to fail at the same time.
Therefore the most likely cause of P0171 and P0174 codes is a vacuum leak. The source of a vacuum leak can be one of many things. The most common cause of a vacuum leak is a leaky hose. Vacuum hoses over time can become dry and brittle. The rubber deteriorates and can leak causing a vacuum loss. Many times a leaky vacuum hose can be found by listening for a hissing sound. A large vacuum leak can even make the car run rough at idle. In some cases it will not idle without feathering the gas pedal.
SOURCE: OBD codes P0171 and P0174
Look on the passenger side of the intake at the rubber elbow attached to the big black plastic tube and then to the intake manifold. Make sure it is not sucking shut and maybe a small hole in the bottom of it.
SOURCE: 1999 ford taurus emission reading p0171 and p0174
just tune up ur car periodicly, clean filter. clean ur sparkplug.
SOURCE: poor idle dtc P1151, P1131,P0174, P0171. runs ok
Change plugs, and Mass Air Flow sensor. This should do the trick
SOURCE: codes P0171, P0174, P0440
This is usually an oxygen sensor, replace the O2 sensor located above the catalytic converter before replacing the evaporator purge canister.
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Hi, Sorry if request is long, but I have supplied all the relevant details. There have been many other similar posts on P0171 etc, and none of the solutions have worked in this instance. I was canvassing new ideas, rather than the well versed solutions, if that is possible. Thank you for your patience. Regards
Hi, we have tried to account for as many variables as possible . But there seems to be absolutely no constant with regard the problem: the tank can be full or quarter empty, it can be hot or cool, wet or dry. Driving conditions can vary. The only constant is that it will occur, and letting the engine idle clears it temporarily. Thank you
Temperature gauge sits at normal, i.e. mid range. Never seems to change once engine is up to temp.
Thanks for that. Being in the UK I am not sure what 'gasline antifreeze' is however (I am sure it is not the same as injector cleaner). I expect there is a UK equivalent but what does it do? That is what I will be asked so if I had an answer it would help. Also what would you hope it might do, clean the pump or something else?? Thank you for your time and thinking on this issue. Regards
Thanks for that. Being in the UK I am not sure what 'gasline antifreeze' is however (I am sure it is not the same as injector cleaner). I expect there is a UK equivalent but what does it do? That is what I will be asked so if I had an answer it would help. Also what would you hope it might do, clean the pump or something else?? Thank you for your time and thinking on this issue. Regards
Hi, we have not resolved the problem, which might be injector related.
It is unlikely (though not impossible) to be O2 sensors.
There is a work round which we discovered when we had to have a new battery. When the new battery was put on, the original problem cleared up, unfortunately about 6 weeks later it occurred again. We therefore thought the problem was electrical related. We therefore took off the battery cleaned all the earth connections and reconnected. The problem disappeared. About 3 weeks later the problem re-occurred. This time we just disconnected the battery, left it off for 10 mins or so and reconnected. Problem gone. It has not yet re-occured (four weeks and going). If or when it reoccurs, we will disconnect the battery, touch the leads together (to drain ecu) and reconnect. My local garage suggest the problem thus is a cumulative problem. Disconnecting the battery clears ecu memory of problem. It gradually builds up until it reaches a critical level which trips MIL and causes ecu to affect the way the car runs.
So try disconnecting the battery, touch leads together and reconnect (maybe after 10 mins or so) and see what outcome is. If this makes a difference it probably is not the O2 sensors (we had all ours replaced and it made no difference). We are also using injector cleaning fluid in fuel to try and perhaps resolve any issues with the injectors, ultimately we will probably have them cleaned (not that cheap tho, about 35 gbp x 6 plus removal). Disconnecting the battery is cheap, easy and quick. Please note you will need an OBD11 gadget to turn out the MIL, it does not go out just by disconnecting battery.
Hope this helps.
Please note above comment was in reply to solution / request posted by dvd711 on March 07 2010
shorten it up some if you want an answer. This is a free forum
As the original poster of this problem (MIL on: P0171 fault code and sometimes P0174 as well), I have to report that it still occurs, but we manage it by resetting the MIL and then disconnecting the battery, touching the cable terminals together and leaving it like this for a few minutes. Then we reconnect battery, start car, reset radio and clock and the light stays off for about 8 weeks, until whole thing sets off again. Since I made the first post the engine spun a big end, so engine was removed and had a complete bottom end rebuild, I also had the injectors cleaned and serviced etc, and various seals replaced. None of this made any difference to the occurance and frequency of the problem. There are so many ideas as to what is going on - whatever it is, it is a cumulative fault that does not trip the MIL until a particular threshold is reached. This is why turning off the MIL and disconnecting the battery works because it clears the ecu's memory. Just disconnecting the battery though will not turn off the MIL (you need a cheap OBD11 meter for that). My advice, don't spend loads of money on a problem that is only a problem about 7 times a year. We have also noticed that when we use premium grade fuel the problem occurs less frequently. Hope this helps. Good luck
This is the self same problem really that I posted about. Whatever you do never seems to resolve the problem because it is a cumulative problem, at least in my experience, and it seems to reoccur every 8 weeks or so. What seems to happen is that the ecu registers a fault somewhere in the air/fuel mix and once the accumulation of this fault data reaches a critical level it triggers the MIL. Our solution now after much anxiety and frustration has been to buy a OBD11 meter, turn off the MIL, disconnect the battery, connect the cable terminals together and leave it like this for a few minutes. Then reconnect battery, start car, reset radio etc and normally fault will not occur again for 8 or so weeks. You need an OBD11 meter to turn off MIL because just disconnecting the battery will not do this. Using cheaper grades of fuel also seems to be an aggravating factor, we only use premium grades now (e.g. Shell Vpower). It seems to be an annoying and persistent problem and is also experienced by some other jag owners locally. The root cause is probably a tiny air leak somewhere that is not enough to be identified but is enough to register on the ecu and accumulate over a period until the crtical threshold to trip the MIL is reached. Hope this helps.
Has the Jag dealer looked at this? Also your reasoning for the light and fuel control codes is all wrong, that is not what is happening with the system, but nice try and very elegantly written.
I am not sure why you are having this problem. When I disconnect the battery and touch the terminals it clears the ECU memory, at least for these fault codes, do you have a secondary power source that maintains sufficient power to keep the ECU memory and the radio memory in tact? Alternatively is your radio code deactivated, which would account for why it is not resetting on power down. Remember that you do need to clear the fault codes and turn off the MIL with an OBD11 meter before you disconnect the battery, if you are not doing this the ECU will retain this information.
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