S type R lack of power with fuel trim results
#1
S type R lack of power with fuel trim results
Afternoon chaps,
New Jaguar owner and this is the first time Ive done any ODB diagnostics, so I'm a little confused about how to interpret the results. The Trim levels seem to be fluctuating quite a lot - is this normal? What could be going wrong (if anything)?
Symptoms: Its fine sometimes, but other its lacking a huge amount of power. When it lacks power it makes a bit of a noise (raspy, almost sounds like exhaust blowing, but Ive checked it and its intact).
Ive uploaded a video of the results, it was mostly behaving itself when I did the video:
ST-FTRM1, LT-FTRM1, ST-FTRM2
LT-FTRM2
Any help with this would be appreciated! Thanks in advance.
New Jaguar owner and this is the first time Ive done any ODB diagnostics, so I'm a little confused about how to interpret the results. The Trim levels seem to be fluctuating quite a lot - is this normal? What could be going wrong (if anything)?
Symptoms: Its fine sometimes, but other its lacking a huge amount of power. When it lacks power it makes a bit of a noise (raspy, almost sounds like exhaust blowing, but Ive checked it and its intact).
Ive uploaded a video of the results, it was mostly behaving itself when I did the video:
ST-FTRM1, LT-FTRM1, ST-FTRM2
LT-FTRM2
Any help with this would be appreciated! Thanks in advance.
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dmdz (09-25-2013)
#5
Thanks JagV8. From what I can gather from my newly acquired knowledge about fuel trims, I am guessing that I have a vacuum leak. Is this a correct diagnosis?
From what I have read, this may be caused by the following
1) Airbox leak
2) Hose from air intake to drivers cam cover
3) crankcase ventilation line from passenger cam cover to drivers side (close to brake booster)
4) Hose from brake booster to intake manifold near throttle body
5) Leaking intake manifold gasket
6) leaking EGR hose/Exhaust manifold tube.
Are there any more usual sources?
Are there any nice ways to guess or whittle down which one is causing it? Can I get away with spraying with carb cleaner and waiting for a rise in engine revs (would this work on a supercharged engine?)
Sorry if these sound simple questions, I've been reading for hours and am getting a bit lost!
From what I have read, this may be caused by the following
1) Airbox leak
2) Hose from air intake to drivers cam cover
3) crankcase ventilation line from passenger cam cover to drivers side (close to brake booster)
4) Hose from brake booster to intake manifold near throttle body
5) Leaking intake manifold gasket
6) leaking EGR hose/Exhaust manifold tube.
Are there any more usual sources?
Are there any nice ways to guess or whittle down which one is causing it? Can I get away with spraying with carb cleaner and waiting for a rise in engine revs (would this work on a supercharged engine?)
Sorry if these sound simple questions, I've been reading for hours and am getting a bit lost!
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#8
Both banks exactly the same?
Not an air leak if LTFT goes UP with revs.
Might be an underreading MAF but other things are possible.
Definitely running CL (closed loop), both banks?
Worth reading engine sensors to see if any looks to have an implausible value.
Kinds of things are in JTIS but here's a pic to give clues OnBoardDiagnostics.com - Engine Basics
(MAT is IAT in our cars)
The O2 sensors are 2 kinds so ignore them for now. No reason to think they're bad.
Not an air leak if LTFT goes UP with revs.
Might be an underreading MAF but other things are possible.
Definitely running CL (closed loop), both banks?
Worth reading engine sensors to see if any looks to have an implausible value.
Kinds of things are in JTIS but here's a pic to give clues OnBoardDiagnostics.com - Engine Basics
(MAT is IAT in our cars)
The O2 sensors are 2 kinds so ignore them for now. No reason to think they're bad.
Last edited by JagV8; 09-25-2013 at 04:17 PM.
#9
Double checked the results this morning after confusing myself over yesterdays results. Definitely closed loop.
The LTFT oscillates between 17.9 and around 9 while at 2500rpm. Stays on 17.9 for a good 30 seconds, then climbs down to 9ish, stays there, then shoots back up again.
Bank 2 is about 0.7 higher than bank 1 at idle.
Does this help?
IAT is around 93F (42c constant)
Maf 0.713 (idle) 8.6 (2500rpm), fuel pressure is 55 +/-1
IGN ADV (DEG) is 5.0 (idle) 42.5 (2500rpm)
MAP 11.2 (idle) 8.3(2500rpm)
O2S12/O2S22 seem to oscillate upwards and down, im guessing thats because of the varying trims. Highest I've seen it is 0.8, lowest is 0.035.
Any further advise deeply appreciated - Thank you
The LTFT oscillates between 17.9 and around 9 while at 2500rpm. Stays on 17.9 for a good 30 seconds, then climbs down to 9ish, stays there, then shoots back up again.
Bank 2 is about 0.7 higher than bank 1 at idle.
Does this help?
IAT is around 93F (42c constant)
Maf 0.713 (idle) 8.6 (2500rpm), fuel pressure is 55 +/-1
IGN ADV (DEG) is 5.0 (idle) 42.5 (2500rpm)
MAP 11.2 (idle) 8.3(2500rpm)
O2S12/O2S22 seem to oscillate upwards and down, im guessing thats because of the varying trims. Highest I've seen it is 0.8, lowest is 0.035.
Any further advise deeply appreciated - Thank you
#10
I don't really know what's wrong but not an air leak into a vacuum line. But maybe something like EVAP purge valve or the like not doing what it should. Have a good look at JTIS e.g. Electrical Guide to understand all the many actuators & sensors and think hard how anything could cause what you see. E.g. it can't be a bad MAF as it wouldn't cycle would it? (Well, it could be underreading all the time as well as whatever is wrong, but chase the weirdness first.) Switch a/c off as it would just be another thing messing around.
Oh - JTIS etc use several names for some sensors (and some are non-standard names anyway). Written by different authors or something.
Oh - JTIS etc use several names for some sensors (and some are non-standard names anyway). Written by different authors or something.
Last edited by JagV8; 09-26-2013 at 03:54 AM.
#11
Ive done an unhealthy amount of reading the past few days, but still trying to get my head around the trim results I've got.
Im leaning towards the EGR valve - could this create the creeping values or is it more likely to be electrical/sensor? Can it self detect that its failing?
By having a high base trim value of 8.5 can I assume I also have a vacuum leak as well as another issue?
Would the purge valve not create a negative value?
Thanks
Im leaning towards the EGR valve - could this create the creeping values or is it more likely to be electrical/sensor? Can it self detect that its failing?
By having a high base trim value of 8.5 can I assume I also have a vacuum leak as well as another issue?
Would the purge valve not create a negative value?
Thanks
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Taken her into a jag specialist. Annoyingly the fuel trims were fine on the day & the engineers havent been able to fault them since having the car. I think the tool they used is auto-logic.
They did say one of my catalysts were breaking up (had a rattle), so I've got a new one on order. (She has covered 128k miles). Is this likely to be the cause of my problems, or merely a long term symptom?
Ive had no fault codes for the last 3 weeks, however when I bought the car there was a big vacuum leak (one of the pipes had popped off). This originally caused the following codes: P0171 - Generic System too lean (Bank 1), P0174 - Generic System too lean (Bank 2), P0102 - Maf or Vaf A Circuit low input, P0112 - IAT Sensor 1 Circuit Low Input And a P1111 (Jaguar system pass). Im not sure if this will have anything to do with it?
They did say one of my catalysts were breaking up (had a rattle), so I've got a new one on order. (She has covered 128k miles). Is this likely to be the cause of my problems, or merely a long term symptom?
Ive had no fault codes for the last 3 weeks, however when I bought the car there was a big vacuum leak (one of the pipes had popped off). This originally caused the following codes: P0171 - Generic System too lean (Bank 1), P0174 - Generic System too lean (Bank 2), P0102 - Maf or Vaf A Circuit low input, P0112 - IAT Sensor 1 Circuit Low Input And a P1111 (Jaguar system pass). Im not sure if this will have anything to do with it?
Last edited by dmdz; 10-03-2013 at 05:29 AM.
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#16
Did you reset the ECU when the air leak was fixed? I don't mean just clearing the codes, but the fuel trims too?
If not, then your strange fuel trims and even the poor performance in certain situations could just be a left over.
Would need one of the S-type experts to chime in if the procedure is the same, but on an XKR you simply disconnect the negative battery cable and touch it to the positive terminal for 15sec.
From there, you can get a clean start and see if the very high fuel trims come back.
If not, then your strange fuel trims and even the poor performance in certain situations could just be a left over.
Would need one of the S-type experts to chime in if the procedure is the same, but on an XKR you simply disconnect the negative battery cable and touch it to the positive terminal for 15sec.
From there, you can get a clean start and see if the very high fuel trims come back.
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