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No need to take the 10% pulley off, but I understand the reasoning of course from a shop like G&G, you want to spend your time wisely and addons/changes from stock add complexity and makes troubleshooting more difficult because of the unknows.
But its not the pulley, except a little higher flow/air pressure might aggravate an issue, that's it.
Sorry, not sure what you mean with power limitation, is that the stumbling you mean, or was there another issue before?
The ignition shown by the ECU is just for 1 cylinder, so not a way to check if there is a retard or not, especially not due to the low updates on a ODB2 device compared to the revs. Hence my question why you thought the ECU was retarding the timing.
There are checks on the IAT2 sensor, so as long as the intercoolers feel cool after a drive with engine still running, that should have been ok.
Fully understand the DIY part, that is how I started with my car and know it now pretty well now ;-)
Thx,
Yes the stumbling under more than 3/4 (1/2 hot) throttle travel when pedal is quickly pushed is what I experience as an instant power loss, it just stops pulling hard. (relatively high throttle opening speed triggers the engine to hold back big time, exhaust note changes as it seems to retard ignition, sounds even like combustion hasn't been finalized and provides a low tone out the exhaust, (haven't any other way of putting it, I understand my observations probably describe consequences instead of causes)
I understand the pulley mod doesn't help in diagnoses as it gives more heat, more air than stock.
Intercoolers get quite warm when idling after a ride. (45-55C, even a bit more on the sides, measured with infrared thermometer) but I recall having the stumbling/powerloss above 3/4 (1/2 warm) of throttle with coolers being only 35C (engine not fully warmed up, <10 min drive, maybe I screwed up the measurement)
Inlet temp on OBD (ELM327) shows 45-50C regularly. Temp dropped a bit when getting up to more driving speed.
LH and RH IC temps are ~5-10C different which also seems odd(?)
Infrared thermometer seems okay but is not a A brand. Testing on random surfaces produces sensible and steady vallues though.
I assume this inlet temp on OBD comes from IAT2, with the supercharged engines, and not from MAF? (If otherwise 2 different MAFs with such high inlet temp indication leads back to MAF wiring again as it is was only 16C outside?....or Engine connector seeing some moisture..)
Yes, when reading through all of this, this car was saved from the breaker when I come to think about it.:-)
Could Cat-converter blockage cause all this?
I did notice a temp difference in Cat converters as well. RH less hot on top of Cat Converter compared to LH, while exhaust tip in back of the car was 10C higher RH compared to LH (beats me).
I can get the engine to high RPM, when slowly pushing throttle, so it seems to be able the handle that exhaust gas flow eventually. At higher speeds and RPM (at WOT) the car does suddenly accelerated more (as should) sometimes (as said it feels not good for the engine to just push along this way too often)
Just now I start wondering if IC temp issue could be caused by blockage in exhaust....?
(great many thanks for sharing knowledge with me and the people yet to come here!)
Last edited by Ekskaar; Nov 10, 2020 at 04:39 AM.
Reason: added picture
I always like to know if everything works as it should, so MAF, airflow/pressure and fuel pressure.
You clearly have an issue that appears when you put load on the engine, but that doesn't change the possibilities as mentioned, its still the same.
The ICs would be much hotter if for instance there was no flow, usually when idling long or just after you have stopped the engine, they get heat soacked from the engine, and become way hotter.
The IAT2 sits in the intercooler, and is a similar thermistor as in the engine coolant and in the MAF. You could check the resistance as that is what's used by the ECU as temperature.
Cats could be potentially the cause, and would be next when all shows to be working fine.
For me to make a judgement, I would 1st need to know the answers to the questions raised, and of course have the coils checked, as that is certainly a good candidate for the issues you have. Especially as you have not the original Denso ones, I have bad experiences with Lucas onces iirc (and should have known -)), they didn't last that long on my car, and after 2 failed threw them all out.
I always like to know if everything works as it should, so MAF, airflow/pressure and fuel pressure.
You clearly have an issue that appears when you put load on the engine, but that doesn't change the possibilities as mentioned, its still the same.
The ICs would be much hotter if for instance there was no flow, usually when idling long or just after you have stopped the engine, they get heat soacked from the engine, and become way hotter.
The IAT2 sits in the intercooler, and is a similar thermistor as in the engine coolant and in the MAF. You could check the resistance as that is what's used by the ECU as temperature.
Cats could be potentially the cause, and would be next when all shows to be working fine.
For me to make a judgement, I would 1st need to know the answers to the questions raised, and of course have the coils checked, as that is certainly a good candidate for the issues you have. Especially as you have not the original Denso ones, I have bad experiences with Lucas onces iirc (and should have known -)), they didn't last that long on my car, and after 2 failed threw them all out.
IAT2 sensor vallues seem quite lineair. I compared with another one I has (have some spare parts left from scrap engine I gave away) I measured both in cold and hot water, same values. And have swapped the IAT2 sensor out with the spare one without effect.
I will go through all your great input once more to see what I can do next. Since engine is apart now I can't measure Air press so that will be some weeks from now.
Coils...Denso ones time 8,...only if I really have to.... $. (still denying I probably do have to)
Databus and RPM signal issues are the most complex I think..due to possible correlation with other problems.. (also intermittent)
Forget the IAT2 I would say (for the moment), if that one works as you say its fine.
With regards to the RPM value you see, it seems not related to the stumbling as you get different results with different loads on the engine.
Prime focus is on the fuel delivery (certainly if you have still original pumps) and COPs for now 9and (so air and fuel pressure during load is needed).
If your car is a keeper, and you enjoy performance and you have still the original pumps, I would swap them without any hesitation, they will fail at some point anyhow.
If you can't drop by to have the cols checked, you may want to work something out with G&G to lend a couple for testing,
Forget the IAT2 I would say (for the moment), if that one works as you say its fine.
With regards to the RPM value you see, it seems not related to the stumbling as you get different results with different loads on the engine.
Prime focus is on the fuel delivery (certainly if you have still original pumps) and COPs for now 9and (so air and fuel pressure during load is needed).
If your car is a keeper, and you enjoy performance and you have still the original pumps, I would swap them without any hesitation, they will fail at some point anyhow.
If you can't drop by to have the cols checked, you may want to work something out with G&G to lend a couple for testing,
Thanks, will do so and report back once assembled and tests done. Could be a month at my speed:-).
(Will take out cats for piece of mind first as acces is little better now, and I have seen an anomaly in honeycomb from rear end...)
I can use gauge I bought for the fuel press (too low range) perfectly for measuring boost pressure at SC lid fuel press line with a T.
I will find a 60PSI fuel resistent gauge somewhere in the personal scrapheap to measure the fuel press under load..
It might not be a keeper because of its high mileage, but I do like performance and the challenge to keep budget low alike, as many say that high performance at low budget is a contradiction in terminis...(until proven otherwise:-))
I would like to keep the car to experiment with (like many) and learn from but already got stuck in getting the (almost) stock setup working:-(..
It was bought pretty cheap...but already I am starting to see that nothing is more expensive then a cheap Jaguar. (lol)
Just changed my pumps today, due to the rattling noise under load and higher RPM. Everything as you described.
My pressure drops directly after rising to 70 psi under load, back to 55 psi or less.
As you can see on the attached file, it looks like the the pumps can't deliver the fuel, if you watch the throttle / pressure graphics.
Unfortunately, the pumps didn't cure the problem.
Looks like I have the same trouble that you described.
But as far as I did read above, you still didn't measure the fuel pressure?
Till now I don't have a solution yet.
Tomorrow I will change the pressure sensor....
Replacing the fuel pressure sensor did not make any difference in my case.
Still have the feeling that one of the fuel pumps isn't running under power, although they are both new.
Looks like the fuel pressure is leaking away (maybe trough the slow running pump).
Other thing I noticed, with this sensor disconnected, the ECU still measures the fuel pressure somehow, read by the OBD to my phone. So there must be another sensor somewhere.
Maybe someone can tell me more about the fuel pump control units, where they are located?
And about the story that one pump is helping under load / 3000 rpm?
Notice that I drive a European car. It's not similar like some USA cars, that have 2 pumps with a fuel outlet. My car only has a fuel line attached to the left pump. The right is feeding the left.
Replacing the fuel pressure sensor did not make any difference in my case.
Still have the feeling that one of the fuel pumps isn't running under power, although they are both new.
Looks like the fuel pressure is leaking away (maybe trough the slow running pump).
Other thing I noticed, with this sensor disconnected, the ECU still measures the fuel pressure somehow, read by the OBD to my phone. So there must be another sensor somewhere.
Maybe someone can tell me more about the fuel pump control units, where they are located?
And about the story that one pump is helping under load / 3000 rpm?
Notice that I drive a European car. It's not similar like some USA cars, that have 2 pumps with a fuel outlet. My car only has a fuel line attached to the left pump. The right is feeding the left.
Hi JPF12,
What Model and MY are you talking about? (S-type 4.2 -R I suspect, and after 2004?) my 4.0 XKR has no fuel press sensor.
People here appreciate new posters to stop by at the introduction thread, maybe something to consider?
Thanks for the fast response!
Yes, 2005 S-type 4.2R
But because of the differences between the two cars, and the exact same problem, there is probably a mutual problem....
We both have upgraded the super charger, I also did the crank upgrade, and it became worse after.
I upgraded in two steps, and the problem became worse too, in two steps.
All logical checks that I did leaded to nothing else than a lack of fuel (pressure).
And I still have no solution, just as you already did almost everything...
Welcome to the Jaguar Forums! It's great to have you with us!
As Ekskaar suggested, please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.
Thanks for the fast response!
Yes, 2005 S-type 4.2R
But because of the differences between the two cars, and the exact same problem, there is probably a mutual problem....
We both have upgraded the super charger, I also did the crank upgrade, and it became worse after.
I upgraded in two steps, and the problem became worse too, in two steps.
All logical checks that I did leaded to nothing else than a lack of fuel (pressure).
And I still have no solution, just as you already did almost everything...
My approach especially if you do not have the Jaguar IDS tool), is to physically measure the air pressure and then also the Fuel pressure. then you will know if that's right or not.
Also the Stype coils can degrade, so not having enough power to fire the sparkplug under load like with Ekskaar, but if you already doubt fuel pressure, I would measure it as suggested.
Cats could be potentially the cause, and would be next when all shows to be working fine.
I am reporting back way too soon as I have not re-assembled the car so could do the tests, but...
As said, now that there is little more room under the hood, and for the reason I was suspected Cat converters somehow, I took them out this morning.
Left is perfect, right is.....well see for yourselves.
Isn't this for 99% sure the cause of the problem?
Good find!
Would certainly do the other checks still as well, just to make sure all is fine and there is no cause left that could do these type of things with the cats
Yup just as i suspected. And was about to write. A little late to the game but in my 70 Cuda after I built a big power stroker motor with huge solid lifter cam ported heads and intake headers converter ignition all the good stuff, I took it to the track and coming off the line it pulled like a son of a gun until I got near the top of the rpm range and it just fell over. I tried several runs and I noticed it was faster if I didn’t put my foot down as far but it just wouldnt pul hard with the pedal to the floor. The problem was the exhaust. after I put the motor in I installed some cheap *** hush thrush Glasspack header mufflers just to break the motor in. but I never got around to changing them out before the track incident. I want to everything but couldn’t figure out what was going on. I took those header mufflers off and I noticed that the 3 inch inlet pipe reduced down to about an inch and a half inside the muffler so the muffler was seriously restricting my exhaust flow. Took them off and put on a full 3 inch exhaust all the way and it pulls hard all the way to 7000 RPM now
Good find!
Would certainly do the other checks still as well, just to make sure all is fine and there is no cause left that could do these type of things with the cats
Thanks, yes will do. Injectors have been ultrasonically cleaned yesterday at G&G, and I have compared spray paterns myself (was not so easy with side feed design)
Injectors are back in the rail now, but will leakcheck with fuelpump jumpered before putting IC's back on. (Can detect leakages in inlet and external that wat)
Remaining concern is the fake Coils, and still want renew plugs to be sure. Will also install boost gauge, and check fuelpress under load.
Also hope databus failure has disappeared...Current suspect is connector under brake fluid reservoir (lowest one, cant reach, must remove reservoir for that. Will do that later, needs new DOT 4 before the trackday anyway..😉
Believe it or not, the melted cat converter was not the (only) issue.
After putting it all back together I had cylinder 6 not firing anymore.
Plug sparked well, but no fuel.
I was afraid the injector was dead after removal and installation but luckily that was not the case. (I had initially taken injectors out only to eliminate them as a possible cause (cleaning/testing)...and it it is a hell op lot of work to redo that)
The cause of Cyl 6 not firing after reinstalling the engine top was the connector for the Bank 2 injectors that was bad (corrosion, amber weather seal damaged and caught up between the contacts somehow)
After cleanup and refitting of the contacts it ran well on idle so I was soo hopeful that the stumbling under power demand would be gone, and so I wouldn't need to do all this tests (Fuel press under WOT, coils replacing etc etc.)
But no... Stumbling not gone....
I have thrown the car aside now for a few weeks. Will pick up after I have regained courage. (and motivation)
1: Intend to replace the bank 2 injector connector, or might as well solder the wires. As I suspect bank 2 injectors may be limited (higher RPM's) by a bad connection still, and this could have been the actual cause all the time...Even though resistance is okay when measured with multi-meter
Lambda voltage bank 2 coincidentally always reads 0.1V when stumbling starts = lean, while other bank has random figures at that moment, AND subject connection caused a cyl not firing AT ALL, in another case I would not have seen the corrosion and worn out pins..)
2: Then measure fuel pressure (or just replace both pumps as I don't know how old they are). 2nd pump make a louder fuel swirling noise, maybe leak housing/tube etc. I hear lots of fuel forced through manifold with both pumps on however and engine off.(+Pressure gets to 50PSI with 2 pumps anyway but only tested when car is static, not using fuel) As said I will get to it soon..
3: Then get 8 (used, from local J-specialist?) A-Brand coils and new iridium plugs to eliminate that as a possible cause.
Regards,
Rob
Writing this up already creates courage (but takes some too:-))
Hi all, I have been using this thread to try and solve the stumbling onder wot (hotter was less throttle more stumbling) problem..
Problem is now solved but I can't prove the cause with actual evidence..
I had renewed plugs and coil packs again which seemed to give little improvement but not really, just psychological effect I guess😉.
After that, when warming up the car would still stumble when power was demanded.
The car was also throwing the can bus error more often, until it did not go away anymore.
That was good moment because I could use this forums amazing info to find the cause of that databus failure. It was caused by the gearlever lighting circuit board. I replaced it and no more databus issues. After a few short drives I noticed it seemed to take longer for stumbling to kick in...Actually I started to realize I needed to take a longer drive to find out if the stumbling was actually still kicking in...And it wasn't!! Problem solved!
I was not expecting the lighting plate circuit board to be able to influence the stumbling at all. But hey, noise on the databus can do strange things apparently. (I guess ECU got a fake TCM command to reduce throttle for gearshift or fake trac command, engine overspeed etc...??)
Now I am writing this I realize the car gave up to 16000!! Rpm on OBD momentarily sometimes. That must have been the canbus disturbance retarding power demand!
On to the next challenges: IRS overhaul and perhaps a 6-speed manual conversion💪.
Thanks for all your input and directions, I've learned a lot from that again! Very much appreciated👍.
Great you found it, it does make sense in hindsight that the high rpm reading was actually what the ECU thought was happening, but how it was caused is a new one (at least for me).
