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My car (XKR 2002 Convertible) was running pretty well and I enjoyed itīs performance.
I did not enjoy the droning and barking I got after installing some cheap-ish exhaust, that got rid of the rear mufflers.
However, all was well and a new exhaust already ordered.
Proud I went to my trusted workshop to get the annual inspection (similar to MOT) and do a service on the car.
Well, I got the MOT and they charged me for these things:
1) 8 Spark Plugs
2) Oil Filter
3) Air Filter
4) Oil
5) Bits & Pieces (irrelevant) to my "Story"
When I picked the car up I was - at first - pleasantly surprised that the car wasnīt barking so aggressively while starting.
It still droned, but definitely a few notes lower.
Taking the car for a spin on the weekend, I am sure I have lost power.
It takes off as before, but it lacks mid range boost and it feels very..."muffled" (hope that makes sense to anyone, but thatīs the best way to describe it)
I drove back to the workshop today and they checked and cleaned the MAF sensor, but it had no effect and they told me they were only using OEM Jaguar parts.
To solve this, I would like your input/educated guesses/expertise on the following:
a) Could "wrong" spark plugs "muffle" the car (i.e. XK8 vs XKR plugs - if there is such a thing)
b) Could I have had a different air filter before and the original one is reducing the airflow and performance (to Standard as it seems?)
c) Could the change of the air filter have "blocked" anything in the air duct system?
d) No idea, where to look...
BTW. I already did the "Are both of your fuel pumps work correctly?" procedure and apparently they do (result 1 - unplugged Main FP fuse: immediate start, running good; result 2 - unplugged Second FP fuse: immediate start, but restricted performance message in dashboard, which disappeard after putting the fusebox back)
I have an OBD II scan tool and could provide Fuel Trim levels, RPM`s and MAF Sensor readings if anyone find them useful or even necessary.
Thanks for reading and thanks to all of you in advance that are sharing some input and insights with me!
Cheers,
Berglmir
One step at a time. Simple things first. Remove the air filter. Take it for a run. Not recommended to run without an air filter for long but a day or so wont do any harm. Not solved?
I know you said you cleaned the MAF but what bit did you clean? NOT knocking you but I too cleaned my MAF but found I had actually cleaned the air temp sensor instead. Read about what I did click me to read
Plugs. The only way to check is to read the name and number on the plug. NGK, champion etc. Especially the size.
This, if you only do one at a time, should indicate any problem point. My main suspect would be the MAF.
On top of this check the braided hose near the MAF. Feels like its made of egg shells it breaks so easy, so be careful when you inspect them. Mine broke WHILST inspecting. These are the pipes I am talking about click me to see the pipes
Thatīs a prudent approach, thanks.
And Iīm not ashamed to admit, that I probably cleaned the temperature sensor as well, thinking thatīs the MAF Sensor.
I really suspect the air filter/air duct and I will test it with removing the air filter tomorrow.
I would double check the MAF be sure the technician put in the correct one. The XKR and XK8 parts are not the same.
Z
I dont think he had it changed. Just cleaned.
However I had similar problems with my car in that it did not go above 3000 RPM. Please note I am talking about whilst driving. If you try to go above 3000 RPM whilst parked the revs will 'bounce'. Try it and you will see what I mean. Even found a video for you, this is after I changed my CAT from a 400 to 200 cell I took the video to demonstrate the noise change. You can hear the 'bounce' at the start of the video.
Update:
As Frankc suggested I removed the air filter (which was this one):
The car started right up, but was a little "jumpy" at first.
I did not really hear a big difference from the exhaust. It was still muffled.
I drove for half an hour, in D, but also shifting manually, to get a good scope of rpmīs.
The car felt a little bit more lively, but not as before.
Take a look at the OBD scan (attached) - if I apply the math I have found in this forum somewhere, that if you divide your MAF (g/s) by 0,8 at around 6000 rpm, it should give you an indication of your actual hp.
If thatīs the case, then Iīm driving with max. 317,85 HP @ 5418 rpm (MAF: 254,28 g/s)
Unfortunately, I have no comparable data from before the trip to my workshop (lesson learned).
So itīs not the airfilter - which is a pity.
The MAF sensor wasnīt replaced - itīs still this one:
But SOMETHING is wrong. Definitely.
Now - should I go for a new MAF (Sensor only, or including suction pipe), OR check the new spark plugs (not sure I can with my crappy toolbox at home)?
After the engine has cooled down, Iīm going to re-install the airfilter and do the same run again, comparing the OBD results.
@Francz - the car revs, thatīs (currently!) not my problem, but thanks for the pointer.
I also checked the tubing from the airduct - they seem to be ok, but need to test properly, when Iīm re-installing the airfilter.
Yeah it's a mystery. I've never experienced a loss of power in my XK8 but I did have it in my L322 Range Rover, where one of the V8 cylinders didn't work. Strangely that didn't flag a CEL warning in the L322. What would be the symptoms on a X100?
Just a thought, I wonder, as the OP had his spark plugs changed, if one of the new plugs aren't firing. The coils and cable harnesses are now old, and I wouldn't be surprised if one of the circuits in these fragile things got damaged during the change. Easily done, as the cable harnesses have to be bent out of the way.
I would first plug your OBDII code reader in and drive the car and see if you capture a code and post the codes. Then I would capture and post your fuel trims as well.
Hard to say what is going on without real information.
Yeah it's a mystery. I've never experienced a loss of power in my XK8 but I did have it in my L322 Range Rover, where one of the V8 cylinders didn't work. Strangely that didn't flag a CEL warning in the L322. What would be the symptoms on a X100?
Just a thought, I wonder, as the OP had his spark plugs changed, if one of the new plugs aren't firing. The coils and cable harnesses are now old, and I wouldn't be surprised if one of the circuits in these fragile things got damaged during the change. Easily done, as the cable harnesses have to be bent out of the way.
That was one of my assumptions as well, however, the engine runs very smoothly (just lacking power) - wouldnīt it be "feel-able", if the car runs on less than 8 cylinders?
Nonetheless, definitely worth checking.
Originally Posted by Gus
I would first plug your OBDII code reader in and drive the car and see if you capture a code and post the codes. Then I would capture and post your fuel trims as well.
Hard to say what is going on without real information.
Gus, my code reader is in all the time.
No codes came up as of now.
The Fuel Trims are included in my latest attachment (Excel file) - unfortunately, I donīt get any more information on fuel trims than that.
But thanks for taking a look!
My first thought if not air filter would be a bad spark plug/coil, but that would cause a misfire, right? As an old-time 'shade tree' mechanic, these computer controlled engines are mostly beyond me but still sounds like faulty MAF if all else checks out.
FWIW, I cleaned my MAF three times before it started working at an optimal level. Since you aren't supposed to touch the actual sensor rods, one has to depend on the MAF spray cleaner to do the job. Anyone who's used a car wash knows that the force of a pressurized liquid doesn't always clean off the grime. Same thing with the spray MAF cleaners.
My MAF "looked" clean after the 1st and the 2nd sessions, but it took a 3rd liberal spray down before it was actually working correctly.
for stubborn MAF cleaning issues try the following. initially spray the sensor, letting the cleaner wash out. turn it upside down and fill the chamber in the head with the spray cleaner and let it soak for ten minutes. rinse out by spray rinsing again. allow to dry. here is where it gets dicey but has saved some expensive or hard to obtain sensors. mix a cup of hot distilled water with a 1/4 teaspoon of Dawn dish washing liquid detergent, mix well. use a pump sprayer to wash the MAF sensor wires and let soak as described above with a final rinse of the soapy water. rinse with fresh distilled water and immediately dry by using the MAF cleaning spray. do a thorough job displacing the water. place the sensor in the sun or in a warm and dry environment for a while. take any oil soaked air filter and bring to a garbage can. place in garbage can. wash out the entire air filter assembly, including the runner and breather tube with said dish washing liquid. install a premium, dry paper air filter such as the top rated AC Delco.
note that there is a weak point in the system seal. it is where the MAF housing tube meets the top of the air filter box. it is not a bad design, but might not age well. i used some Permatex sealant to make it guaranteed air tight. there are a few 8 mm screws to separate it from the top air cleaner cover.
any oily dirt that can get into the system can affect the sensor. there is also turbulence in any intake system and contaminants downstream of the sensor can affect it.
Last edited by CorStevens; 06-13-2019 at 10:47 AM.
Reason: additions
All great suggestions which I will follow to the letter (special thanks to WhiteHat), however, the next thing on my list, is to check the spark plugs.
After making sure it is not the air filter, wrong plugs could be great candidates for this whole mystery.
If only I had a spark plug wrench, I would do it now...but NO...have to buy one tomorrow (and I will buy one that is flexible and long enough for those inaccessible spots )
How about this:
I called my workshop today and asked them which spark plugs they used?
Answer NKG IFR5N10 - so we know these are correct.
I have a long and trustful relationship with the owner of this workshop and he asked me, why I am asking and so I told him.
His answer: Iīm not the only customer of his, that complains about loss of power and he himself has experienced it with his cars too.
Reason being: We are struck by heat wave right now (35 C / 95 F) and all S/C cars suffer, as they suck in hot air and have far too small intercoolers anyhow.
"Set an alarm for 2AM and take the car for a spin. See what difference that makes"...maybe I will.
Just had another thought, yes two in one week , how about disconnecting that battery and leaving it disconnected overnight? Simple to do. My logic. The car actually 'learns' how you drive and perhaps this has become messed up somehow? By disconnecting and leaving it overnight the capacitors drain and it has to relearn how you drive. Just a thought.
Frankc, that procedure brings up question for us somewhat new to XK's. When 'rebooting' by disconnecting batteries like that, what all has to be reset after the battery has been reconnected. There has to be numerous items that do not have a memory that will require reset other than radio stations and clock?? Windows?
Just had another thought, yes two in one week , how about disconnecting that battery and leaving it disconnected overnight? Simple to do. My logic. The car actually 'learns' how you drive and perhaps this has become messed up somehow? By disconnecting and leaving it overnight the capacitors drain and it has to relearn how you drive. Just a thought.
WHOA! So many ideas! And good ones too - I will try this today/over night.
Just one small question though: Do I need to disconnect one of the connectors, or would it suffice to remove the "screw", that apparently is needed to close the circuit?
Originally Posted by SamtheSham
Frankc, that procedure brings up the question for us somewhat new to XK's. When 'rebooting' by disconnecting batteries like that, what all has to be reset after the battery has been reconnected. There has to be numerous items that do not have a memory that will require reset other than radio stations and clock?? Windows?
Thx
SamtheSham - all things in need of re-setting/re-learning are featured in the link Frankc provided.
Cheers!
Last edited by Berglmir; 06-14-2019 at 11:43 AM.
Reason: Typing error
I drove the car today for a bit and was able to test it on the highway for a bit too.
Attached my OBD Scan readings (two tabs: Morning (including Highway) and Afternoon (mainly B-Roads and Hills).
The good news is, that if I apply the math of divide by 0,8, I would have 410 HP (metric; bit less in bhp) @ 5328 rpm (time stamp: 338,8)
I maxed 326 HP in the afternoon @ 5165 rpm in the morning.
The weather conditions have not changed (still 33 Celsius / 91,5 F) and the only thing I did was follow the "reset idle after battery disconnect" process before I started my morning trip.
So I know, the car has some power to give and the MAF seems to work, or at least works sometimes.
My question now is: How can I - if only for the fraction of a second - have 410 HP when the car is supposed to have about 267 KW (358 bhp / 363 hp metric)?
I also have NO idea whatsoever if my Fuel trims are ok, because no matter where I look, I canīt find any reference data that tell me, what they should look like.
(Iīve read the Fuel Trim Reference docs provided here in the forum, but they are far too high level for my understanding)
Hey, nevermind, just wanted to keep you updated.
Cheers and have a great weekend
Berglmir
06-12-2019, 01:57 PM
Mystery in need of solving
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