Hi Folks,

As mentioned I recently replaced the factory original Denso MAF on my 2003 XKR. I'd been experiencing a stumble or misfire at WOT between 3-4000rpm and occasionally under light throttle. The new MAF seemed to fix the misfire & it actually feels like it picked up a few HP. Trouble is it now has an absolute rubbish idle. Seems like it's hunting when idling in neutral or park. Other than that it seems to run fine, start fine etc. I bought the new MAF from Rockauto. It listed it as suitable for my car. It's a DELPHI AF10442. Do you need to reset the ECU or TPS or anything like that when you change the MAF? My car is also fitted with a K&N airfilter.
Any thoughts / ideas would be greatly appreciated.
Thanks in advance
Jeff

 

Jeff, shot in the dark but: any chance the corrugated plastic hose developed a crack?

I hope its something easy mate.

J

 

Could poss be air leak, Would show mostly at idle.

Have a look at your LTFT's at idle and at 2500 rpm (engine up to temp,in park),
This should let you know if you have an air leak after changing the MAF.

Dont know about reset for ECU,TPS on 4.2, I didnt have to on the 4.0 when i changed my MAF.

 

Thanks Guys. My 1st thought was an air leak so spent ages eyeballing duct from airbox to th and I can't see any cracks whatsoever.
What are LTFT's? Are they fuel trims? Don't think my basic scanner reads those...

 

I think you did the right thing replacing the MAF. That will bring nothing but improvement.

You said yours was idling terrible now. I would suspect the crank case breather pipe. Terrible design. Gets very brittle and brakes easily. Have a read click me to read

Personally I would reset everything. Disconnect the negative lead from your battery and put it to one side overnight. That will discharge your capacitors on the car and the car will have to learn everything again, including idle. Will see if I can find you a link to re-learning the idle. Brb

Here you go my resetting the settings topic. resetting the settings Hope it helps, let us know though will you?

 

Another vote for the fragile crankcase breather pipe. These engines have impressive vacuum in the crankcase; just crack the oil cap open while it's running to see what I mean. It doesn't take much of a leak to make the engine struggle to stay running. Gary VanRemortel ("XK8 Bible" in the Sticky Notes) bought the last living new breather pipe a long time ago, but he has some great replacement hose and can build you a new one (if needed). Be sure to save/send him your end connectors off of the old one.

 

Wish I had known about VanRemortel earlier! Oh well. Hindsight is a wonderful thing.

Slightly detracting from the subject you mentioned the oil cap removal. I wont embarrass the actual guy but someone lost their filler cap down into the depths of the car when topping up. He then did something that makes me cringe when I think about it even now. He put a sock, yes a sock, over the hole. Started the car up...................... Sock got sucked in and wrapped itself around a lot of internal parts. Had to have an engine strip down.......... Ouch. He wont be doing that again in a hurry.

Right off to find the pipe wizard...............

 

Nope. Cannot see the Bible, got a link?

 

While a cracked breather pipe may indeed turn out to be the cause of your issue, keep in mind that a number of folks have reported similar poor performance after replacing their MAF sensor with a non-Denso version. The general advice here is to always go with the proper Denso MAF sensor when replacement time rolls around. The extra cost is apparently worth it....

 

+1 on an air leak probably being the cause.

But.... long shot... did you know the throttle body has an adjustment for idle.

Check out this youtube video around 9min in

 

Exit backwards from this thread, count down 3 "Sticky" Threads from the top of the X100 Forum Page, click on "XK8 Bible."

At the bottom of the 2nd page is the newest revision of the bible, Rev "L"; download, print, memorize it, and send kudos to Mr. VanRemortel daily...

 

As I dont have one of these cars, I cant speak specifically about the issue but general rule of thump when it comes to sendors is that the OEM sensors are always preferable to others. Same with spark plugs.

 

What are LTFT's? Are they fuel trims? Don't think my basic scanner reads those...[/QUOTE]

Yes they are fuel trims,
You will have long term fuel trim for bank 1 and for bank 2...(also short term trims but for now you can ignore them)
If you could read them at idle and also at 2500 rpm an air leak would mean at idle the trim value would be higher than at 2500 rpm (engine up to temp,in park)

If you cant see/read the trims you should do a smoke test (this would be the second step any way to identify where the leak/leaks are coming from)

You may not have an air leak but if you do the above then it can be ruled out as the cause of your bad idle, Then you can move on to other things that maybe causing the bad idle...
I would just do a hard reset first and see if that works.
Hope this helps..

 

Thanks Guys. Really appreciate all the advise offered. I will try each of these suggestions. First I think I'II put the old Denso MAF back in, run it up to temp & see if the problem remains. Seems odd to me that with old MAF - no idle problems whatsoever. As soon as I put the replacement Delphi unit in I immediately got the bad idle. I thought at the time it just needed to adjust to the new sensor & readings but now suspect it might be the cheap made in china new MAF. Would seem to be too much of a coincidence that it developed an air leak or blocked breather pipe at precisely the moment I replaced the MAF.
Will keep you posted...

 

Buggar...
I put the original Denso MAF back in. The car certainly seems much more response with the new Delphi MAF - BUT, it idled perfectly with the factory original Denso in it.
I might still try resetting everything with the new MAF but I think it's a bit of a long shot. What are the odds of getting RockAuto to refund me for the one that they listed on their website as being suitable but doesn't idle?
Another long shot. I noticed the dangly hanging down bit on the new MAF was not centered (vertically) in its enclosure - see pic.
It is centered on the old Denso. Could that make a difference?

 

Dont know about a refund unless they sent you the wrong part.?
Have you tried to clean the original one with MAF cleaner.?
Dont know if the hot wire been off centre would make much difference.

good luck.

 

First off thats NOT the MAF sensor. I made the same mistake. Have a read Click Me To Read

The other thing depends on where you are in the world. If your in the UK then your in luck https://www.gov.uk/online-and-distan...for-businesses. You have 14 days to return it, hope you kept the packaging, though its not strictly necessary.

One last thing that sensor does not look right at all. Compare it to mine in the link above. You could also use this as a reason for returning it? Send him my photo and yours. I hope the MAF was over £42 as that is the lower limit.

__________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ ___
Dear Sirs,

I recently purchased a MAF sensor for my Jaguar ******* it arrived yesterday and I fitted it straight away. Our reference : *******************************************

The engine simply did not idle correctly. I put the old MAF back in and it idled fine. Obviously the new MAF sensor you provided is faulty. If you compare these two photos attached you will also see that the Temperature sensor also does not look right. The replacement you provided looks much poorer quality. I think the MAF is not fit for purpose and therefore request a full refund under the distance selling regulations, including postage. I will of course return your MAF sensor if you so wish for you to inspect.

I would be grateful if you would refund me as soon as possible. I do not want another MAF in replacement as I wish to get my car back on the road quickly.

Thank you for your help in this matter.

I look forward to your reply.

Yours ******************

__________________________________________________ __________________________________________________ __________________________________________________ ___________

Hope this helps.

As you can see below a picture of my MAF to save you looking it up. Right click over photo and select "save photo as". Not trying to insult your intelligence just trying to help

 

This is the intake air temp sensor. The value is available over OBDII. Check if there is a correlation with reality. Should be outside air temp, plus a few degrees at idle, closer to outside air temp as you get some speed.

PS: As pointed out before, make double sure the o-ring at the base of the sensor is there, and is a good fit/seal. You can even try and swap this o-ring with the old one to check for a difference. A missing o-ring there has been reported as messing up the reading a lot more than it would seem. Remember, this sensor samples the air flow, so any changes to the flow of air to it could mess up the logic (K&N filter?). Last, you really need to read these fuel trims. Maybe the old sensor put them way out of whack, and this new correct sensor is just waiting for the trims to adjust.

 

Thanks for this. Will disconnecting the negative battery lead overnight reset the fuel trims? If not can it be done without diagnostic tool? If I can reset the trims I'd like to try that with the new MAF.

At the end of this at least we'll know one way or another whether these non oem MAFS will actually work with our cars...

 

Good luck. Yes it should reset the trims too.