As many know, I have a friend that has a 2000XKR. He is a little old school and is much more fluent with pre-ODBII cars.

We have been chasing a p0171 and p0174. The obvious on top has been replaced and it is on both sides and not consistent. Sometimes it will appear in just cruising at 65.

We have all seen or friend Gus's description about fuel trims and I am sure that as been helpful to many. However- this I found and am somewhat baffled

I. Based on the description of how to read fuel trims, an example that if you remove the oil dip stick (and I assume oil cap ) as well that this will be reflected in the ST fuel trims going positive. This happens on my 2005 Stype 3.0. HOWEVER on his xkr2000 this does NOT happen. In fact is you remove or pull up on the oil dip stick or loosen the oil cap enough to allow air- the fuels trims make NO movement at all. Now would this be standard for this engine or does this indicate something else and if so what??


II.The second issue on fuel trims and it does not happen on my stype - is that if you drive with a scanner monitor in real time- if you step on the accelerator at all- I mean even going from 5 mph to 15mph over a 5-7 second time period (not gunning it at all) or if you step on the accelerator at any speed - be it 20-30-40-60 and just do a slight acceleration the fuels trims on the ST run all the way to +25 until you level off at whatever cruising speed you want. They the run at +14-+15 on both sides- just at any cruising speed- again be it 20-30-40-60.

Any thoughts on what might be going on- There are no other codes, it is not consistent and of course with inspection coming and still inc. on the evap and ccm- there will be no passing of the test in Texas. I probably think that is also symptomatic of the problem and the right conditions- no matter what drive cycle we have tried and we have tried all and those 2 monitors will not clear and I fully understand that that may be preventing other codes from showing.

Thanks for help and ideas.

Tom in Plano/Dallas

 

The MAFS may be at fault. Air leaks don't have much impact when the throttle is open. But what about the LTFT? That's a better parameter since the short terms generally bounce all over.

 

What is the situation with the air flow meter? Original, new, cheap refurb, DENSO? There are LOTS of look alike parts that fit just fine, but are somehow producing a different measurement. I had good luck by identifying the right DENSO number for my 2003 XK8, and ordering it on eBay for cheap. Ended up being a Toyota part, and worked just fine. An earlier purchase, reputedly compatible with XK8, but with a different DENSO number gave me erratic fuel trims, just like you are describing, and I returned it.

Have you tried the same test run (with the OBD monitor running) with the air flow meter disconnected? Supposedly, the computer can deal with that to an extent.

How are the fuel trims at idle? Have you investigated the dual fuel pump setup, and are they confirmed working, both of them? There should also be a manifold pressure sensor, maybe the reading is available over OBDII (it is in the 2003+ cars).

 

No indication of any mafs fault- zero codes and passing the right amount of air according to charts on Jagrepair.com

Read back to my posting I do make mention of the LT on cruising.

However I bet if you hooked your car to a scanner and then from 10 mph to 15 mph you slightly accelerated you would not see anything close to +25 on both sides of ST? I am aware they bounce all over the place, but this is the first car i have seen that type of change on slow acceleration or any acceleration at all.

Tom

 

denso- be it original or not- I know not and no way to know.- having once left my mafs disconnected I had a multitude of faults and an immediate RP- so I am not sure that would tell me anything.

What about the oil dipstick test and no response?

Tom

 

You then have to assume it is original. I spent $22 on a suitable new part for my car. You could start there...

 

^^ Agreed. Given the current age of these vehicles, acquiring the appropriate inexpensive Denso MAF sensor from amazon or ebay is cheap insurance. I did so back in February, successfully tested it for several hundred miles in both of our Jaguars, and am keeping it as a spare. I know if we hold onto these cars long enough, I will need it....

You want a true Denso MAF sensor, not an untrustworthy Chinese knockoff. It is worth the $15 or $20 extra cost that you may have to pay....

 

I think "II" may be worth ignoring for now.

But "I" - well, depends on the engine I expect.

Hot engine, parked, idle. What are the LTFTs? Rev to about 2500 and what do they do?

Now... don't do this if you've got LTFTs that have not relearned if you recently cleared the values by disconnecting the battery as you'll just be chasing your own behaviour.

Also, is it running CL (closed loop) in the above? If not, the trims can be lies or at least not much help.

Let's worry about STFTs later.

 

All the ST and LT are within range at idle and 2500- This has been tested numerous times and have posted the results many times before.

Why no ST rise to the positive with the dip stick or oil cap removed?

I am not one to throw parts at cars. How many of you have replaced a MAF that had no code and it fixed the car problem. Also have recently cleaned the MAF, but did not chnage much. CL in all the above.

Tom- Plano

 

They are not that inexpensive for the XKR model and the not the same as the XK8 model.

Tom

 

Unrealistic to expect people to dig back through your old posts.

 

I clearly understand about the idle and 2500.

Here are the last ones I ran
he fuel trims (LT) are showing at idle in the -1.8 and +.8 and at 2500 rpm +5.6 and +6.1.

Nothing there is terribly out of whack Clearly closed loop and had more than 5 months and more than 70 drive cycles to relearn.

I am looking at anomalies and as such- when Gus has gone through extensive teaching of us about fuel trims on this forum and has used from jag or wherever the test of removing the oil dipstick and seeing the fuel trims immediately rise. My S-Type does and a friends 03 XJ does.- back to why it does not on a 2000xkr and why further when I accelerate 1 mph on the car xkr2000- the ST go immediately to +25. I will make a bet to anyone of contributing $50 to their favorite charity- if the same happens in your Jag. with removing the oil dipstick or with acceleration. Does not come close to doing that on 2 other Jags or several other non-jags and would think that is NOT correct.

If you really know- correct me if I am wrong.

Tom

 

There have been multiple reports on this forum of new, proper Denso MAF sensors fixing issues regardless of what the associated codes (or no codes) may have been....