https://www.jaguarforums.com/forum/x...rmance-237221/

 

Interesting. I bought it an OEM MAF. Fuel trims are the same as my screenshots above.

I didn't do a hard reset. I only cleared the codes with the scanner. Should I have done a hard reset instead?

 

I ALWAYS remove the ECM fuse (battery disconnect messes with the clock and other things) to set all adaptations to ZERO when replacing MAFS or H02S.
Clearing the DTCs from the ECM will not clear the STFT and LTFT adaptations.

The replacement MAFS will eventually find it's own adaptation, but the power disconnect will find the adaptation from zero, not a previous adaptation.

If the STFT and LTFT is correct and hovering around zero, you will see it sooner.

 

Did a hard reset. This screenshot is after 15 minutes of just idiling. Didn't bother to drive it, as you could smell how rich it is just from standing behind the car.

 

Negative 20 means it is trying to lean it but it looks like a losing battle.

 

Correct. I see a company sells rebuilt injectors for our cars. How do we feel about using rebuilts? I've gone through the checklist for the rich bank codes. But with my luck, new injectors probably won't fix it.

 

I tried a complete intake manifold w/injectors from a similar engine. (no change)
I still think a replacement MAFS is the best attempt at repair.
The H02Sensors might also be a contributing factor.

 

I installed a new oem MAF in it.
I'll look into the o2 sensors. For what it's worth, my readiness monitors have been complete except for "Catalyst Monitoring", since I bought this car back in February.

 

Here's some interesting reading (attached). I started my "project" that I mentioned above this week, which is to replace some original parts after 18 years and 178k+ miles. The car is running good, but my fuel trims are a little skewed, not as bad as yours and I haven't had any CELs, the SC snout needs a rebuild, install the new downpipes, new motor mounts while the old cats are off, and a few other things. After reading through this paper, I decided to replace the O2 sensors and have the injectors cleaned while I was in there. The SC is off, and I'm glad that I decided to do this as it's a complete mess under the charge air coolers.

The write up is from jaguarfuelinjectorservice.com

 

Good read! I'm stumped on this one. I doubt the injectors would make it that rich, as my long term trims are showing. I'm about to see what the o2 sensors are saying. The car has 4 of them total, correct?
I searched for an aj27s MAF chart. Couldn't find one. Only found NA charts.

@hispeed42 love the fact that your xjr 100 has that many miles! I read some of your older posts. Car has some wicked mods! Should post pics and vid when you get a chance.

 

Leaky injectors usually = neg fuel trims as ecu desperately tries to lean out mixture

You said you were going to pull the blower, get the injectors tested while you’re in there

 

Well yes, if everything is fine(which seems to be the case) the injectors are the last thing. So in that case, yes, blower has to come off to remove the fuel injectors. I wasn't just going to remove the blower for fun, lol!

 

Hmm just came across something interesting. Very weird.


So since my fuel trims were -20% on both banks, I found it odd that the injectors would be so consistent like that. Out of desperation, I wiggled the MAF harness. When I wiggled it, the car stumbled for a second or two. I then scanned it. And all of a sudden, my fuel trims are fine??

 

But it's so much fun removing the blower! And, more fun putting it all back together! When you do it, there are a few things that make the R&R a bit easier that aren't in the workshop manual. Like the wiring harness that goes across the top of the snout and has the connectors to the ECT sensor, KS sensors, and fuel injector connectors. If you pull apart those connectors (the ECT will already be off when removing the cooling crossover) and release it from the cam covers, it will go under the snout. And, when doing the intake elbow, loosen the support brackets a bit to make room for wriggling it to get the bypass hoses off and on.

I'm happy that this car has that much mileage on it, too! It's been my daily driver since I got it in '04. I've only had to have it towed home twice for mechanical reasons, the first was the fuel pumps and the second was what I mentioned above when the MAF went out. I had to have it towed twice for a flat tire, so I don't count those as "mechanical." My upgrades are only the Eurotoys larger SC crank pulley, Mina intake tube with BMC filter, Mina rear silencers, the JagWranglers' Real gauge ECT conversion, and the Eurotoys charge air cooler radiator. I might have to go back to the stock charge air cooler radiator as I've been having overheating issues when going up 'the hill' to the lake. I'm going to replace the water pump with one that has a metal impeller and see if that helps; if not, back to the stock radiator. But it sure looks good with that radiator right behind the grill.

Back to the current discussion, it just might be the O2 sensors that are causing your problem. I've seen some comments that state they need to be replaced every 30k or 50k miles, depending on commenter, and with the mileage on mine, I'm pretty sure that they have a lot of carbon buildup.

I ordered all new O2 sensors after Googling "2002 XJR O2 sensors," since there are no part numbers in the SNG Barratt parts catalog. The Denso Part numbers that came up were 234-9016 for the uppers and 234-4798 for the lowers. After checking out Bob's link above where he states in another thread that he replaced the O2 sensors with the correct Denso part, I went out and checked the part number on the original HO2 sensor, and it's a different number: 192400-3101. Uh-oh. Bob? Bob? Are these going to work? I saw where earlier XJRs use an 8 ohm heating and later ones use a 2.5 ohm.

 

Very nice mods. I was thinking o2's as well. But when I wiggled the wiring for the MAF, car ran rough for a second or two. Then smoothened out. Check fuel trims right after that. And they were perfect. See the screenshots above. Thing is, I don't know if it's the pins on the MAF. Or the wiring itself. MAF is new, so I doubt the pins are bent.

 

The female plug from the wiring harness might need a little help. Check that for looseness and try some dielectric grease if it is. That stuff conducts electricity and you should get good contact.

 

I emailed Denso this morning and they confirmed that the O2 sensor 234-9016 is the same as the original Jag part LNE1684BB. So, both of those part numbers are good.

 

The codes came back, for rich banks 1&2. But only as a stored code. I was watching the fuel trims. They were rich by -20%, the long term fuel trims.

So, I wiggled the MAF harness again. Engine ran rough for a second or two. Smoothed out, and went to trims that look OK to me. Screenshot below after wiggling the harness. The female MAF connector is on solid, and not loose at all. So it looks like my problem is something with the MAF wiring?

 

Brandon,
I only stumbled on your thread just now, too late to tell you about this, but a re-confirmation might still be useful.
The connector of the MAF is a known culprit.
I had the problem myself some years ago, values all over the place from time to time, and I remember some others chimed in to check them, they were right.
I bent the pins slightly for better connection, then installed the connector with some contact grease, never had the problem again.
And for the MAF values, they should not be a whole lot of different for the 4L XJ8 and XJR, surely not on idle.

 

So just bend the pins on the MAF sensor itself? The current MAF in the car is a new OEM. My old MAF isn't bad. So i'd probably bend the pins on the old MAF sensor.