MAF sensor clean up. ....all modern Jags applicable.

[J44EAG]

This sensor is one easily cleanable unit that is so often neglected but so important when it comes to keeping a car reliable. A dirty sensor bulb and hot wire greatly affect performance and can readily generate engine check light and MIL lamp illumination on the car dash panel. Frequently a restricted performance message will also be seen and you will certainly feel the car drop into a very low performance situation.

The MAF sensor is located on most Jaguars immediately after the air filter box within the so called air flow meter tube which attaches to the throttle body air feed pipe. It is usually fixed into the airflow meter tube with between two and four Torx head self tapper screws. Remove those screws and pull the MAF out of its location. You might also separate the sensor from its cable plug and clean that up whilst you have the sensor out of its mount. This image shows the sensor mounted on the airflow pipe.

Having removed the sensor, inspect the hot wire and bulb. They should be shiny clean and not covered in black gunk as seen in this shot.

This sensor hot wire is very delicate and ideally should be cleaned with spray carburetor cleaner or switch cleaner. When I have not had that available, I have used alcohol panel wipe and a VERY soft paint brush to remove the crud. Also clean the plug connector pins and the plug socket. A little electrical grease will help keep any future corrosion at bay after the clean up. It is desirable that you get this sensor wire absolutely spotless as in this image.

After cleaning the MAF, just refit to the car and if you had no fault codes present before you cleaned the sensor, you just start the car up again and off you go. I`m certain you will find a significant improvement if your sensor was as filthy as the one in my second picture.

If you had fault codes present before you cleaned the MAF, then you will have to clear those off using a diagnostic tool or disconnecting the +Ve lead from the battery for at least twenty minutes. If you do that though, you may have to reset the clock and re-enter your radio code after battery disconnection. Ensure you have the radio code before you ever disconnect a battery!

I`ve created this thread about MAF sensor cleanliness after having my X350R give me a few sleepless nights due to repeated check light, MIL light and restricted performance issues suddenly developing. The fault codes can be read and cancelled using a diagnostic tool such as an iCarsoft 930i or a Torque app, Bluetooth ELM327 unit and an Android phone. The Torque and Android combo is presently my favorite method of diagnosing a car and is also a very cheap way of obtaining vehicle diagnostic gear for just a few pounds.

The dirty MAF found on my car today caused my diagnostic gear to find Bank A &B fuel mixture levels to be lean. In other words, too little fuel being delivered to the cylinders. Cleaning the MAF sorted that issue and now normal A & B readings are present again. No more faulting or restricted performance and the car is back to normal.

Cleaning and MAF is quick and easy and should take no more than five minutes to achieve. Recommended preventative maintenance for sure.

Mike K

[PTR200Jag]

Mike, thanks for this.... yet another job for me to do!

I am still having probs with XK8 with random comings and goings of the cel / restricted etc so have also now done this job, posted on XK8 forum, pics etc.

Took me longer than your five minutes though ! had to take pictures !!

Let us know if your problem clears !

[sheldon1]

Mike,
Happy New Year. Do you know the Torx Star size of screw fitting for the Stype 3.0 SE Maf sensor.

ie. T5 T6 or T7

Thanks

Paul

[J44EAG]

I recall it might have been a T6 on the S-type but regret I really can`t remember. Most of the small Torx kits you can buy cheaply and probably locally will surely have one that fits. Sorry I can`t be more accurate with that.

Just had an interesting chat with Tom Lenthal. (TL jaguar at Barkham near Wokingham) about this slight but continued glitching on my 350. Having described the symptoms and my course of diagnosis and attempted fixes to date, he confirms I am on the right lines and the advice given by Rob J in respect of getting things back to normal. He confirms that the thermostat if dodgy can cause an overheat signal via the temperature sensor even though an overheat proper may not be present. The fact is that when a glitch occurs, Banks A&B are shown on the diagnostic as running lean. Had it only been one of the two banks, then it would not point to either a dirty or time expired MAF sensor but rather to an oxygen sensor on just one of the exhaust down pipes and cat. A combined A & B fault could be due to a duff MAF but Tom initially thinks that the fault could be an air leak somewhere after the MAF sensor and the throttle body. However a duff MAF should not be ruled out or indeed should the temperature sensor.

Tom also agrees with Robs diagnosis that a tired temperature sensor could still well be an issue. Faulting tends to occur as the engine is at a half hot temperature. I clear the fault and the engine can run well again until I switch off and restart. It doesn`t happen every time though, which makes the problem a bit of a cuss. Tom agrees that I do need to install a new OE temperature sensor as soon as possible before attempting to diagnose or fix further.

British Parts sent an email to confirm dispatch of the temperature sensor and I spoke to them this morning to attempt to get them to send me a sensor with a 12mm thread rather than the larger threaded unit which a Main Dealer had under the same part number ie AJ8 100 31.

I quickly checked the car just now to ensure jubilee clips on the inlet trunking after the MAF were tight, the same with the plenum to the throttle body and the clip from the trunking to the large ali plenum chamber on top of the supercharger manifold. All appeared tight. At the same time I checked to see that any air or vac pipes were still in good condition and not rotted at the ends or had cracks or splits in them.

That having been done, I have to use the car tonight and will attempt to see if there is any change. The new sensor should be here tomorrow and I`ll fit that as soon as it arrives.

An open invitation to you all here, guys.
Tom Lenthal has agreed to attend the FEBRUARY 2016 Portsmouth Region meeting on MONDAY 8th February at our usual haunt up at The Churchillian to give a presentation. This should be a wild session as he hopes to be bringing Viezu/Paramount ECU remap guru, Gerald Morton with him. ....The Tom and Gerry Show on tour!! Gerald reflashed my old V8 years ago and really does know his stuff. Both he and Tom are pure magic. If you would like to come and meet these two guys, enjoy their presentation and perhaps a meal beforehand, please let me know. All are very welcome.

More news on the glitches tomorrow.

Mike

[PTR200Jag]

Faulting tends to occur as the engine is at a half hot temperature. I clear the fault and the engine can run well again until I switch off and restart. It doesn`t happen every time though, which makes the problem a bit of a cuss. Tom agrees that I do need to install a new OE temperature sensor as soon as possible before attempting to diagnose or fix further.

More news on the glitches tomorrow.

Mike

When you say "faulting tends to occur as the engine is at a half hot temperature" do you mean that as the engine warms up to around half way on the gauge to normal that it pops a "restricted performance" / CEL/MIL light etc ?

I have had this a number of times on the XK8 but it is not consistent.
Get it out of the garage, all ok, let it warm up and around half way up the temp gauge the RP comes on....or drive away when just off the bottom of the gauge and once again around half way up RP comes on.... but then it can go back to no restriction just as easily when it is hot. or it may not come on at all through the warm up to normal but then pops up when at temperature

[J44EAG]

Almost exactly the same fault and description although I haven`t had that full red signal again on the original sensor since it first occurred on the M26 last Monday.

Having now done the work described in my last post, I`m off along the M27 for a ride in an MRI scanner. Not quite so problematical! I bet the car faults at least half a dozen times. Android with me to reset each time. What a pain!!

Looking forward to receiving the new sensor tomorrow. Hope it is the right one!.

Mike

[Norbertflyer]

Thanks Mike, I used Halfords electrical contact cleaner on my MAF sensor. Works well. Quite a few black bits came off, converting the sensor into a nice shiny version afterwards. More power delivery and no acceleration hesitation now.

Richard

[J44EAG]

Frankly, any easy flash off solvent capable of breaking up crank case oil residue will be capable of destroying the gunk on the wire.

As said previously, don`t try scrapping with a hard metal implement or the hot wire will become damaged.

The MAP sensor below the throttle body also suffers from grunge build up. The build up can be astounding and can block the channel to the sensor. It can also make sensor removal difficult if the gunk has aged and hardened through heat. Two Torx screws hold it onto the inlet manifold and an o-ring provides an airtight seal. Once the sensor is off, cleaning can begin. Wear protective gloves, place solvent in a bowl and use a small paint brush to break down the gunk. Often it is easier to attack the MAP sensor by removing the throttle body. This will also be caked in grunge and need a good clean up. Get a new gasket before starting that job.

One thing leads to another!

Mike

[trampintransit]

Once the throttle body is off.... What's the best method to clean that.... Leave it in petrol?

[J44EAG]

Soft, lint free rag and spray carb cleaner. Go easy on the teflon coated area around the throttle plate. Most of the grunge will be below the throttle plate. Ensure all the grunge is removed from the throat, throttle plate and spindle. Ensure you have a new throttle body gasket to hand before you start the job. Wear nitrile inspection gloves because this is a filthy job and the grunge impregnates into human skin.

Do NOT immerse the throttle body in petrol. You will wreck the electronic components and stepper motor.

Mike