I think I may have stumbled on to something with our car for those of us that seem to be suffering from low mileage. I'm not talking about the guys that are getting 25 MPG. I am referring more to those that are only getting say 20-22 MPG and they are being light on the throttle. I made an adjustment to my car tonight and I went from getting around 21 MPG up to 24 MPG. I know it isn't earth shattering, but it was a nice gain. The problem that I have is that I did 2 things at the same time. Both should have helped some, but the question I have is how much did each one help.

So, if you are looking to help me gather data and help others out, let me know. The adjustment is very easy to do, only requires a phillips screw driver, a small regular screw driver, and about 5 minutes of your time. Please note, the adjustment does require a semi delicate hand as if you are too rough with things, you are buying a new MAF sensor (about $100 and up). So, if you are clumsy, probably not the thing for you to be doing yourself.

So, before I get into the actual fix, this is the data that I am looking for. I am only wanting the mileage that you had on the current tank of gas (minimum 50 miles/80KM) and then after the adjustment, the mileage you get afterward (minimum 50 miles/80 KM before reporting). This way we get a fairly representative mileage that you are getting. It is preferable if you can drive the same path for both mileage reportings, but I know that this isn't always possible. So, try to make the two mileage comparisons as equal as possible without going out of your way. After reporting the post adjustment mileage, I would then like you to disconnect the battery for about 10 minutes and then drive another 50 miles/80 KM and then report your mileage at that point too.

Ok, for the part that you all have been wondering about. What you will need to do is to pop the hood and then open up the battery box. This gives you enough room to access the MAF sensor. Use the phillips screw driver to remove the 2 screws holding the MAF sensor in place. Remove the MAF from the intake and then disconnect the plug on the bottom. Now, with the aide of a light, look down the tubes of the MAF. One side will be really hard to look down, the other will be much easier. Look down the side that is easier to look down. Near the bottom of the tube, you will spot 2 thin wires with bulbs in the center. Look at their orientation to the posts on the end. Do these wires run a straight line from post to post? If they do, then no adjustment is necessary. If one or both do not, using the small regular screw driver, apply a little bit of pressure to straighten out these wires. Very little pressure is needed to straighten these out. Please note whether the wires were bent towards each other or away from each other as part of your mileage reportings. Once the wires are straight, reinstall the MAF and drive like you have been.

Finally, after getting the second 50 mile/80 KM mileage, disconnect the battery and see the difference then. Report the mileage then.

If my understanding of how the MAF sensor works, you should see the biggest gain from adjusting the MAF sensor. You will get a little bit more of a gain from the battery being disconnected and resetting the computer. Please note that you should not have to enter the code for your radio, but you will need to reset the time for the clock, adjust the settings for the A/C-heat, and reset the auto-up feature for all the windows (lower a window fully, then lift and hold up the window button until the window goes fully shut and then keep holding it up for an additional 5 seconds, repeat for the other 3 windows).

My engine seems to run a lot smoother and I am also not into the gas quite as much when maintaining a constant speed.

 

Thermo, do you think if you are getting half desent gas milage, and you make this adjustment to the MAF (?)sensor, it would give you better mileage or is this just somethig to help those with poor mileage. The best mileage I have gotten and it was only once so far was 34.8 MPG. Normal is 16 to 22 city and 21 to 26 highway. After I read your information I was thinking of opening mind just to see if the wire were lined up. What do you think?

 

Vai, your mileage is maybe a little on the low side, but not that far from the norm. Due to the variable valve drivetrain, intown mileage will take a bit of a hit. if you want to tweak your car a little bit, go for it. Just keep in mind that the wires need to be parallel with each other. Pushing them closer together doesn't help, spreading them apart doesn't help. The wires need to be a specified distance apart and you can tell that by looking at the posts where the wires are attached and aligning them that way. I will be awaiting your results. Remember, slow, steady hand with light pressure is all that is needed to make this adjustment (if needed).

 

Thermo - great post, however i dont trust myself enough to have an easy hand to be pushing the wires around.. with my luck (and the bad luck the x has brought me lately) i would get myself into problems.

however - disconnecting the battery for 10 minutes, reseting the computer.
I have no idea when the last time this was done (has to be 2+ years)

currently i get around 17mph city 20-21mph highway.

would this be worth a try to make the x run nicer and possibly improve mileage?

 

Thermo, you didn't happen to take pictures while you were doing this, did you? They would really help to know what you're talking about. ;^). Also, do you have a 2.5 or 3.0? And is the mileage range you're referencing city/hwy or both?

I've got a 3.0, and don't think I've ever seen 25 MPG, even in straight highway driving. Granted, most of my driving is in-city. I'll be curious to see if this adjustment works!

 

jn_lego, if you don't feel comfortable doing this, I can understand that. Hence why I said what I did to prevent people putting themselves into the position of having to spend money on their car. I would still be interested in the mileage difference between using old computer data and resetting the ECM and seeing what it is new. I know in my other car club, we see about a 0.5 MPG difference.

Matt, no I didn't take pictures, but I am sure I can get something that would help out people. As for the mileage, I would say it was a mix of 20% city/80% highway (mainly around 55 mph). I think once I get out on the highway and can open up the car to 70 mph, it will get even better. We'll see.

As for what vehicle this will work on, if memory serves me correctly, all 3 engines available in the X (2.5L/3.0L gas motors and the 2.0L diesel) all use the same MAF. So, there is no difference there.

Make the adjustment and get back to me. I am keeping a little record of what happens and going from there. I have been doing this with other problems and it pays off in the end.

 

I think it might be some form of sacrilege to drive one's Jaguar in a manner as to maximize gas milage.

I believe the only way you can morally do so is if you wear an old-guy plaid hat and a pair of those wrap-around "I just went to the eye-doctor and they dialated my pupils" sunglasses, and drive with a turn signal on all the time.

The THROATY ROAR from romping on the gas pedal is worth all the bad milage, but I might be wrong.

Quit fiddling around, you're going to break something. Expensive.

 

Bruce, I never said I was easy on my kitty. I'm just saying that for how I drive, I know I can get more out of the car. So, why not maintain the kitty and get all that you can. By running the car with the engine out of tune, you risk clogging up the cats and the muffler, leading to other expensive fixes.

As for fiddling with the car and possibly breaking something expensive, if I broke the MAF, that would be one of the cheaper things I have broken over my years. You are talking to the guy that ripped the suspension off of his truck shortly after paying $35K for it just so he could install a lift kit. At the time, I had no idea what I was going to get myself into as I had never done any sort of suspension work like that. As I have become older, I have become wiser and now I know just how far I can push things. Hence all the cautions and statements about being easy on the MAF.

 

Sorry if I dare putting my 2 cents here...

I am new to this forum, don't even have the car yet... and know very little about it so far...

Don't know what this adjustment to the MAF sensor is causing specifically. But if you noticed an increased mileage as a result, most likely it somehow changes the voltage signal to the ECU (the computer that control injector duty and spark timing), causing the computer to trim the injectors duty. Now, everything else equal, the engine would run leaner and your margin to detonation would be reduced. I don't know how the ECU works in this car but I believe it processes feedbacks from some sort of air fuel ratio monitor and possibly knock sensor(s). If so, the ECU would then pull timing to restore safety margin - basically by reducing the engine power as a result. If instead the ECU does not have any feedback like that (like in my "crude" Rx7) you better be careful...

It would be interesting if you could log data (tapping the OBII interface?) and compare data to figure out what is actually happening... and learn what your actual air fuel ratios and knocks are.

- Sandro

 

Uhhhhhhh I wish I could get 20mpg

I average 16-17mpg mostly city driving on 91octane. Whack.

 

Sandro, in short, by not having the wires in the correct orientation, the car can not measure the correct amount of air going to the motor. IT then has to default to something a bit more crude (ie, O2 sensors). So, it starts playing a balancing act with what the MAF is telling it and the O2 sensors are saying is coming out of the motor. If anything, the ECU is going to default to running the car a bit on the rich side to ensure no damage occurs to the engine.

 

thermo - after reseting ecu i gained what i beleive to be about 1 mpg

 

I see it... what you are saying is that if the MAF wires are not oriented properly, the sensor let the ECU "believe" that there is more oxygen entering the engine. The ECU then increases the injector duty, ending up running richer than what it could safely be. This is what happens in an open loop control (like in the Rx7). In the X-type (I gather with closed loop control) the ECU would then perhaps compensate some, based on the wide band O2 sensor reading more hydrocarbons than expected. What you call the "balancing act". But not enough - likely acting on the safe side - to avoid the excessive richness.

Still, if it was me, I would be curious to know the AFRs pre and after MAF adjustment. Do you know if this information could be tapped out from the OBDII interface? If so, it could be easily logged with an OBDcom or similar.

- Sandro

 

jn_lego, thanks for that tidbit of information. Amazing how just a simple thing like disconnecting the battery can affect your mileage. Atleast with my truck, I found that disconnecting the battery say every 5,000 miles helped me maintain that higher mileage, but loosing it gradually over that time. IT is something easy to do and I normally timed it when I was doing an oil change anyways. So, it wasn't like I was adding a lot of time to my life.

 

1 mpg isn't much - but it makes me happy.

i have also learned to avoid main stream gas station and go with the smaller ones that use less ethonol. and i keep it on the super 93.

 

Well, through lots of playing with my car, I have it now up to 25 mpg. I have narrowed it down to 1 of 2 things. It was either the brand of gas that I was using (went from Sheetz to Wawa) or the fact that I ran a can of Seafoam through the engine. Unfortunately, I wasn't thinking when I did both of them. I can tell you this that the car definitely smoked a lot when doing the Seafoam. So, hopefully it cleaned things out. I am beginning to think that a lot of my problems were simply from a cat that was starting to get plugged up. I have noticed now that I don't have to be on the gas nearly as hard as I used to to maintain speed. Also notice that accelerating I don't see as big of a drop in the mileage if I am watching it.

Thought I would keep those of you following this updated with my further adventures. I have a little ways more to go as I used to get 27-28 mpg. But, things are still improving, so, we'll see.

 

Thermo, what do you think of the Seafoam treatment? Is it more than just hype? I'll be happy to try it, but would like to know that actually works.

 

Matt, I feel that the Seafoam did something for the car. I will caution you on a few things though. The big one, when doing this, do it away from other people. Atleast my car smoked to beat the band for like 5 minutes or so. I'm not talking about something like the cars that are burning a lot of oil. I am talking like a misquito fogger. When I was driving down the road 2 mintues later, I couldn't see a car behind me. The other thing I will caution you on is that it may trip a few DTC's due to running the Seafoam through. In my case, I got a P1316 and P0301 code (P1316 is inefficient cat warning and P0301 is misfire on cylinder 1). Depending on how your car is, you may see these, you may see others.

In defense of the car, I will admit that I pretty much dumped in the Seafoam and the motor took it like a champ and didn't bog down like my Ford truck or Nissan Altima did. When I did the Seafoam teratment, I removed the line going to the brake booster at the intake manifold and stuck a 6 foot piece of 5/16" (as I recall, whatever size just fit into the opening) tubing into the opening. I then ran the tubing over to the driver's door. This allowed me to sit in the driver's seat, plug the end of the tubing with my thumb as I started the car. Then I removed my thumb and shoved the end of the tubing into the can of seafoam. The motor sucked up the entire can in under 10 seconds. Ideally you want the motor up at temp before starting everything, then start the motor, suck in half the can, kill the motor immediately (allow the Seafoam to sit in the engine to loosen up some stuff), wait 5 mintues, restart the engine, suck up the last half and then finally take the car out for a drive to get rid of the Seafoam from the engine. You will be able to tell if the Seafoam is all out of the engine by manually putting the car into say second gear and then taking the engine up to about 5K RPM. If you don't see smoke, then the Seafoam is gone. But, like I mentioned, it will take about 5 minutes of driving and doing these periodic high RPM runs to clear out everything. I was also mixing in some hard accelerations (from say 20 to 50 mph) here and there to help burn out the Seafoam.

 

Well you certainly had the smoke, but where was the requisite mirrors to complete the trick?

There's more chances of farquing something up by pouring the additive in the inlet- especially overloading a cat converter, so I'd be very reluctant to do this.

Seafoam is great at doing what it was designed for, but not many of us run 1950s vintage outboard motors in our cars.