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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
1. If there is, in fact, a problem, is it associated with the CA catalytic converters that increased the temperature around the intake manifold?
2. Are the ECU algorithms specifically programmed to the IAT sensor location? IOWs, if you move the IAT do you make performance better or worse if you don't bring along an ECU expecting values from a remote IAT?
If it is in the factory location and expects to see a certain temp in the 100's because of the heat soaked up by the intake manifold, then all of a sudden its reading more ambient air because its in the between the air box and manifold no longer stuck in the metal manifold, that could easily make the computer freak out.
If it is in the factory location and expects to see a certain temp in the 100's because of the heat soaked up by the intake manifold, then all of a sudden its reading more ambient air because its in the between the air box and manifold no longer stuck in the metal manifold, that could easily make the computer freak out.
Or dump more fuel because a cold intake charge means a more dense intake charge, which requires more fuel.
For those saying it's a brick and to not expect greater than 10mpg:
-When mine was bone stock (2wd, auto, 4.0L) I could manage 24 on the highway and 19-20 in town consistently.
-Now it's 4x4, lifted 3", huge front bumper, a winch, AX-15, 31" tires, and gas tank skids (probably bad for drag) I now get 17-19 in town and 19-21 on the highway.
If you suddenly have a loss of mileage, something went wrong. A sticky caliper. A bad O2 sensor. You installed a roof top tent... A parachute deployed behind you. Something changed, so it's worth looking at. If it's a sudden drop, I wouldn't expect your normal "slow wearing" items like spark plugs, wires, or cap/rotor. It would be a sensor that suddenly gave up. It does happen.
Right? Especially if the OP decides to go wheeling in Varangerhalvøya in January and the ECU sees a temperature from the IAT that's like 200 degrees colder than it should be? And on top of that, the temperatures are in Centigrade so now ECU is like REALLY confused?
.. if you move the IAT do you make performance better or worse if you don't bring along an ECU expecting values from a remote IAT?
Turns out you might not be able to do that, as the remote IATs are a totally different design. You'd have to take a late-design IAT and a late-design ECU to make that work.
If you're extremely suspicious, buy yourself a $19 scan tool and see the difference yourself.
Doing that won't tell you if your IAT sensor is heat soaked or if your intake air is just preheated by the manifold. It reading a higher or lower temperature doesn't prove anything in of itself.
OR, rather than a drawn out conversation about instrumenting thermal flow systems, let's cut to the chase and please show me documented MPG gains that aren't statistically insignificant.
Depends what you do with that power. Assuming everything is in proper working condition, the biggest variable is the loose nut behind the wheel.
If you want fuel economy, relax. Quit stomping the skinny pedal, stop tailgating, stop rushing up to red lights. Just chill out. You'll get there two minutes later than with all your stupid pushing and shoving your way through traffic.
Except on those days when you get there two minutes sooner, of course, because that happens, too.
Unless you are driving interstate distances, all the time that you gained by hot-rodding through traffic gets annihilated at the next red light, and you start at zero again. Then you do it all again. And again, your gains are zeroed out. Over and over again, and you never learn.
👍 Truer words have never been spoken.
Originally Posted by BlueRidgeMark
There was a thread a few years back that was very active for a few years. Yeah, years. It went on and on. It was all about getting better mileage, and no expense was spared. At the end, the guy who started it and kept it going, after all the mods he did, was getting exactly the same as I was getting in my box stock 97.
He must have been doing it wrong or didn't know about Charley3 tested mods on the other site. " Not all my mods were gas mileage related. I install an OME lift 1.25" front 2" rear, and skid plates, beefed up stock bumper, installed 30x9.5R15C Cooper AT3, and still got 24 mph at 60 mph, or 21 mpg at 70 mph due to gas mileage mods."
Not bad imho for a boxy 4x4 with auto trans, soft tires and replacing parts that we all change anyway and no gimmicky B.S. devices.
Imho good or bad milage from an XJ is relative. Box stock it's damn near a prius compared to a Dodge Ramcharger 360
If OP can get any improvement then that would be huge where he lives.
I've been working on developing a hydrogen fuel cell system for 6 years now. March 2015 was when I began and the first cell I tossed together with cheap parts from Lowe's gave me a persisting 28% improvement on my Ford Focus 2005. I've since graduated on to the Cherokee and a few years back had a 96 Buick Riviera that smelled of gas. I didn't drive it long enough to realize how much mileage there was to be gained if any, but the unburned gas smell in the exhaust went away and there was a noticeable improvement in power (as with the Ford Focus).
My 2000 Jeep Cherokee as it sits normally gets 10 MPG, and I have seen it raise as high as 17-18, but that was with a vinegar based cell I intend to do away with. With a clean water solution results have been more around 30-40% (before I watch it taper off over the course of driving). Tests in the recent year have been hit or miss, but I keep finding things that need fixed here and there and can't accurately tack down persisting mileage tests as a result. I keep thinking it's the ECU, but then I find a vac leak here, a faulty sensor there. Constantly have TPS codes which I've had for years but only recently am I experiencing noticeable problems with it. Basically I'm having one hell of a time knowing whether or not the cell works on THIS particular fuel injected vehicle due to constantly changing external factors. ATM I have a new IAC and TCU on the way. I suspect the IAC I JB welded shut into a static position hasn't helped matters given the vac leaks, and it has become loose itself with the bolts loosening up over time. God knows how long that vac leak has been developing since it's been a long time since I looked at it, probably 2 years now.
I would like to send a cell to you OP, or anyone else interested, for testing purposes. I need real data from vehicles that have less changing external factors. I got a recent batch of parts and will be putting one together for a guy I work with to have him test it out on his vehicle, and another guy I met through work that works at a steel manufacturing facility.
I want to get 5 of these out there on various vehicles. PM me if you are interested.
Janky *** 2005 Ford Focus Hydrogen Fuel Cell
Professional *** 1996 Buick Riviera from 2019 - 7 Gallon Reservoir, Dark Red cell was the Vinegar Addition for Horsepower - Using Vinegar Cell on the XJ Gave Most Mileage But I wasn't a fan of the smell when refilling, or the cost
Prototype *** 2000 XJ Fuel Cell mounted on Bumper for Testing 2020
Secondary Cell on Other Side of Bumper
I would be sending you just the cell itself already assembled. You can wire it with a fuse-tap I will send you to a fuse in the PDC under the hood so it kicks on when the vehicle is on (this is just for testing purposes). In the future the kit will come with a voltage sensing relay so you just wire it directly to the battery and don't have to find a fuse to wire to. Then it kicks on after seeing the alternator charging, then kicks off when 12.8V is reached. The cell will pull about 10 amps.
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Originally Posted by NM-XJ
Doing that won't tell you if your IAT sensor is heat soaked or if your intake air is just preheated by the manifold. It reading a higher or lower temperature doesn't prove anything in of itself.
OR, rather than a drawn out conversation about instrumenting thermal flow systems, let's cut to the chase and please show me documented MPG gains that aren't statistically insignificant.
Not to disagree with you but how do I say this, you're wrong.. Reading what the computer sees from the IAT will tell you if the IAT is reading ambient (outside) intake air temperatures, like it's supposed to. . If it's stock in the manifold, I can promise you, it isn't. Or you could go hook up your scanner and drive it and see.
Reading what the computer sees from the IAT will tell you if the IAT is reading ambient (outside) intake air temperatures, like it's supposed to. . If it's stock in the manifold, I can promise you, it isn't. .
Unless we know what the IAT in-manifold algorithm is, it's apples and aardvarks.
But I have to go back to my original premise. If you tell the ECU that the temperature at the IAT is 38 instead of 162 all you're going to do is enrich the mixture.
That said, it seems to me the oxygen sensor would correct any admixture so you'd eventually be back where you started from.
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Myself I'm of the school that chrysler couldn't have cared less about compensating for it in the pcm. I'm not sure about the enriching fuel but I do know it retards timing when hot. In fact Ill bet when they did move the IAT to the air box they did nothing special to compensate other than say There, we fixed that.
I'm going to go with "It sorta can".
If I start up and let it come to operating temperature then I know what IAT should normally see. In my case it's about 162 degrees:
So now I'm kinda thinking that the XJ engineers know that and programmed the ECU to expect something like that.
Anyway now I grab the intake manifold. If I can grab the intake manifold I doubt it's 162 degrees.
Kinda? The discussion started with the premise that a hot intake manifold heat-soaks the IAT sensor and screws up the numbers. Which is overall a false premise given how IAT sensors are built and function. And your observation generally backs that up. If I read you correctly, OAT < Intake Manifold Temp < IAT Reading. If the IAT reading is higher than anything else it can't be heat soaked...and suggests a weird algorithm/correction/calibration in the ECU. The problem with all of these approaches is that they aren't proving that the IAT sensor isn't wrong. They are just proving that you can move it to a different location and read a different temperature. You can't say the IAT is measuring properly without a secondary known truth source measuring the air temperature at the same location. Everything else is just using circular logic on the IAT sensor.
It pays to remember what the IAT sensor is: a Negative Temperature Coefficient (NTC) thermistor. Super sensitive little buggers. Take a look at the IAT sensor one day. You'll notice a little blue (or other colored) "puck" hanging by two small wire legs inside the sensor "cage". That's the thermistor; the entire piece of technology that is measuring the temperature. And it is wholly surrounded by the air flowing past it. Not much chance to heat soak it by conducting heat through those little wire legs. Nothing else about the IAT has anything to do with measuring temperature except that little puck = it doesn't matter if the threaded body gets hot.
03-01-2021, 04:11 PM
