Birty Dastards Jeep Club
Tech Forum => Workshop => Topic started by: jond on November 12, 2010, 11:38:13 AM
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ive worked out im gettin about 12/14 mpg out of my 2.4 petrol cherokee around town,the computer says about 18mpg,obviously not a great situation with fuel costs being so high so wondering if there is something wrong with it,ive changed the airfilter plus checked tyre pressures (33 psi),ive also bought one of those cheapo diagnostic thingies and it came up with error codes p0122,and p1294 ,i have fitted an after market roofrack but i cant believe it would affect mpg so much,any advice
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firstly he difference between the actual and computer readings is due to the computer being in US gallons.
they are thirsty cars but my daily driver is a 2.5l CJ and i get 23+mpg, saying that the 5.9l V8 when ranted is between 4 & 8 mpg but in a run can get 18mpg.
personally I recon the 2.4l is too small for the car and has to work too hard have heard that the 4l can return better mpg if driven right.
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Google is your friend. search for 'p0122 error code' & 'p1294 error code'. Good luck.
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sounds heavy for a fairly modern engine
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according to some reviews you should be get 24-26 mpg on average so either you have a lead foot or I would be thinking the lambda sensor needs replacing as it must be running rich. course it could be a lot of other things aswell.
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The easiest thing to check is the air filter. If it's clogged up, then you won't get the best mpg.
Use good quality fuel. My experience is Jeeps prefer BP or Shell. I found my old XJ did 5mpg more on ordinary Shell. It could also be worth using putting in the BP or Shell premium fuels for a couple of tanks to help clean the fuel system.
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personally I recon the 2.4l is too small for the car and has to work too hard have heard that the 4l can return better mpg if driven right.
not quite the same but i borrowed my Ma's 1.6 focus for a week and it cost me a fortune coz u have to cane the fuck out of it to get it to move
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cheers for the replies,according to google code p0122 is the throtle position sensor,and code p1294,is idle speed not reached,there has been a problem with the jeep since i bought it in that it idles at about 1000rpm and when you take your foot of the gas it stays at 2000rpm for a few seconds before returning to 1000rpm ,ive also heard an "iac" can cause problems with idling but dont know what it is,what should i do now i put £20 quid in and got 48 mls bit pi££ed off realy as its an ace 4wd :icon_rolleyes:
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i'm averaging 20mpg (380 miles per week) in my little 4ltr and thats driving conservatively. if i play with the traffic then that number drops dramatically
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i would change the tps and if that dont do it prob be the oxygen sensor in the downpipe ( upstream )
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My sister in law had a 2.4 Cherokee; it wasn't especially good on fuel either, but I think it still did better than yours!
Your roofrack will have minimal/no affect round town, but ditch it if you don't use it on faster mway runs.
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how much for a tps,ive found one for £55 on fleabay does this sound ok,is there anywhere else that i can buy spares from thats not the main dealer ,cheers guys
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Lighthouse Jeep is Diss, Norfolk 01953 681237 is the usual non-dealer supplier for the UK,
but don't discount the dealer, sometimes they'll surprise you. e.g. you won't find cheaper
spark plugs than the dealer.
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last time i tried lighthouse didnt have tps for my TJ so had to go dealers
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just checked the tps with a multimeter and it shows 5v with the throttle closed as you open the throttle the voltage drops steadily ,does this sound right,also cleaned the throttle housing and iac valve ,hope it starts :icon_biggrin:
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sounds abouts right, TPS's are usually 5-0v variable resistor
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think that eliminates the tps,computer still showing 17mpg and gettin 12mpg,how do i test oxygen sensor and why would code for tps come up,could a failed oxygen sensor cause the tps code
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unplug it and see how it runs, most vehicle go into a limp home mode when things go wrong, usually so that they engine doesn't run lean and overheat things.
We got a vw beetle that eats them for a living and you know instantly know when they go as the mpg drops and it runs lumpily.
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just checked the tps again,im gettin 4.5v with throttle closed this steadily drops to 1.5v with throttle open does this sound ok ,dont want to spend 50 quid on a new one if its workin
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still think its your O2 sensor.
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how do i test o2 sensor,ive cleared all the codes and taken it for a run and tested it again and no codes came up,computer now shows 21 mpg but i dont think im gettin that, ill work it out when fuel light comes on,car now idles at 900 rpm and runs ok with no smoke from the exhaust however it doesnt accelerate great in 3rd and 4th,maybe with the small engine they were like that new,if i can get 25mpg combined ill be happy
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there is a way of testing them, but you need to put it on an emmisions anyliser to see what the o2 readings are, garages round by us will throw the probe in the exhaust and can tell you in a few secs if there is a problem with fueling, otherwise.
http://www.autodiagnos.com/fileadmin/assets/en/downloads/pdf/technical_bulletins/misc/gea_testing_lambda_sensors.pdf (http://www.autodiagnos.com/fileadmin/assets/en/downloads/pdf/technical_bulletins/misc/gea_testing_lambda_sensors.pdf)
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just a quick up date on my jeeps fuel woes
ive replaced the tps £92 quid from jeep the car drives a lot smoother
ive also had a proper diagnostic test done which tested everything including oxygen sensors, all working fine
however its still gettin crap mpg,fuel light came on drove another 15 miles then put in £25 quid,60 miles later fuel light is back on ,my maths aint great but i reckon thats 5 gallon divide by 75 miles =15 mpg town driving ,could it be the fuel gauge ,i dont think i can afford to brim it with all the money i am spending at the mo,any known problems with the kj fuel tank/gauge ,sure i read something somewhere
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Rather than start a new thread on economy I seem to have a bit of an issue with my 4.0L Orvis.
When I first had it, it did 26-28 on a long run. Just before christmas driving up to Yorkshire it woudn't get over 24. (this is all off the computer thingy) It usually reads about 18mpg on the average counter when knocking about town.
Recently though in the last week it has hammered the fuel big time. I work about 2 miles away from home and it used one segment going back and for to work in one day.
A drive over to the next village today, the average reading struggled to get over 16 and that was driving like Miss Daisy. When first started and the first squirt of throttle its taken to stutter a bit and then pick up. Also, it does feel as though its having to work harder - or maybe changing higher up the revs than it did before. It just doesn't feel quite right.
One suggestion from someone who has had a couple of XJs (apart from things like filter, o2 etc) was to get a new set of injectors - a "matched" set? Would this make a difference?
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Aways start with basic maintenance items like air filter, plugs, leads etc. first.
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...Recently though in the last week it has hammered the fuel big time...
...When first started and the first squirt of throttle its taken to stutter a bit and then pick up...
Symptoms of a bad upstream O2 sensor. Free check - locate the sensor just below the manifold, follow the wiring and unplug the connector. Drive it for a couple of days and see if it runs OK. Check engine lamp will probably come on with the sensor disconnected, but mpg might improve and you probably won't get the stutter.