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[neilhull]

HI I am in the process of fitting a gas kit to my 1997 xj . This has developed a stutter or misfire  :?: . has any one any ideas what could be the cause of this . I can not finish my gas conversion until i sort this out . I have not connected any of the gas electrics or the mixer so this cannot be the cause of the misfire
          cheers NEIL

[scrw]

Have you fitted the mixer to the TB yet? What bits of the gas kit are fitted? Did it do it before you played under the bonnet?

[neilhull]

Have you fitted the mixer to the TB yet? What bits of the gas kit are fitted? Did it do it before you played under the bonnet?

HI SCRW No the mixer is not fitted to the tb .The only bit of the gas kit fitted so far are the tank.the filler. the pipes . I have not dun any electric connections . misfire started the day i started to fit the kit . about two weeks a go i had the same thing but it cleared so yes it started before i played under the bonnet  . i have ordered a new dis cap and rotor arm to see if this helps. I think it might be a sensor but i don't know wich one

[scrw]

Stick in some new plugs (set to 0.8mm for LPG) and leads too.
Could be an exhaust O2 sensor tho....

[neilhull]

Stick in some new plugs (set to 0.8mm for LPG) and leads too.
Could be an exhaust O2 sensor tho....

HI SCRW  will get new plugs and leads but old ones look ok . I thought about the 02 sensor as the misfire only happens when the engine comes up to temp . how do i test this all help appreciated . i need to get this sorted

[scrw]

Need to read off resistance from the O2 sensor (or get a spare to test with)

Not 100% on the Jeep fuel map but from working on programable ECUs on kit cars they use the O2 sensor reading along with the temp sender to map the warmup fueling, if one or other is dodgy you get a missfire during warmup as the ECU goes from full cold fueling to normal warmed up fueling.

[neilhull]

Need to read off resistance from the O2 sensor (or get a spare to test with)

Not 100% on the Jeep fuel map but from working on programable ECUs on kit cars they use the O2 sensor reading along with the temp sender to map the warmup fueling, if one or other is dodgy you get a missfire during warmup as the ECU goes from full cold fueling to normal warmed up fueling.

Will let you know how i get on i wont be able to work on my jeep till sat    as i have work commitments

[Bishops Finger]

Chuck it all in the bin and use petrol....

[scrw]

chuck BF in the petrol & use matches

[Jonny Jeep]

Sounds EXACTLY like the O2 sensor is the problem - or rather the heater circuit of the O2 sensor.

Jeep use a heated sensor, as do most manufacturers. The purpose of this is to get the O2 sensor heated above 300°C (350°C is normal operating temp I believe) which is the temp that the sensor starts giving out accurate info for the computer to use for setting fuel trim. The computer changes mode when it thinks all is good and starts looking at the data from the sensor. If the heater circuit is failed or on it's way out the sensor isn't hot enough to be accurate by the time the computer switches mode. The result is that the Jeep runs rough until the exhaust gases have heated the sensor past the temp at which the data becomes accurate. That's when the engine smooths out again.

Here's how to be sure it's the sensor... Find the sensor in the exhaust pipe just below where the manifold bolts up. Follow the wiring up to the end of the inlet manifold where the connector is mounted. Unplug the connector. Drive the Jeep about for a few cold starts and there should be no rough running as the Jeep cannot use the sensor if it's unplugged and will use it's factory programming instead. Plug the sensor back in and the fault will come back. That will ID the sensor as the cause. Replacing it is the cure.

[neilhull]

Thanks jonny jeep  will try this tomorrow .

[neilhull]

been trying to get the f***ing lambda sound out the pig will not budge will have to take the front pipe off :smt093  

[Jonny Jeep]

Did you try just unplugging the connector to see how it ran? To remove the sensor get the engine up to temp and try it when it's hot, it should be easier. If you remove the pipe to do it try and get some heat on it with a blow torch or something.

[PtP]

I suspect I have a similar problem with my TJ and I started searching for the cost of a replacement and came across this informative link which might be of interest: http://www.picoauto.com/applications/lambda-sensor.html

I have an intermittent misfire when the engine is warm; its fine whilst cold/warming-up. The engine seems to be running lean in general and slightly rough on tick-over as well as sometimes hesitating when accelerating. I’ve already replaced the plugs, distributor cap and rotor arm, so I’m now moving onto the upstream oxygen sensor.

[Panic mechanic!]

it does sound like a lamba sensor if its running lumpily on warm up, Iahve had a few cars where sensors have gone and it generally means the engine falls back to limp home mode, which is generally overfuelling, hence the poor running, btw you  ideally need a lambda socket to get the little buggers out,cos they do seem to weld themselves in,

[PtP]

I came across these two types special sockets whilst looking around. They are listed at the bottom of this link: http://www.cats-direct-shop.co.uk/lambda-sensors.php But I guess you can get the same locally.

[Panic mechanic!]

yup i got one if you ever need to borrow it, they are around £6 when i last brought one, mines the upper type.

[PtP]

yup i got one if you ever need to borrow it, .............

Thanks, I might just take you up on that.  

[neilhull]

Did you try just unplugging the connector to see how it ran? To remove the sensor get the engine up to temp and try it when it's hot, it should be easier. If you remove the pipe to do it try and get some heat on it with a blow torch or something.

HI the sensor is the fault but i can not get it out .I think somebody has tried before i got the jeep . The insulation on the wires have been damage by some one trying to test them . like i said i will have to take the pipe of this Sunday to see if i can remove the sensor in a vice will use plenty of heat. will let you all know how i get on

[Panic mechanic!]

last one i took out that was stuck like yours,was a right bastard. the only way i got it out was the cut the wires off where they enter the sensor then cut the porcelain off so that i could get a normal socket on it and a torque wrench, i think if you took it off and put it in a vice you would end up damaging the exhaust pipe first so be very careful.

[neilhull]

Right i got the little f***er of . first i tried dropping the front pipe this gave me more room to get a BIG shifter on the sensor it still would not move .So next its of with the exhaust  back box came of easy  cat not a chance. So its jack under the gearbox of with the cross member then of with the front pipe with the cat still attached . In to the vice with the pipe get a huge shifter plus a big long bar . OUT comes the sensor :-) . ALL so loosened the sensor in the cat re did threads with copper slip . NO more misfire  :-D   . will fill with gas tomorrow will let you all know how i get on with the commissioning

[PtP]

Well done!

Where did you get the new sensor from and how much was it?

[neilhull]

Well done!

Where did you get the new sensor from and how much was it?

 This is where i got the new sensor http://www.lambdasensor.com/main/mindex.htm  cost £46 including first class post  ordered on a Monday was here on Tuesday . Local motor factors wanted £128 so i gave them the

[xjman]

Hi,
    Glad you found and sorted the problem. My 93 XJ has done over 30,000 miles on LPG, the only problem I've had was a ram air effect into the air intake which sometimes caused it to cut out if going at speed with no throttle.  I blocked off the front of the original intake and made a new opening on the underside of the intake tube, no more cut outs.  So I would say go ahead and fit LPG and save yourself a fortune.

[neilhull]

Yep shes running on gas . I can't tell the difference between gas or petrol . for under £800 money well spent