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[Green Jeep]

9/10 It starts fine just turn the key, like all my other Jeeps. when I bought it, it had been stood for a while and the owner was selling it cheap as he said it cut out at traffic lights, it ran poorly on idle...once warmed up on the way home a good boot and lots of black smoke... much better idle (perfect) and still hasn't cut out at lights.

Sometimes though it doesn't start without cranking over for a while and plenty of throttle, then runs lumpy on idle for a few seconds before running smooth again wondered if anyone could offer any idea's? All filters, plugs changed, dizzy and leads all look fine, new ish.

I have another Cherokee for breaking so I can swap any parts easily.

Thanks in advance Maf

[loosenup]

Hi Green Jeep
Have you checked the Crankshaft position sensor?
Sometimes they work but have an intermittant fault and let you down when you least expect it. Bit awkward to get at as it is on the top of bell housing at rear of engine.
I am far from the most knowledgeable one on here, but it seems to be a common fault on the xj
Hope this may shed some light for you.
Phill

[xjman]

Hi,
    I would try starting it with your foot off the throttle as the computer controls mixture and idling,  giving it any throttle just confuses it. An idling problem once it has started might be caused by the IAC (Idle air control) when I cleaned mine it had a lot of black sooty gung inside.  If you do clean it be very careful as it's not that robust. The CPS can cause it to cut out,  mine used to cut out about 10 minutes after I started it.  I eventually figured out why this was. The bell housing expands as the engine warms up and moves the CPS away from the flywheel, a new CPS can handle this expansion but an old and weak one cannot and bingo the engine cuts out.

[Mike Pavelin]

Long cranking tome on cold startup could be due to fuel rail pressure leaking back through the fuel pump. Next time you cold start, try getting the fuel up first by turning the ignition on for a second, turning off, do it again, turn off, then crank with no throttle and see if it fires up straight away.

[Green Jeep]

Thanks guys, does it mostly when warm, like when we've stopped in a lane....

xjman, it doesn't normally need any throttle... but when the fault occurs it will just crank over for ages, pressing the throttle makes it start.

[Green Jeep]

Jeep has been running fine for a few months... the other night started playing up and now very bad...

Sits at idle at lights as you go to pull away the revs drop down sometimes if you let of the throttle the revs will pick up and it will slowly pick up speed... if it stalls it will only start after 20/30 secs cranking with foot to the floor... fires up lumpy and need to keep some revs, before selecting drive, it will then rev fine and even drive perfectly before playing up again.

I've replaced the IAC from a running breaker that I had, old one was dirty... still same also when you blip the throttle the revs stay high and only slowly fall down until Idle is reached.

CPS sensor problems only happen when warm? I've got poor running from cold (and poor starting, will only start with foot to floor).

"CHECK ENGINE" light is on, did go out once when I disconnected the battery, stays on now...

... Any idea's? Thanks in advance Maf

[Panic mechanic!]

its overfueling by the sounds of it.

[Green Jeep]

its overfueling by the sounds of it.

That sounds very possible, mpg poor even though I have road tyres on at mo...

What controls the fueling is it the main ECU? I have a spare one I can try...

Also changed the throttle position sensor and the other module on the throttle body (three sensor/modules on the throttle body).

There is a flat spot just above idle speed, where the power dips and then gets through it and revs normally... but again slow to return to idle.

[Green Jeep]

Just changed the ECU, much better now, drives spot again, hopefully that's the end of the troubles...

Also fitted a large bore swirl chamber since I had a spare one from my old Cherokee, happy days...

Thanks again for the advice, Maf

[Green Jeep]

Problem of over fueling, cutting out, hard to start etc happened again...

Finally tracked down the problem (thanks Grayspeed) small sensor at the back of the cylinder head was telling the ECU wrong information, luckly I had a spare head and so the fix was free, happy days.

Cheers Maf

[BOP]

Problem of over fueling, cutting out, hard to start etc happened again...

Finally tracked down the problem (thanks Grayspeed) small sensor at the back of the cylinder head was telling the ECU wrong information, luckly I had a spare head and so the fix was free, happy days.

Cheers Maf

Whats the name of the sensor that went down at the back of the head? I've got intermittant poor idling problems at moment and am trying to trace it, maybe the same sensors playing up on mine?!

[Green Jeep]

Whats the name of the sensor that went down at the back of the head? I've got intermittant poor idling problems at moment and am trying to trace it, maybe the same sensors playing up on mine?!

Hi,

Not sure of it's exact name, as you look at the head it's on the right hand side at the very back of the head near the bulkhead, one small wire, the top part (plastic) pulls out and has a spade connector going into the actual temp sensor, I think this is to make it easier to get out, 13mm socket.

I'm sure if you order it from Lighthouse you could discribe it's location and they'd suss it.

Hope it sorts your problems out, cheers Maf

[Mike Pavelin]

Hmmm.. could be the placaebo effect. The sensor at the back of the head is for the temperature gauge only IIRC. There is a similar one at the front for the engine management.

[Green Jeep]

Hmmm.. could be the placaebo effect. The sensor at the back of the head is for the temperature gauge only IIRC. There is a similar one at the front for the engine management.

Very strange... honestly my Cherokee was running real bad, from cold it would cut out, be a bitch to start, cut out, get to traffic lights, idle okish, go to pull away, yep, cut out... starting when warm, took ages... changed the sensor... perfect, hot, cold, idle everything... mpg increased, happy days Maf

[Bubba]

maybe it just had the arse with you  ..........they do somtimes

[Green Jeep]

maybe it just had the arse with you  ..........they do somtimes

The problem has been there since I bought the Jeep (last summer) the last owner couldn't fix it and I bought it for spares, upon driving it home I found it much better than my old Cherokee... it's been over fuelling and sooting up the plugs, now everything is happy days. Cheers Maf

[BOP]

mines definately got the 'ump with me, wont really sit on idle its hunting around then if left to hunt around it'll die completely when at a standstill,try and pull away and it hesitates like its going to die then pulls no problems, annoying thing is it did it going to and from work yesterday, then going to work today it didnt do it at all, just been out to it and moved it and its hunting around and trying to die again! could it be my idle air controller is on its way out? tried cleaning it and puttin it back which worked for about 2 days last week then problem re-appeared again! 

[Green Jeep]

mines definately got the 'ump with me, wont really sit on idle its hunting around then if left to hunt around it'll die completely when at a standstill,try and pull away and it hesitates like its going to die then pulls no problems, annoying thing is it did it going to and from work yesterday, then going to work today it didnt do it at all, just been out to it and moved it and its hunting around and trying to die again! could it be my idle air controller is on its way out? tried cleaning it and puttin it back which worked for about 2 days last week then problem re-appeared again! 

Almost the same probs I was having, idle air controller, you mean the one in the inlet manifold about 2/3's of the way back? When I called Lighthouse they'd never sold one ever... so I kept looking, as per my posts above small temp sensor right at the back of the head resolved all problems, fingers crossed it's an easy fix... cheers Maf