Help needed. Grand Cherokee keeps cutting out.

[grg2023]

Hello, I’m relatively new to Jeeps. I have recently acquired a 1998 model Grand Cherokee Ltd (Orvis) 90k 4.0L auto it has a good quality LPG conversion but is otherwise standard. I think it is the best thing since sliced bread. The only fly in the ointment is a most annoying intermittent fault. The engine cuts out as I am driving along, engine stops steering goes heavy, coasts to a halt not a light in sight on the dash, and the blowers are still running. Knock it out of drive into park, turn off the ignition switch and turn it back on, all the lights come on as normal and the vehicle starts perfectly. This can happen twice a day or once a week any advice you can give would be most appreciated.

[AbyssDJ]

check that the battery terminals are connected properly and not loose

[Bishops Finger]

Also potentially sounds like the O2 sensor......

[grg2023]

check that the battery terminals are connected properly and not loose

Thank you for your response, have checked the battery terminals everything fine there, good solid connections. Any other ideas ?

[grg2023]

Also potentially sounds like the O2 sensor......

Thank you for taking the trouble to respond, this one is not so easy to check, the OBD does not seem to have recorded any problem. I am probably being a bit simplistic but if it was a problem with the O2 sensor wouldn't I expect to see a check engine light?

A new symptom manifested itself today; after it cut out it wouldn't re start for around 30 min. everything seemed to be making the right noises but not firing. Roadside diagnostics (no tools) seemed to indicate no spark. When it did start it was as if there hadn’t been a problem it ran as sweet as could be. I am beginning to think it will have to go I am not equipped with the experience to deal with it and the prospect of funding a protracted series of sessions with my local garage trying to find the fault does not appeal.

[UKJeeper]

I'm thinking Throttle body sensor (TBS). I'll be right back, i have to check with my mate. (yes Stew, THAT mate).

[Bishops Finger]

Hang on for that mate of UK's considered response........    :lol:

[AbyssDJ]

sensor this, sensor that... bloody electronics  :roll: ;)

[Bishops Finger]

sensor this, sensor that... bloody electronics  :roll: ;)

Sadly yes... :shock:

[isle of man]

i believe the cps has this sort of symptom (no spark) when it starts to malfunction.


peter henry

[UKJeeper]

My mate has got back to me. He thinks its the crank sensor (like Peter suggests above), and he used to be a chrysler head mechanic so i'd believe him.

[luffy]

My XJ did this and it was the Crank Position Sensor (CPS) at fault.  One minute everything would be ok and the next minute, nothing.

The CPS is affected by the heat and will start off by playing up intermittantly but will eventually fail completely.  Or at least mine did.

I'm not sure what it's like to change on a GC but on my XJ I did it from above and it took about an hour.

[sardonicus]

mine did the same a while ago,down hill round corners!A bit scary when the brakes and steering goes! 8-[
Does it run a bit low on rpm at idle?on gas.
 I think someone on here suggested disconnecting battey for a few minutes,reconnect  then letting it run at idle for about 10 minutes.this should let the ecu find the correct idle speed/mixture etc.Worked ok for me.
the numerous sensors could be at fault but give this a go first.

[Bishops Finger]

If UK's mate says thats the issue..nuff said :lol:

[grg2023]

Last week I replaced the cps and have had a gloriously un eventful trip to Scotland and back. I would like to thank everyone who took the trouble to help me with this problem.

Ray

[Bofh]

I guess your sorted now but I thought I'd mention another cause of this problem that I sufferd with.  I had the same sort of trouble, always did it on the aproach to a roundabout when breaking.  Engine cuts out and your in trouble.

Well with mine it turned out to be an air leak, there was an intermitant air leak in one of the hoses under the air intake.  Aparently LPG systems are super sensative and will cut out at the slightest electrical glitch or if there's to much air getting in.

Had my problem on and off for a year or two, one roll of gaffa tape later and its never happend since......

[isle of man]

holly thread revival.............



*good point though*





peter henry

[CaptainColourful]

Similar probs with my GC on both gas and unleaded (being generally lumpy to the point of stalling ... yes an auto stalling ! ) so I took it to the guy who fitted the LPG conversion.
He stripped the throttle and cleaned out the throttle sensor unit and it's been fine since. There's a MAP sensor and electric motor thingy (with a plunger thingy that adjusts the amount of air on tickover)  which was covered in gunge .... getting to it wasn't easy even with the correct tools, so I think it was £50 well spent.
 
How you mean what's a "thingy" ?

My advise it to let a bloke who knows sort it before you mess with it yourself ... maybe not the way a lot would prefer to do things, but it saved me a lot of pain ( and the cost of special tools) trying to sort it myself.
 I am not techy as you can see, but an hour with a bloke that knows what he is talking about is far better than days prodding and poking to no avail.

[Bishops Finger]

Couldn't agree more......