Grand Cherokee little problems

[sooki_blu]

I have a 96 4.0 Grand Cherokee and after a bit of advice....

When you startit up, either when hot or cold, the idle is up and down from 200rpm to 700rpm. Even when driving the revs drop up and down the same and the power drops up and down, even when accelerating.
If you boot it a bit when it does it, it will eventually rev ok, then be fine until you turn it off and start it up again when it does it again.

My mechanic thinks the engine temp sensor might do it? What you think?

Another thing, my radiator top hose has a little split in it, but when I went to order one, the parts list said top hose 99 on, for the 4.0 not 97 like mine is. Is the engine different from 99 on?

Where can I order parts from thats not the main dealer!?!??

[Bishops Finger]

Lighthouse Jeep Parts

The idling could be crank position sensor or 02 sensor...

[sooki_blu]

Would the crank position or O2 sensor only show the problem only once you startup though? also, its not immeadiately after starting up, its usually about one minute after, then clears if you boot it a little.

DO lighthouse have  a website? cant find one.

thanks

[Bishops Finger]

http://www.ampar.com/lighthousejeepparts.html

Best you phone them tho....

[isle of man]

Have you tried disconnecting and reconnecting the battery to reset the PCM? 02 sensor would be high on the suspect list after that.

[Bishops Finger]

An idea.. :D

[sardonicus]

I have similar problems on mine when I switch from gas to petrol. It runs really lumpy and the revs are up and down and doesnt run at all well.
A temporary fix is to disconnect the battery for a few minutes,(but make sure you have the radio code !) which will reset the pcm,and should run fine again. mine does untill it has been run on gas again,so i just keep it on gas.
Ive replaced the O2 sensors but didnt make any difference, so I think its probably the crank position sensor,as that was the consensus when discussed on here some time ago.
Its a bit tricky to get to but is a fairly simple job to do,its down the back of the engine by the bulkhead near the bellhousing somewhere i think.
Good luck and keep us posted if this cures it.

[sooki_blu]

Another quick thought - Is the engine the same as the 4.0 in the Cherokee? Seems easier to find parts suppliers for the cherokee online than the grand cherokee. (Mines a P 96)

One last thing - I dont have the code for the stereo, but I do have a Pioneer unit with satnav that Im thinking of dropping in anyway - do I need any specific cables to do it -dont suppose the GC has an ISO on it as standard....

[dxmedia]

It's the same lump,

Yes you need a (very bleeding expensive) adaptor due to the amp which sits under the rear seat. £50 odd for the adaptor. The £5 ones from Halfords don't work if you want all functions.

[sooki_blu]

What functions would I lose?  :?

[dxmedia]

Don't know for sure, I'm still running the original system, but

http://cgi.ebay.co.uk/Jeep-Grand-Cherokee-ISO-Wiring-Harness-Adaptor-PC9-407_W0QQitemZ350305075984QQcmdZViewItemQQimsxq20100116?IMSfp=TL100116227002r18500

is what's needed if you've the amp under the passenger side rear seat.

I presume it's the wiring for the amp which is the issue, standard ISO wiring probably doesn't have everything for remotly switching the amp on and off and all that gubbins, IIRC there's 10 speakers in a ZG with the infinity sound system. A little more than a standard ISO 4.

The cheap ones only work if you don't have the amp, which I think is part of the infinity package.

[sooki_blu]

All my speakers have Infinity Gold written on them, that mean its the amplified system?

[dxmedia]

yes, you need the propper adaptor, not the fiver one from hafords.

[luffy]

The crankshaft position sensor is unlikely to cause fluctuating idle as it either works or it doesn't.  The CPS usually fails when the engine is hot as it's affected by the heat from the exhaust/manifold and when it does fail the engine will just die.  (Happened to me at 60mph on a main road!)

Rough idle could be one of several things- O2 sensor, MAF, throttle body sensor or idle sensor to name a few.  Try disconnecting the battery first as has already been suggested to reset the PCM.

It's the same basic engine in the Grand and XJ Cherokee but the radiator hoses might be different due to the different body shapes and radiator positioning.