Grand V8 uneven tickover

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My 02 Grand Cherokee Overland V8 (high output) has started to have an eratic tickover, not all the time but when it's happening it "hunts" between 600-1500 rpm any ideas please?  :-k

[ronttuk]

vacume leak???

[Bishops Finger]

O2 sensor?

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Thanks will have another look for any leak, but couldn't see any thing obvious, where is the 02 sensor? (it's scary when I look under the bonnet)! and too really wind me up the passanger side heater will only blow cold  so the dreaded blend door has gone, had the drivers side sorted when I bought it in Feb  but on the positive we have just spent a few days off roading in it (Strata Florida was fun) on std road tyres and never got stuck very impressed, but need the lift kit and some cooper sst's  :D  and if you boot it she just go's so well  :lol:

[Bishops Finger]

O2 is somewhere on the exhaust system...

[jonnyk]

Pops

Had the same issue on my 4.7 V8.

Its unlikey to be the O2 sensor as this would prompt the engine management light to come on as would a vacum leak, the most likely culprit is the IACV (Idle air control valve).

This is a plunger type valve that sits on the right hand side (when looking under the bonnet) of the throttle body and controls the ammount of air allowed into the engine (when the throttle is closed).

It often gets carbon build up on it (a common problem on these Jeeps) your best bet is it take it out and clean it. Not a difficult job but you will have to remove the airbox (the bit which has 4.7 High output written on it, held on by 2 bolts) that exposes the round throttle body. On the right hand side of this you have electrical connectors for both the IACV and the TPS (throtle positions sensor) . Disconnect the IADC and undo the 2 Torx bolts. you can then slide it out and clean it up. I used WD40 and a couple of rags, be careful not just to push the muck down into the recess an old tooth brush works well. Then dry it off and slide it back in and just put everything back together.

I originally took this issue to a local Jeep dealer and they were worse than useless and didnt fix the problem, still charged me 2 hours work though!


J

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Pops

Had the same issue on my 4.7 V8.

Its unlikey to be the O2 sensor as this would prompt the engine management light to come on as would a vacum leak, the most likely culprit is the IACV (Idle air control valve).

This is a plunger type valve that sits on the right hand side (when looking under the bonnet) of the throttle body and controls the ammount of air allowed into the engine (when the throttle is closed).

It often gets carbon build up on it (a common problem on these Jeeps) your best bet is it take it out and clean it. Not a difficult job but you will have to remove the airbox (the bit which has 4.7 High output written on it, held on by 2 bolts) that exposes the round throttle body. On the right hand side of this you have electrical connectors for both the IACV and the TPS (throtle positions sensor) . Disconnect the IADC and undo the 2 Torx bolts. you can then slide it out and clean it up. I used WD40 and a couple of rags, be careful not just to push the muck down into the recess an old tooth brush works well. Then dry it off and slide it back in and just put everything back together.

I originally took this issue to a local Jeep dealer and they were worse than useless and didnt fix the problem, still charged me 2 hours work though!


J

Thanks mate, did what you suggested and had a look tonight, and it was covered in black soot,  :shock: so hopefully it will cure it, as it only happend intermittently I will see how it go's over the next few days.  :)

Thanks again for the in depth explanation, much appreciated.   :clap:  :lol:


Chris.

[johnte]

I've been reading this with interest,my Wrangler 4.0 suffers from exactly the same problem, does anyone know if The Wrangler has an IACV or even better - if it has where can I find it. Got to be worth a try, I'm pulling my hair out :doh: with this irritating problem....

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Well so far so good  ;) she has not been misbehaving, and when I start up she used to rev up to about 1600rpm before settling down, now it just revs to about 1200 for a second or two, so much better  :clap: :lol:

[CaptainColourful]

I've been reading this with interest,my Wrangler 4.0 suffers from exactly the same problem, does anyone know if The Wrangler has an IACV or even better - if it has where can I find it. Got to be worth a try, I'm pulling my hair out :doh: with this irritating problem....

Had the same on my GC 4.0 last year. A quick clean and all is well.