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I was hoping someone might be able to point me in the right direction before I bury myself in the engine bay.
As the engine warms up (idle) it begins to idle a little fast unitl it gets to about 1400rpm at running temp, it then begins to pulse between 1200 and 1400 (starvation?). If I put the foot down a bit (>1500rpm) it seems to return to normal behaviour (perhaps a tiny bit sluggish on road)
It started out as intermittant... but seems to be settling in. Seems to be weather independant.
I haven't seen this behaviour before... any suggestions would be greatly appreciated.
Cheers
1996 XJ Jeep Cherokee - VERY red and VERY stock!
2001 KJ Jeep Cherokee - cooked her bad... sitting in the driveway!
[i]- ex Feroza man (eventually died on me) -[/i]
If you take the inlet piping off your thottlebody you'll see a largish hole inside the throttlebody at the bottom of it. This is an air bypass valve that is controlled by the temperature of the coolant flowing through it (coolant hoses run up to it from underneath).
Once the coolant temp beings to rise this bypass valve is supposed to close off completely and reduce the idle speed to ~850RPM. I think you'll find yours is sticking open. To check start the engine with the inlet tubing off (make sure nothing loose can get sucked in the throttlebody!!) and once the engine's up to normal operating temp place your finger over the opening- there should be no air flowing through it. If there is, block it off with your finger and you'll find your idle problem will be fixed.
The valve is an integral part of the throttle body (ie new throttlebody required to fix it......)
I ended up pulling my throttle body off and trying to lever the valve through the openings either side of the butterfly. This fixed it somehow as it hasn't played up again!
Wow... talk about quick response! Thanks for that... i'm gonna run down to the car and have a look now.
And yes... the revving at idle did cause a few Commodores to go careening off down the road at the lights! Hehehe
Cheers
1996 XJ Jeep Cherokee - VERY red and VERY stock!
2001 KJ Jeep Cherokee - cooked her bad... sitting in the driveway!
[i]- ex Feroza man (eventually died on me) -[/i]
Thanks for that, looks as if I might have to go shopping for a throttle assembly... strange that the valve is integral. I hope this isn't the kind of thing that's going to recurr on a regular basis!
Thanks once again for your quick and spot-on advice Murcod.
1996 XJ Jeep Cherokee - VERY red and VERY stock!
2001 KJ Jeep Cherokee - cooked her bad... sitting in the driveway!
[i]- ex Feroza man (eventually died on me) -[/i]
Before you go buying another (I got a price of $135 from a wrecker by the way) try removing the throttle body and levering on the valve through the openings either side of the butterfly. A screwdriver can just get down to it.
May be try some WD40, silicon spray or the like on it too- spray it liberally into the valve opening and exit. Then let it all drain out.
That's what I did to mine and it's been fine since, you've got nothing to lose by trying.
Turns out that the water hose feeding the air bypass valve is (was) blocked by some deposition. Noticed that the valve assembly was not getting hot during running, assumed no water flow.
Poked some wire in there and now all seems well. Must be about time to flush the cooling system.
Cheers for all your help. I would have been lost without your advice Murcod.
1996 XJ Jeep Cherokee - VERY red and VERY stock!
2001 KJ Jeep Cherokee - cooked her bad... sitting in the driveway!
[i]- ex Feroza man (eventually died on me) -[/i]
hmmmm thats odd... cuz my truck is doing the exact reverse of your guy's problem... instead, in driving condictions its ok, but if i'm doing some steady driving, then let off the gas to let the engine drop to idle speed (i.e. at a light) alot of times the engine dies instantly. also... i've managed to keep it running but it seems to try to idle at 500 rpms and keeps sputtering and wanting to die... wtf am i to do...
[quote="simplypv"]its a Strine thing and i just dont understand![/quote]
Regards, PV
Team [size=134][color=red][i]Anti-[/i][/color][/size]Asshat [b][color=orange]#5[/color][/b]- Yank!
murcod wrote: PS: Are you getting strange looks from people at traffic lights because they think you want to drag them?!? I was.
The Fast and The Furious Part 3 starring murcod's feroza - 90 minutes of tire frying madness!
Yep, it's a pretty embarrassing problem to have at the lights........ That would be 90 seconds of clutch frying action too- there wouldn't be too much tyre smoking going on!
I was. 
