Any ecu/fi/electronics/jeep folks out there?
Discussion
OK, so I can build a car with points and a carb, but all this electronic wizardery is a bit of a mystery. My wife's jeep cherokee (4.0 litre 6, petrol) won't run at tick over. You can start it if you rev it up and keep it going by blipping the throttle but it just dies when you take your foot off the gas.
I'm assuming that there is smomething that 'detects' tickover and sets the fuelling & spark acordingly? Logic suggests it can't be a crank position sensor as the motor will run on throttle. And the rev counter works and I'd have guessed that might be driven off a crank speed sensor. And I don't have a wiring diagram, so I've no idea of the inputs to the ECU (and I'm even just assumiung it has an ECU as it's fuel injected).
So, what is it that 'detects' tickover (if that is actually what's wrong - any other ideas?), and any idea where it's located or what else to test?
Bah...what was wrong with points and a carb.
and don't mention Croft where my condensor failed...
I'm assuming that there is smomething that 'detects' tickover and sets the fuelling & spark acordingly? Logic suggests it can't be a crank position sensor as the motor will run on throttle. And the rev counter works and I'd have guessed that might be driven off a crank speed sensor. And I don't have a wiring diagram, so I've no idea of the inputs to the ECU (and I'm even just assumiung it has an ECU as it's fuel injected).
So, what is it that 'detects' tickover (if that is actually what's wrong - any other ideas?), and any idea where it's located or what else to test?
Bah...what was wrong with points and a carb.
and don't mention Croft where my condensor failed...
Idle Air Control Valves are notorious for getting dirty and sticky and they won't always set a DTC code.
"it was the "IDLE AIR CONTROL VALVE". The valve is located on the back of throttle body..easy to remove and clean or replace..but you will definitely have to clean all the carbon and sludge in the throttle body where it's mounted..why no code? or wrong code? well because it is doing what its supposed to do.
You see what happens when the truck is at a light or a stop sign or in park for that matter is, the butterfly closes and the "IDLE AIR CONTROL VALVE" opens letting enough oxygen into the throttle body, in-turn into the engine giving you a smooth idle...but when the valve gets dirty with the carbon buildup, not enough oxygen gets in and the truck stalls because it is running rich at idle..but when you step on the gas the valve is supposed to close "all the way" giving you the correct air fuel mixture(but when dirty or bad it will not close all the way making you run a bit lean while accelerating!
well to fix,all you need to do is check it get some tools out and take a look it won't cost you a thing..
1) disconnect the battery
2) remove the duct off the throttle body
3) disconnect the connector off the idle air control valve.
4) remove the idle air control valve from the the throttle body.(2 screws)
5) clean the throttle body with carb/ throtlebody cleaner. make sure you clean it on both sides of the throttle body with a rag and a small screw driver inside the hole.
6)clean the head of the valve(DO NOT SOAK THE WHOLE VALVE)just the tip so it will seat properly on the throttle body. so cover the the valve with a rag, only exposing the tip of the valve and the spray and wipe until completely clean...
7) put everything back and start her up!!!"
Taken from here:
http://forums.cnet.com/5208-7811_102-0.html?forumI...
and this is what they look like:
http://www.car-stuff.com/cs_auto/mmpb/jeep/cheroke...
"it was the "IDLE AIR CONTROL VALVE". The valve is located on the back of throttle body..easy to remove and clean or replace..but you will definitely have to clean all the carbon and sludge in the throttle body where it's mounted..why no code? or wrong code? well because it is doing what its supposed to do.
You see what happens when the truck is at a light or a stop sign or in park for that matter is, the butterfly closes and the "IDLE AIR CONTROL VALVE" opens letting enough oxygen into the throttle body, in-turn into the engine giving you a smooth idle...but when the valve gets dirty with the carbon buildup, not enough oxygen gets in and the truck stalls because it is running rich at idle..but when you step on the gas the valve is supposed to close "all the way" giving you the correct air fuel mixture(but when dirty or bad it will not close all the way making you run a bit lean while accelerating!
well to fix,all you need to do is check it get some tools out and take a look it won't cost you a thing..
1) disconnect the battery
2) remove the duct off the throttle body
3) disconnect the connector off the idle air control valve.
4) remove the idle air control valve from the the throttle body.(2 screws)
5) clean the throttle body with carb/ throtlebody cleaner. make sure you clean it on both sides of the throttle body with a rag and a small screw driver inside the hole.
6)clean the head of the valve(DO NOT SOAK THE WHOLE VALVE)just the tip so it will seat properly on the throttle body. so cover the the valve with a rag, only exposing the tip of the valve and the spray and wipe until completely clean...
7) put everything back and start her up!!!"
Taken from here:
http://forums.cnet.com/5208-7811_102-0.html?forumI...
and this is what they look like:
http://www.car-stuff.com/cs_auto/mmpb/jeep/cheroke...
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