Stuck in cold enrichment cycle?
11-02-2014, 09:38 PM
#1
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Year: 1992
Model: Cherokee
Engine: 4.0
Stuck in cold enrichment cycle?
Just got a new XJ yesterday. Seems that everything about it is FUBAR but it was $200, so I thought I'd go for it.
As it sits right now, it's an electrical nightmare, and I'm not an electrician. There are bare wires hanging all over the place, connections unplugged that don't match up to any other plug near them.... Ugh.
It will start when it's cold, and idle rough, but not die. When it warms up a bit the idle changes to a different pattern of weird and awful, and eventually it'll die. Trying to start it again is pointless unless you have the pedal to the floor. It feels like it's flooding. Starts back up fine again when it's cooled down.
Not getting a temp reading on the gauge at all. Sensor is confirmed good out of my other jeep so I assume the info is interrupted somewhere along the way. Is there any way to bypass the cold enrichment cycle and convince it that it's running at 190 all the time? Maybe have a button/switch to engage the cold start like an electric choke?
Another weird thing it does is when I try to turn on the wipers, it starts screaming out of the passenger door. That's a totally different can of worms though.
Anyone with any ideas on the fake choke/whatever, let me know.
As it sits right now, it's an electrical nightmare, and I'm not an electrician. There are bare wires hanging all over the place, connections unplugged that don't match up to any other plug near them.... Ugh.
It will start when it's cold, and idle rough, but not die. When it warms up a bit the idle changes to a different pattern of weird and awful, and eventually it'll die. Trying to start it again is pointless unless you have the pedal to the floor. It feels like it's flooding. Starts back up fine again when it's cooled down.
Not getting a temp reading on the gauge at all. Sensor is confirmed good out of my other jeep so I assume the info is interrupted somewhere along the way. Is there any way to bypass the cold enrichment cycle and convince it that it's running at 190 all the time? Maybe have a button/switch to engage the cold start like an electric choke?
Another weird thing it does is when I try to turn on the wipers, it starts screaming out of the passenger door. That's a totally different can of worms though.
Anyone with any ideas on the fake choke/whatever, let me know.
11-02-2014, 09:47 PM
#2
The computer uses a different sensor than your dash gauge does.........
The one that the computer uses to determine how warm the engine is, is the one that is threaded into the thermostat housing on the front of the engine. It has 2 small blades or pins in the electrical connector........
The sensor for the gauge in the dash is much smaller, and is threaded into the top-rear of the cylinder head, by the firewall, on the intake side. It will only have one wire connected to it.................
The one that the computer uses to determine how warm the engine is, is the one that is threaded into the thermostat housing on the front of the engine. It has 2 small blades or pins in the electrical connector........
The sensor for the gauge in the dash is much smaller, and is threaded into the top-rear of the cylinder head, by the firewall, on the intake side. It will only have one wire connected to it.................
11-02-2014, 10:46 PM
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THANKS! Okay, so I had the two mixed up. I thought the rear one was the one the computer read off of.
The front one is good for sure. Had to pull it off my other jeep since the t-stat housing that was on this engine had NO sensor. I don't know why. No spot for one. Not a normal shape as far as I've seen them.
tried running it for a minute earlier to see if it was reading on the dash but it wasn't, so I gave up for the night. Maybe it was.
Still runs rough though. I'll connect the rear and see if it reads tomorrow.
Another question is, on the throttle body you have your TPS and IAC, right? Is the IAC supposed to move, or is it just more of a sensor? Pulled it out and cleaned it, thought the "nose" was supposed to be able to move in and out but it doesn't move at all. is this normal or should I replace it?
The front one is good for sure. Had to pull it off my other jeep since the t-stat housing that was on this engine had NO sensor. I don't know why. No spot for one. Not a normal shape as far as I've seen them.
tried running it for a minute earlier to see if it was reading on the dash but it wasn't, so I gave up for the night. Maybe it was.
Still runs rough though. I'll connect the rear and see if it reads tomorrow.
Another question is, on the throttle body you have your TPS and IAC, right? Is the IAC supposed to move, or is it just more of a sensor? Pulled it out and cleaned it, thought the "nose" was supposed to be able to move in and out but it doesn't move at all. is this normal or should I replace it?
11-02-2014, 11:34 PM
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There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it won't work right. Check that that MAP tube is flawless!
On the left rear of the head is the temp sender. They ARE different between a gauge, and a light, but they both signal it's hot when they ground that wire to "them". (variable ground for a gauge, on/of for the light). Try grounding that wire.
On the left rear of the head is the temp sender. They ARE different between a gauge, and a light, but they both signal it's hot when they ground that wire to "them". (variable ground for a gauge, on/of for the light). Try grounding that wire.
11-02-2014, 11:43 PM
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The IAC is what we have now instead of an idle speed screw. It's a computer controlled bypass of the throttle plate. It has a motor that screws that "pintle", in or out. Un-plugging it just leaves it where it was. A tough one to test, just be gentile with it, put it back with the O ring right.
11-03-2014, 07:36 AM
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11-03-2014, 07:45 AM
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There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it won't work right. Check that that MAP tube is flawless!
On the left rear of the head is the temp sender. They ARE different between a gauge, and a light, but they both signal it's hot when they ground that wire to "them". (variable ground for a gauge, on/of for the light). Try grounding that wire.
On the left rear of the head is the temp sender. They ARE different between a gauge, and a light, but they both signal it's hot when they ground that wire to "them". (variable ground for a gauge, on/of for the light). Try grounding that wire.
11-03-2014, 03:15 PM
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Sorry about the stew..........
11-03-2014, 03:22 PM
#11
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Checked on the map sensor tube. All seems as it should be. Unplugged it while the engine was running and it almost immediately killed itself.
Engine seems to start back up when warm with the addition of the temp sensor. Unfortunately I cracked my thermostat housing when I put it on so I'm on my way to buy a new one. I'll update when I can run it again and check some more things.
Engine seems to start back up when warm with the addition of the temp sensor. Unfortunately I cracked my thermostat housing when I put it on so I'm on my way to buy a new one. I'll update when I can run it again and check some more things.
11-03-2014, 07:01 PM
#12
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Okay, here's a bit of an update.
Got the thermostat housing on (looks freaking weird being so clean), and decided to swap throttle bodies with my other Cherokee.
On my daily driver, the "new" jeeps throttle body causes it to have high (1500-2000rpm) idle, and take a very long time to come back down to idle after revving.
The "new" jeep with my good throttle body still idles a little bit rough, but has great throttle response and runs much smoother once you give it a hint of the pedal.
I didn't pull the TPS or IAC out individually, just swapped bodies, so my question to you folks that know more than me is:
Which part do you think is malfunctioning, based on the above behavior? Thanks.
Got the thermostat housing on (looks freaking weird being so clean), and decided to swap throttle bodies with my other Cherokee.
On my daily driver, the "new" jeeps throttle body causes it to have high (1500-2000rpm) idle, and take a very long time to come back down to idle after revving.
The "new" jeep with my good throttle body still idles a little bit rough, but has great throttle response and runs much smoother once you give it a hint of the pedal.
I didn't pull the TPS or IAC out individually, just swapped bodies, so my question to you folks that know more than me is:
Which part do you think is malfunctioning, based on the above behavior? Thanks.
11-03-2014, 10:58 PM
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Throttle plate home on it's stop? Vacuum leaks. Try the other Iat. Check codes. Grounds and wiring connections. See Cruiser's tips top in my sig, getting the ground half of everything good is just as important as the juiced side.
11-04-2014, 12:33 AM
#14
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Well, I swapped the throttle bodies back and both jeeps run exactly the same. My driver still idles too high and the crapper still runs better. What the hell....