1. Home
  2. Jeep and Willys (new and old)
  3. engine stalling at idle

engine stalling at idle

When I shift to neutral coming to an intersection or stop, my 4.0 FI engine sometimes stalls out. It seems to have coincided with my speedometer not working. Would that be a cause?

I disconnected the connector leading to the sensor/gear on the transfer case and I noticed a three wire connection, so it must be electronically sensed to the speedoemter. Before I purchase another sensor is there anything I can ohm out or check for voltages on the three wire connector? Diagram anyone has?

I also thought about the sensor gear not meshing, so if I disconnect the sensor/gear from the transfer case with the cable connected, turn key to ignuand manually torn the gear by hand, should I see an output at the speedometer if the sensor is working?

waz

Reply to
updawaz00
Loading thread data ...

updawaz00 did pass the time by typing:

I don't think a failed speedometer sensor would do that.

All sorts of causes including a bad engine ground strap, corroded harness or connectors, broken wire, etc. But first, what is the year, and make of your Jeep?

Certain models you can pull the engine codes with this procedure.

formatting link

That's where knowing the year and model will help us. Some years changed color codes.

Your not going to be able to turn it fast enough by hand to see anything.

Reply to
DougW

If it is a TJ, then yes, the PCM does get input from the speed sensor during deceleration. I would suspect the same in a Wrangler.

It is a magnetic hall effect sensor that generates 8 pulses per rotation according to the TJ manual. It needs this to know if you are still moving at closed throttle for a 'deceleration' injector mode or are sitting at a still idle.

I 'think' the pulses are pin 1 and 2 with pin 3 the ground.

I don't have a clue about hand spinning the gear and seeing anything up top, but that should show on a meter as voltage pulses....

The computer needs a stable TPS signal and the plugs and sockets on them can need a clean once in a while, but that usually gives high revs on first start with a stall at the first stop if dirty.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

snipped-for-privacy@hotmail.com wrote:

Reply to
Mike Romain

Doug, 1992 is the year. Make is YJ Wrangler.

Reply to
updawaz00

Mike, It is a YJ, but it may be the same issue you are talking about. I purchased a service shop manual ... should get here by wednesday. It seems to be a gray issue on how to properly troubleshoot a sensor. Somewhere I heard to measure 5 volts... but where and do I have to pierce the insulation while the connector is connected is not disclosed. Hope the shop manual is worth the $100!

Reply to
updawaz00

Actually, if it is pulsed at 5 volts, I should be able to see it on one of the wires as I'm turning the gear, I have an old scopemeter to watch. Of course, I'm assuming the sensor does not have to be grounded to the transfer case and my vehicle works like a TJ.

Reply to
updawaz00

I'm betting the 3 pins are volts input, pulsed volts output, and ground....

I
Reply to
updawaz00

They could be 5 volt pulses. The sensor itself puts out the volt pulse. They only happen when it is spinning so I think a bench test might be in order?

Basically I would put the meter on pin 1 and 2 and hand spin it to see if it pulses. Or 1 and 3 or 2 and 3. It is something like some of the distributor units, they show a pulse on a meter when hand moved.

Mike

snipped-for-privacy@hotmail.com wrote:

Reply to
Mike Romain

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.