tadtv

1996 Laredo. 130k miles. Random quick stumble or stall while idling. Started three weeks ago with a once per day burp or so. Now has gotten steadily worse until today it stalled 5 times while idle at stop lights. Where to start?

Kingfisher

Check fuel pressure.

tadtv

How do I check fuel pressure? From the screw cap on the fuel rail? With a fuel pressure gauge I assume? And look for fluctuations. And that would mean clogged injectors or failing fuel pump? New to this part of the car.

outofrng623

How "random" is it? Start the car, put the car in reverse, does it stall? Does it stall when coasting coming off of the brake? Could be numerous things. MAP sensor, crank case sensor, IAC, TPS Depending on the specifics of your vehicle. There are troubleshooting steps for all of them.

tadtv

Hope this helps but I went away for four days and now it won't start at all. It cranks steady but doesn't start. Where should i start looking. Fuel pump? I thought I heard it come on before cranking. I didn't get a chance to test reverse or braking when it was randomly stalling. Thanks

outofrng623

Could be a lot of things. But, if it cranks hard, think fuel, spark and air issues. Turn the key and listen for the pump. If you're sure you hear it, then turn the key to run, wait 15 seconds, repeat a few times then try to start. If that works it's a fuel pressure issue of some sort. Did you try disconnecting the battery and to reset?

outofrng623

And again. What were your original pcodes?

tadtv

I have not tried the battery/reset. I'll do that tomorrow after I pull the P codes which I haven't done yet either. I think I remember it is on off with the ignition key three times and then the odometer display should l it's the codes?

outofrng623

I'm not 100% sure on your vehicle. May flash the check engine light and count in between pauses or it shows on the odometer. Not sure. But. For me. Yes. Key on, wait, off, repeat, third time would show codes and then "done".
Pull the codes before the reset...

tadtv

Well today I went to work on it and it started right up. I had been trying to get the codes and was turning the ignition on/off a few dozen times. Maybe that pressurized the system? Turns out that after you turn key on/off three times, you have to then wait with it in the on position for at least 15 seconds or longer. I had been not seeing any codes so I would try again. It read out 12 and 11. Fixed a small vacuum hose crack but that I couldn't get it to stall with either. Later I drove around the neighborhood and it didn't stall. Must be a sensor that is on the brink. Just not surer which one.

tadtv

Well I got about 400 feet from home and I Just got it to stall again and it displayed a code 12, 54. And the check engine light is now on. Was sluggish and hesitant and bucking a tiny bit and then it stalled going about 20 MPH. Code 54- Thats a cam sensor BUT did it read/show that because it was sputtering while I was trying to get back down the block or is that the problem. thanks

tadtv

Replaced the cam sensor (code P0340) or (54) which is really called an ignition pickup sensor online or at the auto stores. After a few drives the check engine light went out on its own and all seemed well.

Today, it just stalled again. Try several times to start and it would just start and then run on only two cylinders or so for 5 seconds and then stall. After about 10 minutes I got it into drive quick enough for it not to stall and then all was fine on drive home. I got codes 12, 11, 54 this time. So I guess I'll replace the crankshaft sensor? Help

outofrng623

I'm not in front of the PC at the moment...so I'll ask...what do your codes relate to? I know one was the cam sensor. What do the other two translate to? When I'm in front of the computer I'll check what I have for troubleshooting...

tadtv

Code 12 is PCM lost power hopefully because the battery has been disconnected recently or it could be code bad wiring?

Code 11 is no distributor reference signal detected during cranking. But that could be the engine sputtering as it's trying to start?

Code 54 is the cam sensor AKA ignition pickup sensor which I already replaced.

I'm just going to replace the crankshaft sensor since its cheap enough online $30 and then if its still bad, I will know its either:

1. The connectors at the cam or crank sensors
2. Wiring between sensors and PCM
3. PCM connectors
4. PCM itself

outofrng623

12 could be from when you disconnected the battery, battery disconnected within the last 50 ignition cycles. But, because it didn't come on right away, I am thinking its related to the others...
11- found this really quick online. These are not my words, but, you should be able to test your sensors and connectors this way. To test the crank sensor unplug the connector and test the resistance between the center pin and the pin that goes to the red/light green wire. The resistance should be around 8K ohms or higher. If the sensor measures as a low resistance it is defective.

The cam sensor needs to be tested while connected. An analogue, needle type, multimeter should be used for this. Alternatively a low power 6 volt bulb or an led (and resistor if required) may work. You need to push pins into the back of the connector at the black/light blue and gray/black wires. remove the distributor cap a manually crank the engine using the crank pulley bolt till the rotor point to the eleven o'clock position when viewed from the side of the engine (#6 firing position).

When the ignition is turned on, the multimeter should read 5V (or the bulb or LED should light. If you don't get a 5V reading (or light) you may need to fiddle with the pins to get a connection.

Once you have a reading watch it as the engine is cranked. The voltage should fluctuate between 0 and 5 volts (or the light should go on and off). If you don't have a sync sygnal the sensor should be replaced.


54 Are you fuel injected or carb? Different code for each. If FI, and you already changed this part, what are the odds of getting a bad one, slim...So, with that said. Throwing all three codes together after having the 54 clear out on its own...
I suspect bad wiring, bad coil(s) or bad pcm. Clean your battery terminals, detach, check and reattach your connectors at each sensor, coil, pcm, etc. Clear the codes. Start the Jeep again and start wiggling the connectors at the pcm and wire harnesses. See if you trip the code. If I can find the pinouts for the PCM connectors, I will look to see if by chance, referenced coded items all happen to be within the same PCM connector/harness. In the meantime, see if you can follow the wires from each sensor to see if they all end up in the same place.
For the testing above, back probing the harness connectors. I currently use sewing needles soldered to alligator clips, I push them in and then use the alligator clip to hold my meter probes. You can also just push the needle in and touch it with the probe, but it's a pain.