1997 lesabre that just dies out when driving

[93BONNESSEI]

I have a 1997 lesabre custom that when driving just dies out with no warning. no codes are stored and the dealer can't find anything wrong. When it dies out I just pull over and turn the key off and restart it and won't have any problem till the next day when it will do the same thing. This will happen @ anytime ie. after sitting,drive both long and short times but it will happen @ least once a day.. any ideas???

[Alibi]

Hmm.... first thing that comes to mind is a faulty PCM, ignition switch, or something with the security system.

[Blue Bowtie]

Will the engine restart without turning the ignition fully to off?

[BNaylor]

Thats sounds about right for the dealer and their Tech II diagnostics scanner. A common problem on a SII 3800 is the crank position sensor. When it gets flaky it will most likely not throw any DTCs along with a SES/CEL light.

The CKPS is a Hall Effects sensor and subject to engine heat and intermittent operation. Primary symptoms is engine stalling or excessive engine cranking before it fires up or it just cranks without starting. The proper way to test it is with an oscilloscope by monitoring the 18X timing pulses.

Another suggestion to make sure the fuel pressure is in specs. You can check that with a fuel pressure gauge at the front fuel injection system rail at the fuel pressure regulator Schrader valve.

If you need the specs let me know.

[93BONNESSEI]

I have to turn the car off and then restart it, today I asked my repair shop to replace the crank sensor, they seem to not to hopeful that is the cause but I told them to replace it any way. The shop feels it is much more liky to be fuel related so they are also going to check the fuel pressure from the tank.

[persuazion]

My 99 was doing that when I first got it.It would just die out of nowhere.It was my fuel pressure regulator....maybe you could check that?

[Flatrater]

Bnaylor is correct, a major cause of stalling without a SES light is the carnk sensor. The only thing I could add is to try using a long screwdriver and tap on the crank sensor while the engine is running. If the engine stumbles, dies out, spits o spudders then replace the crank sensor.

There ae many other things that could cause a stall like this but this type of problem is hard to find the root cause.

[redbaron1]

when the 18x has problem the eng will stall the eng will restart with 3x signal.

[BNaylor]

Originally Posted by redbaron1

when the 18x has problem the eng will stall the eng will restart with 3x signal.

Thats an interesting statement. What exactly do you mean by that? It would be nice if you could clarify.

I thought the 3X reference signal was derived from or based on the 18X reference signal from the crank position sensor. 18 divided by 6 equals 3. On a SII 3800 the 3X ref signal outputted from the ICM module becomes Ignition Control Ref. Hi to the PCM module which is used in conjunction with the camshaft position sensor signal to establish timing for the fuel injection system. If you disconnect the electrical connector to the crank sensor which will remove the 18X signal in its entirety all the engine will do is crank but not fire up.

[Bassasasin]

CRANKsensor or, Fuel , Ignition switches.. No code stalling.

I think Ive read Security will not cut off an engine after a period of time for safety reasons.

I also wonder how you can get to the CRANKsaft sensor with a screwdriver.


BAss.

[redbaron1]

the ballancer has 18 & 3 windows the ecm compairs them if the % diffirance i to much it will shut down & you can restart useing the 3x signal. will set 18x code. that is what it said when i was running diagnostics 18x code.

[redbaron1]

the cam & crank sensors changed a lot from 86 up some used one combination sensor others used a cam & only the crank signal from the comb. sensor. you can tell the diff by the rings.Some of the early 3800 used the 18x to compute the 3x signal. then they added the other ring and use it to monitor the 18x signal. then used it for a back up.

[BNaylor]

Originally Posted by redbaron1

the ballancer has 18 & 3 windows the ecm compairs them if the % diffirance i to much it will shut down & you can restart useing the 3x signal. will set 18x code. that is what it said when i was running diagnostics 18x code.

Originally Posted by redbaron1

the cam & crank sensors changed a lot from 86 up some used one combination sensor others used a cam & only the crank signal from the comb. sensor. you can tell the diff by the rings.Some of the early 3800 used the 18x to compute the 3x signal. then they added the other ring and use it to monitor the 18x signal. then used it for a back up.

I see what you mean now. In other words what you are saying is the inner interrupter ring used to generate the Sync pulses on the harmonic balancer was added to monitor the 18X pulses signal. So if you lose the 18X pulses the PCM module will make a decision to operate off the 3X pulses as a backup to establish ignition and fuel injection system timing. After reviewing the GM wiring diagrams I see two signal lines outputted from the crank sensor. The 18X pulses and Sync pulses which appears to become the 3X pulses at the output of the ICM module.

The question I have is when no crank sensor DTCs are set and no SES/CEL Mil light which is common and you get the stalling is it typically the loss of the 18X pulses or the Sync pulses output of the crank sensor or both? CKPS problems are so intermittent at times that it is difficult to troubleshoot. If you review the original post the member mentioned no DTCs set.

So based on what you are saying if I were to disconnect solely the 18X signal line output representing the 18X part of the crank sensor being bad then my engine will start up and operate properly?


Description and Operation Applicable to SII 3800

CRANKSHAFT POSITION (CKP) SENSORS

The crankshaft position (CKP) sensor has a 4-wire harness connector that plugs into the CKP sensor and connects to the ignition control module (ICM). The CKP sensor contains 2 hall-effect switches in 1 housing, and shares a magnet between the switches. The magnet and each hall-effect switch are separated by an air gap. A hall-effect switch is a solid state switching device that produces a digital ON/OFF pulse when a rotating element passes the sensor pick-up and interrupts the magnetic field of the sensor. The rotating element is called an interrupter ring or blade. There are two interrupter rings built into the crankshaft balancer. The outer ring and the outer switch provide the ICM with 18X signals or 18 identical pulses per crankshaft revolution. The inner ring and the inner switch provide the ICM with 3 pulses per revolution, each 1 of different duration. This is called the sync pulse. Each sync pulse represents a pair of companion cylinders. The ICM supplies a 12-volt and a low reference circuit to the CKP sensor, which is also shared by the camshaft position (CMP) sensor. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 signal circuit. The sync pulses are passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The ICM uses the 18X and sync pulses to determine the crankshaft position by counting how many ON-OFF 18X pulses occur during a sync pulse. With this dual interrupter ring arrangement the ICM can identify the correct pair of cylinders to fire within as little as 120 degrees of crankshaft rotation.

CRANKSHAFT BALANCE INTERRUPTER RING

Each interrupter ring has blades and windows that either block the magnetic field or allow it to close one of the hall-effect switches. The outer hall-effect switch sends a pulse called the 18X reference signal. The outer interrupter ring has 18 evenly spaced blades and windows. The 18X reference signal produces 18 ON-OFF pulses per crankshaft revolution. The inner hall-effect switch sends a pulse called the sync signal. The inner interrupter ring has 3 unevenly spaced blades and windows of different widths. The sync signal produces 3 different length ON-OFF pulses per crankshaft revolution. When the sync interrupter ring window is between the magnet and the inner switch, the magnetic field will cause the sync hall-effect switch to ground the supplied voltage from the ICM.



SII 3800 Harmonic Balancer

[Mickey#1]

Interesting thread.

I was under the impression that the 3x signal was used by the ICM to control spark timing when the engine is under 400 rpm. Once rpms are over 400 the PCM controls spark timing. I'm not sure exactly when the 18x signal is used.

[redbaron1]

the stalling with out codes is most likey abab connection or a short the dual positive cable is terrible people don't clean them well enough. also if their is a oil leak it degrades insulation pulling on harness can reproduce the fault.
the ecm will do this to have found bad ecm pulling on harness.