Will not stay running

Tiny
ANTHONY M. SPENCER
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 185,000 MILES
I turned the SUV on, it starts and then it hesitates to stay on (5 seconds) and then shuts off. The idle is rough. I have fuel pressure and the pump is fairly new and working. Haven’t found a vacuum leak anywhere. EGR is clean. Throttle body is clean. Air filter/MAF's is clean. I checked my TPS. I’m stuck and need help.
Friday, May 15th, 2020 AT 8:56 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,103 POSTS
Hi,

Are you sure the fuel pressure is within spec? Also, any smoke from the exhaust? Have you scanned the computer for diagnostic trouble codes? Here is a quick video showing how it's done:

https://youtu.be/YV3TRZwer8k

If you haven't checked for codes, I suggest doing it. I also realize most people don't own a scanner. Often times a parts store will lend / rent one to you.

Now, the other thing that can be causing issues can be a faulty crankshaft position sensor. However, I don't want to replace things that are good. That's why I'm suggesting scanning the computer.

Take a look through this link and let me know if it seems to mirror what you are experiencing. Also, let me know if you have a live data scanner.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Take care,
Joe
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Friday, May 15th, 2020 AT 9:57 PM
Tiny
ANTHONY M. SPENCER
  • MEMBER
  • 2 POSTS
So I have no check engine light, no codes, no smoke and fuel pressure is with in spec. Also I pulled the crankshaft sensor out. It was dirty. So I cleaned it up and it looked good. I put it back in and tried to start the vehicle. Now the SUV cranks and doesn’t run. Also I noticed the crankshaft sensor looks a little different then the replacement. Maybe it’s original? Not sure.
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Saturday, May 16th, 2020 AT 3:26 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,103 POSTS
Anthony: Did you replace the OEM sensor? If so, how was the new one different? I'm going to start by adding the directions specific to your vehicle. Take a look through them and let me know if it is what you did or if you missed anything.

____________________________________

1999 Chevy Truck K Tahoe 4WD V8-5.7L VIN R
Crankshaft Position (CKP) Sensor Replacement
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Crankshaft Position Sensor Service and Repair Procedures Crankshaft Position (CKP) Sensor Replacement
CRANKSHAFT POSITION (CKP) SENSOR REPLACEMENT
REMOVAL PROCEDURE

IMPORTANT: The CKP System Variation Learning Procedure will need to be performed whenever the Crankshaft Position (CKP) sensor is removed or replaced. Refer to CKP System Variation Learn Procedure.

CAUTION: Refer to Battery Disconnect Caution in Cautions and Notices.

pic 1

1. Disconnect the negative battery cable.
2. Raise the vehicle.
3. Remove the CKP sensor harness connector.

pic 2

4. Remove the sensor hold down bolt.
5. Remove the sensor from the timing cover.
6. Inspect the sensor O-ring for wear, cracks or leakage.
Replace if necessary. Lube the new O-ring with clean engine oil before installing.

INSTALLATION PROCEDURE

IMPORTANT: Make certain that the Crankshaft Position (CKP) sensor mounting surfaces are clean and free of burrs before installing the CKP sensor.

When installing a crankshaft position (CKP) sensor make sure the sensor is fully seated and held stationary in the front cover before torquing the hold down bolt into the front cover. A sensor which is not seated may result in erratic operation and lead to the setting of false codes.

pic 3

1. Install the sensor into the timing cover. Lube the O-ring with clean engine oil before installing.

NOTE: Refer to Fastener Notice in Cautions and Notices.

2. Install the sensor hold down bolt.

Tighten
Tighten the hold down bolt to 8 N.m (71 lb in).

pic 4

3. Install the CKP sensor harness connector.
4. Lower the vehicle.
5. Connect the negative battery cable.
6. Perform the CKP System Variation Learn Procedure. See: Vehicle > Programming and Relearning

_______________________________________________________________________

Here are the directions for the relearn, but in all honesty, this won't prevent it from starting.

_______________________________________________________________________

1999 Chevy Truck K Tahoe 4WD V8-5.7L VIN R
Crankshaft Position (CKP) - Variation Learn Procedure
Vehicle Testing and Inspection Programming and Relearning Crankshaft Position (CKP) - Variation Learn Procedure
CRANKSHAFT POSITION (CKP) - VARIATION LEARN PROCEDURE
CRANKSHAFT POSITION (CKP) SYSTEM VARIATION LEARN PROCEDURE
1. Install the scan tool.
2. Apply the vehicle's parking brake.
3. Block the drive wheels.
4. Close the hood.
5. Place the vehicle's transmission in Park (AT) or Neutral (MT).
6. Idle the engine until the coolant temperature reaches 65 C (150 F).
7. Turn OFF all the accessories.

IMPORTANT: If the Crankshaft Position (CKP) System Variation Learn Procedure cannot be completed successfully, refer to DTC P1336 CKP System Variation Not Learned for additional diagnostic information.

8. Enable the Crankshaft Position System Variation Learn Procedure with the scan tool.

IMPORTANT: After the ignition switch is turned to the CRANK position, the Vehicle Control Module (VCM) must see a change in the state of brake switch (Released to Applied) to run the learn procedure. Also, the service brakes and the parking brake must be held throughout the duration of the learn procedure.

9. Apply and hold the service brakes.

IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine will respond to throttle position after the learn procedure is complete.

10. Slowly raise the engine speed to 4,000 RPM.
11. Immediately release the throttle when the engine speed decreases.
12. Turn OFF the ignition for 15 seconds after the learn procedure is completed successfully.

___________________________________________________

I need you to check for spark to the plugs. Also, if you have a live data scanner, connect it and see if there is an RPM signal when cranking.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Let me know.

Joe
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Saturday, May 16th, 2020 AT 9:45 PM

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