6th Gen ('00-'05): Stalling/Hesitation
#11
01-28-2014, 11:39 AM
Join Date: Apr 2010
Location: Mentor, Ohio
Posts: 12,175
Keanne, I was reaching on another theory (and have not found proof yet). My theory was: Perhaps when the Throttle Position Sensor is extremely cold, could it cause bad data going to the PCM (if you have access to a scan tool that can read the sensors when the car is mis-behaving, that would help, as you would see the TPS acting erratic when you are not tapping the throttle).
Typically that part on these modern cars doesn't fail (unless it develops a "dead spot" which can be checked best with an analog volt meter). I have a couple of TPS units in my garage from a couple throttle bodies I've been working on. If you want to try one, just cover the shipping cost and I'll send it your way (I can't say 100% if it's good or bad, but it MIGHT be worth a shot).
Typically that part on these modern cars doesn't fail (unless it develops a "dead spot" which can be checked best with an analog volt meter). I have a couple of TPS units in my garage from a couple throttle bodies I've been working on. If you want to try one, just cover the shipping cost and I'll send it your way (I can't say 100% if it's good or bad, but it MIGHT be worth a shot).
#12
01-28-2014, 11:39 AM
Join Date: Apr 2010
Location: Mentor, Ohio
Posts: 12,175
Lastly, on my quest for TPS data, I found this info about idle and stalling issues on the 3800:
Rough, Unstable, or Incorrect Idle and Stalling
Checks
Action
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
Preliminary Checks
5,000-8,000 ohms (5K-8K ohms)
9,840 ohms per meter (3,000 ohms per foot)
Spark Plug Wire Resistance Police
1,968 ohms per meter (600 ohms per foot)
Additional Checks
Rough, Unstable, or Incorrect Idle and Stalling
Checks
Action
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
Preliminary Checks
• Refer to Diagnostic System Check - Engine Controls .
• Refer to Important Preliminary Checks.
• Refer to Visual/Physical Checks.
Fuel System • Test the fuel pressure. Refer to Fuel System Diagnosis .
• Test the fuel injectors using the following tests:
- Refer to Fuel Injector Solenoid Coil Test .
- Refer to Fuel Injector Balance Test with Tech 2 .
• Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
• Inspect for fuel in the pressure regulator vacuum hose.
• Ensure each injector harness is connected to the correct injector/cylinder.
• Test items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to Diagnostic Aids for DTC P0172 .
• Inspect items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to Diagnostic Aids for DTC P0171 .
Sensor/System • Inspect for conditions which cause an incorrect idle speed.
- Throttle body tampering, excessive deposits, or damage
- Restricted air intake system--Refer to Air Intake System Description .
- Large vacuum leak
• Test the crankcase ventilation valve for proper operation.
• Test the throttle position (TP) sensor and related wiring. Refer to DTC P0123 .
• Test the exhaust gas recirculation (EGR) system for proper operation.
• Test the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive.
Ignition System • Test for proper ignition voltage output using the following steps:
1. Clip the J 26792 spark tester to engine ground.
2. Connect one end of a spark plug wire to the J 26792 . Connect the other end of the spark plug wire to the coil being tested.
3. Connect another spark plug wire between the remaining tower of the coil being tested and ground.
4. Crank the engine while observing the J 26792 . A crisp blue spark should be observed.
5. Repeat the above steps for each coil.
• If spark is not present at the coils, inspect for the following conditions:
- Coils--Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range
Coil Resistance5,000-8,000 ohms (5K-8K ohms)
- Spark plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range
Spark Plug Wire Resistance Regular9,840 ohms per meter (3,000 ohms per foot)
Spark Plug Wire Resistance Police
1,968 ohms per meter (600 ohms per foot)
Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. Ignition components will arc to ground when a secondary component is faulty.
- Defective module
- Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring
• Remove spark plugs and inspect for the following:
- Fouled plugs
- Cracks
- Wear
- Improper gap
- Burned or damaged electrodes
- Improper heat range or reach
• If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
Engine Mechanical • Test and inspect engine mechanical for the following:
- Test compression, refer to Engine Compression Test in Engine Mechanical-3.8L.
- Sticking or leaking valves
- Worn camshaft lobes
- Valve timing
- Bent push rods, refer to Valve Rocker Arm and Push Rod Cleaning and Inspection in Engine Mechanical-3.8L.
- Worn rocker arms, refer to Valve Rocker Arm and Push Rod Cleaning and Inspection in Engine Mechanical-3.8L.
- Broken valve springs, refer to Cylinder Head Cleaning and Inspection in Engine Mechanical-3.8L.
- Excess oil in combustion chamber--Inspect for leaking valve seals.
• Inspect for incorrect engine parts, such as the following basic components:
- Camshaft
- Cylinder heads
- Pistons, etc.
Refer to Symptoms - Engine Mechanical in Engine Mechanical-3.8L.Additional Checks
• Test the exhaust system for possible restrictions. Inspect for the following:
- Inspect the exhaust system for damaged or collapsed pipes.
- Inspect the mufflers for heat distress or possible internal failure.
- For possible plugged 3-way catalytic converter--Refer to Restricted Exhaust in Engine Exhaust.
• Inspect for faulty motor mounts.
• An engine miss condition can be caused by electromagnetic interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a condition exists, inspect the routing of secondary ignition wires, high voltage components (near ignition control circuits).
• Inspect the intake and exhaust manifold passages for casting flash.
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