Mechanics

CHEVY STUTTERS AFTER WARM UP

2000 Chevrolet Venture

Engine Performance problem
2000 Chevy Venture 6 cyl Front Wheel Drive Automatic 138000 miles

Here is all the info I have...

OK...a week ago I posted up about my 2000 Chevy Venture problem. This all started when I tried to pass someone and it acted like the engine missed on me. Barely got it back to my in-laws house. We got it home and my mechanic is just aggravated with it. He did replace the fuel pump with an AC Delco pump as he said the old pump wasn't holding pressure and sometimes wasn't pumping at all.

He said the van starts and idles PERFECT..no missing, not running rough, etc. Drive the van down the road and after it warms up...it starts acting like it misses. Pull over and put it in Reverse...it doesn't miss....doesn't matter if you are in 1, 2, 3 or OD. Slip in in neutral...runs FINE with no missing. He also said sometimes it will stop if you stomp on the gas...sometimes it will stop once you put it in reverse and go back forward. They have had one of the expensive Snap-On scanners hooked onto it...NO CODES WHATSOEVER...ran the van with it connected the whole time and when it would act up...NO CODES...I think I am going to drive him to drinking with this one....the biggest problem is that it is RANDOM..it won't follow a set pattern of doing it! NOW one code constantly came up that is gone now was the P01404 I believe which was something with the EGR...there was a loose vacuum hose coming from the PCV Valve, seen below circled in blue in second photo (this is a photo of the old one so it's not kinked like that), I replaced that and the code hasn't come back..not sure if it was because of the vacuum hose or something happened with the EGR...

Any suggestions...things we have done...

I pulled off the PCV Tube on accident, replaced with NEW Circled in red in second photo
NEW AC Delco plug wires
NEW Fuel Pump
NEW Fuel Filter, FRAM which is what was on there, this was replaced a day or so before the pump...the gas had black crap in it on the gas tank side....black stuff was NOT in the tank so it was coming from the pump.
All work prior to this was just regular maintenance, I had the head gasket replaced this time last year though, had the dancing needle, the leak wasn't bad enough to have junk in my oil.

http://www.illuminationsfx.com/venture/ventureblackstuff.jpg
http://www.illuminationsfx.com/venture/venture3.jpg

Question...replacing fuel pumps...doesn't require a PCM reset does it? The only out of ordinary thing that has happened just before this...was the van started misfiring, blinking SES light...ended up being one of the BACK plug wires had laid on the manifold and melted...we replaced all the wires...my wife RIGHT AFTER that went straight to Raleigh, NC..which is about a 2 hour drive...she said it shuttered once when she was getting off the interstate. Got to her mothers and the next time it was driven was by me...which is when the above started...

Van running fine with EGR P01404 code
I messed around and must have jiggled the wires which caused the flashing SES light and burned wire
Replaced vacuum hose running from PCV Valve, shown above circled in blue
Replaced Spark Plug Wires
drive to Raleigh
Stutter started once down there

That is the chain of events leading to this...
Avatar
JediKnight2
February 2, 2010.



First of all, good job on the info provided. With what you have described, and the presence of the P1404, I would suspect that you have an EGR valve that sticks. This can be intermittent, and what it does is essentially create a large vacuum leak. When you said it happened coming off the interstate, that added some validity as the egr would have been open during the cruise. That code relates to closed valve performance. What that means is, the PCM learns the closed valve value at startup, that value is compared each time the EGR is commanded closed, and if it is not correct the code sets. That doesn't mean that it should set a code each time, it has to be stuck for longer than 20 seconds. Within that 20 seconds, you may be taking action to stop it from stalling like stabbing the throttle, and that may be enough turbulence to unstick it. You might be able to rule it out by making a solid gasket or block off plate to prevent its influence, and drive it for some time to see if the fault occurs. Yes it will set some codes, but the operation should be normal without it, it is strictly for emissions. But it can create running problems if not operating correctly.

Factoryjack
Feb 3, 2010.
Wasn't the egr. It was out of specs on the ohms test. We replaced with acdelco. Still stutters after warm up and no codes

Tiny
JediKnight2
Feb 8, 2010.
Does it symptomatically do this under load. Can you get it to do so by just torque braking it? At 138k, you make no mention of spark plugs. Have they been addressed as well. Is it possible that maybe one has cracked porcelain, and/or carbon tracking? Has it been test driven with the scan tool installed so misfires can be monitored?

Factoryjack
Feb 8, 2010.
Spark plugs were replaced last year when the heads were done. It has been driven with the scan tool and nothing shows out of range from what I understand.

Tiny
JediKnight2
Feb 9, 2010.
Without being able to feel it, I guess I am at a bit of a loss. If it was engine related, you should be able to track something down by misfire counts, fuel trim values, or worst case a hard failure setting codes. Fuel trim values would indicate what the system is doing to combat it when the fault occurs. Positive numbers is adding fuel in response to lean, and negative numbers is pulling fuel back in response to rich. This could give an idea, if it can be observed. You didn't specify whether or not you could get it to act up by torque braking. It sounds like something secondary is shorting, but like I say, without feeling it I can only guess. If it is not evident via engine data, does it feel like something that could exist in the transmission.

Factoryjack
Feb 9, 2010.
Still no luck.I did get a call from a friend of mine last night who said. With no codes and being sensitive after warm up at load. He said he ONE HUNDRED percent thought it was an ignition coil. So my question is this. If it IS an ignition coil or ignition control module. Would the load in Reverse be so different as to allow you to drive? Now when I drove in reverse it would cut out. Just not bog down, it would just turn off. Unlike in any forward gear where it would bog down and cut out? My mechanic is at a loss. He is getting it to Chevy for me in the morning unless we can figure it out today.

Tiny
JediKnight2
Feb 17, 2010.
I don't see where an ignition coil fault would be worse in one range, that the other, the driving characteristics would be the only difference. I am wondering of you don't have an engine ground, ignition ground, or pcm ground that may be loose ar faulty. Maybe the engine torqing in one direction vs the other causes trouble. A pcm ground could explain why it is not setting a code. With the fact that it has had some major engine repair, makes this more of a possibility.

Factoryjack
Feb 18, 2010.
I took the van to the local dealership to have it diagnosed today. And I have to say I am confused and. Confused. As I stated before, the van had NO CODES as read by fairly top of line Snap-on Scanner. Only codes it pulled up were two tensionor air bag codes. It was scanned last night before it was towed. It was started an moved into the parking place and started to pull into the bay. They come back and say there are two codes.P171 and P174. P171 is Bank 1 Lean and P174 is listed as bank 2 lean.I had a new pcv valve and tube in the van for them to put on. No problem there. However, they say there is a transmission code being thrown. But couldn't give it to me. They told me that the engine problem was fixed. Which it ISN'T if it is still bogging down after getting warm. They charge me 162 bucks for from what I understand is putting on a flipping pcv valve and pcv valve tube. Then tell me there is a transmission code. Which I think the Snap-on should have caught. Then said I would have to pay an other 97 bucks for the transmission issue. Which MAKES NO SENSE TO ME.

If the van idles fine. Then warms up and bogs down under load. WITHOUT SHIFTING HARD. IN ANY GEAR. However, bogs down in ANY GEAR. Except Reverse where it will not bog down but turn off if you let off the accelerator.I mean there has NEVER been any transmission shifting issues. It feels like the tech couldn't find an engine issue so passed it off to being a transmission issue. But I don't see where it COULD be a transmission issue. Again. These codes just appeared. Is their scanner system that much different where it would pull codes not seen by a rather top of the line scanner by Snap-on. When this bogging down happens. The vehicle isn't bucking. It is bogging down. You can hear it in the engine. Is it possible that its maybe a bad torque converter? Can they act like that?

Tiny
JediKnight2
Feb 18, 2010.
Did the PCV tube solve the 171 and 174 both banks lean? One other question, has anyone ever pulled the oxygen sensor before the cat and made an exhaust backpressure check?
I will give you some information on torque converter characteristics, as well as a bulletin.
#PIP3144C: Poor Acceleration From A Stop Or Detonation In Gear At A Stop - keywords DTC low MIL ping - (Jun 12, 2009)

Subject: Poor Acceleration from a Stop or Detonation in Gear at a Stop

Models: 1996-2009 All General Motors Passenger Cars and Light Duty Trucks

This PI was superseded to update model years and add an important note. Please discard PIP3144B.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern: Customer concern of poor acceleration, detonation or " ping" at idle in drive or reverse, and/or possible DTC P0101, P0106 and/or P0121 set in the PCM. The vehicle will perform properly after attaining a speed of about 30 - 40 mph. The condition may also be described by the customer or the dealer as a hesitation, stall when putting into gear, surge on acceleration (similar to hitting fuel cut off or rev limiter). The ultimate cause may be a non-holding torque converter stator or damaged stator support shaft within the automatic transmission.

Recommendation/Instructions: Important Note: Do not follow the below diagnostics until published SI diagnostics have been followed COMPLETELY. If all published SI diagnostics have been exhausted the following information may help in isolating a possible torque converter concern.

The following checks should be performed in the event that normal engine driveability checks have not resolved the detonation or " ping" at idle in drive or reverse, lack of power from a stop, stall, and surge on acceleration and or hesitation complaint.

The IAC counts throttle angle and/or MAP voltage and KPA should be compared to a like vehicle in park and in gear after reaching operating temperature. If the counts and map are high or throttle angle is open excessively in comparison this may be a result of high engine load and a torque converter and or stator support shaft related concern.

If the above information does not lead to resolution, follow torque converter diagnostics listed below: The transmission oil cooler outlet line (line to the cooler) should be checked for excessive heat. The Tech II scan tool may be helpful on vehicles equipped with the transmission fluid temperature sensor in the cooler line (mainly front wheel drive). On vehicles that do not have the temperature sensor in the cooler line a temperature probe should be used to check the temperature. The temperature readings should be compared to a like vehicle with the same powertrain option content.

A stall test (brake torque) may point to a damaged torque converter; the stall rpm speed will be lower than a like vehicle. However, poor engine performance will also produce a lower stall speed rpm.

If the torque converter stator or stator support is suspect, the transmission should be removed and THE STATOR SUPPORT SHOULD BE INSPECTED FOR SPLINE DAMAGE. If the stator support splines are damaged the transmission should be repaired and new torque converter installed. If damage is not present on the stator support the concern is either internal to the torque converter stator or an engine performance concern.

Torque Converter Diagnosis
The Torque Converter Clutch (TCC) is applied by fluid pressure, which is controlled by a PWM solenoid valve. This solenoid valve is located inside of the automatic transmission assembly. The solenoid valve is controlled through a combination of computer controlled switches and sensors.

Torque Converter Stator
The torque converter stator roller clutch can have two different malfunctions.

• The stator assembly freewheels in both directions.

• The stator assembly remains locked up at all times.

Poor Acceleration at Low Speed
If the stator is freewheeling at all times, the car tends to have poor acceleration from a standstill. At speeds above 50-55 km/h (30-35 mph), the car may act normally. For poor acceleration, you should first determine that the exhaust system is not blocked, and the transmission is in First gear when starting out.

If the engine freely accelerates to high RPM in NEUTRAL, you can assume that the engine and the exhaust system are normal. Check for poor performance in DRIVE and REVERSE to help determine if the stator is freewheeling at all times.

Poor Acceleration at High Speed
If the stator is locked up at all times, performance is normal when accelerating from a standstill. Engine RPM and car speed are limited or restricted at high speeds. Visual examination of the converter may reveal a blue color from overheating.

If the converter has been removed, you can check the stator roller clutch by inserting a finger into the splined inner race of the roller clutch and trying to turn the race in both directions. You should be able to freely turn the inner race clockwise, but you should have difficulty in moving the inner race counterclockwise or you may be unable to move the race at all.

Noise
Important: Do not confuse this noise with pump whine noise, which is usually noticeable in PARK, NEUTRAL and all other gear ranges. Pump whine will vary with line pressure.

You may notice a torque converter whine when the vehicle is stopped and the transmission is in DRIVE or REVERSE. This noise will increase as you increase the engine RPM. The noise will stop when the vehicle is moving or when you apply the torque converter clutch, because both halves of the converter are turning at the same speed.

Perform a stall test to make sure the noise is actually coming from the converter: Place your foot on the brake.
Put the gear selector in DRIVE.
Notice: You may damage the transmission if you depress the accelerator for more than 6 seconds.

Depress the accelerator to approximately 1,200 RPM for no more than six seconds.
A torque converter noise will increase under this load.

Torque Converter Clutch Shudder
The key to diagnosing Torque Converter Clutch (TCC) shudder is to note when it happens and under what conditions.

TCC shudder which is caused by the transmission should only occur during the apply or the release of the converter clutch. Shudder should never occur after the TCC plate is fully applied.

If the shudder occurs while the TCC is applying, the problem can be within the transmission or the torque converter. Something is causing one of the following conditions to occur: • Something is not allowing the clutch to become fully engaged.

• Something is not allowing the clutch to release.

• The clutch is releasing and applying at the same time.

One of the following conditions may be causing the problem to occur: • Leaking turbine shaft seals

• A restricted release orifice

• A distorted clutch or housing surface due to long converter bolts

• Defective friction material on the TCC plate

If Shudder Occurs After TCC has Applied
If shudder occurs after the TCC has applied, most of the time there is nothing wrong with the transmission.

As mentioned above, the TCC is not likely to slip after the TCC has been applied. Engine problems may go unnoticed under light throttle and load, but they become noticeable after the TCC apply when going up a hill or accelerating. This is due to the mechanical coupling between the engine and the transmission.

Once TCC is applied, there is no torque converter (fluid coupling) assistance. Engine or driveline vibrations could be unnoticeable before TCC engagement.

Inspect the following components in order to avoid misdiagnosis of TCC shudder. An inspection will also avoid the unnecessary disassembly of a transmission or the unnecessary replacement of a torque converter.

• Spark plugs - Inspect for cracks, high resistance or a broken insulator.

• Plug wires - Look in each end. If there is red dust (ozone) or a black substance (carbon) present, then the wires are bad. Also look for a white discoloration of the wire. This indicates arcing during hard acceleration.

• Coil - Look for a black discoloration on the bottom of the coil. This indicates arcing while the engine is misfiring.

• Fuel injector - The filter may be plugged.

• Vacuum leak - The engine will not get a correct amount of fuel. The mixture may run rich or lean depending on where the leak occurs.

• EGR valve - The valve may let in too much or too little unburnable exhaust gas and could cause the engine to run rich or lean.

• MAP/MAF sensor - Like a vacuum leak, the engine will not get the correct amount of fuel for proper engine operation.

• Carbon on the intake valves - Carbon restricts the proper flow of air/fuel mixture into the cylinders.

• Flat cam - Valves do not open enough to let the proper fuel/air mixture into the cylinders.

• Oxygen sensor - This sensor may command the engine too rich or too lean for too long.

• Fuel pressure - This may be too low.

• Engine mounts - Vibration of the mounts can be multiplied by TCC engagement.

• Axle joints - Check for vibration.

• TP Sensor - The TCC apply and release depends on the TP Sensor in many engines. If the TP Sensor is out of specification, TCC may remain applied during initial engine loading.

• Cylinder balance - Bad piston rings or poorly sealing valves can cause low power in a cylinder.

• Fuel contamination - This causes poor engine performance.

Torque Converter Evaluation and Diagnosis
Replace the torque converter if any of the following conditions exist: • External leaks appear in the hub weld area.

• The converter hub is scored or damaged.

• The converter pilot is broken, damaged, or fits poorly into the crankshaft.

• You discover steel particles after flushing the cooler and the cooler lines.

• The pump is damaged, or you discover steel particles in the converter.

• The vehicle has TCC shudder and/or no TCC apply. Replace the torque converter only after all hydraulic and electrical diagnoses have been made. The converter clutch material may be glazed.

• The converter has an imbalance which cannot be corrected. Refer to Flexplate/Torque Converter Vibration Test.

• The converter is contaminated with engine coolant which contains antifreeze.

• An internal failure occurs in the stator roller clutch.

• You notice excessive end play.

• Overheating produces heavy debris in the clutch.

• You discover steel particles or clutch lining material in the fluid filter or on the magnet, when no internal parts in the unit are worn or damaged. This condition indicates that lining material came from the converter.

Do not replace the torque converter if you discover any of the following symptoms: • The oil has an odor or the oil is discolored, even though metal or clutch facing particles are not present.

• The threads in one or more of the converter bolt holds are damaged. Correct the condition with a new thread inset.

• Transmission failure did not display evidence of damaged or worn internal parts, steel particles or clutch plate lining material in the unit and inside the fluid filter.

• The vehicle has been exposed to high mileage only. An exception may exist where the lining of the torque converter clutch dampener plate has seen excess wear by vehicles operated in heavy and/or constant traffic, such as taxi, delivery, or police use.

Lack of Power, Sluggishness, or Sponginess
Lack of Power, Sluggish or Spongy Inspection/Test
Action

DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.

Preliminary
• Refer to Powertrain On Board Diagnostic (OBD) System Check.

• Refer to Intermittent Conditions.

• Search for bulletins.

Fuel System
• Test the system fuel pressure. Refer to Fuel System Pressure Test.

• Test the fuel injectors. Refer to Fuel Injector Balance Test, Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F), or Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F).

• Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis.

• Inspect any items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to DTC P0172 Fuel Trim System Rich.

• Inspect any items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to DTC P0171 Fuel Trim System Lean.

Sensor/System
• Using a scan tool, monitor KS system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description.

Important: : The replacement PCM must be programmed.

• If knock retard is above 10 °-12 °, disconnect the knock sensor, and ground the sensor harness connector. Monitor knock retard on the scan tool, there should be no knock retard present, if knock retard is still present, replace the PCM. Refer to Powertrain Control Module Replacement/Programming.

• Inspect the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description.

• Inspect MAF Sensor and related wiring.

• Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body.

Ignition System
• Inspect for proper ignition voltage output using the following steps: 1. Attach the J 26792 spark tester to engine ground.

2. Connect the spark plug end of the spark plug wire to the J 26792 spark tester; leave the other end of the spark plug wire connected to the coil being tested.

3. Connect the spark plug end of the companion spark plug wire to ground.

The companion spark plug wire is the wire attached to the corresponding coil tower.

4. Crank the engine while observing the J 26792 spark tester; a 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 resistance value outside the specified range.

Coil Resistance
5000-8000Ω (5K-8KΩ)

- 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
600Ω per foot (1 968Ω per meter).

Important: : Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty.

- Defective ignition module.

- Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring.

• Remove spark plugs and inspect for the following conditions: - 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
• Excessive oil in combustion chamber or leaking valve seals--Refer to Base Engine Misfire Diagnosis in Engine Mechanical.

• Low cylinder compression--Refer to Engine Compression Test in Engine Mechanical.

• Inspect for the following incorrect basic engine parts: - Camshaft

- Cylinder heads

- Pistons, etc.

• For more diagnostic aids refer to Base Engine Misfire Diagnosis in Engine Mechanical.

Additional
• Inspect the exhaust system for possible restrictions in the following areas: - The exhaust system for damaged or collapsed pipes

- The mufflers for heat distress or possible internal failure

- The catalytic converter for possible plugged condition--Refer to Restricted Exhaust System Checkand Exhaust Leakage - Not OBD II in Engine Exhaust.

• Inspect for proper TCC operation. Refer to Torque Converter Diagnosis in Automatic Transaxle.

Factoryjack
Feb 18, 2010.
OK. They called me back and said it is the torque converter. However, I called back my friend plus two transmission shops in town. One fairly reputable. And they said the symptoms DON'T MAKE SENSE for it to be that. The clue. It doesn't bog down in Reverse. They said if the TC was locking in 1-3. It would do it in R. Its not. When it starts. You can start the van. Put it in 1 and it bogs down. Immediately put it in N. Idles fine then reverse. And drive on with it not bogging out. The transmissions guys said it just doesn't sound right. Plus I feel like I was lied to about the codes. Which makes me feel like they are being dishonest. Which just plain makes me sick as I should be able to trust the flipping manufacturer of the van!

Tiny
JediKnight2
Feb 19, 2010.
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