2000 Pontiac Grand Prix Long time issue with Knock Retard

Tiny
XXMATTFXX
  • MEMBER
  • 2000 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 120,000 MILES
I've been battling this problem for the better part of two years and everything I have tried has yielded no positive results. The issue is noticed with both driveability symptoms and scan data.

Driveability Symptoms:
-Engine bogs down in situations such as passing on the highway or going uphill. Situations with a sudden increase in throttle, generally before the engine attempts to shift into the next gear.

-after the vehicle has been sitting for an extended amount of time, the engine will take noticeably longer to crank before starting.

-Idle vibration. The vehicle has an idle vibration, most noticeably at the 1000 RPM range when held at this mark with the throttle.

-Idle "missing". I have an aftermarket exhaust system and when listing to the exhaust there are blips of what sounds like a miss. However, this is not picked up with a scantool as a miss. This "miss" can be felt as a slight vibration in the seat.

Scan Data Symptoms:
-Knock retard relative to boost. High amounts of knock retard are presented when accelerating and most noticeably when boost is applied.

-P0420 Code set. Occasionaly I will receive a catalyst below efficiency code. It is very rarely that this code is set, and is not consistent with the above symptoms.

Repairs/Replacements to correct issue:
-Spark Plugs Replaced (ACDelco)
-Spark Plug wires replaced (ACDelco)
-Iginition Control Module replaced (ACDelco)
-Fuel Injectors replaced (Reconditioned ACDelco)
-Fuel Pressure regulator replaced (ACDelco)
-Fuel Pump Assembly replaced (Delphi)
-Fuel Filter Replaced (ACDelco)
-Front 02 sensor replaced (Denso)
-Rear Exhaust manifold replaced (Ported ACDelco)
-Catalytic converter replaced (Magnaflow)
-PCV valve replaced (ACDelco)
-IAT Sensor replaced (ACDelco)
-Lower Intake Manifold gasket replaced (ACDelco Revised Aluminum)

Other previously Installed Parts Status:
-Mufflers (Magnaflow)
-Airbox (Stock)
-Thermostat (Stock)
-Downpipe (Aftermarket 2.5" with bend restriction after cat straightened)
-Supercharger Pulley (Stock)
-Powertrain Control Module (Stock)
-MAF Sensor (Used Stock)

Tests Performed:
-Fuel Pressure Test (at Idle)=Passed
-Fuel Injector Drop Test=Passed
-No Vacuum leaks found

Recent Vehicle Scans:
-Cruise
http://www.scandepot.net/viewscan.php?pk=5153

-Wide Open Throttle
http://www.scandepot.net/viewscan.php?pk=5154

This problem at first seemed to have many possibilities and could be easily diagnosed, however after many replacements of what seemed to be the faulty parts, the problem has gotten more and more frustrating. I have tried for the duration of this problem to seek help on forums specific to my vehicle with little success, or suggestions that I have already tried (hence the detailed lists of where I currently stand)
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Saturday, June 19th, 2010 AT 2:56 PM

15 Replies

Tiny
MERLIN2021
  • EXPERT
I don't see the TPS as replaced, there is a known problem with factory TPS's, here's the bulletin:
Intermittent Chuggle or Fishbite on Light Acceleration or at Highway Speeds with No Diagnostic Trouble Codes (DTCs) (Replace Throttle Position (TPS) Sensor) TECHNICAL SERVICE BULLETIN Reference Number(s): 05-06-04-058, Date of Issue: September 07, 2005 Affected Model(s): 1995-1999 Buick Riviera; 1995-2004 Buick Regal; 1995-2005 Buick LeSabre, Park Avenue; 1997-2005 Buick Century; 1995-2001 Chevrolet Lumina; 1995-2002 Chevrolet Camaro; 1995-2005 Chevrolet Monte Carlo; 2000-2005 Chevrolet Impala; 1995-1997 Oldsmobile Cutlass Supreme, Ninety Eight; 1995-1999 Oldsmobile Eighty Eight; 1998-2002 Oldsmobile Intrigue; 1995-2002 Pontiac Firebird; 1995-2003 Pontiac Grand Prix; 1995-2005 Pontiac Bonneville; with 3800 V6 Engine (VIN K - RPO L36) Related Ref Number(s): 05-06-04-058 ARTICLE BEGINNING CONDITION Some customers may comment on an intermittent chuggle or fishbite on light acceleration or at steady-state highway speeds (typically 80-105 km/h [50-65 mph]) with no PCM DTCs set. This condition may lead the technician to suspect the TCC circuit or torque converter. CAUSE This condition may be caused by intermittent operation of the Throttle Position (TPS) Sensor. CORRECTION In observed cases, the Tech 2(R) is not fast enough to consistently detect this condition during a snapshot. It is recommended to use a DVOM set to the min/max recording mode. Connect the DVOM at the TPS connector (positive lead to TPS feedback signal pin and negative lead to TPS ground pin). Duplicate this condition by driving the vehicle. If the voltage dropout (less than 0.45 v) is recorded on the DVOM, replace the TPS sensor and re-evaluate the vehicle before continuing with other driveability or transmission diagnosis. PARTS INFORMATION Parts Information Part Number Description 24504798 Sensor, Throttle Position (TPS) WARRANTY INFORMATION For vehicles repaired under warranty, use: Warranty Information Page 1
Intermittent Chuggle or Fishbite on Light Acceleration or at Highway Speeds with No Di.
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Sunday, June 20th, 2010 AT 10:48 AM
Tiny
XXMATTFXX
  • MEMBER
That TSB looks familiar but I must have only skimmed it. I ruled that out because I never saw the drop-out on my scan tool. But after readingg more carefully I see now that it says that even a Tech 2 isn't fast enough to catch the drop-off. I will look into this possibility asap and report back. Thannks
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Monday, June 21st, 2010 AT 11:59 AM
Tiny
MERLIN2021
  • EXPERT
Will be here!
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Tuesday, June 22nd, 2010 AT 2:39 AM
Tiny
XXMATTFXX
  • MEMBER
I was really hoping this would be it, but it isn't. No change noticed. While crusing, there is still a threshhold of throttle before acceleration. Such as I can start pushing on the throttle, I hear the exhaust tone get deaper, but no noticeable increase in speed untill I apply more throttle.
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Tuesday, June 22nd, 2010 AT 8:23 PM
Tiny
MERLIN2021
  • EXPERT
If you can hear the engine rev but need more throttle to move, have your transmission checked out.
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Wednesday, June 23rd, 2010 AT 2:33 AM
Tiny
XXMATTFXX
  • MEMBER
I really hope it isn't a transmission problem, it was rebuilt about 15,000 miles ago
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Monday, July 5th, 2010 AT 8:14 PM
Tiny
MERLIN2021
  • EXPERT
Warranty? Go back to the installers and have them check it for you, may be a simple adjustment.
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Tuesday, July 6th, 2010 AT 9:29 AM
Tiny
XXMATTFXX
  • MEMBER
I did have it rebuilt elsewhere, but I removed and installed it myself. I had the person who rebuilt it take a ride with me when these symptoms first appeared, he scanned the car while I drove and assured me that it was something else. He didn't see anything on his Genesis other than the bank 2 02 sensor switching slower than it should.
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Tuesday, July 6th, 2010 AT 4:59 PM
Tiny
MERLIN2021
  • EXPERT
My opinion is if the engine revs but doesnt move the car, the transmission has a problem, was the torque converter replaced with the rebuild? Here's some info about what it could be:
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 transaxle 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 30-35 MPH, the car may act normally. For poor acceleration, you should first determine that the exhaust system is not blocked, and the transaxle is in 1st 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.
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Thursday, July 8th, 2010 AT 12:09 PM
Tiny
XXMATTFXX
  • MEMBER
The vehicle seems to drive much better with the shift selector in "3". I have ScanXL professional with enhanced GM parameters, is there anything in particular you suggest to scan.
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Sunday, July 25th, 2010 AT 3:52 PM
Tiny
MERLIN2021
  • EXPERT
All shift solenoids.
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Monday, July 26th, 2010 AT 2:52 PM
Tiny
XXMATTFXX
  • MEMBER
I've not made any progress with my situation. I did however notice that when ever the torque converter clutch is engaged, the boost gauge lights up any time I apply throttle, and in turn increases knock retard.
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Saturday, March 19th, 2011 AT 10:53 PM
Tiny
MERLIN2021
  • EXPERT
I notice you said front o2 sensor replaced, if you have a scantool that can graph dosplay the sensors, look at the wave on the downstream and upstream o2's, the upstream should switch quickly and the downstream should remain almost flat, very little switching. If that isnt how they are working, fuel mixture and trims will be off and the P0420 code for low catalyst efficientcy will pop. Any other codes? Also if acceleration is normal off the line, but it has poor top end, the converter is probably locking up.
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Tuesday, March 22nd, 2011 AT 7:37 PM
Tiny
IMPALA_NITE_RYDER
  • MEMBER
Would a faulty catalytic converter have anything yto do with this? I am having the same problem with my 2003 CHevrolet Impala. I changed the spark plugs, my wires are at least a year old, I changed out the alternator with a junk yard one this spring, and I jsut put in a junkyard coil pack. Out of curiosity would swapping my individual packs with my old one narrow things down?
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Friday, July 22nd, 2011 AT 8:36 PM
Tiny
MERLIN2021
  • EXPERT
A pugged converter will affect power, so will a weak fuel pump check both, any rattles?
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Monday, October 3rd, 2011 AT 7:36 AM

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