NEED HELP Notorious P0171
- Thread starter benjaminblazer
- Start date
the other place to check is the MAP sensor seal as the sensor seal does seem to shrink with age.
Although that looks more like the heat shield is rusted through, it could be indicative of the manifold below.
Maybe but seems rather suspicious. Anyway, to inspect the exhaust manifold, it has to come off. My 2008 with over 240kkm in rusty ontario does not have heat shields that show that "disease". Yes, where the bolts holds the shield to the manifold are gone (probably from vibration / age of aluminum) but the body of the shield were good. IF the manifold crack is near that sensor, it has more impact than cracks further up in the "y" joint / portion... I think. Good luck if its the manifold as that is lots of fun to work on. :-(
There is one more source for Engine Misfires that is loaded with misinformation or perhaps better described as being a "Horse Before The Cart" sort of Problem: Ignition Coils:
Most people think that it is BAD COILS that create the misfire conditions, but the truth is that Lean A/F Conditions invite the Failure of Ignition Coils that will Misfire under Stress -=First=- while they struggle to Create Ignition Sparks where the Internal Atmosphere Just BTDC... have so little Hydro-Carbon to Air necessary under High Compression to allow the Spark to propagate... that the High Voltage on the Secondary Ignition Coil Side...will oscillate <-- BACKWARDS into the Primary Side of the Coil...and defeat the Coil!
This Lean Condition can cause serious Overheating of the Coil and either Damage or Destroy it and-or be causing the Secondary Spark Energy to try and seek to find Ground -=OUTSIDE OF THE COMBUSTION CHAMBER=- travelling along the Outer Portion of the Spark Plug Porcelain Insulator, while leaving Carbon Tracks to follow inside of the Carbonized, Burned Rubber Boots and leave Carbon Tracings on the Plugs themselves:
www.underhoodservice.com
Using an Oscilloscope can be very revealing and allow you to observe the Ignition Coil Spark Wave Form as either being Healthy like THIS one:
THIS is what a "NO FUEL INSIDE THE CYLINDER MISFIRE" Known BAD Secondary Ignition Wave Form LOOKS like on an Oscilloscope Screen During a SNAP THROTTLE Event when the Engine Compression INCREASES at Higher RPM...Stressing the Ignition Coil to RAISE THE KV Level and Risk Damage to the COP:
So with developing LEAN A/F Conditions... things become UNHEALTHY with the Secondary Side Climbing ridiculously High in Voltage as Compression Climbs and thus, defeating the Spark Plug Gap entirely...inviting ....*Misfires* as covered at THIS Diagnostic Link:
troubleshootmyvehicle.com
..using an Inexpensive Oscilloscope with a PROPERLY GROUNDED "Wand" or "Paddle" used over or adjacent the "Tops of the COPs" (Coil Over Plugs) can pick up the Errant Coil Behaviors and properly pinpoint and Display the problem...ON A RUNNING ENGINE ...Right On The Laptop Screen:
There have been instances where people have tried to Touch the Aluminum Ribbed Cooling Fins of the tops of Ignition Coils...and Burned Their Fingers because of this excessive over-heating problem. Ergo... using a Thermal FLIR Camera or a Laser Thermometer can easily identify individual coils *misbehaving* in the over-heating manner.
For "O"Scope Diagnostic of a CLASSIC EFI Known Good Wave Form...THIS One is illustrative of the *Dimple* in the Wave Trace showing the point at which the EFI Pintle CLOSES in a Good EFI:
Speed Watch through from around 30 Minutes forward to the observe the spots where Jim Mprton describes how Devastatingly LEAN Poor EFI Performance can become a SERIOUS Coil On Plug... Killer:
For Spark Plug Condition and Behavior...THESE Wave Forms can indicate actual Live In Cylinder Spark Plug Behaviors:
Nobody explains these concepts better than Paul "Scanner" Danner as he does in his Rosedale College Automotive Training Classes up in Pennsylvania.
...Watch from around 22 Minutes Onward:
Most people think that it is BAD COILS that create the misfire conditions, but the truth is that Lean A/F Conditions invite the Failure of Ignition Coils that will Misfire under Stress -=First=- while they struggle to Create Ignition Sparks where the Internal Atmosphere Just BTDC... have so little Hydro-Carbon to Air necessary under High Compression to allow the Spark to propagate... that the High Voltage on the Secondary Ignition Coil Side...will oscillate <-- BACKWARDS into the Primary Side of the Coil...and defeat the Coil!
This Lean Condition can cause serious Overheating of the Coil and either Damage or Destroy it and-or be causing the Secondary Spark Energy to try and seek to find Ground -=OUTSIDE OF THE COMBUSTION CHAMBER=- travelling along the Outer Portion of the Spark Plug Porcelain Insulator, while leaving Carbon Tracks to follow inside of the Carbonized, Burned Rubber Boots and leave Carbon Tracings on the Plugs themselves:
COP Connection: Investigating Common Coil-on Plug Misfires – UnderhoodService
For a number of reasons, the trend of modern engine management technology is leaning toward using coil-on-plug (COP) ignition systems. One reason is that COP ignitions are very compact and are very adaptable to individual cylinder tuning. With the exception of a few designs that incorporate a...
www.underhoodservice.com
Using an Oscilloscope can be very revealing and allow you to observe the Ignition Coil Spark Wave Form as either being Healthy like THIS one:
THIS is what a "NO FUEL INSIDE THE CYLINDER MISFIRE" Known BAD Secondary Ignition Wave Form LOOKS like on an Oscilloscope Screen During a SNAP THROTTLE Event when the Engine Compression INCREASES at Higher RPM...Stressing the Ignition Coil to RAISE THE KV Level and Risk Damage to the COP:
So with developing LEAN A/F Conditions... things become UNHEALTHY with the Secondary Side Climbing ridiculously High in Voltage as Compression Climbs and thus, defeating the Spark Plug Gap entirely...inviting ....*Misfires* as covered at THIS Diagnostic Link:
Ignition Coil-On-Plug (COP) Test (GM 3.5L, 4.2L)
How To Test The Ignition Coils. COP Coil Test. Symptoms of a BAD COP Ignition Coil. Chevrolet Colorado, Trailblazer, GMC: Canyon, Envoy, Hummer: H3, Isuzu: Ascender, Oldsmobile: Bravada, Buick: Rainier.
..using an Inexpensive Oscilloscope with a PROPERLY GROUNDED "Wand" or "Paddle" used over or adjacent the "Tops of the COPs" (Coil Over Plugs) can pick up the Errant Coil Behaviors and properly pinpoint and Display the problem...ON A RUNNING ENGINE ...Right On The Laptop Screen:
There have been instances where people have tried to Touch the Aluminum Ribbed Cooling Fins of the tops of Ignition Coils...and Burned Their Fingers because of this excessive over-heating problem. Ergo... using a Thermal FLIR Camera or a Laser Thermometer can easily identify individual coils *misbehaving* in the over-heating manner.
For "O"Scope Diagnostic of a CLASSIC EFI Known Good Wave Form...THIS One is illustrative of the *Dimple* in the Wave Trace showing the point at which the EFI Pintle CLOSES in a Good EFI:
Speed Watch through from around 30 Minutes forward to the observe the spots where Jim Mprton describes how Devastatingly LEAN Poor EFI Performance can become a SERIOUS Coil On Plug... Killer:
For Spark Plug Condition and Behavior...THESE Wave Forms can indicate actual Live In Cylinder Spark Plug Behaviors:
Nobody explains these concepts better than Paul "Scanner" Danner as he does in his Rosedale College Automotive Training Classes up in Pennsylvania.
...Watch from around 22 Minutes Onward:
Last edited:
benjaminblazer
Member