The Path to Misfire Detection

The Path to Misfire Detection
Let’s take a logical approach to troubleshooting a misfire condition.
1. When is the misfire happening?
a. Cold, warm, or hot Engine?
b. Under load (power brake) or at idle?
Trying to find a misfire when it is not occurring is a problem.
Can you replicate the misfire?
Start with the ESCAN
1. Are there any DTCs present?
2. What is Mode6 Data Showing You?
a. Misfire Counters
3. Where are your Fuel Trims at?
a. What’s wrong?
Continue with the eSCOPE ELITE
1. Relative Compression Test (quick 8 second mechanical heath test)
2. CKP Misfire (let’s verify a misfire is detectable and on which cylinder(s))
If it is time to go in-cylinder

Capturing Cranking and Idle-Snap-Idle Compression Wave Forms with your eSCOPE ELITE
Follow this process for every compression waveform you are capturing with the eSCOPE ELITE.
Please connect as follows:

Channel 1 – Exhaust Transducer
Channel 2 – Ignition Trigger
Channel 3 – 300PSI Transducer
Channel 4 – Vacuum Transducer

The ignition trigger can be Inductive as displayed above, back probed to the signal side of a coil or with an eCOP (Coil on Plug Adapter).

You MUST trigger off the same cylinder that you are analyzing. If the 300psi transducer is in cylinder 3 use the cylinder 3 coil or plug wire.

You can set the Range values automatically by simply clicking on the PSI button.

Remember to set the record time to 40.0 or 80ms.

1. Cranking Wave Form Capture
Note: For this capture you will need 7 to 10 seconds of cranking data obtained with the throttle in the closed position and the fuel system disabled to prevent the engine from starting.
Do NOT use Flood Mode to prevent starting.

a. From the “Measure and Deep Rec” tab, click on “Start Deep Record.”

b. Crank the engine for 7 to 10 seconds.

c. Click on “Stop Deep Record”

We are looking for a captured waveform that is like the one below:

d. Click on “Save Deep Record”

e. Save the Deep Recording and name accordingly.

1 Set the System” to “In Cylinder”, this will automatically populate the channel labels for you, if you are in any other cylinder other that 1, set the Channel 2 label accordingly.
2 Choose the correct firing order using the drop down listing next to Firing Order.