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Timing for GM LY7/N36A Engines

Alan Engineer Oregon Posted Latest Edited

Discussion

Driveability

2008 Suzuki XL-7 3.6L (N36A) 5-spd (AF33)

P0300 — Random/Multiple Cylinder Misfire Detected

P0302 — Cylinder 2 Misfire Detected

P0304 — Cylinder 4 Misfire Detected

P0306 — Cylinder 6 Misfire Detected

P050A — Cold Start Idle Control System Performance

Hey All,

I've got a Suzuki XL7 that is suffering misfire on Bank 2. I figured it was probably due diligence to check the cam/crank correlation on that bank since these engines are notorious for these issues. I grabbed a waveform and compared it with a 2007 XL7 known good waveform. Seems to me like its okay, but I'm interested in some opinions.

In the 2008_under_test.png

blue - intake cam

purple - exhaust cam

yellow - crank sense

green - cylinder 2 ignition pulse

Comparing the two waveforms the exhaust seems to be spot on with 5 pulses of the crank matching up with the falling edge of the cam. However looking at the intake it appears that there is a slight variance. Looking at the pulse train between the rising edge and the falling edge of the intake it seems like the falling edge of the known good lines up with a falling edge of a crank pulse, where as the under test is delayed by 0.50ms and lines up with the rising edge of the next pulse. Is this variance enough that I should be worried about the timing? Check out the diagrams below.

diag.net/file/f7ivi0vem…

Thanks,

Alan …

Scott Owner/Technician

Ontario

Scott

Cat plugged ?

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Alan Engineer

Oregon

Alan

Yeah, the cat was plugged. The ceramic media inside was basically all destroyed and plugging up the mid pipe. I cleared the mess and reinstalled the now empty cat to just to make a test but the results were the same. I assume the ECU will run the bank 2 lean because the pre-cat and post-cat O2 sensors will have the same reading, but I have a hard time imagining that it would run it so lean to…

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Colin Owner/Technician

New York

Colin

Anytime ive had a bad chain . It has a po016 06 po017 code in my experience ( ive done 12 chains so far this year) bank 2 usually goes first .

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Alan Engineer

Oregon

Alan

Do you think the above timing diagram indicate a worn chain?

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Sean Technician

Ohio

Sean

1. Make sure your actuator solenoids are unplugged. 2.Make sure you ar 100 percent on known good. This engine gave me hell. I'll see if I saved my waveform tomorrow. Couple years ago. Dealership told me they changed design 4 times within a2 year period mine had all 4 cams having actuators, some ranges had all 4 same, some were intake different than exhaust mine was supposed to be…

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Alan Engineer

Oregon

Alan

That's a good point. I didn't think to unplug the actuators. I assume they are the plugs right next to the cam sensor. I'll have to take a look at a diagram when I get in front of a computer. I'm also kind of skeptical that it's a timing chain issue since like you and Colin said, it's not throwing codes for cam/crank out of time. Right now the bank 2 cat is empty so the pre and post cat O2…

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Stephen Technician

Tennessee

Stephen

Each pulse of the CKP is 6 degrees. So, the half pulse delay would be about 3*. I don’t think that 3* will cause misfires.

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Darren Mechanic

Wisconsin

Darren

Compression waveform on each bank

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