LM7 Misfire on Downhill Coast
Thread Starter
Teching In
Joined: Apr 2018
Posts: 13
Likes: 0
LM7 Misfire on Downhill Coast Hey All,
Finally finished my LM7 swap into my K5 blazer, now im onto the "bugfix" stage of the build. Ive been datalogging everywhere I drive, and I noticed something last night, I am getting a high number of misfire's from my engine when coasting downhill. I dont notice the engine missing and i can step on the gas and it comes to life with no miss. Is this something i need to deal with from a mechanical perspective? Or just de-sensitize the misfire tables and move on.....
Stock engine, freshly rebuilt. Stock tune with VATS deleted. Full smog swap for CA legal(EVAP, EGR, both in place)
Tune, Log, and Layout attached. Misfire is evident at the time marked 09:41:13
Thanks!
Scoutcamper
Finally finished my LM7 swap into my K5 blazer, now im onto the "bugfix" stage of the build. Ive been datalogging everywhere I drive, and I noticed something last night, I am getting a high number of misfire's from my engine when coasting downhill. I dont notice the engine missing and i can step on the gas and it comes to life with no miss. Is this something i need to deal with from a mechanical perspective? Or just de-sensitize the misfire tables and move on.....
Stock engine, freshly rebuilt. Stock tune with VATS deleted. Full smog swap for CA legal(EVAP, EGR, both in place)
Tune, Log, and Layout attached. Misfire is evident at the time marked 09:41:13
Thanks!
Scoutcamper
I'll make this suggestion. Whenever you let off the gas, and especially going downhill where engine load is reduced, the motor gets fat and pops the unburned fuel in the exhaust. This is probably the misfire cause, and it can be tuned out easily.
Teching In
Joined: Oct 2018
Posts: 16
Likes: 8
My LQ4 did this at around 100k miles. I could see it happening while data logging and the converter would unlock and throw a P300 random misfire code. Mine needed a crank relearn. 5 minutes with a Tech 2 and all was good.
