Loud popping at idle
406 sbc, lopey cam, 10-11 inches vacuum at idle, 600 HP Fitech. Had been running generally well except for a flattening out of acceleration at very light throttle between 2500-3000. Over the past few days there is a loud random exhaust pop at light steady throttle, light load such as driving slowly through a parking lot. Now it has increased in frequency. Sitting at an idle there is a really loud pop every 4-5 seconds. My exhaust is loud to begin with but now I'm embarrassed/afraid to drive it. It is like the loudest possible pop you would hear on decel. I updated the software a couple weeks ago after which it ran well and haven't made any changes since then.
Need to show log file so we can look at it. I would think it is an AFR problem.
I hope this works. This is today after I tried reverting to the default calibration.
https://www.dropbox.com/s/y3h2lnn9ch5h71x/Basic%20Sensors7.csv?dl=0
I realize this was a cold start but it is exactly the same warm.
Which cam setting are you using? What are your cam specs and engine size?
Looks to be loading a little. Could be dealing with a tune issue or maybe an exhaust leak.
It turned out to be grossly fouled plugs. The cam specs are .530/.545 lift, 233/241@.050, 106 degree centerline. The previous owner had selected cam setting 4. I am going to start from the default calibration. My understanding is that the higher the cam number selected the richer the base fuel table will. I'm going to use either 2 or 3. It is reasonable to try both and the one which requires the lowest learning value and least trim is the one I want.? Also any suggestion on AFR target for 10% ethanol 91?
You can slightly increase your cubic inch to adjust for 10% ethanol. I would say 5% increase.
Is that better than reducing the target AFR? My 2016 GT350 shows an AFR of 14.1 on our local fuel.
Quote from 65sohc on October 9, 2019, 7:27 pmIs that better than reducing the target AFR? My 2016 GT350 shows an AFR of 14.1 on our local fuel.
You cannot compare AFRs from one engine to another. 10% ethanol content is within the learning parameters of the Fitech. Increasing the cubic inch slightly will reduce the learn.
I have never seen plugs more encrusted with carbon than what I pulled from this engine. I shudder to think what those beautiful aluminum heads must look like inside. This led me to spray water down the intake to decarbonize the combustion chambers and then reinstall the default calibration with Cam #2.