Idle spark fluctuating?
04-19-2019, 07:51 PM
#1
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Idle spark fluctuating? I have been working on my parent's 2004 Escalade with the 5.3 iron block. I recorded a run log (attached) with HP Tuners before and after working on it. I noticed that the spark fluctuates quite a bit. Is it normal for the spark to fluctuate at idle? This is a bone stock Caddy with about 238,000 miles.
I was able to replace the driver's side exhaust manifold gasket, and O2 sensor. The dreaded rear manifold bolt broke off inside the head. A local welder was able to extract it. I got everything (head, intake, seals, gaskets, etc.)put back together. When I ran the scanner, the spark was still fluctuating. It looks like I fixed the exhaust and O2 issue, but I'm not sure about the spark. Can someone take a look and let me know if I am missing something?
I was able to replace the driver's side exhaust manifold gasket, and O2 sensor. The dreaded rear manifold bolt broke off inside the head. A local welder was able to extract it. I got everything (head, intake, seals, gaskets, etc.)put back together. When I ran the scanner, the spark was still fluctuating. It looks like I fixed the exhaust and O2 issue, but I'm not sure about the spark. Can someone take a look and let me know if I am missing something?
04-19-2019, 09:08 PM
#2
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I cannot see the log on my cell but it is normal for the ECU to use spark for idle control.
04-20-2019, 02:49 PM
#3
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As above, i'm on my phone and can't open the log but yes the PCM does use spark to help control idle as the engine responds much quicker to changes in timing than it does to changes in airflow. And yes, you can also see some pretty big swings in timing even at idle.