Need help troubleshooting a misfire problem.
Just to recap some history on my 2015 RS w/ 1.4 turbo and manual 6 speed transmission. It had 63K miles when my brother sold it to me. He said that it had been running rough and giving O2 codes. He found the vacuum regulator diaphram leaking, thinking that it was the PCV valve, on the valve cover and replaced it with a Dorman valve cover. He said that it began running smoother until you turn the AC on; he was turning the AC off to start out in first gear.
I found that the actual PCV check valve was missing and installed the CruzeKit 3.4 rather than replace the intake manifold. I had to play catch-up with some maintainence items (replaced spark plugs, coolant, transmission oil. I found the #4 cyl wire to the plug had corrosion and replaced all four with new boots. It ran fine at idle after that. I checked and was getting the correct vacuum running at hot idle. I did have to replace the coolant outlet and resivoir due to leaks also.
It had been running good for the last couple thousand miles until my son borrowed it last week while his car was in the shop. He came in last night and told me that something was going on with it. He thought that it was a transmission problem. I took it to see my brother to see how it was shifting and feeling. The hour trip down went fine I didn't feel anything wrong. On the way back I felt what I thought was a misfire so I switched my ScanGuage to the page that I had set up to monitor misfire that I had created because of my brother's earlier problems with it. Sure enough it would show a misfire once in a while as I felt them and sometimes not show them. It wasn't one cylinder that was doing all of the misfires. They were scattered among the cylinders acording to the ScanGuage. It never did throw up a misfire code. It did give a CEL for high O2 sensor voltage that I cleared and ran another 30 minutes without another CEL until I got home. I did have some more misfires that would caused slight shudder, but still no CEL.
When I got home I verified that the CruzeKit plug was still in place and there was no new corrosion on any of the plug wiring.
I was wondering if it may simply be some bad gasoline causing the misfires. I'm not sure where my son was getting the gas. I was thinking that I need to get a fresh tank full of premium in it before I start changing parts like the ignition coil pack.
Is there a step by step flow chart type of tests to do for a proper diagnosis of the misfire problem? Thanks for any tips!
Just to recap some history on my 2015 RS w/ 1.4 turbo and manual 6 speed transmission. It had 63K miles when my brother sold it to me. He said that it had been running rough and giving O2 codes. He found the vacuum regulator diaphram leaking, thinking that it was the PCV valve, on the valve cover and replaced it with a Dorman valve cover. He said that it began running smoother until you turn the AC on; he was turning the AC off to start out in first gear.
I found that the actual PCV check valve was missing and installed the CruzeKit 3.4 rather than replace the intake manifold. I had to play catch-up with some maintainence items (replaced spark plugs, coolant, transmission oil. I found the #4 cyl wire to the plug had corrosion and replaced all four with new boots. It ran fine at idle after that. I checked and was getting the correct vacuum running at hot idle. I did have to replace the coolant outlet and resivoir due to leaks also.
It had been running good for the last couple thousand miles until my son borrowed it last week while his car was in the shop. He came in last night and told me that something was going on with it. He thought that it was a transmission problem. I took it to see my brother to see how it was shifting and feeling. The hour trip down went fine I didn't feel anything wrong. On the way back I felt what I thought was a misfire so I switched my ScanGuage to the page that I had set up to monitor misfire that I had created because of my brother's earlier problems with it. Sure enough it would show a misfire once in a while as I felt them and sometimes not show them. It wasn't one cylinder that was doing all of the misfires. They were scattered among the cylinders acording to the ScanGuage. It never did throw up a misfire code. It did give a CEL for high O2 sensor voltage that I cleared and ran another 30 minutes without another CEL until I got home. I did have some more misfires that would caused slight shudder, but still no CEL.
When I got home I verified that the CruzeKit plug was still in place and there was no new corrosion on any of the plug wiring.
I was wondering if it may simply be some bad gasoline causing the misfires. I'm not sure where my son was getting the gas. I was thinking that I need to get a fresh tank full of premium in it before I start changing parts like the ignition coil pack.
Is there a step by step flow chart type of tests to do for a proper diagnosis of the misfire problem? Thanks for any tips!