A while ago, my 2008 SS started running poorly. The idle was really lumpy, it was hesitating and misfiring occasionally and my gas mileage was poor. Could smell unburned hydrocarbon in the exhaust.

The weather finally warmed and I finally had some time to diagnose the problem so I went out to put my OBD2 scanner on it. The scanner returned 15 codes including P0301 Cyl 1 misfire, P0302, 3 and 4 which I assume are misfire on the other cylinders, P2196 HO2S 9r H02S Signal biased rich Bank Sensor 1 2 and P0022 Intake cam position timing over advanced Bank 1. The rest of the codes were these same ones repeated.

My plan was to retrieve the codes that were there then erase them, take the car out for a bit of a drive and the check again to see what codes were tripped so I erased all the codes and removed the OBD2 scanner off the OBD port. I then tried to start the car to take it for a spin but it would not crank. Everything powered on and I could hear the fuel pump prime but the engine wouldn't crank. It was as though the clutch pedal sensor had failed or I didn't have the clutch pedal pushed down (which I did) when I tried starting the car.

I then went and disconnected the battery for a minute or so then reconnected the battery and that did the trick. The engine cranked for a couple seconds and finally started. I then took it out for a couple of short 3 - 5 minute drives and was very surprised to find the car was running great again, No more lumpy idle, no more misfiring or hesitation. Just smooth power. The check engine light also did not come back on. Both times when I finished the test drives, I scanned for codes but both times none had been tripped. Whatever problem I was having seems to have been fixed by what I did.

Can anybody explain this? Why do you think the car suddenly started running like crap and then suddenly started running great again after I erased the DTC codes with the OBD2 scanner and reset the computer by disconnecting the battery for a short period of time? I'm perplexed

 

Could be an issue with the VVT system. Over-retarded, not over-advanced.

I would inspect the wiring to the VVT solenoids.

Check the engine oil level.

Remove the VVT solenoids, checking the screens for debris.

Remove the valve cover and check the timing components. Chain is good and tight, no broken guides. Even rotate the engine to see if the timing marks for the camshafts align.

Once you cleared the codes, the ECM was no longer relying on sensor input. It now will take time and certain driving conditions be met before the ECM can determine that there's a problem, then it will set codes again and place limitations on engine performance.

 

Your celebration may be premature. Even if the CEL light doesn't come on, In 2 or 3 days, scan anyway.

In the future, address a CEL immediately. Sometimes a minor malfunction can cascade into bigger problems.

 

Yes , do all that^^^^^
you’re most likely have to replace VVT solenoids and possibly the timing chain

https://www.obd-codes.com/p0022

 

Rebooting the computer only makes all of the OBD tests to start over again, until they are done there will be no codes and the engine is running in open loop.

 

You might clean your MAF sensor and check the O2 sensor before the catalytic converter.

https://www.obd-codes.com/p2196

Check the in tank fuel pressure

 

You guys were right, the CEL did come back again after a bit of driving around. The car is still running way better than it was, however. It's running quite smoothly actually.

Only 3 codes were returned by the OBD: U0073 CAN Bus and P0011 Intake Cam position (CMP) System twice.

P0011 is typically the intake VVT solenoid, is it not? Time to replace both solenoids then? I'll check the wiring first of course.

BTW, my '08 SS only has about 120,000 km (~77,000 miles) on it so not a high mileage vehicle.

Are these A-Premium solenoids okay quality?

 

If the battery is old OR if it sat in a discharged state for any length of time and sulphated, especially in cold weather, it probably needs to be replaced. Low voltage can set U codes.

The car might be running better, but with P0011, it's not optimal. Replacing the VVT solenoid valves might work. I would start by inspecting the intake one, looking for shavings or gunk. Then replace both. It may be time to do a chain job, especially if oil changes have been neglected.

 

I’ve not used those VVT solenoids, but they are inexpensive.

I’ve only installed the GM genuine ones.

 

So without doing anything on the SS, I checked the codes again the other day and they had changed partially. There were no codes about VVT sensors but I still got a P0011 and codes for misfires on all four cylinders. Then the last code was a P2097 Post Catalyst Fuel Trim System High Limit Bank 1. Too much unburned hydrocarbon in the exhaust past the catalytic converter.

I thought about all these codes that have been coming and going and since I'm no expert I don't know if this is right but I reasoned they all kind of have to do with the computer not knowing what to do with the fuel mixtures it's dealing with or the fuel mixture not being correct so from that I reasoned that the first and easiest thing to do is start with cleaning the MAF sensor which I have never cleaned since I got the car in 2015 with only 34,000 Km (a little more than 20K miles) on it. The car now has a little over 120K Km (or about 75K miles) on it. Was that good reasoning? I figured it was a good place to start, anyways.

I bought some CRC MAF sensor cleaner and removed the MAF sensor. It (the hotwire) wasn't all caked in dirt or grease or anything but it did look a little dirty so I gave it about 15 shots of the cleaner as per the instructions on the can, let it dry and reinstalled it. At the same time, I checked my air filter and although it wasn;t horrendously dirty, it was dirty enough for anyone to say it needed cleaning (it's a K&N) so I've given it a cleaning and now I'm waiting for it to dry before I oil it and reinstall it. I'll be careful not to put too much oil on the filter as I want to avoid excess oil coming from the filter fouling up the newly cleaned MAF sensor.

Once it's reinstalled, I thought I would fire the car up, take it for a spin and see if it runs any better and then check the codes again to see if anything had changed and go from there.

I also bought a can of Royal Purple Max Clean fuel system cleaner because I had heard that it could help clean up the O2 sensor ahead of the catalytic converter which is probably carboned up now due to the engine running so rich for awhile. The video I watched said to insert the hose from the can into a vacuum line going into the intake system, fire the engine up and spray a ton of the cleaner into the vacuum line while revving the engine to about 2K or so. Do you guys agree with this approach? The Royal Purple was expensive so I'd rather take it back for a refund than use it if it's highly unlikely to work. If it could work, where is a good vacuum line to inject the cleaner into?

I also bought an O2 sensor socket so I could remove and inspect it and replace it if necessary. Do you have to get at the O2 sensor ahead of the cat from underneath the car?

TIA