[The Kurgan]

A few days after this service, I got a CEL, that went away (after 4 start-stop cycles) and then came on back again.

I ran the codes, and this is what I got:

118402--Mixture Control Mixture Too Rich, Big Deviation
140010--Misfiring, Several Cylinder Detected
140110--Misfire Cylinder 1 Identified
140310--Misfire Cylinder 3 Identified
140410--Misfire Cylinder 4 Identified
140210--Misfire Cylinder 2 Identified
140004--Misfiring, Several Cylinder Exhaust Gas Damaging
140104--Misfire Cylinder 1 Exhaust Gas Damaging
140304--Misfire Cylinder 3 Exhaust Gas Damaging
140404--Misfire Cylinder 4 Exhaust Gas Damaging
140204--Misfire Cylinder 2 Exhaust Gas Damaging
195002--Differential Pressure Sensor, Fuel Tank Ventilation System, Electrics
1DZ404--Map Thermostat Activation Open Circuit
138A11--Exhaust Valve, Plausibility Implausible Adjustment Time

Currently, the CEL is off, and I filled the tank with a fresh tank of gas.

What are your thoughts?

[Billfitz]

That's normal when an intake valve cleaning spray is used, but if it's done correctly with the requisite driving time after injecting the cleaner the codes should clear straight away. If that's not done then residual cleaner could pool in the intake manifold and continue to cause misfires.

[The Kurgan]

I really hope that's the case. It now has a fresh tank of gas and I will try to find some highway time.

[Billfitz]

The gas isn't the problem. Intake valve cleaner is injected directly into the intake manifold, so it doesn't mix with the gas in the tank. Intake valve cleaner doesn't burn the way gas does, so it will cause misfires, but once it's cleared out of the manifold the engine should run normally. I did mine a few weeks ago. The process went much more smoothly than I anticipated, but I was careful to keep the RPM at 2500 and to inject the cleaner in short bursts rather than long, and to take the required highway drive after the rest time.