Okay, well I don't understand what happened. I advanced timing first, numbers went down. Advanced a few more degrees, cel comes on and my numbers go back up

Advance too much and you may cause pinging which causes the ecu to reduce timing advance significantly and add fuel.... Shouldn't happen from advanced an ignition timing increase of only 3? though. The O2 sensor also has a specific operating temperature range which must be met. As mentioned timing affects exhaust temp, but again 3? should have ZERO effect.

The only code stored was for the O2 sensor? Could have been knocking or excessive pinging. Is the mechanical timing spot on?

When you say "leaned out" are you just using the wrong term for ignition advance? Or are you using a fuel controller and adjusting the fuel for a specific AFR (for which that term is applicable)?



Remember, like I said, there's also the factor about the ECU needing a little time to learn the sensors and driving style. Also, make sure your spark plugs are in good shape and make sure there's no oil leaking in there with them.

Yes I mechanically advanced the timing to 13. My o2 is brand new, I replaced the gasket on it. The code stored was 21, as he was doing the 25mph pull on the dyno the light came on. Code was 51. I checked resistance between terminals and got bad results. However idk if it's my multimeter or the sensor.

Mechanical timing is different from ignition timing... You're adjusting the ignition timing not the mechanical. See the MKIII FAQ section.

Code 51 is not a typical fault error and will NEVER cause a CEL, it doesn't even remain in the ECU once the problem is remedied. I've already stated what it means and the only thing it really affects is transitioning into idle. There are two different circuits in the TPS. The IDL switch circuit (which is all that that error is for) and the TPS circuit which helps the ECU determine how the throttle is being applied. If the resistance is out of spec it may cause some issue with smooth handling but its affect on emissions should be extremely minimal. It is a wear component and should probably be replaced every 75K to 100K miles.

Gotcha im sorry. Well the engine is on 196XXX miles and I think it's the original one. Well the previous code was o2, and then 51. Im just confused cause the code turned on out of nowhere(on the smog test itself)

If there's no code stored it's possible it was excessive ping so make sure you're reading the ignition advance properly and make sure the mechanical timing is properly zeroed out.

I covered why you may get an O2 sensor code with a new sensor already, two possibilities.

If the TPS is bad enough to throw a code it'll be a code 41. Code 51 would only cause idle issues.

alright. Well the idle is fine. Once warmed up it goes down to about 830 to 750. I haven't experienced idle issues. The o2 they reused the half deteriorated gasket, so I put a new gasket on it. Its not soildered its connected from the connector

How would I set the mechanical timing?

I already said, it's in the FAQ section.