OBD2 correct data ranges?

2008 MS3

Is there somewhere I can find all the good ranges for all the OBD2 data?

For example, I know LTFT + STFT should be close to zero, under 10 is ok, over 10 is bad (generally speaking).

I'm kind of just learning some of the finer points of engine management/troubleshooting, and looking for some sort of reference guide that I can identify data that is out of healthy/good range.

(Currently tracking down a stubborn misfire CEL, but would be good to learn all the things for future reference)

 

What's going on with the misfire and CEL? Have you made any attempts at repairs or diagnostics for it?

 

Intermittent misfire on Cyl 1 only, every 100 to 500 miles or so. No drivability issues, pretty rough on cold starts but once it warms up runs like a clock. Both fuel trims surprisingly close to 0, never more than +/-5 on a recent 30 min drive/idle test.

I replaced the plugs and all 4 ignition coil packs OEM. (Prob didn't need to replace but peace of mind for a 14 yo car).

I inspected as much of the wiring as I could, didn't see any obvious issues. Same thing with vaccuum lines.

I ran a couple of bottles of techron through for a few weeks of driving plus a long road trip, went about 3000 miles with no CEL, but just came back on. Right now my suspicion is fuel injector.

So the question about OBD codes is to possibly help diagnose issue (don't want to throw more money at it without knowing exactly what's going on), but also like I said I just want to have a good understanding of the data I'm seeing in general for problems down the road, general care and maintenance, etc.

 

Have you done the valve cleaning? A misfire on cold start could be hardened carbon on the valves then once it warms it softens up and the misfire goes away.

 

I have not done that, honestly haven't done anything as far as "internals" go.

Sounds like that may require actually removing the head? Would there be any way to determine if they need cleaning without cracking the whole thing open?

I should also mention that this is a rebuilt 2008 engine, dealership installed, only about 30k miles on the rebuild. Been intermittent misfire since about 12 or 15k since install.

(EDIT...Just read the Corksport valve cleaning article, looks like you just have to remove the intake manifold which I would have to do anyway if I'm removing the injectors to have them flow tested and cleaned)