Cylinder misfire - better gas milage ?

[lightninhopkins]

Just kidding with the title of course.

Had a check engine light for a few days and a lack of power, so I hooked up the laptop and found cylinders 6,7,8 with random misfires.

Reset the check engine light, but upon firing up the car, I had rough idle again so I'm sure it's still got trouble.

Hmmmm dealer, drop off, waiting, etc. I hate that stuff.

[wolfie]

I am interested in how you were able to check the diagnostics on your car. What software do you use for this? Where do you access the vehicle? Clearly this is way beyond my area of expertise. Please say more.

[lightninhopkins]

You can order a USB kit from this company http://www.autoenginuity.com/

It's approximately $250. You connect it to the laptop via USB, and the other end goes into a module under the dash just under the headlight switch. Almost all cars have this.

I reset the engine light and drove about 40 miles today with no sign of misfire. Maybe it was a one time fluke going over 8200 RPM too many times.

[lightninhopkins]

well, light is back. I drove below 8K all day, but right when i hit 8K RPM, the light came back and P0300 code which is the misfire.

Might be related to the exhaust valve vacuum if something went wrong. I disconnected those exhaust valve tubes a few weeks ago and everything was fine. I'll recheck the hoses and even put the tubes back to see if that was the cause.

Reading some google results, messed up oxygen sensors may cause this too. who knows.

Just thought I'd share this with the community

[geffers]

does the USB kit allow you to change the settings on your car e.g. lights/wiper programming and that sort of thing?

[lightninhopkins]

no, it's only a capture device. the only thing it allows to do is reset the check engine light and read the error.

[bz888]

What an awesome device! I'm buying one today! Thanks for the info!

[lightninhopkins]

It is pretty cool, but you'll get bored of it after a few hours.

Maybe that's just me.

[JOHN.KUSTARD]

Had a few instances of spark plugs going down-causing misfires, M.I.L. light on

[desperado]

I've had the MIL light on twice now due to brief episodes of random cylinder misfire.

Our local Audi R8 tech says the 4.2 in the RS4 is notorious for being "hard on sparkplugs" and (as mentioned above) the RS4 initially came with a new set of plugs to be installed during PDI immediately before delivery to the customer..

What, if anything, have you gentlemen done to keep this problem from recurring?