A simpletons tuning plan?

[aschen]

I havent started up the ol 930 in a a few months. I let the insurance lapse and I am pretty sure it isnt running perfectly. I think it may be a bit lean as it continually coughs and pops off throttle (more than what should be considered normal). I havent taken the time to fully understand how the CIS works. I need to do some reading and figure out how the control pressures effect things and various intricacies of all the add on components. In the meantime I have a plan to get the car running a little better.

Step 1: Buy and install invoative wideband
Step 2: turn various knobs , srtscrews etc until I get as close to 13ish afr off boost and 11ish on boost as I can.

Will my plan work if everything is in reasonable mechanical working order. I really only have the idle mixture control to adjust right?

Take it easy on me I am admidittely CIS ignorant,
Aaron

[mark houghton]

Assuming everything is pretty much stock? Simple tuneup would also entail checking the ignition timing at idle and at 4000 rpm. Check your manual for proper timing with or without the vacuum lines connected.

The Innovate AFR setup should give you a pretty close look at your mixture. I would first adjust the idle mixture to where it sounds to the ear to idle the best (like a carburetor, go for lean best idle then richen up just a tad). Remember that the adjustment screw takes very little to make relatively large changes in mixture, so don't get overzealous....turn it just a couple degrees at a time. Finish by adjusting the idle with the air correction screw at the throttle body to achieve around 950-1000 rpm.

Then, see what your AFR's are doing. You don't necessarily need to be at an AFR of 13, when stoicheometric is 14.7, but let the engine tell you how it sounds. I run mine at about 14.4-14.6 @ idle, but sometimes a bit richer provides a better idle, depending on the car. 11'ish at boost will work fine; just try not to exceed the the low 12's. And remember that the mixture adjustment at idle has most of it's effect at idle, and a more limited effect throughout the rest of the power band. Your WUR will enrichen things automatically on boost and unless something is wrong with it, you'll probably find your AFR's falling right into line on boost.

In summary, about all you can do for a tuneup is adjust the valves, check and/or adjust the timing, replace worn things like plugs, caps, rotors, wires, air filter, set the idle mixture, set the idle speed (with the air correction screw at the base of the throttle valve). As long as all vacuum hoses and intercooler/turbo air seals (O-rings, hoses and clamps) are in good working order so there are no air leaks, you should be successful. You may want to start with a fresh tank of gas if yours is getting old, and eventually run a bottle of injector cleaner as well.

[aschen]

Mark,
Thanks for the great and complete response. The car is 100% stock and believe to be mostly in mechanically good running order. I am not sure if the CIS components are functioning optimally or perhaps there is a vacume leak responsible for the excessive coughing on decel. I am hopeing the wide band can help me figure this out without knowing much about cis.

I appreciate your responce and it was very helpfull.

Aaron