Vitesse MAF kit, misfire solved, but still confused

[cockerpunk]

a couple of weeks ago, i noticed my voltage was really low, like below 13.5 with the headlights on. i have a rebuilt alternator, but digging into it, it seems these Bosch alternators have a really low set point stock, only like 14.1 volts. so it makes sense, in a 30 year old car, to have .6 or more voltage drop between fans, and lights and what not. and while that seems to be the way the factory set up the car, to kinda low charge, i am not comfortable with playing chicken with an alternator that low.

so i found one of these adjustable voltage regulators. bought one, easy to install, plugged it in, turned it up to 14.5 like it should be, happy as a clam right?

no sooner did this happen, then my car started misfiring like crazy on full boost.

so as per a misfire, i started throwing parts at it. plugs, wires, cap, rotor. none of that worked. pulled the plugs, to regap, and they are all sooty. must be running rich ....

so i bought an o2 sensor, and a coil (for good measure). planned on installing them when i get them. i also dropped a couple of pounds on the fuel pressure, nothing big though.

so i also google misfire with the vitesse maf, and get some threads talking about bad grounds etc, causing a MAF kit to sense incorrectly, flood the car with fuel, and misfire rich. great, another thing to look into!

so this morning, i am out with my meter checking all these grounds, checking voltages etc etc. on the off chance and one of those "this is dumb, but needs to be checked off the list anyway" i turn down the voltage regulator back down to that low set point.

car instantly smells better.

take it out for a test drive ... no misfire. pulls awesome again.


so its clear that running an alternator/battery voltage of 14.5-14.0ish causes misfire. i assume this is because the MAF is going higher than it should, meaning more fuel, meaning way rich, meaning misfire. i get that sequence of events.

what i dont get, is why the kit is not designed to be ok with what every other car would consider healthy alternator/battery voltage?

and more to the point ... can i stick a diode or two in there (~.6 volt drop per), to drop the voltage the MAF sees, while maintaining my nice charge voltage?

[cockerpunk]

update on this.

turns out the adjustable voltage regulator is not the issue. AFRed the car, and it made no difference in the rich running condition wherever i put the voltage regulator. so thats good, i can have my cake and eat it too.

i grounded the MAF directly to the battery and the misfire is 99% solved, which means it is a grounding problem. it still does run rich on boost, and lean on idle, which i think points to an intake air leak.



I also emailed vitesse on the subject, and they have been SUPER helpful. they also pointed me to a bit of software they now make that allows you to plug in a laptop and read all the DME variables. I instantly bought that, and i know its money well spent because anyone who has tried to solve engine electronics issues on these cars knows, its pretty awful. and being able to plug in and see and read out. MoMonitor Enthusiast

while that might not be useful for solving this problem, it will be a huge help i know later on in this car's life. as much as i hate OBD motors sometimes, they do make troubleshooting easy sometimes. this should be even better!




so, ill update the thread when i know more. gonna have a shop smoke and/or pressure test the intake to find the leaks, and hopefully clean the back sensor ref ground. i cleaned the other two.