So I've made a couple threads on this same matter before but they died out and I never made any progress. Long story short, I have a miss at idle and steady throttle that I can't get rid of. I ended up thinking I had something wrong with my engine so I pulled it and built it yet I still have the miss. Went to cops to see if it was my coils and still have it. I have taken logs of the events and my battery voltage seems all over the place. I don't know if its just a crazy amount of noise or what... I've cleaned all the grounds I can find and am really out of ideas. It has an na alternator that I put on wired as so:
Really would like to figure this out as it is my daily driver and I'm to the point of taking the car to Begi and paying them mucho deniro to figure it out. Here's some screenshots and also a log of the events.

 

Wait you have an NA alt?

I could have sworn you have the alternator control circuit in your MS...

 

Ok don't judge me as I was even more of a noob back then than I am now. I had issues with my charging system when I got the ms so instead of doing the smart thing and opening it up to see if there was a loose wire (solder broke on one of the connections) I just bought an na alternator and wired it up. Later on I opened it up for something else and say that the wire was just loose but since I had already gone through the trouble I just left it

 

ok. so its still missing?

 

Diagnose?

 

Yesss... Would that make a difference?

 

Bump

 

Ok so I know I have a miss and I'm going to assume that the voltage is another thing. So I can rule out spark as I have changed from the stock coils to cops and its the same. It shouldn't be air, so all that's left would be fuel. Although it seems like its heat related as it doesn't start missing at idle until it is somewhat warmed up. Maybe my voltage is a lacking so my fuel pump can't keep up and I just cant feel it when I go full throttle?

 

I would fully charge the battery, disconnect the alternator and then log a run on battery only. Post results.

 

post logs of miss hit spacebar every time it happens.

 

Screencaptures and logs in the original post show it I think. You can really see the AFRs pegging.

 

Will do, I just have to wait for my engine to cool off for a sec.

Brain- Here's a new log with plenty of markers

 

Here's a log with no alternator. She didn't want to hardly run and was super lean. I'm guessing that might be a problem...

 

OK. That's more like it. What I see from around 61 to 70 seconds is that you can get the car to run, and your variables are steady enough that you could actually begin to tune. You're using a bit of throttle to keep a lean car running -- but at least the readings make sense. Your AFR really doesn't though -- car should not run at 20:1 (but at least it's steady).

Recommendation:

1. Get the alternator sorted. The one you have is drawing your bus voltage way down -- far enough to where engine management doesn't have a chance. Have you had that alternator checked out? Most parts stores will do that for free.

2. If the alternator's OK, then double check that control circuit. Can't help you there as I've got a plain-jane '90 with its original alternator. Brain says your MS will control a stock '99 alternator. Might be a better way to go.

3. Check your wideband settings. That 20:1 can't be right.

4. Once you've got steady voltage and a well-calibrated wideband, tune! I would start by adding some fuel to the idle area VE cells so it runs without throttle input. Go from there.

 

that first log, your alternator isn't working. voltage should be at least around 13.5v on an uncalibrated battery voltage in TS.

on the second log, the voltage makes sense at 10-11v with no alternator attached.

the AFRs make no sense at that point however, as you cant idle at 20:1 AFR.


your TPS and MAT are extremely noisy...I think you have a sensor grounding issue as well.