I have an S13 coupe with a DET in it. I have just gotten the car going again after this winter and am trying to sort some weird issues. When idling the car will try and maintain somewhere in the 12's AFR (i know thats rich i havent had it tuned yet). But when i turn on the headlights/blower motor the AFRS will climb to the mid 14's. I have a quest alternator that is putting out 14 volts at idle. the battery has been relocated to the trunk and grounded using the rear strut bolt. I used a flap disc to sand down the ground before i installed it. I have also used 8 Gauge wire to ground the intake/alternator/cylinder head to the chassis which i also used a flap disc to clean. It has a wiring specialties harness that i bought new. i want to think this sounds like a possible bad grounding issue. maybe theres something im missing. it has a Z32 maf (WS Pigtail) that is also grounded to the chassis the same way. i wouldnt think it being just untuned would cause this issue. Thanks in advance for any advice!

If you have a Z32 MAFS installed, but the ECU hasn't been reprogrammed for that MAFS, that would definitely cause AFR problems. I'm honestly surprised it runs at all.

i prolly should have specified that haha. i have nistune and its setup for the z32 maf. just not actually professionally tuned hah.

float_6969 wrote:If you have a Z32 MAFS installed, but the ECU hasn't been reprogrammed for that MAFS, that would definitely cause AFR problems. I'm honestly surprised it runs at all.

This was my battle when I went over the the PTE SC61 and 850cc injectors on my car. I put in a Z32 maf and forgot to recalibrate for it. Very simple to forget about something like that. I chased it for a month before I realized what a moron I was lol Before I realized what I had done, my car would start up and idle extremely rich (to the point black smoke was puffing out the exhaust) and would stumble and die after a few minutes if I did not give it some throttle input. The AFR would also hover around 12.

Can you put a stock MAF back in there and see what happens? It's been a while since I have played with a CA so I don't know what the pinout is anymore if there is a difference or not.

ive got a quick change maf connector so i could try out the stock one i think. just have to get some couplers to hook it up

I would be willing to bet that's the biggest issue right there. Try it out and report back for sure!

I couldnt find what i did with my stock MAF so i did some digging on electrical. I did multiple voltage drop tests all around the car and found that i did not in fact have a grounding issue. I also while i was in there took out all of my factory idle controls and made a block off plate for the intake, as well as changed out the pcv rubber hose to the intake. this seems to have made a big difference in the way the car runs. hopefully i am onto the problem here. i am in the process of trying to get a rough tune on the car on the street. only issue i have is it is running quite rich under high load and i cant seem to lower that by my fuel map. im pretty new to tuning but i understand the core concepts. I will probably end up taking the ca to a reputable dyno sometime soon when the funds are available to do so.

Then your K (injector constant) may be too high. With the fuel map you can only ADD fuel to the (MAF voltage * K) injector pulsewidth value. If you're at zero in that cell, and still too rich, you have to decrease your K some. Which will in turn throw anything else off balance.

You should put together a fairly good working tune on the street, so you don't waste your dyno time with the basics. Dyno should only be used for final tweaking, especially if you're on a budget.

So i am still battling the problem where when an electrical load is applied to the car ie.. brake lights , blower motor, headlights. the car runs at least a whole point or sometimes 2 points richer on my wideband. i have made sure the car has good grounding, but i am trying to think of what might be the cause of this. maybe someone with a similar issue before?

anyone that has their battery relocated to the trunk. does your power wire from the battery run out the same hole/rubber grommet in the firewall? im thinking i might be getting some inductive interference maybe from this?