I have a 1999 1.8 mx5 , Its running a HKS turbo kit and rx8 injectors. My tuner has just installed a AEM fuelling/ ignition biggy back unit. All has gone well and getting 210lbs torque and 205 hp at just under .6 bar. The issue... At 1500 rpm the car, fuel cuts, goes really lean and tried to cut out. The rest of the map is fine. We have been on the dyno for days! but just keeps doing it. Aem has asked us to fit a 1k resistor in the maf line. Has anyone has this problem ? please help I want my mx5 back :(

is it 1500 rpm or at a certain maf voltage?

looks to be at a certain maf voltage, but not 100% on that. was fine before the aem was fitted.

anyone?

sorry, if its at a certain maf voltage, and if you can tell it to add more fuel at that maf voltage and see what happens

I realize it's too late for this but you can use the AEM f/iC to eliminate your MAF. You'd have to go back to non boosted and do a ton of data logging with the F/iC. You then build a voltage MAP chart based off of your MAF readings. Otherwise the resistor might be the next best thing.

I have a similar issue that I just discovered. What I've seen in the data and suspect as the culprit is some noise on the sensor data, in my case the WOT signal on a 1991. The 1k resistor is interesting because it would provide some low pass filtering depending on the capacitance in the FIC side of the circuit. That is one of the options I'm considering to attempt to address the issue in my car.

I would try that resistor but be prepared with a selection from 500 to 10k ohms to be sure you can optimize. Knowing their system as they do perhaps the 1k is right on the mark.

thanks for the responses, Its back at the tuners now, As on cold start it just cuts out , takes about 6 attemps to get it running. Shows massively lean on warm up and jults and judders. After 15 mins of holding the throttle up above 2k , can starts to run fine. when hot fault goes. Dont know why the aem is effecting the standard ecu when not on boost!

My car seems to have almost the same issue. After getting the car dyno tuned with the fic install, the car seems to hesitate and jutters when I cruise with light pedal effort. As soon as I press more, it comes alive and pull nicely. Happens at 3450 at 60miles on the highway. If I go slower, the wideband dont even show any numbers at all. then, as soon as I press, the tune in the FIC seems like to go over the OEM ecu tune and it goes good...fluctuating from 16.9AFR@ 3450 to 11.0@3750+rpm when boost hit in a fraction of 300rpm ...

I've been working on tuning mine on a NB1 with M45. At full throttle no boost the stock ecm will run afr of 12/1. I actually needed to pull fuel slightly before entering boost. The problem for me was that under lighter load conditions the ecm is not adding nearly as much fuel. This meant that if I tuned WOT for a 13/1 afr at 0-1 psi, I was pulling 7% of fuel on the 0 psi row. This is not appropriate unless you are under heavy load. I ended up putting zeros in that row up to 4000 rpm, then interpolating the following rpm break points until I was at -7% of fuel at 5500. That seems to have solved my low load lean condition. When you are at 5500 rpm and above , you probably are not at low load at that psi. I also am using a fixed input to the O2 map (voltage mode) to put the car into open loop at about -1 psi so I can force the car to transition to open loop sooner so I don't have as many variables to deal with in this load range. My MAF is totally bypassed and does not even enter the FIC.

Just my experience...yours may vary. Good luck.

the fixed input in voltage mode and MAF bypass is interesting, could you teach me more on that???

I've been out of town and just saw this response. I will try to respond a bit more tomorrow evening.

Mr. na,
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