Hi Guys,
two days ago i had a problem with my miata. A little backstory, the car has a forged engine (1.6 miata nb motor head, mazda 323 gtx 1.6 turbo motor block, forged rods and pistons), 900 ccm fuel injectors, custom exhaust manifold, Garrett GT2860R, CAI, MAF delete, walbro 255 lph fuel pump and a VEMS Ecu.
I bought the car and it was running fine but a little bit rich. Idleing at 950 +-30 when at operating temperature. I wasnt that much at home in the past few weeks so the car has been driven lately every one or two weekends, but the last couple of days it seemed like it was running even more rich than normally(strong fuel smell) and the rpm were dropping low when i would turn into neutral or stop at a red light. I was thinking maybe there is a vacuum leak or maybe the lambda is old so it sends the wrong signals to the ECU, but i wanted to take a look at that.
Fast forward to two days ago i was meeting a friend and we were looking at the car, it was running in idle on the parking lot and we were looking at the tuning program to see what was happening there, the car was around 13-14 AFR in idle and it just goes out. The car wasnt struggleing or something, it shut down as if i turned the key. I tried to start the car, everything seems to work, fuel pump, spark plugs, it cranks but it wont start.
Then we proceeded to check the spark plugs, they were black and the plug on cylinder 4 was a little bit wet, we cleaned them, tried to start the car, same issue, i contacted the last owner he thought the spark plugs just needed to be replaced.
The next day, i bought new plugs, replaced them and it is a little bit better. After that on the first few attempts to start there was white smoke comming from the exhaust which i assume is from unburnt fuel from the starting and once i heard the alternator whineing. After a couple of times it got on but was just working on 400-500 rpm as if all cylinders arent working. When i press the gas pedal the rpm go up to 1100 rpm and wont go higher no matter if in neutral or in a gear.
Does somebody know what is causing the problem or what could i check? What could cause the car just to turn off like that when idleing?
