Apparent rich misfire - help
 

Hi all,

Appreciate any guidance in advance

I've recently developed a highly rich condition with stft sitting at -29.9 at idle with12afr (commanded at 15), I'm beginning to suspect that a ignition coil has failed but not sure how to diagnose this with certainty

For context, it's a ecutek tuned turbo 86, been running great for 4 years, no hardware or software changes to note of late. I am alittle Sus about potential disabling of DTC code so can't check for misfire dtc to confirm, or atleast nothing is popping up when I scan for it

Confident I do not have exhaust or intake leaks which tend to produce positive fuel trims anyways. I was thinking it may be o² sensor? But it appears to be reading a corresponding voltage to the measured afr, seems like the less likely culprit

What do you guys think?

could be leaking injector
excessive fuel pressure


dirty maf sensor


but just guessing


maybe log some idle with ecutek cable and post up to www.datazap.me

Stupid question probably, but what does your air filter look like?

It's a cone K&n filter sitting inside bumper. I've custom made an enclosure for it, doubt it's the filter to be honest, it's a high flow arrangement

I'm just wondering if it's dirty. Rich conditions on many cars can often be due to a dirty air filter. Not enough air flow for the fuel to burn cleanly. Your ECU sees that and tries to compensate by reducing the amount of fuel. You're turbocharged also, so you're pulling more air through that filter, it's going to clog up faster.

When was the last time you checked and/or cleaned it?

Maybe 10,000km ago or so, car is only on 55k km, I would say it stays fairly clean due to the location and the small mods I did around the filter, good idea on that though

Just an update, I have since pulled out 3 of 4 ignition coils and did an ohm test on the pins and they seem to come out good so far. I'll try get the 4th out, and maybe even spark plug if possible.

From my last drive the issues occured on very light load application, i.e. full DI so don't think it's a port injector issue also . Anyone have an idea on which sensor would cause such issues if faulty? Maybe map? O²?

UPDATE: MAF looks alittle oily, thanks Steve, map getting cleaned too. I'll report back if this changes anything

If that K&N filter is one that you oil to help capture dirt and dust, and you found that the MAF sensor that’s in there to be oily, your air filter could still be the original source of the problem. Is your MAF sensor upstream or downstream from the turbo? If It’s downstream, and your turbo is also oil-cooled, you might have an issue with oil getting past the seals and spitting it into your throttle body and also onto your MAF sensor. Not sure how your setup is though, but that would be something to look at if the sensor is getting oily.

After you clean your MAF sensor, and if that temporarily fixes the rich condition, after a hundred miles or so of some spirited driving, you should pull the sensor back out and check to see if it’s oily again. If it is, then you need to figure out where the oil is coming from. The oily and dirty sensor will fool the ECU into thinking that there is more air flowing into your engine than there actually is, which it will then attempt to compensate for with more fuel....up to a point, at which it should then start throwing a code or two.

Update to close thread.

Problem solved, appears to be dirty maf and/or map sensor. Car running fantastic now particularly at very light loads

Good to hear, but keep in mind what I said in my last post. If your MAF sensor gets oily again, there’s a reason.