running progressively more rich?

[Hulakatt]

Over the last few months I've noticed my car running progressively more rich and by that I mean that I have more and more unburnt fuel wafting out of my exhaust pipe at idle and under exceleration. My rear bumper has a smear of fuel on it above the exhaust pipe and the inside of the exhaust is coal black and shiny. I pulled the MAF sensor to check it and it looked pretty dirty, no idea when or if cleaned last. Could a dirty MAF be causing my troubles? Any other sensor to check?

I have some MAF cleaner on it's way, figure I ought to take care of that either way.

 

[Alin]

Not sure what exactly the symptoms are for a dirty MAF, but it needs to be cleaned right away!! I isually clean mine once a year when i clean the air filter and swap spark plugs.

 

[Batmobile_Engage]

A dirty MAF could be the cause of this. When I've had MAF issues, I didn't notice soot or unburned fuel, but the car would get jerky during acceleration, because the MAF wasn't metering the air properly so the engine would see drastic changes in AFR. If you have a Cobb AP or another way to log, reading the MAF voltage would be a good way to verify MAF operation. The voltage range of the MAF is 0-5 Volts and it should swing up and down through that range between idle/normal driving and boosted driving. In my case, my MAF was stuck outputting somewhere around 1.1 Volts. I cleaned and reinstalled in and the symptoms, as well as the MAF voltage problem went away.

Be very careful cleaning the MAF so that you don't damage the element. MAF cleaning time is also a good time to clean/replace your air filter.

It's also possible that you have a small boost leak. But we should rule out the MAF before moving in that direction.

 

[Real Auto Dynamics]

About 9 times out of 10 it turns out to be a leak. Typically richer conditions under acceleration means the leak is after the turbo somewhere. Another thing that causes gradual rich conditions over time is an increasingly dirty and clogged air cleaner or a deteriorating catalytic converter.

I might prescribe a boost leak test and a smoke test to rule it out a leak. Otherwise you are just guessing what is wrong.

If you have the ability to log then that would help us determine the cause.

 

[Hulakatt]

I'll get set up tonight to log some data over the next day or 2 and set up a MAF gauge on my AP.

Thanks guys!

 

[Hulakatt]

Off the cuff MAF voltage readings driving to and from work today:
Low/High .8/3.96
Idle 1.22

 

[Batmobile_Engage]

Off the cuff MAF voltage readings driving to and from work today:
Low/High .8/3.96
Idle 1.22

That seems okay. What do you think [MENTION=9]HolyCrapItsFast[/MENTION] ?

 

[Hulakatt]

It didn't seem too far out of what I'd expect but I cleaned it last night anyway. Significant visual difference on the intake side, went from soot black to the same brown as the other side.

 

[Real Auto Dynamics]

I want to see fuel trims. MAF voltage really won't tell much or at least it is not the whole picture. The fuel trims will tell you if it is adding fuel or taking away and under what conditions.

 

[HolyCrapItsFast]

I want to see fuel trims. MAF voltage really won't tell much or at least it is not the whole picture. The fuel trims will tell you if it is adding fuel or taking away and under what conditions.

It would also help to see a wide band reading. :tup: it is helpful to compare it to the stock sensor and to see what is going on in open loop.

 

[Hulakatt]

How can you tie a UEGO into the stock ECU? Any way, that would make things a lot easier for me.

Oh, found out this was a boost leak and also from not having the right tune for running a FMIC. I've since gone back to the TMIC stock style setup and replaced the holy exhaust header and I'm running 10x happier!

 

[Grinder34]

How can you tie a UEGO into the stock ECU? Any way, that would make things a lot easier for me.

Oh, found out this was a boost leak and also from not having the right tune for running a FMIC. I've since gone back to the TMIC stock style setup and replaced the holy exhaust header and I'm running 10x happier!

I doubt there's an easy way to tie it in. Maybe with a raspberry pi you could have it spit out the stock narrowband voltage ranges the ECU would expect and effectively replace the stock narrowband? I'm out of my depth here though.