As the thread title states, how exactly do you know if you are misfiring particularly with the AEM EMS? Is there something in the logs that give a misfire away?

We pulled this log off my car while it was being dyno tuned a few weeks ago, and we could not figure out what exactly is causing the oscillation in MAP readings as the boost increases.

Here is a screen shot of the log my tuner gave me:



We have tried moving the MAP sensor around on the manifold, and it appears to make a slight difference, but nothing mind blowing. We tried remote mounting the MAP sensor as well, but again, nothing came of it. We even tried a different 5bar map sensor also, thinking that the original one was defective, but again, no dice...

My tuner suspects misfiring, and mentions that the car just feels "wrong". The shop putting in the wrenchwork on the other hand is convinced that it is not a misfire issue since the car is able to complete a dyno pull without breaking up, and posts smooth and uninterrupted dyno plots.

What I am also curious about is whether the HKS DLI I have on the car could be masking an obvious misfire where the car would be stuttering and falling on its face.


Penny for your thoughts guys

 

Anyone?

For those who messaged me about it, the MAP Filter is not being used at all here...

My question is more toward whether this is what you tend to see the map sensor doing as boost goes up when you're misfiring?

 

You won't always see the map reading act crazy unless the misfire is quite frequent and for several events. If you have any misfire at all you can usually identify this by doing internal logging and set engine speed to a fast log channel. When you step through the log you will see rpms stay the same or slightly dip just as if the car was knocking but the knock sensor will not be showing knock. Looking at your log it seems you probably have more than one issue going on and its probably going to be difficult just by looking at the log and not able to feel and hear how the car is reacting.

 

Thanks very much for your input GTVEVO. I really appreciate it.

I have shown the screen shot to a few AEM tuners as well, and some suspect electrical interference also. Sadly with these ECU's they won't put a CEL on like OBDII that will tell you exactly where you need to scratch...I am hesitant though to just jack up the MAP smoothing since we could be sweeping important information underneath the rug so to speak

I'm working on getting an actual datalog from the car to post up for you guys to see.

 

what map sensor filter are you running? i use a value of 8.

i try to run my map sensor located in the plenum between the air funnel & plenum cieling / also directly in-line with what ever port you choose. go figure, this is what aem recomends & this is how the factory mounted it on the oem plenum.

run the map sensor as close to the plenum as possible. buscur or rre makes a map sensor adapter that bolts on to the oem plenum within the oem location.

rre sells theirs for $25-.

make sure your wires are ok & the pig-tail going to the map sensor isnt used or shagged out = making the map sensor connection crap. my pigtail was worn out like a 50 year old *****. whenever i wiggled the map sensor pig-tail going into the sensor, i was able to see the map sensor value change +/- 10psi while the car was off with the ignition on.

new pig-tail = very good...you can almost say that about any un-used / low mileaged tail.

 

Thanks for the input Aby, I Appreciate it. I'm using AEM's 5 bar map sensor currently, with no smoothing yet. My tuner did not want to turn it on yet since the map signal was bouncing around so much at the top end.

I will definitely get the shop to check the pigtails also. They shouldn't be problematic I wouldn't think, since the car has not been on the road since the AEM went in a couple of months ago. We have tried 2 AEM map sensors with the same result

 

^ do you have any internal logged data? any data logged onto your laptop?

dont think of the filter as "smoothing" so much, as a means of eliminating noise.

no need to have the dog chasing a tail that doest exist.

pm'd

 

I'd check all the electrical connections, just to make sure the signal isn't dropping out sporadically. That map signal seems extremely noisy even for misfire, but it's hard to gauge without the load scale on the left axis instead of %.

 

Thanks for the input everyone. I'm grateful.

Let me ask this... Does everyone run with that MAP filter on???

I'm just trying to get an idea of just how common it is to use the feature really...

 

Hey Aby,

I unfortunately don't have any logged data or anything to show at all from the car at all.. All I have is the screenshot posted. In fact, I have never even used the AEM software at all... All I know is that there is one running the car at the moment. I have seen the AEM box in the car once, know it is silver in colour, and that's about all I know about it

I am curious though.. Why is the MAP filter there? I mean, is it not important for the ECU to be able to detect everything that is going on in the intake manifold?

I unfortunately have not been able to find out more about the map filter function and what AEM's intended use of it is.

I remember that when we first ran into this issue, AEM's tech support simply told us to try different mounting techniques and locations to stabilize it all. They never even mentioned Map Filter at all.

I am also curious about something the tuner mentioned to me, about how the car felt as if it was not running correctly.. COuld that be because of the constant fluctuation that was going on here, causing the ECU to select fueling and timing from different areas as a result of what the map sensor was doing?

 

one more question!

for those of you using the map filter function, what kind of map sensor oscillations are you seeing with the function off completely?

 

Usually when I tune a car or my own I always setup the map filter to its default on the EVO which has always been 4 to my knowledge. Its been a while since I fooled around with it but I am pretty sure I set it to zero and it looked as if the reading was basically faster and was able to pick up the smaller changes but it never jumped around as it shows in your example log. This was with an earlier version of software also before the 1.19 version so they could of made revisions to the filter since then also.

My advice would be remove the DLI and anything extra tagged onto the cars system except what the EMS needs. ReTest any sensors including the CAS and Crank trigger sensor and keep trying to determine the result of your issues. It probably won't hurt to call AEM and send the box in for review. If you look at your log in your first post it looks as if you are loosing resolution as more load is put on the car which is very weird.

Too bad you don't know anyone in the area with an AEM box for the EVO just to do a quick test.

 

Thanks for the suggestions GTEVO.. i will try having the shop remove the HKS box from the equation. I think if the car is misfiring, it should be much more obvious with it in place really.

CAS and Crank sensor tests will be performed also.

Times like this i really miss OBDII

 

I don't see any missfires in the log.. If you see the AFR spike lean, that would show missfires.

 

thanks very much for the input guys, i really appreciate it! We found the culprit...we shielded the wiring of the map sensor as well as used a map sensor adapter also, and all of a sudden, the signal smoothed right out without using the map filter function. At 18psi, I believe it moves around less than 1/2 a psi iirc, which is well within acceptable limits.