I have an 03 Evo 8 that I bought used and the car came with an aem series 1 installed on it. For some time now I have been trying to convert it back to run on the stock ecu. However when on the stock ecu the car goes very lean around 3700-4500 rpms. Does not matter what gear you are in or what throttle percentage it always does it at that rpm range. Everywhere else the car runs fine on the stock ecu. I can run it WOT from 4500 to 9000 at 28psi and no problems. Also idle and just driving it around if I shift before 3700 the car runs great. It's just in that 3700-4500 area that it goes lean. The strange thing is I can install the aem back in the car and it runs fine in that area. No problems at all within that rpm range on the aem. I have tried changing out all the sensors, different ignition system, fuel system, another stock ecu, etc. I have worked with Aaron from English Racing as well as Tom from tscomptuned so it is not something in the rom. I am at the point now that maybe something in the car is wired different for the aem and the stock ecu does not like it. I just have no idea where to look based on the problem it has.

I have attached an Evoscan log of what the car does if anyone wants to take a look at it.

Here is a video of it:


I am hoping someone on here can help me get this figured out. It's been driving me crazy for a while now.

Thanks for your time,
Tony

 

Can you upload as a CSV file?

 

It would not let me upload it with a .csv extension so just change the .txt to .csv. Sorry forgot to mention that in my first post.

 

Have you tried forcing the car to run in open loop under a certain load level? Does it go lean when going WOT? I've never given my car part throttle up to 5500. I kind of wonder if maybe the front o2 sensor is on its way out.

 

Yea Tom tried running it in open loop. Yes it does the same thing no matter what position the throttle is at. The car did not come with a narrow band 02 sensor so I bought a brand new one and I have also tried one out of a friends car as well.

Thanks,
Tony

 

Crazy, wish I could help. Have you tried another wideband just to rule that one out of the equation?

 

Yea no doubt. Thanks for the suggestions. The car breaks up and runs rough when it goes lean and you can see the IPW dropping out in logs so it's not just a bad reading from the wide band. Tom tried adding a ton of fuel to that area and it made no difference.

I added a video to my first post so you can see and hear what it does.

 

EDIT

......Nevermind, reread the whole thread and answered my original question.

However I do have one more, is this an AEM that was meant for an Evo or a 2G specifically? It will work either way but there are wiring differences, so if it was a 2G computer used in the Evo 8 and not a 8 specific one there could be wiring that has changed.

Aaron

 

The sticker on the side of AEM has 1313 written on it. The serial number on it matches with the box I got when I bought the car and it says it's for an Evo 8.

Tony

 

Anyone else have any ideas?

Thanks,
Tony

 

Moved at OP's request.

 

Well I swapped the entire engine wiring harness out and it still does the same thing. The one thing I did discover was if I keep the car in vacuum in the problem area 3700-4500 it does not do it. It only does it under boost and I mean any boost at all. If the aem boost gauge reads 0 boost it does it but anything in vacuum it runs fine through that area. Maybe this will give someone an idea of what it could be.

Thanks,
Tony

 

Maybe something is up with the fpr? Is there a vacuum line kinked or someting? Fuel filter/sock on the pump? Have you run it on a dyno with a fuel pressure gauge on it?

To me if there is nothing weird in the rom, the must be something mechanically going goofy in that rpm range.

 

I have tried two different fpr's an aeromotive and now the car has a fuel lab on it.

Checked the vacuum line which comes directly from the magnus intake manifold to the fpr and have even replaced the line just for the heck of it.

Brand new fuel filter and socks. Purchased a brand new BR double pumper setup about a month ago thinking the fuel system that was on the car might have something to do with it.

I have no awd dyno's near me. =( It does have a fuel pressure gauge on it but it's under the hood on the regulator.

Yea both Aaron and Tom have tried different rom's on the car so I don't think it's a rom issue. Just trying to figure out what would cause the problem in that specific range has been a nightmare. Just makes no sense why the car will run just fine on the aem and not on the stock ecu. Seems to me if a sensor was bad it would show up on both ecu's. I really thought after talking with Tom that car was wired differently for the AEM since that's what came in it but after changing the whole harness out that's obviously not the problem.

 

not sure of any of this will help you, but have you tried

- dirty injetors
- injector latency
- injector scaling
- sprak plugs
- plus leads >>> unless you are running a COP kit

cheers