Within the next two weeks I will be switching from the AEM EMS to a stock ECU. The whole reason behind this is two-fold. First off, I want to be able to pass local emissions so I can legally register the car and simply be on the up and up. Second reason is that I want to be able to tune my own car. I hate not knowing exactly how my car is running.

To this end, I've recently purchased two brand new OEM o2 sensors, an AMS high-flo cat and an AEM UEGO. I all ready have EvoScan and EcuFlash along with the tactrix cable. I'm a little concerned because the car is moderately modified. The mods are as follows:

AMS 30R turbo kit
AMS high-flo cat
Borla cat-back
DTM 280 cams
AEM Methanol Injection Kit
ARP Headstuds
Exedy Twin-Disc Clutch
880cc injectors
Walbro fuel pump
VIP Garage single-piece UICP
Precision FMIC w/ LICP
Hallman MBC

I'm concerned because I'm not exactly sure where to start. I've printed off and read the sticky on how to tune your evo. I've also done a lot of searching here in the ECU Flash section. I believe the first thing I'll need to do is scale my injectors, then possibly my MAF? I also plan to start tuning on low boost, ~18 psi and without meth. Any advice would be greatly appreciated.

-Bill

 

yeah if you are going back to a stock ECU you will need to:

- get the injectors scaled properly, search in the injector scaling thread for an approx scaling + latencies, page 5 has a proceedure by Eric (l299gst) which will help
- turn of your meth stuff
- turn the boost down (maybe even swap to a GM 3port + ECU controlled boost)
- richen up the fuel map a LOT
- drop timing by 5* in the high load areas
- do some 3rd gear pulls (or dyno time) and start tuning fuel/boost/timing

If its a stock MAF then you shouldn't need to bother

 

Thank you very much Tephra. It's great to have someone so knowledgable give advice on here. This is exactly why I posted.

-Bill

 

Update:

Okay, I've had the Evo converted back to the stock ECU. I'm running a stock ROM that I'm going to modify myself. However, I've ran into some trouble. The car is barely running. When I purchased the car I was told it had 880cc injectors. So, accordingly I've set them to 800cc with ECU Flash and set the latency values based on a table I found in the injector scaling thread here on EvoM. I'm also running a de-screened MAF. But that hasn't made the car run very smooth, my most important issues are below.

The issues:
1. The car will idle pretty well on first start up but it will barely idle once it's warmed up. I did change the idle rpm setting in ECU Flash from 800 something to 1100 for the higher temp settings. That seemed to help somewhat. It's strange, if I'm driving and come to stop, it'll die. From then on the car will want to die, it won't want to idle at all. If I get to a stop and then give it some throttle for a couple of seconds then it will settle at 1100 rpms like it should and be ok.

2. I'm throwing codes, the only one that's consistent so far is the vehicle speed sensor, which is plugged in. The other codes are intermittent, currently I have a fuel pump relay code as well.

3.Overall drivability is pretty poor. I'm just babying the car to and from work right now (less than 5 miles each way) because I have to. I'm sure it has to do with the injector settings, but I feel like with a stock ROM and with the injectors somewhat scaled and with the injector latencies altered, I feel like it should be running a little bit smoother. I have not even attempted to boost the car or run it hard AT ALL. I understand the car is not tuned correctly.

 

Whats your wideband saying when your car is trying to die at idle? That might clue you in on the problem. Did you mess with the timing at idle?

 

Check that the MAF wires are in the correct pins on the ecu, I have converted several cars from AEM back to stock ecu and I remember having to switch one pin on the ecu from the MAF, I dont remember off the top of my head which one, but get the pin out for the ecu and the MAF and check that.

Also, are you running VTA, or recirculated?
What intake do you have? Is the MAF relativly close the stock possition? I have had several cases where someone made their own intake pipe and the car ran like crap b/c the MAF was pointed down for "cold air intake" which caused the car to run terrible, I think due to backwards airflow. With this case, the car would start out idling fine, and slowly degrade at a light or as it sat......

also +1 on the wideband readings.......

--- Not sure if this is the case on your car, just wanted share some of the things I have seen converting back to stock ecu.....

 

The WB at idle is erratic. It seems to jump from 12 to 15, but I'll confirm that later on today.

Denver:
I am currently running VTA because I have the AMS intake on the car (just a 3" hard pipe that connects to the MAF) my MAF is relatively close to the stock location, stock orientation at the least. It doesn't point down or at an extreme angle or anything.

Can you explain more about the MAF wiring? They did splice into the MAF wiring for the EMS AIT sensor, but that's all I know and all I did was remove that wiring from the stock MAF wiring harness.

Also, I don't have a filter on the car, will that effect how it idles?

Thank you for all the help so far.

 

normaly they cut and slice two wires at the MAF, you have to resolder those together to the correct wires on the MAF plug. Ive seen several times one wire (I dont remember which) is moved at the ecu, if you can find the pin out for the maf connector, and the pin out for the ecu, check to be sure they are in the correct location. I cant remember if it was an evo8 or a 9 that had this problem....... but check it if you can, Ill see if I can find some note (If we wrote any down) of which wire and where it went...... I dont remember either if there was A CEL or not, but you can check with evoscan to see if the maf is working correctly, open evo scan and watch I think it is airflow on evoscan, it should change as you rev the car. If it does not change sugniciantly, the maf is not functioning propery.

Also, as a rule, I have never touched the maf interals, I learned my leason on my 91 with that one..... but I dont think the lack of honey comb is your issue......

(forgive my terrible grammer and spelling....)

 

No problem. I'll check with EVOScan on the way home. Thanks so much Denver!

 

Try scaling the injectors to 790 or so, in ECUflash the injector scling used does not exactly match the size of the injectors. Read the thread tephra pointed you to above. You may also get some help by increasing the timing in the idle cells to 7 deg.

MB

 

Thanks for the help all. I reset my ECU and for whatever reason that fixed all my idling issues. It now idles at the targted 1000-1100 rpm's even after being warmed up. After getting that taken care of I've started driving around and logging through mitsulogger. My LTFT mid is at -12 so I still have some adjusting to do.

Funny that you say that burgers because that's what I ended up setting my injectors to in ECUFlash.

 

Oh, also, I didn't realize EvoScan can't really read trouble codes. I used my Scantool and found out my two codes are P0403 and P0300. Ones EGR and the other is misfire.

 

You can use scantech for trouble codes, its free.... I think you can get it from the activematrix forum. Its also a nice tool to have for watching fuel trims. It can be tricky to get it up and running the first time, and occationally it has issue connecting the first time but it does the job.

 

I'm currently using Mitsulogger to log fuel trims. My fuel trim mid is -13. Which I understand is not where it needs to be. So I increased my injector scaling number.

I do have a question though. I've done some 2nd and 3rd gear pulls now that the car is running ok. My AFR's up top are 10.2-10.5 and I'm still running stock timing with no knock on 18 psi and pump gas on my 30R. In the 4000-5000rpm range I actually have instances where load increases (like it should) but then dips for a second before shooting up. I'll post the excel file when I get home I just wanted to see if anyone had any insight into this. Is this a boost issue or what?

-Bill