Installed the F/IC today and now I have a miss? (01 Impreza RS)

[brydon]

As the title says, I installed the F/IC today. It started after throttle comp with no problems. I performed the RPM set also with no problems.  It idled great and reved great.  I also verified that the timing control and the fuel control works great. After a short cruise I relized it has a miss around 3000rpms if I give it some load. It is on the stock injectors and a zero map in the AEM.  It will free rev past 3000rpms with no problems it will also pass it easily if I give it very little load.  The miss also seems to clear up after 3000rpms but i have not verified high rpms yet because I want this solved.

It appears to be related to the crank sensor. Also I don't have the cam sensor hooked up, just the crank sensor.  Although it retards timing perfectly. Verified by a timing light.  Slew Rate setting maybe? Or is it something I haven't thought of?

Any help would be appreaciated. I want to switch to 750cc injectors to see if the AEM will control them well enough.

Thanks
Brydon

[brydon]

So I played around some more today and discovered that with the crank sensor only tapped on it does the same thing.  It misses a little and then it will take off. Quite violent went driving.

How could the injectors be causeing this? One more question when wiring up the injector outputs. Are you suppose to go injector 1 with injector 1; 2 with 2; etc. Or is it the injector in the next firing order?  Like I have a 1-4-2-3 firing. so injector 1 to injector 1; injector 2 to injector 4; injector 3 to injector 2; etc. 

Also how does the FIC know if it is a 4 or 6 cylinder? Automaticly or did I miss something?

[JN]

Most likely the injectors will not cause the "stumble".  With values of "0" in the fuel map, the F/IC just passes the signals through.  Injector 1 on the F/IC does not need to be connected to injector 1 on the engine.  However, the Injector 1 in and out must be tied to the same cylinder.  I typically connect injector 1 to cylinder 1 and so on.   Does your car have mag or hall style sensors?  How do you have the wires connected?  Also, some engines will work fine with just the crank sensor.  The cam sensors are only needed if the factory ecu detects a phase shift between the cam and crank signals. 

[brydon]

It is a mag style sensor.  Right now it is just the crank sensor. I had it hooked up the same way on another engine management.  The + side of the crank sensor is cut and the - side is just T'ed on since Subaru grounds one side of the sensor and only uses the positive side for signal.  It reads perfect. And functions perfect.

The only problem is above about 30% throttle it has random misses starting at 3000rpms.   Even with the crank signal wire T'ed on not cut it does the same thing. It is very odd.

[JN]

How much timing are you pulling out, if any?

[brydon]

0-2 degrees at when it happens. Nothing that should cause a miss. I have had alot more pulled with no problems but that was on another engine management.  But I'm not even boosting yet. It is mostly just the transition between light to moderate throttle.  I'm a little stumped.

[brydon]

Okay here is some more info. I logged the car missing. There is two logs that I put together into one file and only put in the information just before and after the miss.

It appears to be turning the fuel off.

Let me know what you think.

Thanks
Brydon

[brydon]

Okay day four of screwing with this thing. No matter how I hook it up it continues to have the miss.  I'm guessing it is one of two things. But most likely the AEM is not outputing what the stock ecu wants to see. Without a scope and a dyno it would be hard to tell. It could also be the AEM not picking up the signal correctly all the time.

Because Subaru's ground one side of the MAG sensor they get a positive and a negative input on the positive input to the ECU. I have a feeling it can't reproduce this signal to the ecu. Although it idles and cruises great with the negative or positive mag wires hooked up on the positive input to the ecu. It will not run under moderate throttle. Although in boost it seems to come back to life and go.  i get the same effect with both negative and positive input to the ecu cut or even with just the positive T'ed onto the positive input wire. So even T'ed on it is clipping the signal.

If no one has any ideas by tomorrow, which I guess short of a Subaru only update to the firmware, I will be giving up and returning the AEM F/IC.  i guess I will have to go with something I know will work.

Thanks
Brydon

[Raj]

Any luck with your problem?  I'm having the same exact issue with a 96 Neon and would like to know if there is a fix.

[brydon]

Not yet. I have tryed everything I can think of. I have even used another piggyback to send it a perfect signal to the AEM. It does the same thing.

[SB]

Are you getting a check engine light? Have you tried checking for fault codes with an OBD2 scanner?


Before looking at your logs, my guess was that the Subaru ECU might be unhappy since the FIC is altering the Crank signal but not the Cam signal. Some ECUs check the timing between the crank and cam, if they are too far from each other that could indicate detonation. Try connecting the Cam signal to the FIC as well.

Do you have any issues when free-revving in neutral? Can you get the RPMs above 4000?


What is your engine setup? Do you have an aftermarket turbo installed?

[brydon]

Are you getting a check engine light? Have you tried checking for fault codes with an OBD2 scanner?

I have no check engine lights from the AEM. I get a P0420 after cruiseing awhile. But that is because of my lack of cat. I have had that for awhile. I own a OBDII scanner so scanning and watching fuel trims/rpm/load/etc is not a problem.

Before looking at your logs, my guess was that the Subaru ECU might be unhappy since the FIC is altering the Crank signal but not the Cam signal. Some ECUs check the timing between the crank and cam, if they are too far from each other that could indicate detonation. Try connecting the Cam signal to the FIC as well.

I'm leaning towards the crank sensor not being the problem after lots of trouble shooting. I have hooked the crank up many different ways including not even cutting the crank wire, just T'ing it on and it still misses at the same point.  I have also hooked the cam/crank up at the same time with the same issue. It idles and cruises great. If you try to go up a hill while cruising it will miss.  I have also switched to another engine management that alters the crank and that has no problem with high load and high rpms.  I have also hooked that engine management up to feed a perfect signal into the AEM and then the car still misses.

Do you have any issues when free-revving in neutral? Can you get the RPMs above 4000?

I can rev to redline in neutral.  I can also do that in first fairly well because there is not enough load. But second-fifth sucks.  On a side note the car runs fine up above 4000 rpms. The only problem I have is related to moderate load. It will miss a bunch and then take off with no problems in the upper rpms. Untill I shift then it misses again.

What is your engine setup? Do you have an aftermarket turbo installed?

Engine is stock with an AVO turbo kit. The engine management that came with the kit works fine but I want to go higher boost and I need direct injector control for larger injectors. The 4-5psi it runs now is fun but not fun enough. I also have forged pistons/cams/springs/retainers to go in but I leaving the motor stock until I am happy with the engine management.

On my last impreza I had a emange ultimate hooked up to it that had direct injector control. It worked really well. So I know I will not get a CEL for the injector wires being cut.

Also The car has no problems with the jumper plugged in. Also something even odder, if that is a word.  If I disconnect the crank sensor wire to the AEM but leave the AEM and everything else plugged in I have no problems. I of course read no rpms and have no control over anything but I thought this might help in an idea.

I have two more idea to try to narrow down where my problem is coming from. I will connect the crank sensor with the AVO engine management after it as a buffer between it and the stock ecu to see if still misses. My other idea is leave the crank sensor connected to the AEM but the injector wires disconnected. To see if it still misses. Although both ideas don't really help me out in the long run because I need both working without anything in between.  If those all fail then my third option is to buy another emanage ultimate because I know it works.  But I have AEM EMS's in two other cars and love them so I decided to try more products from you guys. Besides it goes well with the UEGO and AEM boost controler i have to put in the car.

[brydon]

Okay, so I took the car out with my OBDII scanner and watched the rpm/fuel trims/load sites/timing.  It appears the the problem is completely in the AEM.  The factory ecu appears to never lose the crank sensor and when it misses it compensates by adding fuel because the AEM just turned the fuel off.  I'm really convinced now that it is the fuel injector driver that has an issue.

I read that they have a cross over point for the injectors to go from real time to next cylinder fire for altering the injector control.  Could there be some bad part of the software/firmware here?  It blows my mind that it misses transitioning from low load to high load but not in high load or low load.  Bad unit? Bad firmware?

It also appears that the AEM never loses its RPM signal so that confuses me even more.

Any ideas are good ideas?!?

It also appears I'm not that only person having this problem!? My injectors are denso 310cc stock injectors. They measure 14 ohms.  The injector response time is 710usec at ~12 volts.  Although I have played with the response time with no improvement or change.

[JN]

Have you tried putting zeros in your fuel map?  Does that effect the "miss".

[brydon]

I have been running zeros everywhere. A zero fuel and zero timing map. Same issue.