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

[matlfp]

I had the same problem at low load,it miss not everytime at about 3500rpm.I unplug the aem for the timing (crank and cam sensor) and put a nother box a split second for the timing adjustment and everything work fine.I'm working on a chrysler product.If nothing is find to solve the problem i will return the aem and put back the two box i already got.
Thank

[brydon]

I had the same problem at low load,it miss not everytime at about 3500rpm.I unplug the aem for the timing (crank and cam sensor) and put a nother box a split second for the timing adjustment and everything work fine.I'm working on a chrysler product.If nothing is find to solve the problem i will return the aem and put back the two box i already got.
Thank

If you unpluged the cam/crank sensor then you don't have a rpm signal.  That would make your fuel control about as good as a fancy SAFC.  I would really like to know the fix.  I'm almost positive this is an AEM issue not wiring or configurable.  I also have no CEL codes soft or hard.

[matlfp]

I just clamp the crank input for the fic to have the rpm working.

[Raj]

Yea you could just tee into the crank and cam wires and that would give you the rpm reading and full control over fuel but it wont do anything with the timing which is a big reason why someone would buy this.

[brydon]

Yea you could just tee into the crank and cam wires and that would give you the rpm reading and full control over fuel but it wont do anything with the timing which is a big reason why someone would buy this.

NO NO NO! It still has the miss! I have done this. I have also buffered the signal from the ecu and it still misses exactly the same. I am almost certain it is some how injector related.

[Raj]

You know, I missed that you allready tried that in your post.  That does sound pretty fishy though as it shouldnt alter the signal as we understand it.  I'm sure you tried using just the cam signal and if so, did it produce the same miss?  What did you use as a buffer?  Normally capacitors work but a diode across the wires could sustain any spikes in the signal that the fic could be producing.  I'm with you though, your going to need a scope to see wtf is going on.

[brydon]

You know, I missed that you allready tried that in your post.  That does sound pretty fishy though as it shouldnt alter the signal as we understand it.  I'm sure you tried using just the cam signal and if so, did it produce the same miss?  What did you use as a buffer?  Normally capacitors work but a diode across the wires could sustain any spikes in the signal that the fic could be producing.  I'm with you though, your going to need a scope to see wtf is going on.

I really need a scope and a dyno because I have no problems until I load the car. So idle and reving show no issues.  Looking at my OBDII scanner it thinks there is nothing wrong.  Watching the AEM log files it momentarially lists the injector outs as 2 when they are ~30. So either the AEM cannot read the injectors momentarially or the crank angle is momentarially output as somehting incorrect and the ECU cuts fuel.  But it most be quick because I can't catch it on the OBDII scanner.

I have used diodes and other engine management to buffer the ECU.  I thought using another engine management would work because the ecu would be seeing a signal I know wont make it miss but it didn't.  I have also tryed pull down resistors on either side of the AEM to see if it was a signal problem do to my car only haveing 6 crank teeth.

And it has to alter the signal somehow at every point.  The inputs read the ecu outputs and then drive the injectors and the crank is most likely analog (mag sensor) in and a digital output.

[Raj]

Well, heres another possibility.  Pull the crank sensor out and check if it has oil and crud on it.  If so, clean it off and try it again.  I know crank sensors fail alot om these motors which leads to misses and eventually no-starts on stock cars.  It is possible that the fic is more sensitive to this where the stock ecu has more of a buffer?  Worth a shot.  Hopefully I could put some time into mine this weekend and get it fixed.

[brydon]

Well, I've tried new sensors and all sorts of wiring configurations. It seems that there is just something wrong with the AEM. Funny thing is the Subaru uses a similar crank/cam sensor as the Scion TC.  Maybe I have a bad unit. Anyway I have 10+ hours into this now and no success so i will be putting this in the deap dark reaches of my closet and going with the emanage ultimate. I at least know that works and has the same features and more.

On a side note I hooked my new AEM UEGO up and it works great.  My factory ecu is really quick with the front o2.  When it misses you can see it go lean real quick and then the ecu brings it back a little rich. 

Still not sure if this is a injector problem or a crank problem.  I still have a feeling it is injector based because T'ed on to the crank it misses also I T'ed on to the Cam sensor with the crank wire just to get an RPM signal and it does the same thing at the same point.  Is there some sort of switching point in the AEM at 2500-3000rpms or maybe a certain injector duty cycle.

[bkcomm]

Looking for an update on the injector cut issue.
I have an FIC waiting to go into a 2004 rs but I want to
hold off until a fix if any is made available.
Any idea if this is a hardware issue or something upgradeable
like with the AEM standalone & the WRX?

[brydon]

i have a AEM EMS on my WRX and love it. I however have not figured out why the AEM F/IC is missing. I think it is tooth related or something a miss in the firmware.  Or it is just my box. Try it on your car I would like to have confirmation that it is not my car or my box. Or confirm it.

[Pirken]

i think it is the box, have the same cut om my 3sgte engine. it cuts at 3100-3200 rpm.

[brydon]

i think it is the box, have the same cut om my 3sgte engine. it cuts at 3100-3200 rpm.

I think you are the forth person I have now that has the same problem. At least the forth I have seen on the forums.

[brydon]

Okay after a week or so of doing nothing I finally got in there and backed to stock the injection wiring. I was cruising around and it reved out fine. Just like the AEM wasn't there. I then drove around alittle more and it appeared to be fine.  Then after 10mins of driving the miss came back and never went away. It went from great to missing very quickly.

Sounds like a capacitance or inductunce noise problem, maybe?  Everything is well grounded.  Bad box?

So for fun I deinstalled the AEM F/IC and hooked the crank positive input up to a signal generator. and the output to a hand held scope.  Guess what miss it misses at high frequencies.  I would guess this shows about 2500rpms.  So if a perfect signal does the same thing then I'm guessing my crank sensor is not the issue.

Any comments from AEM? 

Oh, one more thing. It is something with the crank positive input because the miss is there even just with a single crank positive input T'ed on to the crank signal.  Not even cutting the wire just T'ed.

I think no more testing can be done but I will entertain ideas for testing.  I have a moderate amount of equipment and lots of knowledge. Let me know what you think or if I should just send the box back!?

Thanks
Brydon

[SB]

Brydon,

I haven't been working very closely with the FIC project, but here's a theory or two:


Your issue could be hardware related, having to do with the response time of the circuitry.

It could be software related as well: since the FIC was designed to work with such a broad range of vehicle, it's not unlikely that there are a few sensors we haven't tested yet.


If you don't mind helping us troubleshoot, I'd appreciate more info about the signal you're creating with your function generator. I can test a similar signal on a few of the FICs here at AEM to see how they compare. At what frequency is the FIC having trouble keeping up? What is the signal's voltage and duty cycle?


If you wouldn't mind putting an oscilloscope to the sensor while it's on the vehicle running the stock ECU (without the FIC), that would be helpful also.

Thanks,
Scott