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Discussion Starter · #1 ·
Hey guys, ive been prowling these forms forever, and although nearly every question ive ever had has been answered here, or somewhere online, i have a unique situation that i need assistance with.
I have a 1996 GC8 WRX with a recently swapped 1996 EJ20g on a U8 ecu. Car is stock other than a catless TBE

My problem is that at exactly 6500 rpm, seemingly every gear, (1st, 2nd, and 3rd) the car will hit what seems to be an imaginary rev limiter. I will have my foot down, but it will go "bap bap bap" and not rev past 6500, just sitting there, but its not violently jerking like a misfire either.

I also swapped in a 6k ECU from a v2 sti, and had hesiation earlier, around 5500 and was able to get a little farther to about 6k but it wasnt good.
But to counter that, ive read online that the 6k ecu doesnt go well with early model wrx motors sometimes, so im not sure if thats a definitive test as the ecu might just not work well with the motor.

SO with the stock u8 in the car she hits an imaginary Rev Limiter at 6500

Let me start by saying ive recently went over the entire car chasing a random stall issue, that turned out to be my Maf. In that process I had replaced

  • Maf 3 times (finally with oem replacement fixing stall issue)
  • Spark plugs
  • recent Coil pack conversion with 04 wrx coils.
  • checked turbo inlet and repaired small cracks
  • Fuel pump replaced with 225lph
  • Fuel filter replaced
  • Cam and Crank sensors (swapped with ones from junkyard ej25 dohc, but am going to purchase brand new today and try.)
  • New alternator belt
  • New battery ( battery and alternator seem to be fully working)
  • Refreshed some grounds.
  • Throttle body cleaning


At this point im not sure as im onto little things i may have forgot, like im going to clean the boost solenoid.
IF anyone has experienced anything like this or just has any advice it would be really appreciated.
 

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Do you know what tune is on the ecu? I had one with a wack-ass tune once and the car wouldnt rev past 4k, we got it retuned and it was fine
 

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1995 EZ30 Coupe
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Double, triple, and quadruple check wiring, especially on the WRX coil conversion. Maybe check eBay for another ECU?
The only time I've had an issue like this it was a damaged piggyback causing a brutal misfire, thought my ECU was fried or something because it wouldn't rev past 6200ish.
Good luck.
 

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Discussion Starter · #4 ·
Do you know what tune is on the ecu? I had one with a wack-ass tune once and the car wouldnt rev past 4k, we got it retuned and it was fine
it should be completely stock v1 u8 ecu. Double checked it is the proper ecu for my injectors and model year etc.
 

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Discussion Starter · #5 · (Edited)
Double, triple, and quadruple check wiring, especially on the WRX coil conversion. Maybe check eBay for another ECU?
The only time I've had an issue like this it was a damaged piggyback causing a brutal misfire, thought my ECU was fried or something because it wouldn't rev past 6200ish.
Good luck.
Im going to go over it again, the soldering i trust but possibly one of my crimps on the ignitor bypass is loose. Can i ask you to elaborate on the damaged piggyback and what exactly you mean by that/where it was? Because it seems thats almost near identical to my cutout point.

Also i did try the other ECU but only seemed to make the issue worse as stated, but when i was in the process of swapping ECU's, i noticed i had 2 wires on my harness that had been tied into, that the tie in wire was going to no where, just cut and hanging. Im not sure if that is an uncommon thing or not.
 

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Discussion Starter · #6 ·

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If the hanging wire is just tapping into another wire, it's probably from a sensor or something that was installed by a previous owner, and I'm sure you can remove it without problem. If it's actually a pinned wire into the ECU, I'd be looking for a wiring diagram.

My piggyback is an AEM F/IC 6. They have a lot of great features, but seem to be made of less robust electronic components than say our factory ECU's. I've read multiple accounts of people getting strange readings or behaviors from the FIC, often AEM would replace the unit with an undamaged one. (Probably for a price.)
If I have any values in the ignition timing table, I get the horrible misfire. If I zero out the table, no misfire at all.
Also, I'm only using one O2 sensor input channel on the FIC, but both channels register voltage in the same pattern, the second channel just has lower values. This leads me to believe there's a short or something in the unit, with voltage bleeding from one circuit to another.
It still controls fuel great though, so I'm using it in conjunction with an Apexi S-ITC.

If you're already suspecting a poor connection, especially in the ignition system, GET ON IT, SON! My money is on this causing the majority of your headaches. I've had soooooo many crimped connections fail, and it looks like the wire is still in there...
 

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Discussion Starter · #8 ·
If the hanging wire is just tapping into another wire, it's probably from a sensor or something that was installed by a previous owner, and I'm sure you can remove it without problem. If it's actually a pinned wire into the ECU, I'd be looking for a wiring diagram.

My piggyback is an AEM F/IC 6. They have a lot of great features, but seem to be made of less robust electronic components than say our factory ECU's. I've read multiple accounts of people getting strange readings or behaviors from the FIC, often AEM would replace the unit with an undamaged one. (Probably for a price.)
If I have any values in the ignition timing table, I get the horrible misfire. If I zero out the table, no misfire at all.
Also, I'm only using one O2 sensor input channel on the FIC, but both channels register voltage in the same pattern, the second channel just has lower values. This leads me to believe there's a short or something in the unit, with voltage bleeding from one circuit to another.
It still controls fuel great though, so I'm using it in conjunction with an Apexi S-ITC.

If you're already suspecting a poor connection, especially in the ignition system, GET ON IT, SON! My money is on this causing the majority of your headaches. I've had soooooo many crimped connections fail, and it looks like the wire is still in there...
My man, thank you for the detailed reply, i appreciate it and i needed the positive energy this morning cause the frustration is mounting haha! Damn the F/IC is a whole nother world im just now looking into , im grateful i dont have to deal with an issue on one of those yet lol. impressive for figuring it out how you did.

Thats that then today me and my pops will go through and check all electrical we can get our hands on, fingers crossed. i dont trust some of the original jdm etc scanner wiring, or boost gauge/turbo timer stuff going on up there.

One reason i know i have a draw somewhere in my electrical is when i turn my signal light on, my abs light on the dash flickers with it from the power draw. But i was not assuming this would directly be related to my issue, on further inspection maybe it is related.


I did a little test yesterday and ran wastegate psi and the issue still persists, so i know its not to do with bcs. Electical here i come:geek:
 
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