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Old 07-10-2018, 12:50 PM   #1
car_freak85
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Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default V1 EJ20G High Load/High RPM Cutout

I'm in the process of resurrecting an EJ20G-powered 1987 RX coupe. As I catch up on the two previous owner's deferred maintenance, I've noticed that the car tends to cut out in high load, high(ish) rpm situations. It almost feels like a boost/fuel cut or a rev limiter, but I don't believe it's being caused by those safeguards. This happens after a few WOT pulls through the gears at my low boost setting (10 psi) and pretty quickly at stock boost (14 psi).

I've gone through the fuel system, new 255lph Walbro, new filter & soft lines (original, stock injectors though, waiting for my RobTune to upgrade). I've done the EJ coil-on-plug conversion in preparation for a RobTune, new NGK Iridium plugs (out-of-the box gaps), new green label MAF and I have a new, OEM o2 sensor that I'll be installing shortly.

The problem seemed to improve after the new fuel pump (can make more heat soaked pulls at 10 psi with a couple more pulls at 14 psi before it cuts out).

I spoke with SuberDave, who built the car, and he suggested dropping my plug gap down to .2xx, since he had experienced spark blowout on a similar set up in the past.

What do you folks think? I don't want to install the RobTune ECU and 550 injectors until I've got this sorted out.
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Old 07-23-2018, 05:35 PM   #2
car_freak85
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Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

I spoke with SuberDave over the weekend and he suggested keeping the plug gap under 0.030. Any thoughts on that tight of a gap?
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Old 07-27-2018, 05:26 PM   #3
contaminatrix
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Member#: 435611
Join Date: Dec 2015
Chapter/Region: International
Location: Nairobi
Vehicle:
2002 SG5-2.0-XT-JDM
45A, originally 18L

Default

also check your system voltage - ensure it's good
also, one time i had a bad map sensor and it did the same thing - violent cut but car wouldnt go off.
switch map sensor with known working one and revert.
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Old 08-02-2018, 12:54 PM   #4
car_freak85
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Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

I installed a brand new OEM MAF only a few hundred miles ago, new OEM o2 sensor is now installed. I'll be re-gapping the plugs this week or next. Also on the hunt for WRX coil packs with the longer boot (I think I have STI packs).

Just take the voltage reading at the end of the coil harness? What should I be looking for, number wise?
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Old 08-13-2018, 07:23 PM   #5
wtdash
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Join Date: Apr 2004
Location: N. Idaho
Vehicle:
2002 WRX GG>>
2016 Focus RS

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Fixed yet?

The post above is for the MAP not MAF,...if you missed that.

and you've checked for stored codes?

Changing plugs is a PITA on the DOHC so I understand your reluctance. But I don't see why it wouldn't do it all the time if the gap was an issue...I just know if never fixed any of my related issues.

I'd be more suspicious of the coil packs?
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Old 08-15-2018, 12:05 PM   #6
car_freak85
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Member#: 13530
Join Date: Dec 2001
Chapter/Region: NWIC
Location: Cascadia
Vehicle:
EA63 , EA81T, EJ20G,
EJ205

Default

Pulling plugs on an EJ20G isn't so bad.... if it's installed in a different chassis! (It's in a 1987 Subaru RX: @templeoffuji on IG)

I pulled the plugs on Monday and re-gapped them down to 0.028 in. While I was in there I replaced the plug boots on the coil packs, two of the original boot/spring combos were shorter than the others, despite the all four coil packs having the same part number.

At full, stock boost (14 psi) I was finally able to make multi-gear WOT passes, got the engine good and hot and it still pulled strong, no more power cut!

Where is the MAP sensor located on this engine? Got a part number?

Have not checked for codes yet, but I will do that today.
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