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Old 07-27-2007, 11:28 AM   #1
BoostAddictPL
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Question 3500rpm cut out - EJ20G with USDM WRX Ignition Coils

"PROBLEM FIXED!" (read below)

We've got one last thing to resolve before the '91 Legacy Turbo with a EJ20G engine swap's back on the road. One of the sensors seems to be hooked up incorrectly, because the car sputters at ~3000-3500rpm. It revs up to that point quickly, but at over 3000rpm it hits something that sounds like a bit of backfiring and it won't rev any higher. If anyone has any suggestions on which sensors to check, it would be appreciated. We'll start with completely re-wiring the JECS MAF, but what other sensors could be causing the ~3500rpm cut-out?

More info on the progress of this swap can be found here:
http://bbs.legacycentral.org/viewtop...er=asc&start=0


Thanks!
P.
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Last edited by BoostAddictPL; 08-08-2007 at 03:14 PM.
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Old 07-27-2007, 01:47 PM   #2
Matt Monson
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That kind of sounds like the car is in limp mode. Either that, or it's dumping way too much fuel before the turbo has fully spooled up to take advantage of it. I installed a Momentum 40T on an '02 WRX a while back and that's exactly what it did with the bigger injectors and bigger turbo until we could get it to the dyno for a tune. It would just hit a wall at 3000rpm if we were on it full throttle. You could rev it all the way to 5000rpm if you went partial throttle and kept it out of boost. The car owner drove it too and from work for 2 days without a tune with no issues as long as he didn't dip too deep and overfuel it.

I would see how throttle position alters the behaviour...
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Old 07-27-2007, 01:55 PM   #3
BoostAddictPL
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Thanks for your reply.

So it doesn't sound like a MAF wiring issue to you?

The car runs almost the same if we disconnect the TPS... I guess we'll look at the wiring there next.

Is there any simple way to check what's causing the car to be in limp-mode right now?


Cheers!
P.
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Old 07-27-2007, 03:42 PM   #4
johnny p
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The vehicle speed sensor will cause the same thing to happen.
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Old 07-27-2007, 03:46 PM   #5
BoostAddictPL
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Even when the vehicle is not in motion?
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Old 07-28-2007, 12:25 AM   #6
Jaxx
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if it wasn't hooked up right
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Old 07-28-2007, 09:21 PM   #7
BoostAddictPL
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Exclamation EJ20G Engine + ECU in '91 Legacy Turbo update

We've verified the following today:

- The car is running on all 4 cylinders
- Spark is on all 4 cylinders at the right time (using the USDM WRX Ignition Coil conversion with 4 brand-new WRX Ignition Coils)
- Injectors are working correctly on all 4 cylinders (we replaced the current EJ20G injectors with a new set just to make sure)
- The JECS MAF is sending the right signal (no CEL code when the MAF is connected, but the MAF code shows up when we disconnect it)
- The TPS is sending the right signal (no TPS CEL code)
- We even checked for a plugged cat by disconnecting the downpipe and letting the exhaust gasses straight out.

The engine is running worse with the MAF connected. If we disconnect the MAF, it idles smoother and doesn't stall. If we connect the MAF, the engine has a harder time getting up to revs and sometimes stalls.

If anyone has any suggestions what could be causing this EJ20G to cut-out and backfire at ~3000-3500rpm, please give us ideas... 'Cause we're running out of them and we'd really like this '91 Legacy Turbo with EJ20G Engine + ECU back on the road


Thanks in advance,
P.
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Old 07-28-2007, 10:19 PM   #8
Hurley 2.5 WRS
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sounds like a bad maf
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Old 07-28-2007, 10:36 PM   #9
BoostAddictPL
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We originally thought that a bad MAF was the problem, but we tried 2 different JECS (green) MAF's, tested both of them on a stock '96 Impreza 1.8 and they worked correctly on that car.

Could someone confirm that the EJ20G ECU will accept the Vehicle Speed Sensor signal from a '91 USDM Legacy Turbo cluster? Or do we need to modify the Legacy cluster in some way to send out the correct VSS signal to the EJ20G ECU?

What kind of a VSS signal should we see when the car is standing still? From what I've seen so far, it's getting O when the car is not in motion.

If anyone has any suggestions on what else could be causing this 3000-3500rpm engine cut-out (that feels like a limiter), they would be appreciated.


Thanks,
P.

Last edited by BoostAddictPL; 07-29-2007 at 11:47 AM.
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Old 07-29-2007, 01:57 PM   #10
johnny p
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what are the part numbers on the 2 MAF's you have.
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Old 07-29-2007, 02:15 PM   #11
BoostAddictPL
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Question

Both of the MAF's that I have are the green JECS ones with the following part #'s:

JECS A 22680 AA160
A 36-000 R60

Serial# 1524A



Is this the right MAF to be using with the EJ20G Engine + ECU?


Thanks,
P.
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Old 07-29-2007, 02:40 PM   #12
johnny p
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tHAT is the correct one, at this point you'll have to read the cell codes,have you tried at all.
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Old 07-29-2007, 02:44 PM   #13
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We've read all of the CEL codes and as of right now everything seems to be working 100%.

If we disconnect the MAF, we get a code 35 (Faulty MAF).
When the MAF is disconnected, the car idles smoothly.

When we re-connect the MAF, the car sometimes stalls on idle, but there is no more CEL code for the MAF.

We're not getting any other CEL's as of right now with all of the sensors connected.

The car seems to be running too rich and the engine always hits some kind of a cut-off point at 3000-3500rpm. Does that sound like some kind of a limp-mode? How can we check what's causing the ECU to jump into a limp-mode on the EJ20G?


Thanks,
P.
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Old 07-31-2007, 10:47 PM   #14
BoostAddictPL
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Exclamation

UPDATE:

Today we've hooked up the EJ22T ECU and ran the wasted-spark setup on the EJ20G, just like on the original EJ22T. We used the original EJ22T MAF, EJ22T Coil-Pack and the original EJ22T ignitor. Engine fires up, doesn;t really want to idle with the MAF conected and shows the same symptoms as before:
- engine starts cutting-out at ~3000rpm. It backfires and revs go down.
- tachometer starts "jumping" at higher revs. It's even more noticeable now with the

Our conclusion:
- cam & crank sensors are probably faulty. We cast our votes for the crank sensor. I'll get both of these sensors new from the stealership tomorrow and we'll see if that solves our problem.

Does that sound reasonable? Did anyone encounter problems like this because of a faulty cam or crank sensor?

Cheers!
P.
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Old 08-08-2007, 03:18 PM   #15
BoostAddictPL
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PROBLEM FIXED!!!!!!!!!

I've just replaced the stock EJ22T Cam/Crank sensors with the USDM Impreza 1.8 N/A ones and now the engine revs past 3500RPM up to redline. It pulls hard and doesn't backfire!

If anyone ever encounters the same problems as I did in my EJ20G conversion, do the following:
1) USDM Ignition Coil conversion
2) Fresh set of working Crank/Cam sensors

...We have one more problem to resolve though. Teh car won't idle with the MAF connected. We're using the green JECS one from the USDM Impreza 1.8L N/A. When we disconnect the MAF, it runs no problem, but with the MAF connected it stalls on idle. We're tried 2 working JECS MAF's so it's not the sensor. We've checked the continuity on the MAF/ECU wiring as well.

If anyone has any ideas on how to proceed and to fix this idling problem, please give us a shout!


Thanks!
P.
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Old 08-09-2007, 02:42 PM   #16
BoostAddictPL
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Another leap forward.

The car now revs up to redline smoothly and idles at ~1000rpm. We've hooked up the JDM STi 3-wire MAF and that solved the idling problem! It's weird how everyone was telling me to use the 5-wire Green JECS Impreza 1.8L N/A MAF with the EJ20G Engine + ECU, while the 3-wire JDM STi MAF seems to be the right one with my setup. I guess the ECU that I have must be a JDM Impreza WRX ver.2 one and the right MAF for it is the 3-wire now.

The only thing is that the car now runs way too rich at idle. I guess we'll have to tune it now.

Other than that, everything works 100%.


P.
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Old 11-12-2010, 06:26 PM   #17
94sti=gc8
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Default maf

did you know that the maf for 1.8 has the same number as the 2.5 forester
the one for 1.8 does not work for ver 2 ej20g but the 2.5 n/a does work
so for anyone thats looks at this

p.s

1.8 has 5 plug
2.5 has 3 plug

i just found out cuase of my swap
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Old 11-24-2010, 03:18 PM   #18
TommyAtomic
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Ok so just so I am following along. You replaced the EJ22T Cam/Crank sensors with the USDM Impreza 1.8 N/A Cam/Crank sensors to fix most of your issues?

And your remaining issue was solved by installing the correct maf?
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