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Old 07-25-2013, 10:17 AM   #1
spoogevac
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Join Date: Jul 2013
Default JDM GDA 2000 WRX afterfire under WOT plus poor mpg

I'm an Australian living in Hong Kong.

I have a JDM GDA 2000 WRX (its bug eye) with EJ20 and Auto.

Bought the car second hand, it ran hard and used little fuel but the trans was toast.

It had exhaust system and APEX-i on it that had been "tuned" for the car apparently. A HKS blow off and a earthing kit but thats about it.

I had the trans rebuilt and everything was fine until one day a thermo fan died.

When the guy replaced it he did not do the clamp up tight on the top radiator hose and it slipped off a bit pushing it into the alternator which cut a hole in it.

I basically lost all my water on the highway on a very very hot day.

I got home and when it cooled i replaced the hose and refilled it but it now must of had a warp because the water was getting pressurized by the exhaust gas (was filling over flow, was not the cap).

I then had the motor rebuilt and not knowing how sensitive the motor was to changes decided to swap out almost everything I could with bigger better after market parts.

I got bigger intake, throttle body, silicone pipes, K&N Typhoon CAI, 600cc injectors, up pipe, down pipe, way bigger intercooler plus the STI scoop duct and splitter plus a bunch of other stuff that's not relevant (forged crank, pistons ect).

It was only after the mechanic got the parts that I worked out you could not just swap the injectors without tuning the car.

He did not fit the bigger intake or throttle body but he did fit the injectors after I told him not to. The car ran rich as hell and he thought it was the APEX-I system so he hacked it out.

I got the car back running like ****, using stupid amounts of fuel with boost that was fluttering around like a spastic.

I managed to fix the boost problems and get a correct map for the injectors with the help of a guy on romraiders (I have wideband and can log)

Over this period of time I had never used WOT as I was afraid the car would blow up and I needed it for work.

After the tune I got confident enough to start pushing it.

At around 80% I would get a sort of horrible crackling like stumble and a backfire when I let off.

I changed the plugs and gave it a few runs at 90 to 95% and the backfire was gone and the boost stable and working correctly.

The car was still using more fuel than it had before the rebuild but way better than with zero tune so I left it and drove it slowly to work for a year.

Now the MOT come up and it failed CO2. It was meant to be 0.5 and it got 1.0.

I read online that cars that are driven slowly everywhere and put on the test cold can read higher than if you give it a good clean out so I gave it a few 100% throttle bursts and ran it in 3rd for a bit on the highway.

I did notice that there was a crackle and backfire when i let off but i felt it was only when i got off it because you cant really stay on it very long here (very built up city, lots of cameras and cops).

I added a reducing carbon additive to the fuel but didn't want to risk a fail again so I got a dodgey friend to take it to a place where he knew the tester.

The drawback is this guy raped the **** out of my car and said that it had gotten 1.5 on the CO2 test (much worse)

Now the thing seems to stumble at the top end under WOT with a crackle and always backfire when you let off. It also sometimes has a wobble on cold start (runs but the car wobbles like a counter weight was spinning)

I have been told the tune is not the problem and I trust the guy, blueufo is his username on romraiders I think.

He suggests one injector might be spraying too much throwing off the wideband as it reads an average.

My question is what would you guys change first?

Its done 70'000km (around 43000 miles).

Should I change coil packs first?

I am fairly certain the CAT is now toast from running super rich for a long time and me never driving the car above 3k rpm for ages.

The front O2 its brand new, i just replaced it this year.

Side information.

DTC TEMPORARY: P0500 VEHICLE SPEED SENSOR A
DTC TEMPORARY: P1518 STARTER SWITCH LOW INPUT
DTC TEMPORARY: P1591 NEUTRAL POS. SWITCH LOW INPUT (AT)
DTC TEMPORARY: P0136 REAR O2 SENSOR CIRCUIT MALFUNCTION

I logged these codes a while back. Since then I have cleaned up the earth point to the guard, to the trans under the IC, the headlights, and ever point on the earthing kit.

Basically any earth point you can see or get to from above (cant raise it here to get under it)

I pulled all the plugs from the ECU and gave them a blast with electrical cleaner.

No idea if it cleared the logs as I haven't checked again but I will ASAP.

Does this sound like most likely coil packs, a dodgy injector or something else?

Any advice is appreciated.

My car shows 14 plus volts when running with everything turned off and 13 to 14volts with ac and lights on (goes up and down).

Coil packs are expensive but I can have them here fast from Japan if people agree that's the first place to look.

Thanks again.
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Old 07-26-2013, 12:10 AM   #2
CRX7
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99 Impreza
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2 things made my car run rich:
Not recirculating the bov and not using a Denso O2 sensor.

My cat cleaned up after some long highway runs after I got the above two problems fixed. The other thing it could be is your MAF if you have a new den so O2 sensor.

I had stumbling problems at high rpm before I changed the coil packs.

BTW, I used a wide and to diagnose my issues. I got an AEM UEGO

Last edited by CRX7; 07-26-2013 at 12:17 AM.
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Old 08-14-2013, 12:54 PM   #3
spoogevac
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I have the exact same wideband
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Old 08-14-2013, 12:55 PM   #4
spoogevac
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Oh and what do you mean by recirculating the BOV?

I have a HKS and can't really see anything on it to adjust.

If i put my hand over it and rev it even slightly (2000 or so) it pushes air when I let off. Is this normal?
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Old 08-14-2013, 12:59 PM   #5
spoogevac
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Oh and news to hand, just replaced coils and plugs and it idles way smooth, have not tested it more than a lap around the block though.

I will see how it acts after a tank or 2.
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Old 08-14-2013, 03:08 PM   #6
Vlad
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Join Date: Oct 2003
Chapter/Region: Tri-State
Location: NY
Vehicle:
02 WRX
Powered by Sti V9 Spec C

Default

You can post in the 2.0 forum, in the EJ207 Owners thread.

While this forum is for pre 2002 cars, it is designed for the USA understanding of this. In US, before 2002, you did not have a WRX or an Sti.
So the New Style Bugeye actually belongs in the 2.0 forum.

Your engine is an EJ207 and we have a good thread going on there, with several good tuners on-board. Come over there and let's see if anybody can help you.
Pull some logs, to have available.
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Old 08-15-2013, 08:45 AM   #7
spoogevac
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Okay thanks.
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Old 08-21-2013, 11:51 AM   #8
Stunko
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Check for hairline cracks in the dump pipe. I had one in mine and had the same symptoms as you. Quick weld and it was back to normal
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Old 09-04-2013, 11:58 PM   #9
CRX7
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"Oh and what do you mean by recirculating the BOV?

I have a HKS and can't really see anything on it to adjust.
If i put my hand over it and rev it even slightly (2000 or so) it pushes air when I let off. Is this normal?"

It is normal if you want to vent to atmosphere. However it made me run very rich, venting to atmosphere.

Thus by your statement you have a Non-recirculating type BOV which will make you run rich. The air you feel let off on your hand needs to be fed back into the intake system after the MAF sensor. We have a MAF based ECU which measures the air taken in right after the filter. If you release the air through a Blow Off Valve BOV to atmosphere, you have lost some of that measured air and thus will run rich.

Why do you have an HKS BOV? What happened to the stock BPV and recirculating hose?
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Old 11-01-2013, 08:02 AM   #10
spoogevac
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The car came with the HKS.

I am now heading down the path of a rec BOV.

I am looking at a Perrin PSP-INT-600BK.

The thing is it looks like there is no way in hell of me connecting up the recirc to the silicone intake without removing the intake manifold.

This in one way is good because I want to zip tie all the vac lines I cant reach just incase but it looks quite involved and I will need gaskets also.

Is this a good time to grab an STI manifold?

Just how hard is it to remove and will I need some kind of sealant on the gaskets?

My car seems to have no problem reaching boost its just getting roughly 18 to 20 km less to the 3/4 mark than it was.

Before Id reach 150km to the 3/4 mark no problem with the exact same setup. Now its consistently 130 ish no matter how careful I drive.

Am I on the right track with a vacuum leak?

New plugs, new coil packs, only other thing left is the air meter I guess.

As stated really no drivablility or idle issues at all. Fires up first time every time and idles smooth as silk if not slightly low.
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