Fuel Cut Issue

EvilAsPie · Post by **EvilAsPie** » Fri Aug 10, 2007 4:20 am

I'm new to the forum, but bought a car from a member here. He is also a member on another local forum, where we met.

I'm having an issue with the car cutting fuel the second the car hits 0 pressure on the boost gauge.

I bought the car from "rad rex" w/a TD04, TurboXS DP to full custom exhaust, JDM WRX TMIC, Turbosmart MBC, mugged intake mod, this: http://fcd.chrispaiano.com FCD, and boost gauge.

The car ran great when i got it. Last weekend i decided to start working on the car a little. The first thing i wanted to do was move the FCD. It was mounted on the dash and i wanted to conceal it a little more. So i rerouted it along the firewall under the dash and in the little cubby by the steering wheel.

Monday driving it to work it was fine until i got half way there. I shifted to 5th got back on the gas (was barely on boost) when all of sudden fuel cut! I got back off the gas a little and the car picked back up again. harder on the gas, fuel would cut. The second it came off vacuum it would cut.

I first thought it had to be the FCD wiring. Since the scotch locks that come with this FCD usually suck i rewired the FCD that evening. That seamed to fix the issue. I drove it around a little with no problem.

Wednesday i took it to work again, i got a little down the road and the problem came back!!

So today i checked all vac lines, intake connections, all plugs for anything loose or undone. Couldn't find anything. The car makes good vac so i shouldn't have a leak. I rewired the stock FC unit without the FCD just to rule it out. Still happening. I removed the MBC and plugged back in the stock one. Still happening. I don't even have to drive the car. From an ideal if i mat the gas the pressure goes to 0 and car fuel cuts. Get off the gas and car starts idealling again. I don't get it.

The car does have a minor exhaust leak at the up-pipe to turbo, but that shouldn't make it just stop running like this, right?

When moving the FCD i think i plugged it in upside down once as both red and blue lights came on and the car didn't run well. Could i have damaged to stock FC unit? Could the stock FC unit have gone bad? Am i totally barking up the wrong tree? I'm concentrating on the FCD because it's the only thing i've touched since i bought the car.

This is my first time diaging a turbo car. Please help a noob out.

Thanks.

rad rex · Post by **rad rex** » Fri Aug 10, 2007 10:10 pm

I am furiously searching for a fix but I'm also requesting some help for a good guy that bought my evil car.

EvilAsPie · Post by **EvilAsPie** » Fri Aug 10, 2007 10:28 pm

In my searched i came across this thread.

http://bbs.legacycentral.org/viewtopic.php?t=32015

That sounds the exact issue i'm having. I even plugged the FCD in upside down once while moving it and both LEDs came on. But the actual problem didn't start till later.

I'm hoping i don't need a new ECU.

Thoughts?

I'm thinking about PMing bmxkelowna to see if he found out anything else to fix the problem.

rad rex · Post by **rad rex** » Sat Aug 11, 2007 3:11 am

Pie, I came up with this thread also

http://bbs.legacycentral.org/viewtopic. ... +cut+boost

I would first pull what codes the ECU has and go from there. If there aren't any new codes then reset the ECU and see if the problem goes away. The MAF sounds more reasonable than the whole ECU

You can IM me on MSN using my email ADDY, or just give me a hollah

bmxkelowna · Post by **bmxkelowna** » Sat Aug 11, 2007 3:22 am

sounds just like what happened to me in that thread two of the wires may have touched shorting out the map sensor in the ecu
try replacing it if you can just make there are no shorts so you dont fry another one

EvilAsPie · Post by **EvilAsPie** » Sat Aug 11, 2007 4:18 am

I tripped checked my vac lines and wiring today. Problem still exists. I also pulled the codes. I got:

15 Injector #2 issue.

24 Air Control Valve

32 O2 sensor

41 A/F learning control

44 Duty Solenoid valve (Wastegate)

45 Pressure Sensor & Pressure Exchange Solenoid Valve.

From that it looks to be that 24 and 45 could be causing the rest of them. Those are what the FCD wired into and if i shorted the ECU out to not read them that would make sense.
bmxkelowna, were you getting any other codes besides 45?

I have plastic JECD maf off a 99 obs that i might try just to see. Also i'm going to try to test the Pressure sensor and valve, i just need a pressure pump/tester. I might try to use my air compressor set to the right pressure (if i can get it that low).

I figure i will test and check everything i can before spending money.

I'm going to try clearing the codes tomorrow, we'll se how it goes.

rad rex · Post by **rad rex** » Sat Aug 11, 2007 4:28 am

I was doing another search on CEL's in general, it seems that if you use the black connectors to check for codes it gives you both the current AND the old codes. After the ECU reset you should have a better idea.

bmxkelowna · Post by **bmxkelowna** » Sat Aug 11, 2007 8:22 am

nope i only got 45
and when the map sensor is not getting the right signal it goes into a limp mod and does not boost
ive had 45 from a vac line to the map sensor coming off and the ecu shorting out from the same fcd

BXSS · Post by **BXSS** » Sun Aug 12, 2007 1:33 am

It looks like testing the FCD connector while it is off the car is a good idea, I did that & both LEDs turned on indicating that polarity was reversed.
Had I not looked @ this post I may have toasted my ECU...

Has anyone had any other issues with the CPE FCD, I'm a little nervous about putting this on my car after reading this post...?

EvilAsPie · Post by **EvilAsPie** » Wed Aug 15, 2007 2:20 am

So i finally got around to clearing the ECU and checking for accurate codes today.

Code 45 is now the only one present.

So it seams, and makes sense that i have the same issue bmxkelowna had. So i guess i'm in the market for a new(used & working) Turbo ECU. If any one has one for knows of one please LMK.

Thanks for the help.

bmxkelowna · Post by **bmxkelowna** » Wed Aug 15, 2007 5:42 am

a semi local old school Subaru guy here is using n/a ecus on the turbo cars because they have no fuel cut built into them. from what ive heard hes had no other problems so far

biggreen96 · Post by **biggreen96** » Wed Aug 15, 2007 6:26 am

Have you tested the MAP sensor yet? If you're getting code 45 then go after that, don't chuck out the ECU.

EvilAsPie · Post by **EvilAsPie** » Wed Aug 15, 2007 3:11 pm

About this MAP sensor; i've read a lot of threads regarding my issue and a lot of people talk about a MAP sensor in these cars.

I understand that the t-leg uses a MAF to actually measure air and adjust fuel, and some people have said that there also has a MAP to controls other "stuff."

I have a 2000 RS that does use a MAP sensor to control fuel and does not have a MAF. I've looked on the leg for a similar MAP and can't find one. Also i don't know why a MAP sensor would need vacuum. It's an electronic sender that tells the ECU the air pressure in the manifold. Or at least that the way it is on the RS.

Since everyone says the MAP on the t-leg has a vac line i found a vac diagram. I saved it here: http://s88.photobucket.com/albums/k174/ ... vacuum.png

I don't see a MAP sensor anywhere? Am i wrong?

When people say MAP are they actually referring to the "Pressure Sensor & Pressure Exchange Solenoid Valve?"

If they is the case i have checked the vac lines running to that unit many times with no change.

There is a check for the Pressure Sensor & Pressure Exchange Solenoid Valve that i can do. I haven't had time to do it yet. But since my scenario and symptoms are exactly the same as bmxkelowna i thought i would go after that first.

Post by **Legacy777** » Wed Aug 15, 2007 5:42 pm

Yes....MAP sensor = pressure sensor.

The pressure exchange solenoid valve is separate.

The MAP sensor is NOT in the ECU as bmxkelowna posted above.

Test the MAP sensor itself, and make sure it's working. I'd also recommend putting the wiring back to stock. You may even want to just run some temporary wires in case the wiring got messed up. That'll help you narrow things down.

EvilAsPie · Post by **EvilAsPie** » Fri Aug 17, 2007 3:27 am

So i found a guy only a couple of hours away from me who has a couple of Turbo ECUs. And i happen to be headed in his direction this weekend for an autox.

Hopefully i will be able to pick one up, but I have a couple of questions.

Are MT and AT ECUs the same?

What do used Turbo ECUs usually sell for?

Post by **Legacy777** » Fri Aug 17, 2007 5:48 pm

For the turbo legacy, yes the AT & MT ECU's are interchangable.

$100 for a used turbo ECU is about norm...

EvilAsPie · Post by **EvilAsPie** » Tue Aug 28, 2007 1:08 pm

A couple of weeks ago i picked up a working ECU and Pressure Sensor & Pressure Exchange Solenoid Valve. I tried the Pressure Sensor and Valve first, with the same results. So i swapped the ECU and the car wouldn't even run!?! I pulled it back out checked the part numbers, turns out the one i bought from a guy kinda local was for an N/A.

But the guy was pretty cool, and had made a mistake. He has a bunch of rotting subarus with at least 3 SSs. He just grabbed teh wrong one.

So he was able to send the right one to me, got it yesterday, installed it last night, and drove it to work today! Runs great again!

So, as far i can tell the FCD did fry my ECU, and this guys http://bbs.legacycentral.org/viewtopic.php?t=32015. But in the write up on the chrisp FCD is says this,
"don't worry, I have protection in place in case you connect it backwards -- nothing will be damaged. It just won't power up. If this happens, reverse the connector and all should be fine."

Which despite frying my ECU it did definitely power on, both lights came on instead of just the blue on.

Has anyone else experienced this, or plugged in the backwards and had it not power on?

Should i let Chis know? It would be pretty easy to make a "key" so it couldn't be plugged in backwards.

I'm supper happy to have my car running again, even w/out the FCD, 10psi is still a blast!

Thanks for everyones help.

rad rex · Post by **rad rex** » Tue Aug 28, 2007 1:29 pm

Glad to hear you got it resolved Pete.

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Fuel Cut Issue

Fuel Cut Issue