ECU and Fuel Injector Issues
Results 1 to 12 of 12

This is a discussion on ECU and Fuel Injector Issues within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; First...history of problem (sorry for the length) 1. My 2008 WRX had the fuel pump replaced with 37,000 miles on ...

  1. #1
    Registered User JaySin's Avatar
    Join Date
    Mar 2008
    Location
    SE Michigan
    Posts
    276

    ECU and Fuel Injector Issues

    First...history of problem (sorry for the length)
    1. My 2008 WRX had the fuel pump replaced with 37,000 miles on it...hard start issue. This didn't fix the issue.
    2. Fuel Pressure Regulator replaced. This also didn't fix the issue.
    3. Replaced ALL injectors. My car was not holding pressure after shutting off for a period of time...basically bleeding down. This DID fix the issue.

    Second...new problem: The dealer tech is telling me the pressure is holding, but states that the pressure is 'weird' at first crank...shooting up to 40 something PSI then falling back down to normal pressure. He stated something along the lines of the injectors are getting a signal to stay open or open prematurely after the engine is turned off. I don't quite understand this or how it could happen. He stressed that my new injectors will go bad again and the problem will return.

    Third...My car was tuned on a Mustang AWD dynamometer and on the road by a reputable tuner a few years ago...never had any problems until now. The dealer is blaming the ECU program and is telling me I need to put it back to stock or it will happen again. Any logic to this? Does anyone have any insight on this? Did I get a bad tune or is something else going on?

    I'll be happy to answer any questions you may have in order to get this figured out.

    Thanks!

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Admiral Ackbar the 1st mycologist's Avatar
    Join Date
    Oct 2005
    Location
    Late Devonian
    Posts
    12,800
    I Support ClubWRX
    You really need to contact the tuner and see if they can make any sense of the situation in light of the changes they made to the map. Otherwise, post the map and maybe someone can figure out if anything is wrong.
    "From a little spark may burst a mighty flame." - Dante
    "The stitch is lost unless the thread is knotted." - Italian proverb

  4. #3
    Registered User JaySin's Avatar
    Join Date
    Mar 2008
    Location
    SE Michigan
    Posts
    276
    mycologist...thanks for the advice. I did contact the tuner, but he no longer works for the tune shop I got it done at so I tried his personal email. I don't know if I'll get a response. So I'm guessing you think it could in fact be a bad tune? If it was...then I've been driving with a bad tune for 3 years and didn't know it. Ugh.

  5. #4
    Luke Skywalker Mikie13's Avatar
    Join Date
    Oct 2006
    Location
    Palmyra, NJ
    Posts
    20,643
    I'd still take it back to the shop then at least. They should have a tuner of some sort that may be able to decipher any issues, or look at logs of some sort.

    It's very possible a tune could cause a problem like that, especially if the problem never happened while it was stock. What all mods do you have?
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
    2012 Lightning Red WRX Sedan Stock...for now Soon to be OpenSource tuned by: Mattypants @ WTF Tuning
    "If I have 10 ice cubes and you have 11 giraffes, how many pancakes can fit on the roof? Purple, because aliens donít wear hats" -Ying

  6. #5
    Registered User JaySin's Avatar
    Join Date
    Mar 2008
    Location
    SE Michigan
    Posts
    276
    No major engine mods...just an AEM CAI and SPT catback exhaust. Everything else is stock. I'm pushing about 200 WHP and 300 WTQ and the stock turbo is pushing 16.9 PSI instead of the stock 11.6 PSI. I got a CEL once last year P0244 'Turbocharger Wastegate Solenoid A Range/Performance (High Input)', but I cleared it and it never came back. I think the wastegate can't handle the boost and it gets stuck open sometimes allowing a little boost creep. Or it's just worn out. I don't baby my WRX by any means. I don't want to bring it back to that tune shop...reputation has taken a nose dive.

  7. #6
    Luke Skywalker Mikie13's Avatar
    Join Date
    Oct 2006
    Location
    Palmyra, NJ
    Posts
    20,643
    So you're technically Stage 1 with an intake...hmm. And that's incredibly weird to see that much difference between torque and power. Any other shops you can go to that can perhaps retune?
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
    2012 Lightning Red WRX Sedan Stock...for now Soon to be OpenSource tuned by: Mattypants @ WTF Tuning
    "If I have 10 ice cubes and you have 11 giraffes, how many pancakes can fit on the roof? Purple, because aliens donít wear hats" -Ying

  8. #7
    Registered User teflon_jones's Avatar
    Join Date
    Apr 2007
    Location
    8000' up in Colorado
    Posts
    6,753
    Yeah like Mikie said that's a HUGE difference between TQ and HP and way bigger than anything I've ever seen. ~50 more TQ than HP is about the biggest I've ever seen (though that is a pretty normal difference), but you're at twice that. That alone makes me suspect something isn't right with the map he developed. Did you ever ask why there's such a big difference? What was the answer? That TQ number is also really, really high for a stage 1 car with only an intake and catback, and is also very high for 16.9 pounds of boost. Do you have a dyno graph that shows that, or where did you get those numbers from? Something tells me that number isn't true, and with those mods and that much boost you're probably at around 215ish WTQ. Stock HP to the wheels is about 186 so 200 with stage 1 makes sense.
    Last edited by teflon_jones; 04-26-2012 at 03:37 PM.
    Scott
    Past Subies - '11 STI Limited stage 1+ and '04 STi stage 2+
    '13 Wrangler Rubicon - custom front bumper w/12k lb winch & off-road lights, skid plates, diff guards, etc.
    '04 Porsche 911 Turbo GT2 clone 600 HP/TQ
    '77 F-150 heavily modded for off-roading

  9. #8
    Registered User JaySin's Avatar
    Join Date
    Mar 2008
    Location
    SE Michigan
    Posts
    276
    It's legit. Trust me. The guy that tuned it has done HUNDREDS of turbo Subarus and I do have the printout to prove it. He spent many hours on it...with the AWD Dyno and roadtest combined. My car has ridiculous off-the-line launches...virtually no turbo lag and the peak torque comes in at a VERY low RPM. It's a torque monster. This is besides the point...wasn't posting my numbers for kicks...just looking for troubleshooting advice on the injectors. I did get an answer from the tuner directly and he explained in detail the way my car works. I am VERY happy with my tune and the numbers are fine as far as I'm concerned. See reply:

    "First of all, the static fuel pressure on EVERY fuel injected Subaru that I'm aware of is 43.5psi (3 bar). The fuel pressure of the car while it is running is 43.5psi + the pressure in the intake manifold (e.g., if you're at wide-open throttle at 20psi of boost, the fuel pressure at that moment is 63.5psi). If you were to disconnect the vacuum reference line from your fuel pressure regulator while the car was idling, the fuel pressure would jump up to 43.5psi. So, I would *expect* to see 43.5psi in the line while the car is cranking (with intake manifold pressure being at/near 0psi). Also, it is not unexpected for the pressure to slowly bleed off when the car is turned off... but this is NOT due to fuel leaking through "open injectors"... which brings me to my next point.

    Once the car is turned off, the ECU stops sending signals to the injectors. If one of your injectors was sticking open, that would be a physical issue (bad injector, debris in the fuel, etc... all very rare) and would have nothing to do with the ECU. There is no signal that the ECU can send to an injector (ECU only sends power or no power... open or close) to make it "go bad".

    Finally... generally speaking, the tuning done with the Cobb AccessPort (or any ECU reflash, for that matter) does not change the logic within the ECU, only the mapping. This means that there is more or less timing, fuel, and boost. On your car, those maps were only modified in the "high-load" areas. Cold/hot startup, idle, and cruising should be completely unaffected."

  10. #9
    Luke Skywalker Mikie13's Avatar
    Join Date
    Oct 2006
    Location
    Palmyra, NJ
    Posts
    20,643
    That is an interesting reply, and does make sense. I'm not positive on the numbers he says though, but that's why he's the tuner.

    I think the next best step is to run some logs during some WOT pulls and when you see problems, just to verify everything is looking ok.
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
    2012 Lightning Red WRX Sedan Stock...for now Soon to be OpenSource tuned by: Mattypants @ WTF Tuning
    "If I have 10 ice cubes and you have 11 giraffes, how many pancakes can fit on the roof? Purple, because aliens donít wear hats" -Ying

  11. #10
    Moderator Donkey's Avatar
    Join Date
    Apr 2005
    Location
    Da boonies
    Posts
    6,005
    I Support ClubWRX
    Doesn't really sound like an issue to me. The fuel pump is what actually is holding the pressure in the system. Any car will lose pressure in the fuel system overnight,even more after a couple of days. Have you tried just letting the fuel pump prime before starting? Just turn the key to "on",wait for the pump to prime (5 seconds),then when the pump cuts off start the car. Also the pressure shooting up to 40psi is normal. What you where told about the 43.5psi is completely true. Once manifold vacuum is built it should be around 35-38 psi at idle depending on your elevation and barometric pressure. Also these cars use a fuel pump ECU. At idle the fuel pumps voltage is limited to 33%,then low load/throttlecondition get 66% and WOT100%
    Last edited by Donkey; 04-27-2012 at 05:54 AM.
    Resident Adviser @ WTF Tuning, LLC
    2002 FORESTER S
    1998 FORESTER S




  12. #11
    Registered User JaySin's Avatar
    Join Date
    Mar 2008
    Location
    SE Michigan
    Posts
    276
    Yes, I've done the prime trick. I usually have to turn the key a few times before starting it to get it to start immediately...once doesn't usually do the trick. That gets old after year...believe me. So far after a couple of days...it's been fine with the new injectors. So...conclusion...not 100% positive still what the problem REALLY was, but it's working better for now with no need to prime. The car is driving fine...no bouncing idle...no stalling...no hard starts. I will be sure to update if any further issues arise. If anything...I'll bring it to a reputable tuner shop next time for a thorough once over before replacing anything. It's just annoying not really knowing what the issue was or is before replacing a fuel pump, fuel pressure regulator and all the injectors. Did one thing fix it? Did a combo of things fix it? Was it really a bad set of injectors? A lemon perhaps? Who knows...

  13. #12
    Luke Skywalker Mikie13's Avatar
    Join Date
    Oct 2006
    Location
    Palmyra, NJ
    Posts
    20,643
    yeah waiting 5 seconds like that is like waiting for a diesel engine to prime. So annoying
    The Hawk-Eye Alliance #90|The Blobeye Syndicate #0|The Stink-Eye Mob #0|N.E.R.D. Founding Member & #3
    2012 Lightning Red WRX Sedan Stock...for now Soon to be OpenSource tuned by: Mattypants @ WTF Tuning
    "If I have 10 ice cubes and you have 11 giraffes, how many pancakes can fit on the roof? Purple, because aliens donít wear hats" -Ying

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •