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Old 08-17-2019, 10:08 PM   #1
lphthephunk
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Default Hard start, dies when pressing gas

UPDATE: See post 17

Edit: car is 2006 wrx

Hey guys, just finished a rebuild and had a hard time getting it started due to no spark. Figured out the wiring issue, but I'm left with something else.

The car will only start when I have gas fully depressed (fuel cut out), idles rough and smells pretty rich. It also dies if I try to give it gas.

I did the screw driver method to listen to the injectors clicking and they all seem to be clicking. I'm not really satisfied with that though and will still end up pulling the manifold to check them.

Before I start this, I was wondering if there's anything else obvious that might cause this same thing after a rebuild, or just having the battery disconnected for a long time.

I know that the ECU needs time to relearn it's fuel trims, but I wouldn't think the base map would be so bad that it would cut off if I give it gas.

I'm hesitant to let it idle for very long with this issue.

Any thoughts?
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Last edited by lphthephunk; 08-31-2019 at 01:26 PM.
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Old 08-18-2019, 12:13 AM   #2
lphthephunk
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Also noticed that there is a tear under the turbo inlet pipe where the clamp goes. Would this be enough to cause this issue?
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Old 08-18-2019, 08:28 AM   #3
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Quote:
Originally Posted by lphthephunk View Post
Also noticed that there is a tear under the turbo inlet pipe where the clamp goes. Would this be enough to cause this issue?
Yes, that could do it.
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Old 08-18-2019, 05:02 PM   #4
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Quote:
Originally Posted by lphthephunk View Post
Also noticed that there is a tear under the turbo inlet pipe where the clamp goes. Would this be enough to cause this issue?
Yes that would definitely cause it. Also check for vacuum leaks.
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Old 08-18-2019, 06:59 PM   #5
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Quote:
Originally Posted by stu View Post
Yes that would definitely cause it. Also check for vacuum leaks.
So I've got the intake off again, and there is in fact a large rip where the hose clamp goes on at the turbo side. I'll definitely be replacing this with an aftermarket unit, but wouldn't a vacuum leak like this cause a lean condition? I don't know if it explains why I have to cut fuel off in order to start it
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Old 08-23-2019, 08:02 PM   #6
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Update: replaced the turbo inlet with a Tomei unit, but am still experiencing the same problem. I cleaned the MAF and it briefly seemed okay (ie: I could actually rev it to about 2500 rpm and it would come back down to idle).

When I hade the intake manifold off, I loosely set it back in the engine compartment with the fuel rail attached, hooked up the wiring harness and primed the pump. I could see no gas leaking from the Injectors.

I still have to start the car at full throttle, it will dip and rise in rpm a couple of times and then sit right below 1000rpm. Giving it any gas will cause it to stall.

I'm really at a loss here because I can't explain why I would need to start it in fuel cut out if the injectors are not leaking.

Do you guys have any more ideas? I am coming close to exhausting all options I can think of at this point.

Last edited by lphthephunk; 08-23-2019 at 08:32 PM.
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Old 08-23-2019, 10:01 PM   #7
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Look around for any loose hoses and vac lines. Try resetting the ECU. its one of those thing you have to just keep searching for. What is you Vacuum at idle?
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Old 08-23-2019, 11:43 PM   #8
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Quote:
Originally Posted by stu View Post
Look around for any loose hoses and vac lines. Try resetting the ECU. its one of those thing you have to just keep searching for. What is you Vacuum at idle?
I'll have to hook up a gauge and actually test that, but it's probably the next step. Does this seem like something small I'm just missing? I feel like I'm just going to find something blatantly obvious
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Old 08-24-2019, 12:49 PM   #9
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Just to rule out leaks, you might want to do a boost leak test - I usually use < 5 psi. If it doesn't hold that, and it's leaking out, find the leak(s) and correct them.

It could be something else, but a boost leak test is usually a good thing to start with.
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Old 08-24-2019, 01:35 PM   #10
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Quote:
Originally Posted by heiche View Post
Just to rule out leaks, you might want to do a boost leak test - I usually use < 5 psi. If it doesn't hold that, and it's leaking out, find the leak(s) and correct them.

It could be something else, but a boost leak test is usually a good thing to start with.
Awesome, I will try this as well. Thanks!
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Old 08-24-2019, 07:15 PM   #11
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Another update: there is gas coming out of my tail pipe. The thing is running pig rich, but the injectors are not leaking. Something is telling the injectors to just push excess fuel. I replaced the front 02 with a new unit when doing the rebuild. Maybe it's a faulty unit?
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Old 08-26-2019, 10:59 PM   #12
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Bump. Been too busy to run aforementioned tests, but hoping to get some more suggestions to do along with them.

I also took the intake off again and manually tested/cleaned each injector. All are working fine and spraying fine. Still seeing fuel dribbling out tail pipe after a few minutes of idling and seeing some whitish gray smoke accompanying it.

ALSO: I forgot to mention that I did the air pump delete and haven't gotten a tune yet. I wouldn't think that would effect the car this much though.

Last edited by lphthephunk; 08-26-2019 at 11:21 PM.
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Old 08-27-2019, 03:16 AM   #13
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have you tried starting it with the MAF disconnected completely?
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Old 08-27-2019, 11:21 AM   #14
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have you tried starting it with the MAF disconnected completely?
I did and it hardly starts. Idles incredibly low and dies almost immediately.
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Old 08-27-2019, 10:29 PM   #15
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It appears I may have gotten ahead of myself with saying that fuel is coming out of the exhaust. It appears to just be condensation dribbling out. There is no fuel odor. I guess I just made a quick assumption due to the signs pointing to rich mixture.

Still haven't figured this out though. Hoping to pressure test intake lines tomorrow or Thursday.
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Old 08-28-2019, 06:39 PM   #16
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I'm going through my injector plugs to make sure they aren't shorting out. Maybe I'm crazy and my previous leak test wasn't successful after all.

They are getting power when the key is on of course. When I probe their negatives with the key on, I get a very faint light for ground. Is this normal for the fuel injectors? Wouldn't a partial ground like that still trigger the injectors to open?
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Old 08-31-2019, 01:26 PM   #17
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I found out that injector 4 was not getting a pulse. I suppose it is normal to see a slight ground with the key turned on at the harness. Please correct me if I'm wrong because that could be the whole issue.

I fixed the wiring issue to the #3 injector and replaced the front O2 again just to be sure. Car is still hard to start and is idling pretty rough still. Also, I'm pretty sure it is just condensation out the tailpipe since I'm not getting any black smoke.

For the fuel pressure test, I'm getting 40 psi with just the pump primed, 40 psi at idle, and when I remove vacuum to the FPR I'm at about 42-45 psi.

According to my OBD2, vacuum at idle is about 14 in/hg which is roughly 6psi.

I have a new MAF coming in the mail today just to rule that out.

Thanks again for any replies. It helps me troubleshoot.

Last edited by lphthephunk; 08-31-2019 at 03:23 PM.
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Old 08-31-2019, 03:18 PM   #18
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Did you upgrade the injectors during the rebuild?
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Old 08-31-2019, 03:19 PM   #19
lphthephunk
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Quote:
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Did you upgrade the injectors during the rebuild?
No they are the stock WRX blue ones
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Old 09-01-2019, 07:14 PM   #20
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MAF was reading approx 8.0 g/s at idle and short term fuel trims were showing about -14. Looks like the O2 is trying it's hardest to correct the problem. I replaced the MAF and got the same readings.

Why would the MAF be reading so high? It might be worth noting that I replaced this sensor with a Duralast unit from AutoZone. I might try getting one of their OEM refurbished ones. I'd rather not shell out the cash for a new Denso until I know that the MAF is the culprit.

Any other reason why I would be reading so high on the MAF at idle?

Edit: the only reason I've found online for this would be a boost leak. Guess I'm going through the lines again to double check everything. As always, all ideas are appreciated!

Last edited by lphthephunk; 09-01-2019 at 07:43 PM.
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Old 09-01-2019, 08:18 PM   #21
heiche
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Did you try a boost leak test?

Here is an example I just found:
I usually don't bother capping off everything, but just run low pressure, like 4 or 5 psi. Good idea to remove the oil cap as he says.
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Old 09-01-2019, 09:32 PM   #22
lphthephunk
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Quote:
Originally Posted by heiche View Post
Did you try a boost leak test?

Here is an example I just found: https://www.youtube.com/watch?v=MkzuyDuSmbE
I usually don't bother capping off everything, but just run low pressure, like 4 or 5 psi. Good idea to remove the oil cap as he says.
Thanks for the link! I'm actually just returning from the store with all the hardware to assemble a tester. I'm going to put it together in the morning and report back with what I find.
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Old 09-01-2019, 10:40 PM   #23
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a boost leak wouldn't happen at idle though. Boost leaks are post-turbo vacuum leaks, and they only cause richness when your turbo is pushing positive pressure.

You could try looking at each of the spark plugs and comparing them to each other to see if one particular cylinder is having an issue.

I've had issues like this before where one of the injectors was so clogged that it was just p*ssing gas on the cylinder wall in one of the cylinders. Getting the injectors cleaned by a reputable shop fixed it.

If you were using the current MAF before the build, I wouldn't suspect that as the culprit, myself. If it IS new to this build, I'd try swapping back to the old one if possible or temporarily swap one with a fellow Subie friend's.
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Old 09-01-2019, 10:47 PM   #24
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Quote:
Originally Posted by BeastianSTI View Post
a boost leak wouldn't happen at idle though. Boost leaks are post-turbo vacuum leaks, and they only cause richness when your turbo is pushing positive pressure.

You could try looking at each of the spark plugs and comparing them to each other to see if one particular cylinder is having an issue.

I've had issues like this before where one of the injectors was so clogged that it was just p*ssing gas on the cylinder wall in one of the cylinders. Getting the injectors cleaned by a reputable shop fixed it.

If you were using the current MAF before the build, I wouldn't suspect that as the culprit, myself. If it IS new to this build, I'd try swapping back to the old one if possible or temporarily swap one with a fellow Subie friend's.
Thanks, that is very good to know. I had all injectors out prior to this and bench tested them. I squirted carb cleaner through them and supplied 12 volts to each one to open and close the injector. The spray patterns looked okay for being the original injectors. Probably could have been better, but they didn't seem bad.
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Old 09-01-2019, 10:57 PM   #25
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Also, it is probably worth noting that all cylinders plugs are fouling out equally
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