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Start up problem no one can solve...
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Start up problem no one can solve...
Start up problem no one can solve...
Start up problem no one can solve...
Start up problem no one can solve...
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Old 11-14-16, 09:52 AM   #1
inpuressa
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Default Start up problem no one can solve...

I have an issue with my 08 STI where the dealer, and 2 shops could not figure out.
It is a startup issue where the car would take about 5 sec(or longer) of cranking to start up.

Here are some things to note:
1. Car needs to be parked for at least 15-20min for the hard start to come in.
2. Car will start up fast like normal if it is within say a few min. (eg. start up from a stall or filling up tank)
3. Once I can get the engine running, it doesn't matter if its hot or cold, it will start up fast as long as its within a few min.
4. In the morning, while the engine is warming up, the idle feels a bit rough.
5. On long stops like overnight or from work, upon start up, I see white smoke come out from the exhaust that lasts for a second and goes away completely after. (smells like gas)
6. Once the engine is warmed up, the car runs perfectly fine, no stumbles, no smoke, has power, etc.
7. Engine oil level ok, no milky look, no smoke from oil cap. Radiator levels ok.
8. The exhaust constantly smells like raw gas, like it is running rich.

In a nut shell, time seems to be the biggest factor involved in creating this.

Car has 75000 miles, Cobb AP stage 2 w/catted DP.
Perrin turbo inlet, everything else stock.
No CEL at all.

Want to get to the bottom of this.
Any suggestions would be appreciated.
Thanks

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Old 11-14-16, 12:19 PM   #2
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Default Re: Start up problem no one can solve...

Did this start after a mod or certain event?
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Old 11-14-16, 01:44 PM   #3
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Default Re: Start up problem no one can solve...

Sounds like a fueling problem and the timing on when it happens indicates it might be heat-soak which could be caused by a weak fuel pump, but the other symptoms point elsewhere, like a bad fuel pressure regulator or injector(s) giving you too much fuel.

It might be helpful to monitor fuel pressure for a while, admittedly it can be kind of a PITA to install a gauge but there are diagnostic kits that include any common fuel line fitting, so some cars are a snap, others not so much. AFAIK the EJ ECUs don't monitor or compensate for deviations in fuel pressure, even the newest STis. IDK how bad it would be in that rat's nest on top of the motor, lol....

Also check fuel pump wiring, your car is a bit new to have corrosion issues there but I've seen some badly corroded fuel pump wiring before, usually in the harness plug at the pump.

Have you replaced or checked spark plugs yet? I could see that as a possible issue too...
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Old 11-14-16, 02:32 PM   #4
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Default Re: Start up problem no one can solve...

There's a one way check valve that holds fuel pressure after you shut the car off, when it goes bad it'll take extra cranking to prime the lines. They usually fail in the way you are describing also with it starting hard after 15-20 min of sitting since it usually won't drain the line in a couple minutes.
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Old 11-14-16, 03:44 PM   #5
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Default Re: Start up problem no one can solve...

Unplug your maf and see if it runs better, or try cleaning it. Assuming you still have a maf sensor that is.

Do you have a way to monitor your A/F ratio?

I popped a cylinder when my maf went bad and the motor was doing the same thing. Had a really rough start up, flooded the hell out of the cylinders. Sounded like an airplane attempting to start or something.

But give that a try, as well as testing the o2 sensor for proper resistance and voltage through out.

Maf clicks in my mind when you say it runs better once its warm, because its just running off itself during warm up.
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Old 11-14-16, 04:25 PM   #6
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Default Re: Start up problem no one can solve...

Thanks for the ideas guys.

The problem gradually came about, not after a mod or anything.
The MAF is a known, good one.
I just had the plugs changed out about 2 months ago.
I inquired about the fuel system to a private shop, but they insisted that they have to test other areas first (hence racking up the labor fees). They charged me $400 just to change out plugs
I will revisit the fuel pressure system to see how it reacts to daily driving. As you guys said, I have a feeling that it is fuel related.

I do have the Cobb AP, so I do monitor the AFR and it seems to stay within the 14.7 range. Not sure if the O2 sensor is reading is accurately though. Can they seemingly work fine, but just reading things weird?
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Old 11-15-16, 02:46 PM   #7
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Default Re: Start up problem no one can solve...

Still worth a try with the maf. Never over look something simple
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Old 11-15-16, 03:12 PM   #8
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Default Re: Start up problem no one can solve...

Quote:
Originally Posted by inpuressa View Post
Thanks for the ideas guys.

The problem gradually came about, not after a mod or anything.
The MAF is a known, good one.
I just had the plugs changed out about 2 months ago.
I inquired about the fuel system to a private shop, but they insisted that they have to test other areas first (hence racking up the labor fees). They charged me $400 just to change out plugs
I will revisit the fuel pressure system to see how it reacts to daily driving. As you guys said, I have a feeling that it is fuel related.

I do have the Cobb AP, so I do monitor the AFR and it seems to stay within the 14.7 range. Not sure if the O2 sensor is reading is accurately though. Can they seemingly work fine, but just reading things weird?
I think it's a coolant temperature sensor issue or cranking fueling. When you turn your ignition ON go to your monitor settings on the AP and check the coolant temp the ECU is reading and report back. You can also reflash your map, sometimes there's a small bug.

If you have access to a fluid pressure gauge, you can check your fuel pressure pre-start up. It's easy if it's just the fuel pressure regulator, takes 5 minutes to change.
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Old 11-15-16, 03:35 PM   #9
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Default Re: Start up problem no one can solve...

Quote:
Originally Posted by STi Addict View Post
I think it's a coolant temperature sensor issue or cranking fueling. When you turn your ignition ON go to your monitor settings on the AP and check the coolant temp the ECU is reading and report back. You can also reflash your map, sometimes there's a small bug.

If you have access to a fluid pressure gauge, you can check your fuel pressure pre-start up. It's easy if it's just the fuel pressure regulator, takes 5 minutes to change.
Yea, makes sense.

Would add fuel on start up thinking its cold and needs it?
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Old 11-15-16, 03:37 PM   #10
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Default Re: Start up problem no one can solve...

Quote:
Originally Posted by farmboss View Post
Yea, makes sense.

Would add fuel on start up thinking its cold and needs it?
That's right, the colder it is the more fuel it dumps to help it start - but if it's actually not that cold, it's counter productive and won't fire properly.
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