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Old 10-17-2011, 06:39 PM   #1
wrxstijdm
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Member#: 254590
Join Date: Aug 2010
Location: Costa Rica
Vehicle:
1998 V4 Impreza STI
EJ20K engine

Default Weird issue when starting

Guys,

I have a weird issue when starting my car...

I usually put the key on the "On" position, wait for around 10 secs for the fuel pump to "send" the fuel, then crank it...

It always starts perfectly, goes up to 1200 rpms, but then comes down to 500 rpms (the car almost shuts off) during 5 seconds and then back to 1200 rpms and idles perfectly.

What could be the issue during those 5 secs?

I have cleaned injectors, changed fuel filter, plugs (as regular maintenance, not to fix this), but situation has not changed...

If I press a little the gas pedal before it comes down to 500 rpm, during those 5 secs, then the issue doesn't take place.

It happens both when the engine is hot or cold... But if it is hot, it lasts only like 2 secs...

Other than this, car runs perfectly fine...
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Old 10-18-2011, 08:57 AM   #2
pmugabi
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Air leak, maybe from a BOV.
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Old 10-18-2011, 08:59 AM   #3
wrxstijdm
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No BOV, car is absolutely stock...
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Old 10-18-2011, 12:17 PM   #4
TommyAtomic
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There is a somewhat standard list of things that contribute to weird starting issues.

Plugs/Coilpacks
Coolant temp sensor
Fuel pump
FPR
Dirty/defective MAF

Also cam sensors are frequently mentioned as the cause of weirdness.
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Old 11-13-2011, 12:06 PM   #5
wrxstijdm
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EJ20K engine

Default

Just a heads up on this, in case somebody has a similar issue....

I installed a grounding kit on my car and the problem dissapeared! I guess when the car starts all sensors need to have a good "electricity flow" or something like that...

Anyways, I'm glad I fixed this
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Old 11-15-2011, 12:23 PM   #6
lagopodous
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I was having the same issue and did some research on here and found it to be the IACV. Problem fixed, but now I get a studdering problem. Feels electrical as it will be there one minute, no matter what RPM, and then its like someone flipped a switch and it goes back to normal. You can hear it in the exhaust note even. Cant seem to find any consistancy to it. I think ill reset the ecu first, then check my plugs. I did the coil conversion already, been running great for the last 4 years but this one has me stumped on where to start looking. Any advice is mucho appreciatedo!
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Old 11-15-2011, 01:10 PM   #7
TommyAtomic
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Do not reset the ecu first. This is not a troubleshooting step. It will not help.

Make changes first. Repair/replace suspicious parts FIRST - THEN reset ECU.

Check your coolant levels and take a look at what evoscan or similar software thinks of the readings from your coolant sensor. You may need a new coolant sensor. Also you may just have a bad batch of fuel. Winter fuel (oxygenated fuel) is generally complete crap and can result in some fuel trim weirdness.

Its possible that you are experiencing false knock. Evoscan or similar software may be able give you more info to check that.
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Old 12-08-2011, 12:12 PM   #8
wrxstijdm
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Problem is back again... I figured it only disappeared cause the ECU was reset... So now that the ECU "learned" again, the issue came back..

Any idea what the issue might be?
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Old 12-08-2011, 12:38 PM   #9
TommyAtomic
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Quote:
Originally Posted by TommyAtomic View Post
Do not reset the ecu first. This is not a troubleshooting step. It will not help.

Make changes first. Repair/replace suspicious parts FIRST - THEN reset ECU.

Check your coolant levels and take a look at what evoscan or similar software thinks of the readings from your coolant sensor. You may need a new coolant sensor. Also you may just have a bad batch of fuel. Winter fuel (oxygenated fuel) is generally complete crap and can result in some fuel trim weirdness.


Quote:
Originally Posted by TommyAtomic View Post
There is a somewhat standard list of things that contribute to weird starting issues.

Plugs/Coilpacks
Coolant temp sensor?
Fuel pump
FPR
Dirty/defective MAF

Also cam sensors are frequently mentioned as the cause of weirdness.
Also add dirty injectors to the list.
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