fuel trim gurus: stalling right after reaching operating temp.

TexRex2002 · 06-01-2005, 10:58 PM

ok master tuners:

I think I have a fuel trim problem. when I start the car up in the morning it runs just fine. By the time I get to my first stop sign though, my engine has reached normal operating temparature, and when I push the clutch in and let off the gas my rpms plumment to like 300 (for a split second), rebound to 750 and I get a CEL.

a minute or later everything is peachy. When I let off the gas the needle drops quickly until about 1500, where it's fall slows noticably and it settles into idle nicely.

Every single morning it is the same thing: CEL at my first stop sign.

My guess is that the ECU learns one set of fuel trims when the engine is cold, and when the motor is warmed up those fuel trims cause the engine to stumble (upon letting off the gas) for the minute or so it takes for the trims to re-learn.

Anyway, that's my hypothesis. Anyone have thoughts or advice on how to fix? I do have deltadash and a TXS tuna. I should mention that this is on a hybrid WRX/STI motor with modded stock injectors.

The problem is especially bad if I let off the gas right after the car being under load (i.e. hauling ass before stoping at the first stop sign).

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mcowger · 06-01-2005, 11:06 PM

So what kind of EM are you running with this? UTEC?

Uncle Scotty · 06-01-2005, 11:46 PM

Try this.....

In the am when the car is as cold as it is gonna get.......do an ECU re-set.

Get in the car and start the car WITHOUT TOUCHING THE THROTTLE AT ALL.

Let the engine come to operating temp....the fans will come on when it is at temp.....Shut the car off, and take the key out.
Start the car and drive it normally.

See if that helps.

TexRex2002 · 06-02-2005, 12:03 AM

yes UTEC

Uncle Scotty:
Are you suggesting that as a permanent fix?

Thanks

Uncle Scotty · 06-02-2005, 12:33 AM

....I'm suggesting it as a potential cure for the current issue.......if you have not reset the ECU for a while, it may just work wonders for ya.

x99percent · 06-02-2005, 10:14 AM

If you have DeltaDash, then check what your fuel trims are once the car is fully warmed up.

Air/Fuel Learning #1 <-- The important one
Air/Fuel Correction #1 <-- This should be oscillating at/about 0%. If not, wait longer.

Report back with your results.
Also, exactly what CEL are you getting? (read this using F4 in DeltaDash)

TexRex2002 · 06-02-2005, 02:59 PM

the CEL's are MISFIRE 1,2,3,4

I'll check the fuel trims and report back.

x99percent · 06-02-2005, 05:16 PM

Quote:

Originally Posted by TexRex2002

the CEL's are MISFIRE 1,2,3,4

What *exactly* are you doing when you start the car?

Many people are noticing that if you turn the key to the "ON" position and then WAIT for a few seconds before actually starting the car, most "cold misfire CEL" issues go away.

TexRex2002 · 06-02-2005, 07:35 PM

I start the ignition, let the fuel pump prime and start the car. the cels are n't when it is cold. it throws the cel right after it gets warmed up.

the problem is worse if I am on the brakes, by the way.

I have quadruple checked every single fitting and hose already looking for a vac leak, by the way...

Uncle Scotty · 06-02-2005, 10:38 PM

Quote:

Originally Posted by TexRex2002

I start the ignition, let the fuel pump prime and start the car. the cels are n't when it is cold. it throws the cel right after it gets warmed up.

the problem is worse if I am on the brakes, by the way.

I have quadruple checked every single fitting and hose already looking for a vac leak, by the way...

...how about the brake booster hose.....?????

x99percent · 06-03-2005, 11:36 AM

Quote:

Originally Posted by Uncle Scotty

...how about the brake booster hose.....?????

Good call.

TexRex2002 · 06-03-2005, 01:49 PM

I know it's not leaking coming out of the intake, but it may be leaking by the booster. I'll check tonight.

Thank you very much for the help everyone.

I'll be sure to post the cure once I figure it out....

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06-01-2005, 10:58 PM	#1
TexRex2002 Scooby Specialist Member#: 36303 Join Date: May 2003 Chapter/Region: TXIC Location: Houston Vehicle: 06 Evo IX silver	fuel trim gurus: stalling right after reaching operating temp. ok master tuners: I think I have a fuel trim problem. when I start the car up in the morning it runs just fine. By the time I get to my first stop sign though, my engine has reached normal operating temparature, and when I push the clutch in and let off the gas my rpms plumment to like 300 (for a split second), rebound to 750 and I get a CEL. a minute or later everything is peachy. When I let off the gas the needle drops quickly until about 1500, where it's fall slows noticably and it settles into idle nicely. Every single morning it is the same thing: CEL at my first stop sign. My guess is that the ECU learns one set of fuel trims when the engine is cold, and when the motor is warmed up those fuel trims cause the engine to stumble (upon letting off the gas) for the minute or so it takes for the trims to re-learn. Anyway, that's my hypothesis. Anyone have thoughts or advice on how to fix? I do have deltadash and a TXS tuna. I should mention that this is on a hybrid WRX/STI motor with modded stock injectors. The problem is especially bad if I let off the gas right after the car being under load (i.e. hauling ass before stoping at the first stop sign). * Registered users of the site do not see these ads.

06-01-2005, 11:06 PM	#2
mcowger Scooby Specialist Member#: 77483 Join Date: Dec 2004 Chapter/Region: NWIC Location: Seattle, WA Vehicle: 2009 Audi A3 2.0T q Lava Grey	So what kind of EM are you running with this? UTEC?

06-01-2005, 11:46 PM	#3
Uncle Scotty Scooby Guru Member#: 16200 Join Date: Mar 2002 Vehicle: OK Houston we have an Uncle	Try this..... In the am when the car is as cold as it is gonna get.......do an ECU re-set. Get in the car and start the car WITHOUT TOUCHING THE THROTTLE AT ALL. Let the engine come to operating temp....the fans will come on when it is at temp.....Shut the car off, and take the key out. Start the car and drive it normally. See if that helps.

06-02-2005, 12:03 AM	#4
TexRex2002 Scooby Specialist Member#: 36303 Join Date: May 2003 Chapter/Region: TXIC Location: Houston Vehicle: 06 Evo IX silver	yes UTEC Uncle Scotty: Are you suggesting that as a permanent fix? Thanks

06-02-2005, 12:33 AM	#5
Uncle Scotty Scooby Guru Member#: 16200 Join Date: Mar 2002 Vehicle: OK Houston we have an Uncle	....I'm suggesting it as a potential cure for the current issue.......if you have not reset the ECU for a while, it may just work wonders for ya.

06-02-2005, 10:14 AM	#6
x99percent Scooby Specialist Member#: 27108 Join Date: Oct 2002 Chapter/Region: MWSOC Location: Detroit-ish, MI Vehicle: 2004 STi 2004 A4	If you have DeltaDash, then check what your fuel trims are once the car is fully warmed up. Air/Fuel Learning #1 <-- The important one Air/Fuel Correction #1 <-- This should be oscillating at/about 0%. If not, wait longer. Report back with your results. Also, exactly what CEL are you getting? (read this using F4 in DeltaDash)

06-02-2005, 02:59 PM	#7
TexRex2002 Scooby Specialist Member#: 36303 Join Date: May 2003 Chapter/Region: TXIC Location: Houston Vehicle: 06 Evo IX silver	the CEL's are MISFIRE 1,2,3,4 I'll check the fuel trims and report back.

06-02-2005, 07:35 PM	#9
TexRex2002 Scooby Specialist Member#: 36303 Join Date: May 2003 Chapter/Region: TXIC Location: Houston Vehicle: 06 Evo IX silver	I start the ignition, let the fuel pump prime and start the car. the cels are n't when it is cold. it throws the cel right after it gets warmed up. the problem is worse if I am on the brakes, by the way. I have quadruple checked every single fitting and hose already looking for a vac leak, by the way...

06-03-2005, 01:49 PM	#12
TexRex2002 Scooby Specialist Member#: 36303 Join Date: May 2003 Chapter/Region: TXIC Location: Houston Vehicle: 06 Evo IX silver	I know it's not leaking coming out of the intake, but it may be leaking by the booster. I'll check tonight. Thank you very much for the help everyone. I'll be sure to post the cure once I figure it out....