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Old 11-30-2008, 04:14 PM   #1
sebast120
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Member#: 194765
Join Date: Nov 2008
Vehicle:
2004 WRX STi
silver

Default cold start hesitation

I have a problem during cold start, it takes a while for the starter to barely start the engine, and once the engine is started, it hesitate for a while (2 to 5 sec) to get a good idle, depending on the tempeture, the colder it is, the harder it's for the engine to start.

I looked around and I got three thing that I'm thinking of:

Idle aire control valve;
EGR (exhaust gaz recirculation);
MAP (manifold absolute pressure).

I'm still trying to find out how to test these...

Anybody have any idea???
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Old 12-01-2008, 04:09 PM   #2
05EJ25
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Join Date: Aug 2005
Chapter/Region: Tri-State
Location: Peekskill, New York
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05 CGM STi
Stage TSP

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Funny you start this thread, my car acted really weird yesterday. I started it and didn't warm it up (I'm retarded) drove down the street to my uncles and shut the car down. Came outside an hour later started the car and had the worst rough idle ever. AFR's where in the 18's and just stumbling everywhere. Took a while to regain itself, then when I was driving if I hit anything over 12 PSI the car would stumble on it's face. By the time I got home the car was idling fine. I shut it down and restarted it once I got home. Took it for a ride and the hesitation started to go away under boost the few times I spooled. This morning I started my vehicle for it's 25 min. warm up cycle I do and the car ran fine the whole time to work, no stumbling no nothing. Yesterday was a COld wet humid day. I'm starting to think the car was totally loaded up and just couldn't get the fuel out of it's system yesterday and now it's back to normal again. I shall never start my car and drive it cold EVER! lol
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Old 12-01-2008, 04:14 PM   #3
Engmus
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Default

Quote:
Originally Posted by 05EJ25 View Post
Funny you start this thread, my car acted really weird yesterday. I started it and didn't warm it up (I'm retarded) drove down the street to my uncles and shut the car down. Came outside an hour later started the car and had the worst rough idle ever. AFR's where in the 18's and just stumbling everywhere. Took a while to regain itself, then when I was driving if I hit anything over 12 PSI the car would stumble on it's face. By the time I got home the car was idling fine. I shut it down and restarted it once I got home. Took it for a ride and the hesitation started to go away under boost the few times I spooled. This morning I started my vehicle for it's 25 min. warm up cycle I do and the car ran fine the whole time to work, no stumbling no nothing. Yesterday was a COld wet humid day. I'm starting to think the car was totally loaded up and just couldn't get the fuel out of it's system yesterday and now it's back to normal again. I shall never start my car and drive it cold EVER! lol

25 minute warm up cycle? Thats rediclious and unhealthy. Your going to have fuel wash on cylinder walls, and just because the engine is warmed up doesnt mean the rear diff, or transmission oils have warmed up.

Your best bet is to get in, start the car and let it idle for maybe 30 seconds and then drive easy (less then 3k RPM shifts).
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Old 12-02-2008, 09:24 AM   #4
05EJ25
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Originally Posted by Engmus View Post
25 minute warm up cycle? Thats rediclious and unhealthy. Your going to have fuel wash on cylinder walls, and just because the engine is warmed up doesnt mean the rear diff, or transmission oils have warmed up.

Your best bet is to get in, start the car and let it idle for maybe 30 seconds and then drive easy (less then 3k RPM shifts).
Please stop. It's not ridiculous. 10-15-20mins is not bad at all (sit there in traffic and idle for that long before, I assume this is really bad too?), Been doing it since I own the vehicle new in 05 have 99k on the clock and 30k on an FPgreen and other supporting mods. The WORST thing you could do is drive the car slowly cold. The car will load it's self up and personally the car should cross over OL/CL before you drive it to begin with usuallly takes about 5-6mins. Stop the nonsense please. In the Summer that's a different story but in the winter, you should be shot for driving a modified anything without it reaching operatiing temperature first. You drive it slow anyway, you don't hammer it straight out and you certainly don't just hop on the highway before the car is warmed up completely to go to work with an aftermarket setup of anytype on your car i.e. boost controller, upgraded turbo, larger injectors, FMIC. K thanks bye.

As for the driving after 30 seconds, your throttle response is ridiculously delayed and when you come to stop the car will idle like crap and then regain itself. If you think you are washing out the cylinder walls at idle warm up you should see what you are doing driving it cold and letting it go ridiculously rich on acceleration then crazy lean when you take it out of gear and it tries to re-establish cold idle and stumbles on it's face then evens out. Not nice in stop and go traffic, last thing you want on the road is a non responsive vehicle that can't even keep up with traffic.

Last edited by 05EJ25; 12-02-2008 at 09:35 AM.
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Old 12-05-2008, 09:38 PM   #5
sebast120
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Wow, thanks for the psot, it doesnt answer my problem but its good stuff to read. Personnaly I start my car for like 5-6 min, once it has a good idle at 700 RPM, Oil temp at lest at 100F and engine collant at normal temp, i consider it's good to go, easy tho! Once i drove the car for a good km or two, I start to give her gradually. We don't want boiling oil to jump in the cold turbo...
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Old 12-07-2008, 06:04 PM   #6
AndyH
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2005 S4 Avant

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Originally Posted by sebast120 View Post
... i consider it's good to go, easy tho! Once i drove the car for a good km or two, I start to give her gradually. We don't want boiling oil to jump in the cold turbo...
I doubt the oil is 'boiling' after idling for 5-6 minutes. Also, doesn't the oil pump through the turbo as soon as the engine is running, as well as coolant? So the turbo is likely around the same temp as the oil or coolant when you actually pull away.
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