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General E46 Forum
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Old 02-18-2013, 09:06 AM   #1
icecolde46
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Join Date: Feb 2013
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Talking what is the connection between cold start misfire and Second Air Pump?

I have tried to replace a lot parts for my 2000 323i and the cold start misfire problem still happens.

I am very positive that the more cold the temp is (around 32F), the misfire seems worse.

I got only random misfire codes, a strong feeling of car shaking, and a big smoke out of the tail pipe.

And today, fortunately, I got a new code hopefully providing me more clues. It is p1421.

I have read some threads on this forum. this one shows exactly the same symptoms as mine. it is a bad sap.

http://www.e46fanatics.com/forum/sho...d.php?t=852552

I am not sure how SAP can affect the cold start misfire.

Last edited by icecolde46; 02-18-2013 at 09:08 AM.
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Old 02-18-2013, 11:22 AM   #2
Zchild
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Before you replace the SAP I would check the vacuum line that runs from the SAP to the rear of the motor... It can become brittle and break in sections which can cause misfires. It is a little difficult to reach the portion behind the motor. Just my two and a half cents worth!
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Old 02-18-2013, 12:04 PM   #3
dreyo27
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Quote:
Originally Posted by zchild View Post
before you replace the sap i would check the vacuum line that runs from the sap to the rear of the motor... It can become brittle and break in sections which can cause misfires. It is a little difficult to reach the portion behind the motor. Just my two and a half cents worth!
thats what i had... I ripped it when i was doing my vcg
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Old 02-18-2013, 12:52 PM   #4
Zchild
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Quote:
Originally Posted by dreyo27 View Post
thats what i had... I ripped it when i was doing my vcg
I disconnected my vacuum hose while replacing my VCG as well and had the accompanying CEL...
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Old 02-18-2013, 03:13 PM   #5
rudycoop
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There is a switch that runs the vacuum that opens the check valve to allow the SAP to blow air into engine. If any of those aren't working right you could have that problem. I had the code and it was 2 hoses broken. The switch is under the back of the intake manifold. Don't just check around the valve cover, because mine was broken at the switch under the intake. I have big hands and it was a little of a pain to work with. You definitely have to take the cabin air filter assembly out and the black plastic wall that pulls out.
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Old 02-18-2013, 04:16 PM   #6
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

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