what is the connection between cold start misfire and Second Air Pump?

icecolde46 · 02-18-2013, 09:06 AM

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.

Zchild · 02-18-2013, 11:22 AM

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!

dreyo27 · 02-18-2013, 12:04 PM

Quote:

Originally Posted by zchild

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

Zchild · 02-18-2013, 12:52 PM

Quote:

Originally Posted by dreyo27

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...

rudycoop · 02-18-2013, 03:13 PM

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.

jfoj · 02-18-2013, 04:16 PM

Suggest you read the first link below in my signature for more info.

02-18-2013, 09:06 AM	#1
icecolde46 Registered User Join Date: Feb 2013 Location: texas Posts: 57 My Ride: e46 View My Garage	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.

02-18-2013, 11:22 AM	#2
Zchild Registered User Join Date: Mar 2006 Location: Columbia, Maryland Posts: 1,640 My Ride: 2000 BMW 3XXi ZSP View My Garage	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! __________________ V/R Zachary Pullins Sr. National Capital Chapter BMWCCA NCC Member Recognition Chairman NCC High Performance Driving School Registrar NCC Auto-X BOD Liaison DIY Senior Committee Coordinator 2006 E90 325Xi & 2000 E46 3XXi " Vision without resources is just hallucination"

02-18-2013, 04:16 PM	#6
jfoj Registered User Join Date: Nov 2009 Location: Fairfax, VA USA Posts: 5,183 My Ride: '06 330CiC, '03 M5 View My Garage	Suggest you read the first link below in my signature for more info. __________________ 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 Lower hose fan switch O-ring - BMW #13621743299

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02-18-2013, 03:13 PM	#5
rudycoop Registered User Join Date: Nov 2012 Location: San Francisco Posts: 206 My Ride: 3 pedal 330i View My Garage	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.