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Loud whirring noise when starting engine cold

19454 Views 14 Replies 11 Participants Last post by  jimvw57
What is that noise you ask ?? Well thanks to many of our fellow contributors, it is the air pump which charges the exhaust to reduce emissions from cold-engine starts (I hope I got that right). Its a mild whir that lasts up to 33 seconds then stops. So what does it sound like when its about to die ?!?!? Here - listen to mine! (Smart Air Pump Noise - YouTube) If yours is quieter than that, I wouldn't worry too much about it.

For those of you in California, there's a 7-year, 70,000 mile warranty on the emissions-related parts, so the fix should be free... I'm going to take it in to the dealer in a couple days to get it fixed. I'll post if there's any issues.
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Does not sound like it will be around much longer.
It's hurtinfercertin!

It sounds like one of our 5hp circulator pumps at work that had it's impeller come loose.
Took it in today to have the air pump replaced ... $800+ job, but thankfully it's still under the 7/70k CA Emissions Defect warranty. BUT ... the reason why it went is that the "combination valve" which keeps exhaust from coming into the pump once the engine is running has gone and it supposedly is not covered ... although I'm going to argue that one. That's an additional $260 parts and labor....
People might argue against the extended warranty, but from the fuel pump and the air pump being replaced it would have already paid for itself. I didn't get it, but thankfully I've got the emissions warranty here to help. I'm thinking it wouldn't have been a bad idea for the 7/100k extended warranty. I've only got 66k on my car and I also have that "won't go into gear" transmission issue to deal with still.
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...I don't hear that pump anymore....oh wait...I don't have that pump anymore....

Jetfuel...silly me....
...I don't hear that pump anymore....oh wait...I don't have that pump anymore....

Jetfuel...silly me....
How did you delete the pump??
...easy...removed plug...removed the hold down bolts thru the right wheel well...removed pipe and pulled out....
...I do have a different exhaust manifold and no catalytic converter on the Barney special hair dryer installation...

Jetfuel...thanks Paul....
Loud whirring noise when starting engine cold Reply to Thread

Hello our smart car does the same thing only when cold. no codes in car either. So just disconnect the air this right?
Thank you
The pump is there for a reason. Jetfuel does not have a stock car, something about an aircraft engine or something... I would suggest leaving the pump alone. it only runs for a bit and then shuts off. Turn up the radio if it bothers you.
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The noise is ear piercing, i don't think any one could listen to this that long.I going to check all the hose to the pump and see if one is plugged at all first. Thank you
From the 451 Intro to Service manual

Secondary air injection
Engine 132 is fitted with a secondary air injection
pump (electric air pump), which injects additional
fresh air in order to reduce exhaust gas emissions
after a cold start and to accelerate the warming of the
catalytic converter to its reaction temperature.

The necessary air is injected into the exhaust ports in
the cylinder head by the secondary air injection pump
via the combination valve. The secondary air injection
pump is actuated by the ME-SFI [ME] control unit via a

The secondary air injection pump switchover valve is
supplied with vacuum from the vacuum reservoir at
the intake manifold via a check valve.
When actuated, the secondary air injection pump
switchover valve releases vacuum to the combination
valve. This opens and the air injected by the
secondary air injection pump passes through to the
exhaust ports in the cylinder head.
The injected air reacts with the hot exhaust gases in
the outlet port. The carbon monoxide (CO) and hydro-
carbon (HC) are oxidized. This "afterburning"
process increases the exhaust temperature and
reduces pollutants.

The duration of secondary air injection is dependent
on the coolant temperature.
The secondary air injection pump is only actuated at a
coolant temperature of 45 °F to 97 °F (7 °C to 36 °C)
and for a maximum duration of 33 seconds.
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Ditto per JimVW. Your car will start throwing codes and the Check Engine light will illuminate if you disconnect it.
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There could be a problem with a pump bearing if it is as loud as you make it sound. normally they are not that loud and I certainly wouldn't call it ear piercing. Might be time for a video or a recording to demonstrate how loud it is. Or a drive to the dealer to have them evaluate it to see if it is normal.
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