The air pump on my '02 VRS runs for the normal period after initial start up but I have noticed that it also comes on intermitantly at other times when the engine is upto temperature. It tends to be when the car is idling and it just comes on for a few seconds then goes off. I am certain that it is not the cooling fans (as the air pump makes a different noise and it occurs at times when the fans would not be running ie after a 10 minute journey with no traffic/stopping).

I have changed the temperature sender with a new genuine one but it is still doing it.

Is there anything else that could cause it?

does the temp guage go up and down a bit when driving?

No, the car warms up quickly and maintains 90 degrees. Thermostat was changed about 4 months ago as the car was slow to warm up and then temp would drop if heater was put on.

The air pump on my '02 VRS runs for the normal period after initial start up but I have noticed that it also comes on intermitantly at other times when the engine is upto temperature. It tends to be when the car is idling and it just comes on for a few seconds then goes off. I am certain that it is not the cooling fans (as the air pump makes a different noise and it occurs at times when the fans would not be running ie after a 10 minute journey with no traffic/stopping).

I have changed the temperature sender with a new genuine one but it is still doing it.

Is there anything else that could cause it?

Is this a problem? My car has always done this until it is completely warmed up (i.e temp gauge at 90 for a good 5 minutes)

No, the car warms up quickly and maintains 90 degrees. Thermostat was changed about 4 months ago as the car was slow to warm up and then temp would drop if heater was put on.

Sorry to drag the topic up, but I'm experiencing something similar:

My octy takes a fair while to warm up according to the gauge, but normally stays at 90 once it has. I've noticed recently that when I put the aircon on and set it to warm, the temperature gauge drops slowly by up to ten degrees. If I switch back to econ but keep the temp setting the same, it'll go back up to 90 in less than a minute but will then fluctuate up and down slightly. When it's in one of these moods the fuel economy plummets, suggesting that it's overfulleing because it believes it's running cold. Does that tally with your experience?

Sorry to drag the topic up, but I'm experiencing something similar:

My octy takes a fair while to warm up according to the gauge, but normally stays at 90 once it has. I've noticed recently that when I put the aircon on and set it to warm, the temperature gauge drops slowly by up to ten degrees. If I switch back to econ but keep the temp setting the same, it'll go back up to 90 in less than a minute but will then fluctuate up and down slightly. When it's in one of these moods the fuel economy plummets, suggesting that it's overfulleing because it believes it's running cold. Does that tally with your experience?

you deffo need to replace temp sensor it is fecked

Just found this useful info. Clears up what the secondary air pump does, and what activates it. Also confirms in my mind that it is infact totally pointless! Especially if you've removed your cat!!

Anyway, hope someone finds it interesting...

'Secondary air injection system

Operation

Air is injected downstream of the exhaust valves by the secondary air system for up to 100 seconds after a cold start (+5�C�+33�C coolant temperature). This enriches the exhaust gas with oxygen, initiates a post-combustion and thus shortens the heating-up phase of the catalytic converter. Actuation is performed by the Motronic control unit �J220- through the secondary air pump relay �J299- to the secondary air injection valve �N112- (changeover valve) and combination valve. In addition, after each subsequent engine start (up to an engine temperature of max. 96�C), the secondary air system is switched on in the idle speed range for 10 seconds and checked by the self-diagnostics. The lambda control must be active for this purpose.'

This seems to state that the pump will run for a max of 1min40secs initially. Then run for 10secs whenever at idle up until a coolant temp of 96 degrees has been reached, in which period it also runs diagnostics to check it's all working properly. This seems to tally up with what mine does exactly.

Looking back at this it also explains why the pump doesn't run when it's very cold in the winter and the car is stone cold.

Edited 14 October, 201015 yr by Bodge

you deffo need to replace temp sensor it is fecked

Had the chance to test it today whilst hooked up to diagnostic kit. The temperature sender seemed to be working perfectly, and the needle ran the full sweep on the the dash test as expected. With the car standing still and running stable at 90 degrees, switching the aircon on spun both fans up and the temperature read directly from the sender started to drop immediately until it hit 70 degrees about 3 minutes later. At that point the needle had barely moved, so it shows that's just a general guide and not an accurate display. Looks like the thermostat is either sticking or just not opening and closing fully, shall be sorting that in the week.