New thread as there's too much old/new info clashing. Need a fresh start.
Problem:
- Lacking performance after AOS change (lacking in low/mid range torque)
- P0491 and P0492 error codes (Secondary Air Injection pump), but the pump is operational
I'm certain it's a vacuum leak.
Here's the chain of events so far:
1. Car was performing perfectly about 2 months ago.
2. Air/Oil Separator failed, bad performance and smokey start up
3. Replaced AOS, all fixed but performance was around 90% - lacking torque and bogging slightly. All pipework
seems to be okay.
4. Replaced MAF, no change.
5. Occasional weird sounding SAI pump on start up, but not all the time
6. P0491 and P0492 stored error codes (SAI ineffective on both banks)
7. Disconnected the pipe to the SAI pump to see if it blows air - it works great and blows incredibly strong, so the pump is fine.
8. Disconnected all pipes and re-connected. Car ran perfectly for a few days, even the codes cleared themselves, then slowly went back to 90% performance and same error codes.
Few things to note:
- P0491 and P0492 codes point to a bad SAI, but both can also be triggered by a vacuum leak.
- Playing with the pipework used to change its performance slightly as mentioned above.
- Since owning the car, whenever the SAI pump used to come on (either cold start or at traffic lights), revving the car used to cause pops and crackles due to the extra air. This no longer happens since I've been having problems.
- Starting the car on a cold start no longer gives its normal higher revs which slowly settle. Instead the revs instantly rest on around 700rpm, even on a cold start, as if the engine was warm.
- I've tried spraying different engine areas with carb cleaner but it makes no difference to the revs.
- I've just tried to remove the oil cap while the engine was running to see if it made a difference. It does, and the engine starts to splutter, but there's a very loud hiss sound that comes out of the engine bay, and
not the filler cap when it's removed. See video here:
https://www.youtube.com/watch?v=tgSXwZ-nVpk
Should I hear this coming from the engine? Maybe it's coming from a split or crack, or perhaps it's normal? Ignore the blue tape on the valve, that's me wondering if air was escaping it.
Guys you've been amazing so far, but I still need as much help as I can. I'm running out of patience with this car very fast.
Thanks
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