Noises noises noises!

Mn10 · Post by **Mn10** » 26 Jun 2020, 05:43

Hi all,

I just replaced my MAF sensor with a Bosch refurbished one and while the engine seems to respond better, I am now getting a noise from what seems like the rear of the exhaust. I’m puzzled as to what this could be. (Noise could’ve been there from before and I didn’t realize). The noise kind of sounds like a 2 stroke engine idling and it gets louder as I accelerate.
There’s also a hissing noise from the brake pedal when I press it down all the way. Weird thing is that there’s no noise in the other 90% of pedal activation. The noise is constant and ever since I installed the new sensor, it makes the idle erratic. Again though this is when you press it all the way, up to 90% activation there’s no noise or issues. (Not sure if broke booster or not)

If it helps, there were 3 check engine lights codes before I installed the new MAF sensor.
2-3-2
2-3-1
1-1-3

The double exhaust noise is what worries me.

Thank you.

My car is a 1994 Volvo 940 GLE

Post by **volvolugnut** » 26 Jun 2020, 17:04

Recent rust through on the muffler or other exhaust system?

volvolugnut

lummert · Post by **lummert** » 28 Jun 2020, 18:13

I'd certainly check out that possible vacuum leak caused by the brake booster when pressing the brake pedal.

Mn10 · Post by **Mn10** » 10 Mar 2024, 06:20

Updating this for any future readers who may come across something similar:

I've just realised that I never replied to this, but, @volvolugnut was correct, it was definitely rust in the exhaust. The noise had just happened to show up as soon as I had swapped over the MAF sensor. A new section of piping and all was well.

Edit: The codes popping up were a combination of different issues. Upon further inspection with my mechanic we had figured out that some of the spark plugs were in need of replacement, most of the spark leads were weak and there were possible issues with the fuel pressure regulator and the MAF. Also the brake booster had a slight vacuum leak. After replacing all of that, the car has been running well for about 4 years now. To anyone who has this issue with multiple check engine light codes popping up without much of a cause, I would recommend starting with the spark plug and spark leads and working your way from there. Also If you notice a vacuum leak issue, especially with the brake booster, and you replace it with a working refurbished one, there is a chance that the refurbished one will fail quickly as well (as I learnt during my troubles lol). It has been a few years but if I remember more information, I'll try to update this comment.