99 S70 GLT Engine B5254T [Vacuum leaks, hoses, Snorkel] Topic is solved

Post by **Chuck W** » 09 Jan 2025, 09:22

Grantkat wrote: 09 Jan 2025, 05:38 I will rent a fuel gauge set up and test the fuel pressure.

Another question - any idea about why the engine was chugging and "dieseling". That seems beyond a fuel delivery issue?

If it's getting starved for fuel, it'll act like this and give you no throttle response. It will also come back all at once when the system repressurizes.

As mentioned above, I also forgot about the DBW system in the 99-00 P80s. Those could cause some issues like you're seeing if you've got a buggy unit that's giving irregular readings.

Post by **Grantkat** » 09 Jan 2025, 11:45

Hi Caesium,

can you please explain what a sweep test is and how its performed?

Post by **Grantkat** » 09 Jan 2025, 11:59

quick update. I rented a fuel pressure test kit unfortunately it did not have the correct size adaptor for the schrader valve on the S70. So I used a tire gauge.

I released the pressure at the valve, turned the key to on 2 times without starting and got 20 PSI.
I repeated the test and got 20 PSI

Post by **Grantkat** » 09 Jan 2025, 12:12

just tested running - 55+ PSI at idle.

Post by **abscate** » 09 Jan 2025, 12:56

Grantkat wrote: 09 Jan 2025, 12:12 just tested running - 55+ PSI at idle.

That looks good.

Post by **Grantkat** » 09 Jan 2025, 15:34

Ok so I have eliminated the fuel pump and fuel pump relay.

So what to look for next?

Also - question: I double checked by vacuum lines to make sure all were in place and secure, I also checked all the connectors MAF etc to make sure no sensor was disconnected or loose. While doing this I noticed something:
There is a pipe from the air filter box going to the back of the engine and down. I cannot see where it connects as there are things in the way, but where ever it connects back there it is loose ie can be jiggled/moved - is that normal?

Post by **Sveedy** » 09 Jan 2025, 16:03

That pipe goes down to your turbo. It is secured, or should be, with a hose clamp. If it is loose, then unmetered air is getting into the system.
No bueno...

Post by **Grantkat** » 09 Jan 2025, 16:25

ah ok thank you. I will get under the car and see what gives

Post by **Grantkat** » 09 Jan 2025, 16:26

can it be accessed from underneath?

Post by **Chuck W** » 09 Jan 2025, 17:57

Grantkat wrote: 09 Jan 2025, 15:34 Ok so I have eliminated the fuel pump---

Not necessarily.
If you're not monitoring FP while driving, you really haven't ruled it out. It could idle for hours and not skip a beat. It's a PITA, but you need to see what it does when the engine acts up.

It was also mentioned to investigate the electronic throttle.