Boost/Idle issue

[le mans]

Result!

[ash2050]

I had this intermittent boost issue where the car used to go in limp mode and wouldn’t boost above 0.3 bar.

Under continuous boost in 3rd/4th gear, it would cut fuel and throw you back in your seat.

After checking numerous things from wastegate, n75,boost leaks etc, it turned out to be the rubber vac hose from the inlet manifold which connects to the plastic green vac hose through bulk head - going to the ecu to the MAP sensor.

It was totally crushed (see pic)

Replaced the short hose and no more boost problems!

[yeet-brick]

Soo update time. Ive been doing a large number of things to the car including a new timing belt kit and billet cog and more boost leak testing. Ive found no more obvious leaks and for the first few minutes of driving i get up to 16-17psi but once the car warms up and i come to a stop and go again, back to only 5psi. I suspected an issue with my tps since my idle was funky and sure enough there is no continuity between pins 4 & 6 and no audible clicking when opening the throttle slightly. Could my boost issue possibly be related to a bad tps, or will that only address my idle problem?
Also i spoke briefly with Marc @EFI and showed him the codes I got and he claims a vacuum leak could most likely be the culprit of my boost issue since i have both the lambda control limit not reached and maf codes, causing the ecu to go into limp mode when dealing with boost. Might just take it to him to have him do a smoke test
codes.PNG

[psiconauta911]

Maybe your wastegate as to much shaft play and doesn´t seal and doesn´t hold boost! Maybe that is why it was removed!

Had that problem!

[newsh]

Disconnect the N75 and run the car to see if it makes any difference.

With engine idling. Put your hand on the N75 (if you can reach it) and blip the throttle, can you feel it vibrating?

Make sure the vac line is connected to the ECU and there are no leaks in it. Best to test with a mightyvac from the engine bay.

Disconnect the MFTS and see if you get your boost back, URS doesn’t normally restrict boost when this sensor goes wrong but who knows..

[yeet-brick]

Good news, the new hose fixed the revving issue and the idle surging, bad news I now get no more than 5 lbs of boost on full tilt. Ive pretty much ruled out any possible other boost leaks so maybe a bad N75?

[newsh]

If there are no leaks the inlet tract will hold 1Bar for 30 seconds or so, maybe more.
There will be a little air getting past valves and piston rings obviously so it won’t hold indefinitely.
With a big leak like that you will get no pressure at all.
It’s worth disconnecting the breather system from the MAF hose when you do the test to rule out problems with the one way valve under the IM.

[LSG]

I'm surprised the smoke test and pressure test did not point you to this although happy you have got to the bottom off the problem with the car. Now its out for a . Best wishes Lynn

[SteveH]

That's certainly going to cause a massive boost leak!

[yeet-brick]

Unless a different turbo with a built in WG like a K04 has been fitted?

No its got the stock K24, po took off WG thinking it was stuck open. And i sure hope its still good, guess we'll find out once the crossover pipe gets replaced

[yeet-brick]

Thanks for the responses everyone, I did indeed find quite a large boost leak coming from a couple of tears in the crossover pipe. One was only visible from under the car and the other under a clamp. Grabbing one from a junkyard tomorrow, wish me luck!
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[newsh]

Unless a different turbo with a built in WG like a K04 has been fitted?

[newsh]

If the car had been run without a wastegate I’d be looking to see if the turbo is still functioning!

[SteveH]

Certainly sounds like the classic symptoms of a boost leak.

[add]

You really need to do a proper leak test by pressurizing the inlet tract with compressed air and spraying soapy water on all the boost hoses etc
Search the forum,there is a how to thread somewhere
Also nice going getting a running urs for $1500!!