Holden VR v6 - vacumm testing for unsmooth idle

Post by **vlad01** » Tue Dec 19, 2023 8:42 pm

Have you got a pressure gauge you can hook into the fuel line?

If so, what reading are you getting with and without the vac line?

Pete30nz · Post by **Pete30nz** » Sat Dec 23, 2023 1:50 pm

Hi Vlad,

This is with the engine running. Sitting about 3 bar, 43.5 psi. The needle is bouncing a little.

Post by **vlad01** » Sat Dec 23, 2023 2:03 pm

Is that with the vac line connected and the engine running?

From my calc, you should see about 43psi running without the line. About 33 psi with the line and running.

Pete30nz · Post by **Pete30nz** » Sat Dec 23, 2023 2:08 pm

That sounds about 10psi difference with or with out the vac line on the regulator.

Maybe that's the issue?

Seems to start ok at first
I did see a iac code, and at some point a vac error code.

But I'd have to check that again for codes stored

Pete30nz · Post by **Pete30nz** » Sat Dec 23, 2023 2:09 pm

vlad01 wrote:Is that with the vac line connected and the engine running?

From my calc, you should see about 43psi running without the line. About 33 psi with the line and running.

Yes with engine running and vac line connected

Post by **vlad01** » Sat Dec 23, 2023 2:20 pm

If its not dropping at idle with the vac line connected, then it will be over fueling it, making it run like shite.

Pete30nz · Post by **Pete30nz** » Sat Dec 23, 2023 2:37 pm

Ok, some good learning here for me.
So, do the injectors get 43.5psi at first start, then it gets regulated to 33 odd psi afterwards?

Could I adjust it to 33 psi manually, to see how it acts?

Post by **vlad01** » Sat Dec 23, 2023 3:24 pm

Yes, as soon as the engine fires the vac will pull the fuel pressure down some 10ish psi assuming a vac of 30kpa these engines normally idle at once warmed up.

It will only see the full 43.5 psi at WOT or blipping the throttle deeply.

I suppose adjusting the reg could help you see and confirm things.

Pete30nz · Post by **Pete30nz** » Sat Dec 23, 2023 3:46 pm

Also, is there a way to use a vacumm bleeder to hook to the reg vac port to act as vacumm.

Pete30nz · Post by **Pete30nz** » Sun Dec 24, 2023 12:18 pm

Hi

I've adjusted the fuel pressure reg while engine is idling.
It's now adjusted to the suggested pressure about 34psi running.

I think there's still some issue, maybe vacumm or idle air control related? Idle seems to do the wave every now and again (idle up and back again).

Will take a screen shot or live data shortly.

Pete

Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle

Re: Holden VR v6 - vacumm testing for unsmooth idle