Vacuum hose


I’m suffering some problems wth my VHPD engine. I posted a question about the bad emissions and i checked all the answers without any improvement.
I just checked the vacuum hose by taking it off but nothing happens, hose on/off or even suck on it or blow in it, the revs don’t change.
Does anybody know what should happen if i pull the hose off ? Should the revs come up or go down (i thought the revs should go down and the engine off). And if what can be the problem ?

I was at Wouter’s place playing around with the vacuum hose to see what happens. I’ve started blocking the hose (which on a normal K with a MEMS means it really idles bad (limping) or even dies. On Wouters car… no effect at all.

Then I pulled the hose from the vacuum resevoir (on the ECU side). Nothing happened. Blocked the hose, no reaction. Put pressure on the hose, sucked on the hose… no reaction.

I assume the internal pressure sensor in the ECU has gone awol, but it would be nice to be able to test this…

Could someone with a K-series powered Exige be so kind to block the hose (just by folding and pressing it) and let us know if there’s a reaction in terms of bad idling or something like that?

Which part of the vacuum hose are you playing with? If it’s the part that goes dirctly to or away from the vacuum reservoir then doesn’t it just serve the intake resonator valve and so will have not effect on idle?

Which is the right one to check if the vacuum works fine ?


I’ve played with both ends (the engine end and the part running from the resevoir to the ECU. No reaction from whatever end.

It should change, a lot.
To me, you’ve had a leak for a long time in your vacuum system, but the revs have been stabilized some other way, and now when you remove/plug the hose nothing happens because you still have another leak.

In my VHPD I noticed the routing of the hoses was poor and they were rubbing and wore through in some places, sending my revs all over the place.
Suggest you check all the vacuum hoses one by one.

Got to get used to this software… Constantly writing replies, never post them due to this preview thingy… arghh…

Anyway, I’ve disconnected the vacuum hose running from the ECU to the resevoir. AFIAK, that’s one single part.
It seems connected at the other side as I have put pressure on it and have sucked on it. There’s no reaction from the ECU, so either this hose is completely blocked or the pressure sensor inside the ECU is fooked I’d say.

We’ll pull the passenger seat out to gain access to the ECU and have a look there…

Thanks for letting us know

AFAIK the MAP sensor is external to the ECU on the Exige and 340R, it is mounted on one of the upper chassis rails on the gearbox side of the engine bay.



I finally found the MAP sensor, i putted in new spark plugs and cables. After that the revs stabilized about 20 seconds on 1500 and after that down to 1200.
As i took the vacuum hose of from the inlet of cylinder no 4 the revs went immediately down to 1200 even after i turned the revs up to 4000. Still don’t know what wrong with the vacuum.

Sorry I can’t be of more assistance - I’m not really sure I fully understand your problem?

THX Steve, i’m going for an Emerald now and hope te solve the problem with that investment.