vacum drop off

[gotrice?]

okay on the weekend i was sitting in my car just letting it idle abit when i noticed the boost gauge(factory standard one) would sit at the 9-10o'clock postition then every so often just drop to the maxumam vacume postition. but the engine didn't change at all.
any ideas?
faulty boost gauge?

[AB]

Possibly dodgy electrical connections between the boost sensor, ecu and dash. Could also be something gumming up the vac line to the boost sensor, although I don't remember if that needs a signal to give the readout on the dash or not.

Either way, the factory dash guage does not actually give a read out of the boost/vac level, it is just what the ecu thinks the pressure is, that is why you wont notice any difference to the idle, because nothing is changing engine wise.

[Cordzboy]

My experience with this problem is that it's caused by crap in the pressure sensor on the PCB inside the case. Pull it apart, get a can of electronic spray cleaner stuff, and squirt :D

[Junkers]

I think AB is closest, If it were anything restricting or leaking in the vac line or sensor it would give poor readouts of around the 11oclock or so postion, most likely electrical IMHO.

[gotrice?]

11 o'clock vac at idle is normal isn't it?

[AB]

I duno about you Starion guys but my stock Cordia vac guage points down at idle, pointing at 11oclock would be almost straight up, about where it is at max boost, although that is more the 1oclock position, so your gauge must face the other way, my needle is pointing to the right.

[Junkers]

11 o'clock vac at idle is normal isn't it?

No thats a bit off target, most starions I've seen sit between 8.5 oclock and 9.5 oclock, If i were you I'd replace the pipe and then look at a new map sensor or at least check the connections.

[Abalistic]

A very badly leaking brake booster can make the vacuum gauge change.
As you put your foot on the brake vacuum is lost thru the booster.
It can even make the engine run rough if you pump the pedal, as mind did.
A.

[whitie]

I also have a similar issue to what gotrice? stated.

Just recently the boost meter on the dash has been starting at normal and then randomly moving all the way to maximum. It doesnt seem to do it all the time and it does seem to do it more when I brake- which seems weird. I have an external boost meter which seems to indicate that nothing is wrong.

Also, about two weeks back my oil pressure guage on the dash stopped working, could these two symptoms be related?

What steps should I take to rectify this problem? If you could put them in simple form that would be great as Im not super car savvy...

[Junkers]

What do you mean by maximum? so it's pointing at 12 o clock or right over into the red.. as if it were boosting?

[SpidersWeb]

If the vac needle is reliably flicking between the same vac values at idle, and its in time with the engine beat, my book says compression is munted in that cylinder. e.g. if it drops at idle every 4th beat.

If it just does it every once and a while, then Id vote for electrical or a failing vac component.

[whitie]

What do you mean by maximum? so it's pointing at 12 o clock or right over into the red.. as if it were boosting?

A little. Its more like it just slowly makes its way all the way to the right hand side of the dial the same way a temperature guage slowly gets hotter and it just settles there for a while like its not working then works then doesnt- very intermittent.

[Junkers]

My money is on electrical for obvious reasons, I'd think more along the lines of your actual map sensor being stuffed.
If it were the wiring I'd look for tremors in the gauge or fast direct movements vs the arm moving slowly across the gauge face like yours does.

My first step to recommend would be to replace the map sensor or go for a drive with the vaccum line that goes to your map sensor disconnected and blocked, see if it still has the same character.

[whitie]

My money is on electrical for obvious reasons, I'd think more along the lines of your actual map sensor being stuffed.
If it were the wiring I'd look for tremors in the gauge or fast direct movements vs the arm moving slowly across the gauge face like yours does.

My first step to recommend would be to replace the map sensor or go for a drive with the vaccum line that goes to your map sensor disconnected and blocked, see if it still has the same character.

Thanks for that info. The guage does move around wildly, up and down as well as resting all the way to the right hand side (more often than not when I break for some weird reason) plus its not even all the time it stuffs up, about 1 in every 2 or 3 trips- sorry its kind of hard to fully describe something like this eh? :) Anyway with my oil pressure guage stopping working also, do you think they could possibly be related as if so, what would be the cause?

Finally, if its just a map sensor, how much do they run at cost wise (australian $). Can you get them second hand? (should you get them 2nd hand?)

I appreciate your help.

[Junkers]

Don't think it's related to your oil pressure gauge problem, do you know where your oil pressure sensor wire is located?

My old map sensor used to do exactly that, violently move round except after a minute it would die, you can't buy new map sensors you'll have to find one from a wrecked starion, they pretty much plug in so it's something you can easily do yourself.