Idle vacuum pressure

smagnotta

SuprSal
Apr 5, 2005
202
0
0
WashPa
Just wondering what my boost controller should have as a vacuum value when the car is idling? It looks like around 16.5 (a little past the 16 hash mark). Is this normal? Why I am asking is the car idles a bit rough (misses).

Thanks,
Sal
 

mkIIIman089

Supramania Contributor
Mar 30, 2005
3,061
0
36
Ohio
Thats on the low side of normal IIRC. It might be more accurate to get a mechanical vacuum guage thats more accurate to check for sipping or spiking... that will tell you if there is a problem with many things. http://cygnusx1.net/supra/techtips.html go to the vacuum reading thing and it talks all about this.
 

smagnotta

SuprSal
Apr 5, 2005
202
0
0
WashPa
Thanks for the link. From what I saw it could be late ignition timing. Looks like the one thing I didn't check could be it...
 

supra_dre

New Member
Apr 1, 2005
14
0
0
not sure if i'm on the right subject, but my Profec B II reads around -80 (-8) psi at idle.
 

smagnotta

SuprSal
Apr 5, 2005
202
0
0
WashPa
I thought I should be around 20. Oh well at least it is steady at 16.5 and does not fluctuate. Looks like I need to see if the valve timing and ignition timing are OK. The car has 121,000 miles and the timing belt was changed by the previous owner at 75,000 miles. Maybe I will replace that too since I am in there checking the timing...

I have taken this car apart so many times... :p
 

Idealsupra

Supramania Contributor
Mar 31, 2005
2,390
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Orlando
www.tampabaysupras.com
smagnotta said:
I thought I should be around 20. Oh well at least it is steady at 16.5 and does not fluctuate. Looks like I need to see if the valve timing and ignition timing are OK. The car has 121,000 miles and the timing belt was changed by the previous owner at 75,000 miles. Maybe I will replace that too since I am in there checking the timing...

I have taken this car apart so many times... :p


16 isnt that bad...do you ever look at it after you drive for a bit? mine is usually around 15-17 until it warms up and then it idles around 20-22...

timing could cause a low vacuum but 16 isnt that bad really...
 

flubyux2

Madd Tyte JDM yo ®
Apr 2, 2005
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st. pete, fl
www.myspace.com
what, knowing that metric vaccum readings arent important???

no one else mentioned that average vaccum is 500mm/hg. i figured thats useful information for those of us running a Metric boost guage... like anyone w/ a Defi, HKS or GReddy... you know.
 
flubyux2 said:
what, knowing that metric vaccum readings arent important???

no one else mentioned that average vaccum is 500mm/hg. i figured thats useful information for those of us running a Metric boost guage... like anyone w/ a Defi, HKS or GReddy... you know.

I don't think he knew you were being serious, he probably thought you were trying to be funny or something...
 

flubyux2

Madd Tyte JDM yo ®
Apr 2, 2005
1,019
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st. pete, fl
www.myspace.com
lol. cmon guys, i always try to be funny!

i typically dont postwhore to post whore... i make ita point to say something constructive even if the main basis of my reply is off-topic... like when i make fun of Jayson for being jewish or something like that.

but anyways, 500mm/hg is about average for good vaccuum. alot of times, it can fluctuate either way by 50mm/hg depending on idle speed, isc steppery or timing.