am i getting false vacuum reading?

94talonawd · 10-16-2005

ok. here is the problem.
my car has bad vacuum at idle. note that my car does have an idle surge. the idle surge isnt bad, i dont even think it is idle surge. i just hear misfiring and my rpm moves around 700-900 rpm at idle. i tapped the boost gauge line to the fuel pressure line. when im at idle my vacuum reads like at 3-4. when im at idle reving the car to like 1,500 rpm, my vacuum will go to 15. i tried tapping the boost gauge to the p port on my tb, and it was even worse. i was getting 0 vacuum at idle. when i drive the car around the vacuum is pretty good. its only bad at idle. what are my vacuum readings supposto be? could i be having a vacuum leak somewhere? i did a boost leak test and i was only hearing a very little leak coming somewhere from the intake manifold or tb. if i have a vacuum leak will it cause my car to idle poorly?

TheBlizzard · 10-16-2005

First of all, start using the fucking shift key so we can tell where your sentences start and end.

For your question:

Have you done anything with your timing lately? If your timing is off that will cause low vacuum at idle.

Jakey · 10-16-2005

What kind of car?

94talonawd · 10-16-2005

sorry. Well it is for a 1g TSi AWD. When I first bought the car, the timing on the crank pulley was set advanced like around 20 degrees. When i took it home i set the base timing back to 5 degrees. I dont know if any of the teeth might have skipped. I was guessing that might be the problem. I was also going to replace the Intake manifold Gasket because i thought that it was leaking from there, but it looked pretty hard to take off so i had decided to ask you guys to see if there was any other problems i should also look into. I am pretty sure it isnt the intake manifold leaking, im pretty sure my timing has skipped some tooth. What would be the easiest way to check if my timing skipped a teeth?

TheBlizzard · 10-16-2005

Check it. Line up the mark on the crank pulley and see how many teeth its off. Pretty simple.

EclipseGST · 10-16-2005

Put the #1 piston to TDC as marked on the crank plate, also take out the spark plug to make sure, if the marks on the cam gears line up with the dowel pins pointed up then you are fine. 1 tooth is quite noticable when checking.

Outlaw1 · 10-17-2005

Quote:

Originally Posted by TheBlizzard

First of all, start using the fucking shift key so we can tell where your sentences start and end.

For your question:

Have you done anything with your timing lately? If your timing is off that will cause low vacuum at idle.

That's hilarious.

Now for the question. You should see somewhere in the area of ~15in/hg at an idle. Make sure the line on your vacuum guage isn't pinched. With 3in/hg I'd expect the car to idle like crap.