boost gauge fluxuates

[hydrastas]

i just installed a boost gauge finally, i've yet to figure out my weird idle problem but at idle the vac on my gauge bounces so rapid between -6 to -10 psi that it's blurry? after reving it up and letting off it will read -18ish like normal though... on the positive side i went WOT and it said my boost was only 5? should i check for boost leaks before i go and try to set my mbc to 15 psi on this gauge?

 

[r1991_4g63t]

you should be reading a steady 17-20 inches of vacuum at idle, sounds like you might have a timing issue? i wouldnt turn it up past 12 unless you have the mods to back it up

 

[hydrastas]

i checked the timing a few weeks ago and it was either perfect or 5 off . i plugged in my vacuum pump where the boost gauge is and it has the exact reading so im pretty confident the gauge is working. would a boost leak be the cause if im only getting 5 psi?

 

[r1991_4g63t]

you need to check the timing marks on the timing belt. i wouldnt even try to make boost til you figure out why you have such low vacuum

 

[hydrastas]

i ended up installing my mbc and seeing no change in my boost. turned it like it said(1/4 turn at a time) a few times and eventually cranked it to all the way tight after no changes were seen. my boost never changed from 5 psi except for the shift between 2nd and 3rd, the psi would jump up to 7 and go right back to 5. it stays at 5 psi between 3k-6k rpm range. as for the timing, even if it was off how long would it take to change it seeing as how i have a 95' car and the sensor isn't on the left side.

 

[r1991_4g63t]

your not understanding what im saying. not the timing as you would check it with a timing light. you need to pull the timing cover off and check to make sure all your marks are lined up. DO NOT try to make boost until you figure out why your vacuum is so low.

 

[snowborder714]

Where are you getting the source for your boost gauge?
How do you have your mbc hooked up?
Do a boost leak test.

 

[hydrastas]

k i tried lining up the timing marks and it seems it's off 2 teeth or so. i've got my boost gauge on my fpr line and mbc is hooked up with nipple opposite bleeder hole on the wastegate and the straight one on the turbo itself. is it a big pita to readjust the timing belt?

alright this is what im looking at, im not familiar with the terms but is this off 2 teeth?

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[snowborder714]

What marks did you line up and which marks do you think are off by 2 teeth?

It's not a big PITA, but it's not an easy, hour project. I just did mine this past week and what took the most time was compressing the tensioner using a bench vise and making sure the tensioner was installed correctly. Just follow the VFAQ (and other tech articles) and you should be fine. And when you think you have the belt installed correctly, before you pull the pin, check over your timing marks a bunch of times and make sure everything's lined up.

You need to line up both of those marks. Put them directly in line. You'll have to rotate the engine clockwise pretty much the whole way around. The dowel pins on the cam gears need to be in the 12 o'clock position and you need to line up both of those marks. Then you take a straight edge and see if those marks line up with the head (look for the gasket line behind the cam gears).

 

[hydrastas]

i tried getting both the dowels in the 12 a'clock position but the exaust one goes up to 12 and the intake one is more at 1 a'clock, i can't seem to line them up.

i managed to come across another thread stating

You mentioned that your engine and ignition timing have been verified. Have you also checked that the timing marks on your intake and exhaust camshaft sprockets line up perfectly at top-dead-center for cylinder #1? I had a timing belt replaced some time ago and had a lopey idle and lower-than-normal vacuum following the belt change. It turned out that the intake camshaft was off by a single tooth (exhaust camshaft was OK). After having this problem corrected, the idle returned to normal and my vacuum at idle also returned to normal.

would this be similar to my issue regarding the intake cs being at 1 o'clock?

 

[snowborder714]

i tried getting both the dowels in the 12 a'clock position but the exaust one goes up to 12 and the intake one is more at 1 a'clock, i can't seem to line them up.

Put the intake cam dowel pin at 12 o'clock. Once you do this, the exhaust dowel pin should be a little past 12 o'clock (inwards towards the intake cam).

Here's a good read to explain some of the timing stuff. Specifically post #48 will explain why the dowel pins won't both be at 12 o'clock. The way he typed it may be way over your head (as it was for me until someone else explained it), but it's basically saying hey offset the exhaust cam from the factory 3* while the intake cam is straight up:
http://www.dsmtuners.com/forums/cylinder-head-short-block/301391-resolved-my-timing-off.html

 

[r1991_4g63t]

i managed to come across another thread stating



would this be similar to my issue regarding the intake cs being at 1 o'clock?

YES this is what i was thinkin had happened, once you change the belt and get it set right, along with the 2 lower marks on the crank and oil pump, your car should idle around 17-20inches of vacuum. and then yyou should be able to creat boost. but still wouldnt go over 12 until you get other stuff done, your car wont like it trust. i did it wednesday and my car doesnt like anything over that

 

[hydrastas]

tomorrow im going to spend all day adjusting this thing, the belt still looks to be in good shape though. the engines had 45k miles on it, it'd prob be best to just replace it now but i'll just get the experience in doing it this time and at 60k i'll just do it again.

wow it's like i have a different car, no more shaking and idle problems. vacuum holds right at 19 at idle now and when i put it in gear the rpms are nice and smooth. only problem i've ran across is that my fpr solenoid hose going to my intake blows off when i make boost. is it ok to hook up a mbc with the bleeder side going to the wastegate and the other end going to the other nipple on the turbo that the bcs used the two on a t?