Story is, my car now only pulls 12 Hg vacuum at idle and the needle fluctuates ever so slightly. Redid almost my entire engine's vacuum lines, and that failed to solve the problem. Under heavy engine braking I can get it to 17 (what it idled at before), but even when its as warm as it gets it will not pull more then 12 at idle. The idle is perfectly fine, rock solid 800rpm. Could an exhaust leak (I have a largish one) or a leak in my ghetto intake pipe cause low idle vacuum?

As well, this just started a couple days ago, and I can't replicate the problem no matter how hard I try, but sometimes my car seems to lose fuel delivery almost completely sporadically for a second or two at most. At idle, it will stumble but catch again before stalling. At part throttle, it will sputter and buck but eventually smooth out again. Kicking the transmission down to burn up a hill, the car ran fine - totally fine, but just as it transitioned into boost, my blinky AF gauge stayed all the way lean for about two seconds, the car had no power, and then all the sudden it went to rich like it usually does and the car picked up a LOT.

The last problem makes me think my FMU is dying, but that shouldn't affect idle and part throttle when it shouldn't be doing anything.. should it? Fuel lines aren't leaking, put on a new vacuum hose and that did not solve it (even though the old one was loose as hell), fuel pump should be alright now...

DO a compression test. You might have a blown motor.

www.cnnmotorsports.com

Originally posted by extreme97nt
DO a compression test. You might have a blown motor. www.cnnmotorsports.com

holy fuck
I get zero oil coming out of my engine thru my valve cover breather, though, absolutely none, even after that rather stressful leaning out under heavy load (and if a compression test comes up with a low cylinder, doesn't that mean that I should also be pouring oil out this breather?). Car feels perfectly fine now, no odd knocks or tapping sounds or anything. Just drove it for almost two hours just to see if it would mess up again, but it didn't, so I assume that I fixed whatever was wrong, but the vacuum is still low.

Start the car, let it idle and pull the oil dipstick out. Put your finger right up to the opening of the dipstick tube. If you feel large puffs of air, or can see smoke puffs, you cracked a piston ring land. If there is minimal air movement at the dipstick, then do a leakdown test as you may have a leaky valve, a cracked vac line, or some other leak between your TB and the cyl head.

Originally posted by Matt_95tgs
Start the car, let it idle and pull the oil dipstick out. Put your finger right up to the opening of the dipstick tube. If you feel large puffs of air, or can see smoke puffs, you cracked a piston ring land. If there is minimal air movement at the dipstick, then do a leakdown test as you may have a leaky valve, a cracked vac line, or some other leak between your TB and the cyl head.

piston ring lands are fine, just went and checked that. I'll have to learn (and do) a leakdown test tomorrow. timing is a possible culprit too, I'll check that as well.

Originally posted by Matt_95tgs
Start the car, let it idle and pull the oil dipstick out. Put your finger right up to the opening of the dipstick tube. If you feel large puffs of air, or can see smoke puffs, you cracked a piston ring land. If there is minimal air movement at the dipstick, then do a leakdown test as you may have a leaky valve, a cracked vac line, or some other leak between your TB and the cyl head.

Hold on a sec here... are you saying if there's any air at all coming out of the dipstick tube then there's a cracked ringland or leaky valve?

Reason why I'm looking for confirmation is cuz I've not heard of this before, was curious, and checked my own to see for comparison. Granted I've got a nasty gaping hole on my exhaust manifold that's blowing lots of hot air (impairs my ability to detect a tiny airflow out of the tube).

When my car was cold, I turned it on & put it in neutral... cupped my hand around the tube end to block exhaust & tried to tell w/ my finger. From what I can tell, I believe there's a very small bit of air blowing out. It's very difficult to tell for me right now, but it loox like 50/50 that it might be. Definately no large puffs or smoke tho.

What consititues something being wrong? Large puffs & smoke? I'm assuming/hoping so...

I know for a fact that I've got a small leak w/ my my vac lines somewhere... gonna be putting in a vaccum distributor block/manifold in prob ~1 month & redo everything. My car runs & idles perfectly, no knocks or pings, no backfires... everything just as it should be.

Just got my attention here, clarification pleaz?
- J

maybe check your timing for that low vacuum?

Originally posted by BlackMagic
maybe check your timing for that low vacuum?

Yeah if motor is fine check to see if you jumped a tooth on youcrank or cams. That usually leads to an eratic idle.



www.cnnmotorsports.com

Originally posted by extreme97nt

Originally posted by BlackMagic maybe check your timing for that low vacuum?

Yeah if motor is fine check to see if you jumped a tooth on youcrank or cams. That usually leads to an eratic idle. www.cnnmotorsports.com

..and low vacuum if the valves aren't opening/shutting when they're supposed to.


Brian

http://forums.2gnt.com/dcboard.php?az=show_mesg&forum=8&topic_id=91378&mesg_id=91408&page=

My reply in this thread just a bit ago, just want to point out so it doesn't get lost in the middle... clarification?

- J

Originally posted by J
http://forums.2gnt.com/dcboard.php?az=show_mesg&forum=8&topic_id=91378&mesg_id=91408&page= My reply in this thread just a bit ago, just want to point out so it doesn't get lost in the middle... clarification? - J

Did you just post in the same thread a link to your posting in the same thread? A link to a post in the same post?

Lame. :nono

The reason was cuz I did a reply to a message way up above & it put it in the middle, rightly so... it's just that if anyone is like me, they don't read anything up above assuming they've already gone through it.

Yeah, it's lame, but I'd never see it otherwise myself & I was concerned...

Pleaz excuse my lameness, lol
- J

Originally posted by J
The reason was cuz I did a reply to a message way up above & it put it in the middle, rightly so... it's just that if anyone is like me, they don't read anything up above assuming they've already gone through it. Yeah, it's lame, but I'd never see it otherwise myself & I was concerned... Pleaz excuse my lameness, lol - J

lol.

yah dont want to derail this thread but i would also like to see an answer to J's post. I have a tiny bit of air coming out of my oil dipstick at idle. Compression is 220 across the board. no smoke coming out of dipstick but a little bit of air. Just wanted to see if this is a problem or just some windage getting up there from the crank.

A tiny bit of air is normal. Large puffs indicate either pressure escaping the cylinder either past the rings or though the head gasket and into an oil drain. Small air puffs are normal because rings have gaps in them. The larger the puff, the more pressure you have escaping the cylinder. It's just an easy down and dirty way to troubleshoot.

Thanx for the heads up Matt! My head can now rest @ ease.

Good to know!
- J