What does this vacuum mean?

[cp2295]

http://www.youtube.com/watch?v=OETcowMUD6E

I'm thinking ignition related? Don't know. Don't have any vacuum leaks and my compression is good at 130-140psi for all cylinders.

 

[ab_slack]

It seems to me like it is acting pretty normally. I can't comment on the absolute numbers. The gauge suggests at idle it is low but at higher RPMs it sits in the normal range. But are those ranges on the gauge right for your engine? I dunno. And hitting the throttle quickly causes it to plummet, yes that does tend to happen. Is it going too low in that instant? I dunno, but I think in some spots it drops right out.

I guess my question is what problem are you trying to solve? Or is it you see what looks like low vacuum and trying to fix that?

The only thing I can say for certain it means is that the particular vacuum port you had that hooked to sucks. I know, a bad joke, but I couldn't resist.

 

[cp2295]

No I was hooked into the booster, and it isn't steady and is low from what I've read..but maybe I'm just too much of a perfectionist...��

 

[adsm08]

Most engines will produce 15 to 20 inches at idle. Idle vacuum should be higher than part throttle, or WOT.

I would not worry about it apart from your poor idle. Find and fix the idle issue, then re-evalute.

A restricted exhaust will usually produce a gradually decreasing vacuum, settling around 2 to 8 inches.

 

[JP02XLT]

It's a miss, hold a piece of thin cardboard / heavy paper, over the exhaust and you should be able to see it suck the cardboard back into the exhaust as it misses, then try it again as you remove each plug wire, you will have 2 pulses until you find the cylinder with the misfire, then only 1 pulse, that will be the cylinder in question. My guess is either plug, wire, or injector, I dont think it's bad enough to be mechanical (as in a valve) etc.

JP02XLT

 

[cp2295]

It's a miss, hold a piece of thin cardboard / heavy paper, over the exhaust and you should be able to see it suck the cardboard back into the exhaust as it misses, then try it again as you remove each plug wire, you will have 2 pulses until you find the cylinder with the misfire, then only 1 pulse, that will be the cylinder in question. My guess is either plug, wire, or injector, I dont think it's bad enough to be mechanical (as in a valve) etc.

JP02XLT

Yeah it shouldn't be I just rebuilt the engine a year ago! It's just never idled good and I've been wondering for a while now.. Replacing all this stuff and no results! I'll try your trick tomorrow and inform you the results..

 

[cp2295]

Most engines will produce 15 to 20 inches at idle. Idle vacuum should be higher than part throttle, or WOT.

I would not worry about it apart from your poor idle. Find and fix the idle issue, then re-evalute.

A restricted exhaust will usually produce a gradually decreasing vacuum, settling around 2 to 8 inches.

I've been trying to find the issue of the poor idle for a while now..

 

[cp2295]

Just a side note, I did have to install the cmp sensor from scratch as the machinist I sent the block to removed it without marking anything and all I had was a crappy picture to work off of. I followed the Haynes manual in how to put her in but every time it would throw a damn code. The picture had the sensor set at least 45 degrees different than the manual (id say complete opposite, more like 90 degrees). So I just looked at the picture and set it in that way (engine set at tdc of course) and put it in that way and I haven't had a code since I did 9+ months ago.. My question is though could that be throwing my fuel timing off or would I have a code by now?

I looked at TSB 00-24-08, which talks about the faulty ignition coil and my coil falls within the numbers listed. Maybe it's the bad coil causing this?

 

[kimcrwbr1]

It`s a bit low have you changed the PCV lately? Is the timing holding steady and have you checked the timing chain for slop? It should be 17hg or above at an idle and 20+ at higher rpms. plug the PCV with your thumb and see if it improves. Could also be a dirty EGR valve creating a vacuum leak. Are the plugs all the same color nice toasty brown?

 

[cp2295]

It`s a bit low have you changed the PCV lately? Is the timing holding steady and have you checked the timing chain for slop? It should be 17hg or above at an idle and 20+ at higher rpms. plug the PCV with your thumb and see if it improves. Could also be a dirty EGR valve creating a vacuum leak. Are the plugs all the same color nice toasty brown?

Yeah I have plugged the PCv valve and have a new egr valve.. They are actually red, I think from seafoam.. But I ran a vacuum check on my engine before that (a few months) and had the same vacuum and brown plugs, and how do I check slop? It's a new chain and gears. I might've installed it wrong though? On a timing gun I am at 10 degrees when I give it a little throttle. At idle however it's all over the place.. I'll check tomorrow and confirm that though.. (Again it was a few months ago that I did that)

 

[kimcrwbr1]

The best way I found to find a vacuum leak is with a length of vacuum tubing, put one end up to your ear and search around with the other just be careful of moving parts. The closer you get the louder the hissing will be.

 

[cp2295]

The best way I found to find a vacuum leak is with a length of vacuum tubing, put one end up to your ear and search around with the other just be careful of moving parts. The closer you get the louder the hissing will be.

I have no leak, I got a smoke test done and I got no codes

 

[kimcrwbr1]

Maybe you can try adjust the camshaft syncronizer using the vacuum guage ignition timing could very well be the issue try and achieve 18hg at an idle with the engine at normal operating temperature. Just throwing stuff out there

 

[cp2295]

How in the hell could I do that without setting codes!? I hate computers... Why not just a simple old distributor.. I know how to time that!

 

[JP02XLT]

If you have seafoamed it lately I have seen it coat the plugs with a glaze that will cause a miss, Also on the cam sensor the timing could be off just a bit and cause lower vacuum, but not the miss that you seem to have at idle.

JP02XLT