I did a vacuum manifold test and need some help
08-16-2009, 03:00 PM
#1
Registered User
Thread Starter
Join Date: Jul 2008
Location: GA
Posts: 1,062
Likes: 0
Received 0 Likes
on
0 Posts
I did a vacuum manifold test and need some help
.............
Last edited by buckz6319; 05-21-2010 at 02:17 AM. Reason: deleted first video and and did a redo of the vacuum test which is much better
08-16-2009, 03:18 PM
#2
Registered User
Join Date: Aug 2005
Posts: 183
Likes: 0
Received 0 Likes
on
0 Posts
Could be a leaky valve or weak valve spring,but it seems to hold steady for a little while?I would check plugs and wires and all vac hoses before anything,then do a leakdown test.Good luck
08-16-2009, 07:01 PM
#4
Registered User
Join Date: Mar 2008
Location: Temecula Valley, CA
Posts: 12,723
Likes: 0
Received 4 Likes
on
4 Posts
Overall, your vacuum is really good. 20" is almost too good to be believed. You're valve clearances are all within spec?
I did see the gauge shift slightly from just below 20 to just above 20 and back periodically. I'll look at the video a few more times and try to come up with something.
... now, at right about 2:45-2:50 in to the video, the needle starts jumping around sporadically. That is an indication something odd is going on. I would suggest using a timing light with the gauge and find the cylinder that is firing or misfiring when the gauge flicks around like that- (point the timing light at the gauge).
I did see the gauge shift slightly from just below 20 to just above 20 and back periodically. I'll look at the video a few more times and try to come up with something.
... now, at right about 2:45-2:50 in to the video, the needle starts jumping around sporadically. That is an indication something odd is going on. I would suggest using a timing light with the gauge and find the cylinder that is firing or misfiring when the gauge flicks around like that- (point the timing light at the gauge).
Last edited by abecedarian; 08-16-2009 at 07:03 PM.
08-23-2009, 04:57 PM
#7
Registered User
Join Date: Mar 2008
Location: Temecula Valley, CA
Posts: 12,723
Likes: 0
Received 4 Likes
on
4 Posts
the point of using the light on the gauge is not specifically to find a misfire but to find which cylinder is firing when the gauge deflects. Knowing which cylinder just sparked can help us time which cylinder is firing, which is opening an intake valve, which is opening an exhaust valve, etc.
Make sense?
Make sense?
Trending Topics
08-23-2009, 05:21 PM
#9
Registered User
Join Date: Mar 2008
Location: Temecula Valley, CA
Posts: 12,723
Likes: 0
Received 4 Likes
on
4 Posts
what I'm getting at is that if you see the vacuum gauge flick down when #4 cylinder fires, it could be the intake valve on #4 (but not likely), or more likely, #2's intake valve isn't closing properly, since #2 follows #4 in the firing order (1-3-4-2), or #1 intake valve isn't opening at the right time.
That is not absolute gospel, but when you can relate something (a drop in vacuum) to a known event (spark plug firing) you are able to narrow things down: what is happening at the same time #4 plug is firing, and which of those can affect vacuum?
That is not absolute gospel, but when you can relate something (a drop in vacuum) to a known event (spark plug firing) you are able to narrow things down: what is happening at the same time #4 plug is firing, and which of those can affect vacuum?
Last edited by abecedarian; 08-23-2009 at 05:22 PM.
08-23-2009, 05:33 PM
#10
Registered User
Join Date: Aug 2009
Location: ST. Louis
Posts: 80
Likes: 0
Received 0 Likes
on
0 Posts
95 4runner 3.0 auto 183,+ miles...if you know how to read a vacuum gauge please watch the video and give me some advice on what my engine is doing
...This is the second time(first time was a little misleading) I've ever used one of these
help with misfire....any advice will be appreciated
[youtube]-7SArE6s5rA[/youtube]
I did a redo because I don't think the first test went vary well
...This is the second time(first time was a little misleading) I've ever used one of these help with misfire....any advice will be appreciated
[youtube]-7SArE6s5rA[/youtube]
I did a redo because I don't think the first test went vary well
Thread
Thread Starter
Forum
Replies
Last Post
Blamalam
86-95 Trucks & 4Runners
22
03-12-2022 07:34 AM
justdifferentials
Just Differentials
1
09-17-2015 06:14 PM
