Secondary runners opening early

[rendyx]

Here's an odd observation about the runners:

When we snap the throttle open, we can see the runners start to open. Now, they may open only part way, and then close. In other words, they open gradually, not all at once. Also, they seem to open more around 3200RPMs, if you start from idle. If you hold the RPMs at about 2000, then snap the throttle, they don't open right away (they open about when they should normally). Any thoughts?

 

[93EmeraldMTX]

make sure the wire is hooked up on the back of the engine by the vacumn canister.

 

[jthomas68]

They don`t "snap" open quickly as if spring loaded,they do somewhat open gradually,so what you`re seeing may be normal.But,if you do think they are opening too early,i`d look into a vacuum leak.They are held closed with vacuum,if it`s leaking,they may not stay closed properly.

 

[rendyx]

The problem is that if the throttle is pushed briefly while keeping the rpm under 4000, the runners open up and then close. We just finished replacing the vacuum lines, so I am pretty sure that is not problem.

YamahaSHO

 

[AutoSHO]

rendyx:
The problem is that if the throttle is pushed briefly while keeping the rpm under 4000, the runners open up and then close. We just finished replacing the vacuum lines, so I am pretty sure that is not problem.

YamahaSHO

Sounds like the vacuum canister on the back of the intake is leaking, or one of the diaphragms in the actuators is torn, and creating a vacuum leak.

 

[rendyx]

I did notice that when the vacuum canister is shaken, it rattles. So would this be a sign of failure of that part?

 

[AutoSHO]

rendyx:
I did notice that when the vacuum canister is shaken, it rattles. So would this be a sign of failure of that part?

Sounds like something internal might be broken. Do you have a spare intake around, or access to someone else's car? You could swap it to see if it fixes it.

*walks out to see if his vacuum canister rattles*

 

[AutoSHO]

AutoSHO:

*walks out to see if his vacuum canister rattles*

Nope, no rattles. Sounds like your problem.

 

[srfdude]

rendyx:
Here's an odd observation about the runners:

When we snap the throttle open, we can see the runners start to open. Now, they may open only part way, and then close.

LOL, not old enough to remember vacuum windshield wipers, eh? When you went up a hill the wipers stopped. When you snap open the throttle, the vacuum naturally drops drastically, and if the reservoir isn't big enough to take up the slack, vacuum-controlled servos, etc. will momentarily operate.
Mike

 

[Trojan Man]

Hey Pat,
When I was putting my upper end back together a few months ago, I seem to remember my secondaries doing the same exact thing when I was playing around with them. If they only open briefly and then close, I wouldn't worry about it too much.


BTW, I fixed my clutch today and added some Sycromesh... WOOOHOOO!