Intake Air Control (the 3500rpm one) causing rough running?

[drummerwill]

So for the past few months I had been suffering from this random engine bogging and backfiring under acceleration. It seems its not uncommon on this forum, although I fixed the problem by replacing my IAC assembly, not replacing the usual things. Which is why I'm curious about it.

I found that a vacuum line on the solenoid (that comes from the chamber it's mounted to) had broken off. So I went to the junkyard and got a new one for $25. I put it in and it seems to have fixed the problem. But after some more research into the matter it appears that piece is not exactly necessary when an aftermarket intake is installed.

Which brings me to the situation: I went and unplugged the solenoid yesterday and the engine began to act up once again. So I pulled the vacuum line that connects it to the manifold(?) and capped it. But that actually made it worse! So I hooked it all back up and everything is fine again.

But the mystery still remains for me as to why a "noise suppressor" for a stock intake is causing my motor to run rough even though I have a short ram. I'm open to any thoughts on the matter. Though I've already ruled out the possibility of a mouse living in my motor just F"ing with me for fun.

[Accrdwgnguy]

Well a vacuum leak is going to give you issues no matter what

[deevergote]

Right. Just plug that vacuum port. It's not the lack of sensor, just the open vacuum port that's causing the issue.

[drummerwill]

I was figuring it would, thats why I initially replaced it. But when i capped the vacuum line later on it went back to the same old... Although I'm not sure plugging the line with a #12 sheetmetal screw and wrapping it in hot pink ducttape really keeps the line from leaking.

[deevergote]

I've plugged lines that way!
Well, minus the pink tape...

[drummerwill]

I'm glad to know I'm not alone with putting a screw in the end of the line. haha...

Is there a better way to go about capping it though? Maybe i'll just get a compression cap from the plumbing section at work and try that.

[Fleetw00d]

So I pulled the vacuum line that connects it to the manifold(?) and capped it. But that actually made it worse! So I hooked it all back up and everything is fine again.

But the mystery still remains for me as to why a "noise suppressor" for a stock intake is causing my motor to run rough even though I have a short ram. I'm open to any thoughts on the matter. Though I've already ruled out the possibility of a mouse living in my motor just F"ing with me for fun.

Just to be sure, what exactly did you cap? Did you pull the line from the solenoid and plug the line, or pull the line from the manifold (throttle body) and plug the line, or plug the port on the manifold? As long as you plug the vacuum (I've done it on my 90 LX and 93 EX, 93 LX's didn't have this setup) the control doesn't know it (there is no sensor to verify that the solenoid actuates) and it shouldn't affect how the engine runs.

[drummerwill]

I pulled the line that runs from the manifold to the black plastic chamber. I just pulled it off from the black plastic piece and plugged the vacuum line at that end, so it's still connected to the manifold.

There's also this little thing that is in the middle of the vacuum line as well but i dont know what the heck it is. it's about 1/2" in diameter and maybe 1/2" long, kinda clearish with a red thing inside one end, looks similar to a lawnmower's fuel filter. i dont think it is original to the car but it's on the vacuum line between the manifold and the plastic box and it's been there since ive owned the car. I'll take a pic and let ya'll take a gander at it and ponder what it could be.

[drummerwill]

Here's a pic, sorry im posting from my phone so the photo quality isnt exceptional.

[drummerwill]

Hey i got it all working alright, I think i had another vacuum leak on that line so i went to advanced and i didnt know that they actually do make plugs for capping off vacuum lines. So I capped it at the manifold and it's all good now. Thanks!