mjquillici

I've been having high idle issues for a while, and I finally realized that the cap to the dash pot is broken (see attached photo). Where the heck do I find a new one? Nobody seems to carry them. If necessary, I'll head to the junkyard. All suggestions are welcome.

Thanks!

scope103

Seems unlikely to be the cause of high idle. Have you run through the setting procedure?
http://personal.utulsa.edu/~nathan-b...93throttle.pdf
Does the dashpot seem to retract with your finger OFF the VTV hole?

The purpose of the dashpot is to reduce damage to the exhaust (and increased emissions) caused by the throttle "slamming" shut suddenly. In other words, if you have a light foot you CAN drive it with no dashpot at all. I wouldn't recommend removing the dashpot, and I would try to fix a broken one, but I don't think that is the cause of your problem.

toyota4x4907

I drove my '95 for 3 years after the screw in the dash pot fell off.. I never had an exploding exhaust nor did I drive....conservatively.
The only way the dash pot will cause high idle is I'd the screw is set too high, but I can't remember if its even possible to set it that extreme.

mjquillici

My thinking is that with the back broken off, it can't hold a vacuum, and so the plunger won't retract as it should, thus leaving the thottle slightly engaged (above idle).

I did manually retract the plunger and the idle dropped immediately. It appears that the screw is contacting the throttle assembly, and causing it to stay slightly open (at least that's what I think). I did the multiple times, and as soon as I retract the plunger on the dash pot, the idle drops to about 750 RPM from 1250 RPM, or so.

Gamefreakgc

In this rare case, yeah it sounds like it's your dashpot. But a cracked cover would not make any difference, it's just to keep dust out. BTW, your engine runs just fine with it off.
I would not just try and adjust the screw (someone must have messed with it) but also clean your throttle body on the inside. Take of the air cleaner hosing and clean out all the built up gunk: this can also keep your throttle from closing. Do this before adjusting the screw, just in case.

Also, I bought a dashpot with a broken cap and it worked better than my old one.

Inferno451

In my experience it's actually pretty common for the dashpot to cause inconsistent high idle. It's purpose is to slow down the throttle butterfly and often the throttle return spring is too weak to completely overcome it. I had to completely remove my dashpot to get the throttle to completely close without my help.

scope103

While you're examining your dashpot (as a possible cause of high idle), don't overlook the throttle opener. http://personal.utulsa.edu/~nathan-b...93throttle.pdf

It holds the throttle open when vacuum disappears. So if you think your throttle return spring is too weak to overcome the dashpot, first check that the engine is running, there is vacuum on the throttle opener, and the throttle opener has retracted.

It's all the manual; you just have to follow instructions.

mjquillici

Thanks, Everyone.

As it turns out, the dashpot was, in fact, the cause of the high idle. Good call Inferno 451. It appears that the return spring on the throttle body was not able to overcome the resistence of the plunger on the dashpot. Whether that is because the throttle body is dirty, or because the dashpot is old and sticky is something that I have not yet addressed. BUT, the high idle problem is fixed, so I'm happy about that.

Thanks again!

Punchy

The boot over the spring sometimes gets hard and wont flex as well.
I just drilled mine out because I prefer the harder decel, Its been that way for 280k mi I put on the engine.

If you don't find one just drill the valve out and Krazyglue tack the cap on.

Thkpage

where did you happen to find one ?