Idling very high, especially when hot

[Austin's 86 LX]

Hi :) I've been lurking this forum for about the past few days as a guest (I've had my 3g for a couple weeks now) and I've found lots of useful information on repairing carbs but I'm not sure if I should fix mine myself or leave it up to a mechanic.

I took my car to my mechanic to have everything checked out last week and along with replacing the brake master cylinder, head gasket, distributor cap, cv joint and ball joint he mentioned that I might need to get my carburetor rebuilt soon. Well, soon has become now, I was out driving for quite a bit in the ~100 degree weather yesterday and when I arrived at one of my destinations and put my car in park it started idling at about 3k rpms. I went inside and came back out to start it a few minutes later and it was on its way to 4k rpms when I shut it off and it shook for several seconds and let off an odd scent on the passenger side. I had noticed on my way there in start and stop traffic that when I would let off the brakes it would start to accelerate up to 20mph without even giving it any gas.

I managed to get it home later that day with it starting fine and idling around 2k (which has been the average) after the drive home (only about 5 miles).

My biggest question is whether it's something I could repair on my own or if I should pay my mechanic $600 to rebuild it. I've seen a lot of talk about vacuum lines and was wondering if someone with no prior experience could replace those.

I just wanted to check first because I'm starting to distrust my mechanic since he tried to sell me new brake pads and rotors only to change his mind the next day when I told him the last ones were put on about 15k miles ago. I was lucky enough to get a 3g with a big fat envelope full of maintenance records and receipts ;)

[Dr_Snooz]

That's a tough one really. I don't trust any mechanics anymore. Fortunately, I'm good enough that I can do all my own work. Rebuilding a normal carb falls toward the more advanced end of the DIY continuum and these carbs give even the pros fits. They definitely are not the place to begin doing your own work. So you don't want to DIY, but you don't want to trust it to a mechanic either.

Yeah. Good luck with that.

[Austin's 86 LX]

Just drove it a pretty short distance and it acted fine. Then again it's pretty cool out and it hasn't been driven all day.

I wasn't planning on rebuilding the carb myself but if it turned out to be something like a vacuum hose or adjusting the fast idle speed I wanted to try.

The father of a close friend of mine is a mechanic and he's supposed to be really good, the only thing keeping me from taking my car to him the first time is that his shop is at least an hour's drive away and I'm not sure I'd be able to get rides back and forth. I guess if need be I'll see if he can do it the day I take it in and I can watch and learn a little bit since I know nothing about cars.

Thanks for the tip though, I'm glad I'm not the only one who doesn't trust them. And your sig reminds me of something a friend of mine told me when this problem first started appearing, "if you can't fix it with a hammer, it's an electrical problem."

[greentee76]

Next time it does it check and see that the throttle cable is not hanging up. Even the small snap in clamps it runs through can be enough to compress the the cable cover and prevents free movement of the inner cabling. The fact that it passes directly over radiator/exhaust manifold area means it deals with the hottest area of the engine comp. It is no wonder the lubricant is pretty non existent after 20+ yrs.
FYI I bought a new cable from Honda and still had this problem, I am only able to snap it into one of the snap clamps and still have it release correctly. Also check the tension on the cable as a little slack on the carb end will help with this as well.
I hope this is your simple problem. Good luck!

[Austin's 86 LX]

Next time it does it check and see that the throttle cable is not hanging up. Even the small snap in clamps it runs through can be enough to compress the the cable cover and prevents free movement of the inner cabling.

Thanks for the tip. I'll see if I can handle getting to the cable and checking it out by myself. I'm a complete noob when it comes to cars. I've only been driving two years and I've never done anything more than jump a car or change a headlight bulb :sad2: but I want to learn!

So I'm assuming it's nothing to do with the fast idle valve since it starts out normal and gets worse as it heats up?

[greentee76]

You should be able tyo handle it no problem. Remove the air cleaner assembly and look for the cable going to the carb. It is black plastic and larger diameter than the vacuum lines. Trace that back around the engine bay and eyou will see where it goes into the firewall on the lower driverside. Along the way you will see the clips that help route it.
the next time it idles high pop the hood and remove the cable from the clips. You may have to get back in and blip the accelerator to see if the idle comes down. If it does reconnect the clips one at a time to see if it sticks. I think mine is only in one of the clips. As long as you can keep it away from hot parts it will be fine.
The tension adjustment is on the carb end of the cable. It's fairly straight forward - loosen look nut turn adjustment nut to tighten or loosen and tighten lock nut back down.

[Austin's 86 LX]

You should be able tyo handle it no problem. Remove the air cleaner assembly and look for the cable going to the carb. It is black plastic and larger diameter than the vacuum lines. Trace that back around the engine bay and eyou will see where it goes into the firewall on the lower driverside. Along the way you will see the clips that help route it.
the next time it idles high pop the hood and remove the cable from the clips. You may have to get back in and blip the accelerator to see if the idle comes down. If it does reconnect the clips one at a time to see if it sticks. I think mine is only in one of the clips. As long as you can keep it away from hot parts it will be fine.
The tension adjustment is on the carb end of the cable. It's fairly straight forward - loosen look nut turn adjustment nut to tighten or loosen and tighten lock nut back down.

Thank you so much for the in depth instructions! I wanted it "spoonfed" like that to me but I was too afraid to ask. I found the thread with the shop manual though so that should help in the future. I'm gonna try this as soon as I get home from work tomorrow morning.

[Austin's 86 LX]

Good news! Sort of...
After using some carburetor cleaner it has mostly stopped idling so high but has been pretty sluggish and just not all that great. So I talked to my friends dad, the mechanic, and he drove it around and agreed that I should just put in a new carb rather than get a rebuild kit that possibly lacked the part I needed. So I got a Weber .32/.36 and he's installing it today for half his usual price :) I'm excited to get my 3g back tonight!

[greentee76]

You'll like it alot more with the weber. I didn't see if yours is manual or auto, but on my manual it moved the powerband to a much more usable place to make cruising alot more enjoyable. It takes a little tweaking to get the fine points worked out on the weber, but def. worth it. Ask any questions around here and there are a couple weber specific threads floating around here.
Good luck and let us all know how much fun you are having with your "new"car.

[Austin's 86 LX]

Didn't get it back tonight :( Hopefully I will tomorrow, he didn't realize what exactly I had gotten (he thought I was just replacing the original) so his quote on time was a bit off.
Mine is auto so I don't think I'll notice an effect on my cruising. As far as the tweaking goes, I hope it's something I can do myself, the threads on here look extremely helpful but I'm such a novice to this, hopefully I'll catch on lol.

[greentee76]

Roodoo2 is the guy to talk to as far as the auto/ weber combo. It might take a little adjustment of the TV cable for the trans to get it smooth. Nothing you can't handle.
Good luck!

[Austin's 86 LX]

Roodoo2 is the guy to talk to as far as the auto/ weber combo.
Then I might have to drop him a PM!
This thing definitely needs some tuning, it idles at a good speed but when I turn on the ac it drops down to about 500 rpm and feels like it's gonna die.

Edit: Then I drove it out quite a bit today in the heat and it started idling way too high again. This is worse than before :'(