4AC Idle Problems

[Low&Slow86]

Hello guys, I looked around on the forums and couldn't find anything that would help me with my problem, so I am making a new post to ask this question.

I have a 87 SR5 with the 4AC in it good ol' carburetor-ed motor (Fun!) so my problem is sometimes when it feels like it, it won't start, the motor will turn over and it will kick on but immediately die, it goes up to about 500-600rpm then cuts out, I can keep the motor going by feathering the throttle, at stop lights and signs (Not Fun!) after a little bit of driving it will keep the idle at around 800-1000rpm does anyone know what the cause of this could be? I have been told by multiple people that it is either my carb needs to be rebuilt or that there is a vacuum leak somewhere

[Clouds]

If you don't get any helpful responses soon, I would pop over to 4acpowered.forumotion.com to check their forums.

Good luck with the fix

[yellowsnow4free]

Hello guys, I looked around on the forums and couldn't find anything that would help me with my problem, so I am making a new post to ask this question.

I have a 87 SR5 with the 4AC in it good ol' carburetor-ed motor (Fun!) so my problem is sometimes when it feels like it, it won't start, the motor will turn over and it will kick on but immediately die, it goes up to about 500-600rpm then cuts out, I can keep the motor going by feathering the throttle, at stop lights and signs (Not Fun!) after a little bit of driving it will keep the idle at around 800-1000rpm does anyone know what the cause of this could be? I have been told by multiple people that it is either my carb needs to be rebuilt or that there is a vacuum leak somewhere

I'm actually having a similar problem with my SR5. It starts great when cold, but after stopping and starting it up again, it idles really low, like 500 RPM. Something about being hot I guess.

Anyway, I can say that I think my carb needs a rebuild, as it looks like it's leaking a little around the throttle cable attachment. And with the massive amount of vacuum lines on the 4AC, mine are probably due to be replaced too.

As Clouds said, http://4ac-powered.forumotion.com/ is a great place to ask this, however, the forum has been kinda dead lately. There are enough people with SR5's on here that hopefully you can get a more informed response.

Good luck with the fix! Please post back here telling us what you did to solve the problem

[Low&Slow86]

Thanks guys, looks like I'm gonna be doing a Carb rebuild soon, hopefully that helps out, it hasn't been doing that lately but she is a picky with starting, I played around with the idle on the carb that helped a little, it is still at like 1200rpm and sometimes 1500rpm when its hotter out, which sucks that's part of the reason why It wont pass smog...

[yellowsnow4free]

Thanks guys, looks like I'm gonna be doing a Carb rebuild soon, hopefully that helps out, it hasn't been doing that lately but she is a picky with starting, I played around with the idle on the carb that helped a little, it is still at like 1200rpm and sometimes 1500rpm when its hotter out, which sucks that's part of the reason why It wont pass smog...

Yeah, I'm thinking my idle problems are due to my carb as well. I've got a spare and a rebuild kit; now to just sit down and do it.

1200 to 1500 RPM is way high for a 4AC; should be around half that depending on what options your car has.

Mine is fluctuating around 650 - 800 RPM. I'm hoping that'll be fine for smog this Saturday.

[hachipirate]

I recently had similar problems with a recent purchase of an '87 ae86 sr5. The idle would fluctuate 200-300rpm around the 1100rpm mark. After 3 or 4 cleanings, rebuilds, and cussing sessions I stepped back to square one and checked that all the vacuum hoses were EXACTLY where they were supposed to go. My brain fart cleared I and saw my mistake. After the correction it's got a steady idle where it needed to be. Good luck with yours!

[yellowsnow4free]

I recently had similar problems with a recent purchase of an '87 ae86 sr5. The idle would fluctuate 200-300rpm around the 1100rpm mark. After 3 or 4 cleanings, rebuilds, and cussing sessions I stepped back to square one and checked that all the vacuum hoses were EXACTLY where they were supposed to go. My brain fart cleared I and saw my mistake. After the correction it's got a steady idle where it needed to be. Good luck with yours!

So it turned out to be an incorrect vacuum hose?

[hachipirate]

I recently had similar problems with a recent purchase of an '87 ae86 sr5. The idle would fluctuate 200-300rpm around the 1100rpm mark. After 3 or 4 cleanings, rebuilds, and cussing sessions I stepped back to square one and checked that all the vacuum hoses were EXACTLY where they were supposed to go. My brain fart cleared I and saw my mistake. After the correction it's got a steady idle where it needed to be. Good luck with yours!

So it turned out to be an incorrect vacuum hose?

It's kind of looking like a combination of things in fact. I had the hoses from the EBCV switched and one had a hole. What I've found today is the EGR diaphram isn't holding vacuum and is likely slightly stuck open. I think the combination of both is causing a simultaneous lean/rich vacuum leak making the idle all wonky. Now to find an EGR.

[hachipirate]

Don't think anybody will read this, but small update. I hate the TVSV. Plain and simple. After trying 2 different ones I still get an incorrect and fluctuating vacuum signal to the AAP. So I plugged the hose to the AAP. It's only used for cold starts below 50C anyway. Passed smog, now need to fine tune it and figure out the bog after hot restart that goes away after running a few minutes. Always fun. Hope you figured yours out.