Hi Idle - '91 Corolla LX (4A-FE)

[ksanchez71]

I've recently noticed that my idle has been gradually getting higher and higher on my 91 Corolla LX (4A-FE Engine). I tried lowering the idle speed by adjusting the screw by the throttle body however, its all the way down.

I currently have an idle speed of about 1850-2000 RPM. I also replaced all the plugs, installed new wires, distbr. cap & rotor. I also tried adjusting the mixture to lean it out a bit, but that didn't help either. All vacuum hoses are connected. Anyone have any suggestions?? Can use the help!

Thanks...

[storyr]

mine idles that high when I first start it up in the morning, up the the 2000rpm when it is especially cold. But I drive it for about 3 minutes and it goes away, does yours continue to idle high?

[Flashmn]

might be that the coldstart jet is jammed open

[ksanchez71]

No my Corolla idles like this all the time, in whatever condition cold or hot. Any other suggestions?

Hot do you unjam the cold start jet and where is it located?

[fredk]

YA SCREWED UP, ya gotta get that idle stop screw back to where it was, or, the easy way to set it is back the screw out till it touches the stop tab with the butterfly shut EASY in the bore, dont put more pressure on it when it goes shut than the return spring has on it or you might bind it in the bore and bend it getting it un stuck again. Then back the screw out about a 1/4 turn at a time until the butterfly comes off the stop easily with no noise or binding off the stop, this is the quick way to do this, and clean up the throttle bore inside while your at it. Get it running again, the idle should be hi or pretty close to where it was before you messed with the stop screw, now put your hand over the intake and kill the motor, its gonna pull pretty hard but dont let go, as the motor dies, or if it stays running, it should die pretty quickly, listen for a hiss sound, thats a vacuum leak, thats where the motor is getting air other than through the idle port, fix it, if no hiss, get it going again, pull the hose off the egr valve, did it slow down? if not put a hose on the egr valve and put the other end in your mouth, SUCK, the motor should go nuts, if not, it might be not opening or stuck open with carbon, take it off and clean it up and see if it is working right, if still no luck get it going again and plug the hole inside the throttle body ahead of the butterfly, it should just stay running if no vacuum leaks and the egr is closed, and you got the butterfly right, BINGO, you found the problem, if your check engine lite was on before, you might have a freaked collant temp sensor telling the ecu that your motor is cold allways, or the thingie under the throttle body that controls idle might be bad. Unhook the AC idle upper hoses to isolate it also

[REN69]

change your thermostat, your engine is not reading the temperature correctly, therefore it thinks its still cold so it keeps the revs up to warm up faster.

[TekPhobia]

Originally posted by fredk
YA SCREWED UP, ya gotta get that idle stop screw back to where it was, or, the easy way to set it is back the screw out till it touches the stop tab with the butterfly shut EASY in the bore, dont put more pressure on it when it goes shut than the return spring has on it or you might bind it in the bore and bend it getting it un stuck again. Then back the screw out about a 1/4 turn at a time until the butterfly comes off the stop easily with no noise or binding off the stop, this is the quick way to do this, and clean up the throttle bore inside while your at it. Get it running again, the idle should be hi or pretty close to where it was before you messed with the stop screw, now put your hand over the intake and kill the motor, its gonna pull pretty hard but dont let go, as the motor dies, or if it stays running, it should die pretty quickly, listen for a hiss sound, thats a vacuum leak, thats where the motor is getting air other than through the idle port, fix it, if no hiss, get it going again, pull the hose off the egr valve, did it slow down? if not put a hose on the egr valve and put the other end in your mouth, SUCK, the motor should go nuts, if not, it might be not opening or stuck open with carbon, take it off and clean it up and see if it is working right, if still no luck get it going again and plug the hole inside the throttle body ahead of the butterfly, it should just stay running if no vacuum leaks and the egr is closed, and you got the butterfly right, BINGO, you found the problem, if your check engine lite was on before, you might have a freaked collant temp sensor telling the ecu that your motor is cold allways, or the thingie under the throttle body that controls idle might be bad. Unhook the AC idle upper hoses to isolate it also

You are aware there is an idle screw on the TB for air bypass? I don't think he farked with the throttle stop screw.

Might be a good idea to check timing too, if it's too far advanced the idle will be a bit high.

-Tim

[Pineapple]

Or you got a vaccum leak somewhere. Get a can of throttle body cleaner, start the engine, spray the cleaner around the intake and power steering pump. When you get close to a leak, the engine will stall.

[fredk]

I know about the bypass one, I just hope he didnt mess with the butterfly stop, I have seen peoples cars come in on the hook because the gas pedal cable is broken and the butterfly is bound up in the bore

[Pineapple]

Butterfly in the bore? You mean cylinder bore?

[TekPhobia]

If you back off the throttle stop screw all the way, the butterfly will cut a nice little notch in the throttle body bore when it gets shut. So... it gets stuck.

-Tim