Idle Problems With 4Afe Auto Cold And Hot - Corolland: the Toyota Corolla Forums

Hi I have just got a 93 corolla auto, when you start it in the morning the idle is too low like the choke is not coming on and it will stall if put in gear too early, then it will drive ok when warm and tickover about 1100rpm in neutral,

then if it gets warm in traffic and you stop the engine, when you restart the idle is too low again and car tries to stall, if you drive a while it seems to be ok when you have done a few miles, this is very frustrating, is there anything I can do?

does anyone know where I can plug by obd2 in as the disagnostic plug under the bonnet is not obd2 is there a plug for obd2 anywhere in the car?? thank you

Need a bit more information. Mileage? When you noticed this issue starting? Anything the preceded it, ie. recent repair, new electrical work, etc.?

Unfortunately, this model year only supports OBD 1, OBD 2 didn't become standard until the 1996 model years.

If your check engine lamp is on, you can still ping on the internal diagnostics, involves shorting two pins in the diagnostic port under the hood and counting the number of flashes from the CEL lamp in the gauge cluster. There are a number of online resource to walk you through that procedure.

But likely with this particular issue, it probably will not set any trouble code. This sounds more like an idle air control issue - especially when you restart the car after it warms up and it idles differently.

Could be from a number of possible culprits - could be as simple as the throttle body needing a good cleaning, IAC valve needing cleaned, issue with the EGR system (leaking vacuum, clogged EGR tube, stuck modulator, damaged plug wires, cap, rotor - worn plugs, clogged injectors, leaking injectors, poor chassis grounding, adjust low idle stop, etc.

Might be a good idea to start with a comprehensive tune-up, especially if the car hasn't had one in a while or seen routine maintenance. To rule out any simple maintenance issue causing these particular symptoms - then diagnose it from that point.

Just bought the car, it starts from cold and idle is too low, then when driven it's ok, but when restarted the idle goes too low and stalls, its auto so not easy to stop stalling, there are no misfires i'm certain its not a plug or service issue, no eml is on, just seems as if the choke does not come on when cold and idle is way too low when warm but i cant find any idle adjustment, no vacuum leaks maybe a sensor but I have no idea where to look as its an unusual issue,

There is an idle adjustment screw on the throttlebody, but I would save that as a last resort. Sounds more likely to be an IAC (idle air control) valve or TPS (throttle position sensor) issue to me. Could also be a maintenance issue as well - as you just bought the car.

Faulty coolant temperature sensor can also cause this sort of problem. Sometimes a good cleaning of the throttle body will "fix" this low idling problem. Pretty easy and quick to do, so that would be high on my list to get done.

Vacuum leaks can also cause an erratic idle, could try the old school method of spraying all the vacuum hoses, hose unions, around the TB, intake manifold, etc. Need a spray bottle filled with water + couple drops of detergent (safest, won't eat anything under the hood) or fast evaporating solvent - works well, but will eat rubber and plastic, so need to be careful on the amount used.

You'll know when you hit the source of the leak, as the idle will noticeably speed-up when you hit it with the spray. Comprehensive tune-up would be first on my list, if this was my car - especially if the history of the car is unknown. Eliminating these simple things will go a long way in speeding up the diagnostic process.