93 Corolla Low Cold Idle - Corolland: the Toyota Corolla Forums

Hey guys,

Just joined today! Have been trying to find a Corolla wagon for quite a long time and finally found one this past weekend. 93 with 140k miles and minimal rust. Put almost 500 miles on it already and absolutely loving the gas mileage!!! The last couple days I have been having a little issue with it in the mornings. When it is cold, it will start up normal and just lose rpms (sometimes just dying out). Other times it will continue to run but very very low (appears to be around 500 rpms). If it is at night the rpms are low enough to dim the headlights until the rpms raise. Once it warms up it idles around 1k rpm and idles super super smooth. I am sure someone has posted similar to this on here and I apologize for the double post. Just curious if anyone has seen this and what the cause/fix of the issue is? I was thinking possibly an egr valve? There is no check engine light on. Any help anyone can give would be awesome!

Congrats on your find and welcome to the forums. Corolla wagons, atleast ones in good shape, can be pretty hard to find. 140K on a 7th gen Corolla is nothing - take care of it and it will run for a long, long time.

EGR usually causes problems when the engine is hot and slowing from a higher RPM - like coming off a highway ramp and slowing to a stop at a stoplight. Usually not involved with idle issues from a cold start unless there is a leaking vacuum hose.

Vacuum leaks can affect idle quality in a number of ways. Other possibilities include a dirty throttlebody, clogged injectors, weak ignition, binding in the throttle cable, etc. - lots of possibilities. Have to start narrowing the field with stuff that you've done so far to diagnose this.

Since you mentioned dim headlights when the idle is low - something like a bad or weakened battery can load the alternator enough that it could pull the idle very low. Poor chassis ground points are another strong possibility as well (this was the case with my 8th gen Corolla).

Might just need a comprehensive tune-up and a strong run on the highway. A quick visual check for loose, damaged or missing vacuum hoses would be a good idea as well.

Congrats on your find and welcome to the forums. Corolla wagons, atleast ones in good shape, can be pretty hard to find. 140K on a 7th gen Corolla is nothing - take care of it and it will run for a long, long time.
EGR usually causes problems when the engine is hot and slowing from a higher RPM - like coming off a highway ramp and slowing to a stop at a stoplight. Usually not involved with idle issues from a cold start unless there is a leaking vacuum hose.
Vacuum leaks can affect idle quality in a number of ways. Other possibilities include a dirty throttlebody, clogged injectors, weak ignition, binding in the throttle cable, etc. - lots of possibilities. Have to start narrowing the field with stuff that you've done so far to diagnose this.
Since you mentioned dim headlights when the idle is low - something like a bad or weakened battery can load the alternator enough that it could pull the idle very low. Poor chassis ground points are another strong possibility as well (this was the case with my 8th gen Corolla).
Might just need a comprehensive tune-up and a strong run on the highway. A quick visual check for loose, damaged or missing vacuum hoses would be a good idea as well.

Thanks for the quick reply. I bought the car with a new battery in it. The battery was actually strong enough to short out the old alternator, so that was replaced before I bought it as well. So new battery, new alternator, new plugs and wires and the rest of the ignition system appears to be pretty new. I will start looking for a vacuum leak somewhere. I may try some seafoam or injector cleaner through it on the next fill up to see if that helps. The car did sit for a while before I bought it (48k miles in 10 years) so dirty or clogged injectors might be a possibility. I just thought it was strange that literally after running or driving for a min or two the issue hides itself and then runs GREAT. I have just had to baby it for a few min when it first starts. It will need wheel bearings at some point so I may have some questions on those as well soon!

Does it smoke at all on start up? Does it idle well when you do a warm restart?

Stumbling, rough idle on a cold start that "automagically fixes itself" after running for a couple of minutes is almost a trademark sign of a vacuum leak. As the engine gets a little heat into it - the potential leak seals itself from thermal expansion effects.

Another possibility is a bad coolant temperature sensor - though this would also affect how the car shifts when cold as well (automatic transaxle only). Could be returning a temperature higher than normal, so the PCM is not enrichening the mixture enough to prevent this idle stumbling.

Warm restart it works just fine. This morning it was a little warmer here and I didnt have the issue. I haven't noticed any smoke at all when starting. It is a 5-speed so wouldn't be able to check the shifting of the car. I am leaning more and more towards a vacuum leak with it somewhere. I will have to take a look around under the hood and see if I can find any brittle looking hoses, or any hose that look like they are not in fully seated