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Discussion Starter #1
Hi all. I got this 1995 Corolla some 6 months ago. So far i've changed oil, timing belt set and all seals on tb side, thermostat, radiator, spark plugs.
Problem is i can't get rid of the high idle. It is a base throttle body, without the iac valve, just the tps. It is always between 1100-1400 rpm. Except sometimes for a quick stop for a few minutes (engine warm), then after i start the engine it sits arround 750 rpm and even surges for maybe 1 minute, and it goes up to 1100. Intake hose was cracked, i fixed that. No obvious air leak. Cleaned the throttle body (without removing it). So far nothing changed. The idle adjust screw is at 0 point. I dont want to mess with the tps and cable side of the flap. Any suggestions?
Thanks

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I think the power steering is also capable of raising the idle RPMs.

You can try capping off the vacuum lines to see if that ferrets out a non-obvious vacuum leak.
 
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Over the years of owning many Toyota’s, I have found high idle problems caused by leaking vacuum lines several times. You will probably find dried out hoses with cracks on the connected ends or where the hose is bent on an angle.
 

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Discussion Starter #4
So far i can't find any obvious leak. I sprayed it with brake cleaner and no obvious difference.
This morning outside temp. is slighly lower (below 0 C), so it even raised to 1800, and even started to go up and down, when standing on a red light.
What i realised, when i got at work, is that the small hoses that should take coolant to the TB, to warm it up, are no near warm, i can hold them by hand. Maybe it is clogged, and the valve can't warm up and doesn't open (it has the mechanical iac walve, not electrical). That is my best logical guess. I'll try to clean it up, without removig the TB or dissasemblying, i have no spare gaskets. Anyone has experience with the aux valve on the TB?

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So far i can't find any obvious leak. I sprayed it with brake cleaner and no obvious difference.
This morning outside temp. is slighly lower (below 0 C), so it even raised to 1800, and even started to go up and down, when standing on a red light.
What i realised, when i got at work, is that the small hoses that should take coolant to the TB, to warm it up, are no near warm, i can hold them by hand. Maybe it is clogged, and the valve can't warm up and doesn't open (it has the mechanical iac walve, not electrical). That is my best logical guess. I'll try to clean it up, without removig the TB or dissasemblying, i have no spare gaskets. Anyone has experience with the aux valve on the TB?

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Sounds like you might have located your problem! Good luck...
 

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Discussion Starter #7
Sounds like you might have located your problem! Good luck...
Yes i did. After i poured warm water to warm up the valve body, and after a few secconds and a cup of water, it started to go down and cemented itself to 750-800. So it is working, which is the good news, but the coolant passage is likely clogged. Before i get back from work, il do it again, and hope with some higher rpm driving it will unclogg itself. If not i'll try to clean it, and the hoses, without taking it off. If not....i'll figure something out, silicone will do the job for the gasket.

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It could be clogged, or it might just be air-locked.
 

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Yes i did. After i poured warm water to warm up the valve body, and after a few secconds and a cup of water, it started to go down and cemented itself to 750-800. So it is working, which is the good news, but the coolant passage is likely clogged. Before i get back from work, il do it again, and hope with some higher rpm driving it will unclogg itself. If not i'll try to clean it, and the hoses, without taking it off. If not....i'll figure something out, silicone will do the job for the gasket.

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Did you find a resolution to this? My car has twice not raised the idle when being cold-started in sub-freezing temperatures. Both times I hit the accelerator and then the revs came up and stayed up until warm-up, like normal. The second time it did this, it actually triggered the CEL. Today I read the codes and got a PO501 (I think it was) for the IAC, and also a PO136 for the upstream O2 sensor I just replaced - but I can see the 136 being because maybe the injectors were squirting more fuel, but the IAC wasn't letting in more air?
 
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Discussion Starter #10
Did you find a resolution to this? My car has twice not raised the idle when being cold-started in sub-freezing temperatures. Both times I hit the accelerator and then the revs came up and stayed up until warm-up, like normal. The second time it did this, it actually triggered the CEL. Today I read the codes and got a PO501 (I think it was) for the IAC, and also a PO136 for the upstream O2 sensor I just replaced - but I can see the 136 being because maybe the injectors were squirting more fuel, but the IAC wasn't letting in more air?
No, i still haven't found the time do fix it, it was cold couple of weeks. But i hope to do it soon. But, since you mentioned you had the code for the IAC, i suppose yours has the electric IAC valve, mine is a mechanical thermostat like type of IAC. If you have the electric type, there are many videos of how to clean it. Maybe it has collected some dirt or carb bildup. Easy to clean. And after tapping the pedal all went well.
But, mine is obd1. You mention p0501 and p0136, what engine and year is yours? The 501 is listed as a generic code for vehicle speed sensor? Maybe there is no connection to the IAC, maybe just a coincidence.

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I might've gotten the code wrong, but it definitely said IAC.
Mine is a 1997 with the 7A-FE and automatic. It is OBD2.
 

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Discussion Starter #12
Well if it starts to do it more often, a good clean should do the job.

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My 96 DX has exactly the same behavior It idles up around 1100 and only after it is completely warmed up and I shut everything off and don't touch anything Will it sometimes drop back down to around 700 where it belongs. My car, I took a throttle body from the junkyard and meticulously polished and cleaned it out got new gaskets and observed full functionality of the thermomechanical valve and it has good flow going to the water jacket but still does the same thing.
 
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