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autotech2612

Idle Quality - Low To High When During Cold Temperatures

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For the third day in a row, my '02 Corolla has exhibited the following idle issues.

 

When it's cold out, lately below 40 degrees, I start the car and idle is not high as it should be. It only goes up to about 1300 and acts sluggish.

 

When I back out of the driveway (stick shift) and put the car in neutral, idle speed goes up dramatically, sometimes as high at 2100.

 

For the first two days, this was very high until the car was fully warmed up. Then, idle was normal (after a good highway drive).

 

Tonight, however, after a highway drive, car fully warmed up, I arrived at a stop light and put the car in neutral. It idled to about 1800.

 

I then drove another mile and then shifted into neutral to coast before turning onto my street, and the idle was back to normal again (800).

 

Pulled into my garage and before shutting the car off, idle was still normal.

 

I swapped out a MAF sensor I had sitting around. No change.

 

All I can think of now, because this just started happening in cold weather, is that it's a faulty ECT sensor. (The temperature gauge is working correctly, though)

 

Can anyone help?

Edited by autotech2612

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trap

Water temperature sensor # 89422-16010 for EFI is on left side of ebgine head, behind throttle position sensor. It appears to be also for the temperature gauge.

 

Have you replaced your intake manifold gasket, and inspected your intake manifold for corrosion and leaks?

Edited by dom

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Dom, the intake manifold gasket has not been replaced. Someone told me I can spray water or some kind of solution to see if it's leaking. Is that the way, or is there a better way to detect leaks?

 

I don't see any corrosion; it's in very nice shape.

 

Have to take out air cleaner box to get to the sensor. I replaced it last year after having gauge issues. Today I ordered a replacement under limited lifetime warranty:

 

http://shop.advanceautoparts.com/p/bwd-intermotor-engine-coolant-temperature-sender-wt5051/18480854-P?searchTerm=coolant+temperature+sensor

 

Perhaps I should have stuck with an OEM part?

Edited by autotech2612

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It should be ok. What brand did you put in the first time, and did it fix your gauge? Was the original a Denso? My original one is still fine at 283,000 kms.

 

http://www.rockauto.com/catalog/x,carcode,1432913,parttype,4748

 

I could likely tell if your intake manifold gasket is leaking by looking along the edge of it for evidence of blown aerated oil/dark grimey sludge. It's more obvious to the trained eye looking at condition of gasket and traces of channeling on it once the manifold is removed... Gasket is so cheap and easy to replace, and so critical for proper engine function. I would definitely replace your 13-year-old gasket at that mileage.

 

http://www.rockauto.com/catalog/x,carcode,1432913,parttype,5424

Edited by dom

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Actually, there is no aerated oil or sludge whatsoever. I'm not opposed to replacing it, but it does not look easy to me. Perhaps there's a YouTube video out there detailing step-by-step.

 

The brand I installed last time is the one listed in the link I supplied. BWD/Intermotor, which I believe is still Standard Motor Products. It did fix the gauge issue.

 

I don't know if the original was a Denso.

 

I did pick-up the replacement ECT today, but temps have risen to the fifties, so I won't know for sure if the ECT was faulty until it gets very cold again.

 

I'm surprised RockAuto doesn't have a Denso ECT sensor listed.

 

Edited by autotech2612

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I watched several YouTube videos about changing the gasket before I changed mine.

I needed confidence. It really was not bad at all. It just looks intimidating. Everything is straight forward and goes back together easily.

Just don't forget to put the hoses back on. And don't scrape anything with a razor blade like I did. Just clean with a soft cloth or something.

I scratched the aluminum.

I took the opportunity to clean my pcv hose and throttle body.

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What was the reason for changing yours, Snow?

 

Did you notice any difference after the replacement?

 

So far, I am only able to locate just one video of a Corolla intake gasket replacement. However, mine is a 2002 and the one in the video is a 2005.

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It was more common for the composite intakes on the 9th gen Corollas to have intake gasket issues compared to the tubular metal ones on the 8th gen - but still something that should be checked out, just to rule it out as a possibility.

 

Anything you can spray down there - soapy water, WD-40, solvents, etc. - those will work for checking for vacuum leaks. Basically any part you spray that causes the idle to increase or stabilize is the likely leak point.

 

Could be a number of things causing this idle issue - ECT sensor failure is one possibility. Could also be a bad IAC valve, dirty MAF, vacuum leak (colder weather causing thermal contraction), dirty throttle body, TB icing (especially if you did a coolant line bypass), bad gas, grounding issue, faulty TPS, etc.

 

I'd start with the simple stuff first - clean the TB and MAF, test the ECT with a multimeter, check on vacuum leaks, pull plugs and make sure the ignition system is fine. Then start looking to swapping parts, sensors.

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I'll be updating Friday because we'll have a high of 30 and a low of 20. I have installed a new ECT. The true test will be on that cold day to see if it acts up.

 

Thanks again guy for your help. It's appreciated.

 

The links are helpful, dom. Looks like I can knock that out in 45 minutes or less.

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Autotech ...I had rpm constantly searching between 1000 and 2000 when cold in the winter.

As mentioned earlier, more common on my 9th generation.

It fixed the problem and mpg economy increased.

 

 

 

 

 

Edited by Snow Tire

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It was more common for the composite intakes on the 9th gen Corollas to have intake gasket issues compared to the tubular metal ones on the 8th gen - but still something that should be checked out, just to rule it out as a possibility.

 

 

I performed the spray test and the visual test. I have absolutely no leaks from this gasket. I did the spray test twice in three days.

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As Snow Tire mentioned, it may be more common on 9th gen Corolla, but replacing the gasket on his 8th gen like yours even though it wasn't obviously leaking, cured his severe idle hunting problem, and mpg improved... You won't definitely be able to find such minute leaks which could be on the invisible side underneath, with a visual inspection or a random spray test. Replacing the gasket will give you an excellent opportunity to clean your intake manifold, inspect it and all your vacuum and PCV hoses' condition for good snug and sealed connections... We'll let you test your new ECT sensor first.

Edited by dom

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Dom, I'm still going to perform that task of replacing the gasket and cleaning the intake. Gasket is really cheap.

 

I installed the Intermotor ECT tonight. I did not disconnect the negative battery terminal like I did last year (which caused the ECU to idle bizarrely as it tried to apparently "re-learn" parameters).

 

This Intermotor part is the same in the link at the top I posted. It's also manufactured by Standard Motor Products.

 

I am convinced my Corolla is rejecting this brand. The one that was in as of tonight was a spare I had lying around that is also made by SMP. When I put it in, the gauge arrived to the middle in the usual time frame it takes during 35 degree weather. However, it did act a little bizarre earlier when it was 40 out after I had let me car sit for an hour-and-a-half. Started it up, idled up, then pulling out of the parking lot, started going to 1900, then to 1600, then fine. The rest of the way home was fine.

 

I arrived home and installed the new ECT (same brand and part number). Car sat for four hours. Started it up, idles fine. However, the gauge takes a lot longer to get to the middle mark. Very noticeable. Also, idle seemed fine at 35 degrees. No low idle when cold and no very-high idle after pulling out of the driveway. Just the way it should be.

 

I have now gone through five of these sensors and each one acted a little different from the other.

 

It seems as though this car is picky when it comes to non-Denso parts. An aftermarket PCV wasn't an exact fit for my Corolla, so I ended up going to the dealer to get the part and have no issues with the Denso PCV. I also opted to replace the thermostat last year with a Denso. No issues.

 

Last winter, one of the coldest on record in Michigan, I had to go through three of these sensors from Advance Auto Parts. The one already in the car when I bought it was having gauge issues and would never idle to 800 because the gauge would never get to the mid-mark. I replaced it. Seemed to work for awhile, and that one went bad too. Then the third one seemed okay until this fall when it got cold again. Idle issues once again, but the gauge worked fine until I did the swap out with the sensor I had laying around. (then had that issue tonight).

 

At this point, I think it may be best to bite the bullet and go with a Denso sensor. My car just seems to be rejecting the aftermarket one.

 

What do you think?

Edited by autotech2612

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I think you should replace your intake manifold gasket and check your hoses... There are 2 types of PVC valves for your 1ZZ-FE.

 

PCV valve # 12204-22041 with green Loctite has M16 (16mm diameter) x 1.5mm threads. It takes a 22mm or 7/8" (22.225mm) wrench or deep socket

PCV valve # 12204-22051 with pink Loctite has 3/8" BSP threads (16.6624mm diameter), 19 TPI (1.337mm threads). It takes a 3/4" (19.05mm) or 19mm wrench or deep socket.

 

What was wrong with your original Denso ECT sensor? SMT has an economy grade of parts that is not stellar.

Edited by dom

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