I have a 93 corolla wagon (California emissions equipped) and its running rough at idle in gear. I bet this has been covered to great lengths but I have replaced quit a bit at this point and i would like some expert opinions before I push on further. I have been to several dealers who either can't figure it out, have to get aproval to work on it, or don't know that they made a corolla wagon for 93(maybe I need to find a better dealers).
My current guess is that the IAC Valve needs cleaning, but I haven't been able to locate tutorials online for cleaning it, I kind of need diagrams(couldn't find anything in the Hanes manual either)
List of things replaced:
Spark Plugs
Spark Plug Wires
Distributor
Rotor
Motor Mounts
Main O2 Sensor
The list of replaced things is longer but these were the ones that might have been related
List of symptoms:
Runs fine in park and neutral
When shifting from park or neutral the engine idle seams to drop really low for about 3 to 5 seconds (Not certain, no tachometer)
My current guess is that the IAC Valve needs cleaning, but I haven't been able to locate tutorials online for cleaning it, I kind of need diagrams(couldn't find anything in the Hanes manual either)
Welcome to the forums! The IAC valve is really easy to clean. First you start by removing the air intake hose that leads from the airbox to the throttle body. Simply undo the hose clamp and slide it off (the airbox doesn't have to be removed). Then disconnect the electrical plug for the throttle position sensor (black unit on the rear of the throttle body) and the plug for the IACV. Then remove the coolant hoses from the bottom of the IACV. They'll simply pull down when you release the clamps (just make sure they stay standing upwards so you don't lose any coolant).
Once that's done, open the throttle by hand by pulling the lever and slip the accelerator cable out. As it's an automatic, also remove the kick-down cable and bracket. Now you can remove the nuts holding the throttle body on. There are two nuts and two studs. All you have to do is remove the two nuts, then remove the support bracket and the throttle body will slide right off.
Then you just flip the throttle body over and remove the four screws from the IACV (make sure you put a fair amount of pressure on the heads as they become easy to round due to old age). Once you've got the IACV off, clean it thoroughly with carb cleaner. Wait for it to dry and then reinstall it to the throttle body. If problems still persist then check the resistance of the connector. You shouldn't need a new gasket for the IACV or the throttle body. The IACV gasket is rubber and the throttle body gaskets are metal - Both of which typically last a long time. If the gaskets look to be in poor shape however, definitely replace them.
Here's a pic which may come in handy:
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The Following User Says Thank You to Kiwi-Corolla For This Useful Post:
those 4 phillips screws can be tough to get out, make sure you have a good philips bit and use a pair of vice grips on the screw driver shaft for extra leverage. It also helps to use a hammer to hit the screw driver down into the screw for extra bit and to help jar it loose. Worse case you have to use the vice grips to grab the heads of the screws.
Yeah, I remember almost rounding one of mine off a while ago. A good way I've found is to use a ratchet with a bit-piece adaptor and Phillips tip on the end. This way it allows you to put pressure on the top of the ratchet while turning the handle, which provides excellent leverage. I've removed many stubborn screws that way.
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Yeah, I remember almost rounding one of mine off a while ago. A good way I've found is to use a ratchet with a bit-piece adaptor and Phillips tip on the end. This way it allows you to put pressure on the top of the ratchet while turning the handle, which provides excellent leverage. I've removed many stubborn screws that way.
Welcome to the forums! The IAC valve is really easy to clean. First you start by removing the air intake hose that leads from the airbox to the throttle body. Simply undo the hose clamp and slide it off (the airbox doesn't have to be removed). Then disconnect the electrical plug for the throttle position sensor (black unit on the rear of the throttle body) and the plug for the IACV. Then remove the coolant hoses from the bottom of the IACV. They'll simply pull down when you release the clamps (just make sure they stay standing upwards so you don't lose any coolant).
Once that's done, open the throttle by hand by pulling the lever and slip the accelerator cable out. As it's an automatic, also remove the kick-down cable and bracket. Now you can remove the nuts holding the throttle body on. There are two nuts and two studs. All you have to do is remove the two nuts, then remove the support bracket and the throttle body will slide right off.
Then you just flip the throttle body over and remove the four screws from the IACV (make sure you put a fair amount of pressure on the heads as they become easy to round due to old age). Once you've got the IACV off, clean it thoroughly with carb cleaner. Wait for it to dry and then reinstall it to the throttle body. If problems still persist then check the resistance of the connector. You shouldn't need a new gasket for the IACV or the throttle body. The IACV gasket is rubber and the throttle body gaskets are metal - Both of which typically last a long time. If the gaskets look to be in poor shape however, definitely replace them.
That is really helpful information. The picture makes it look easier than I thought it was going to be, also you writeup covered my main concerns such as what to do with the coolant lines and gaskets. I will take care of this when I have a little more time on my hands.
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UPDATE:
So I did a quick test using a paperclip between the TE1 and E1 terminals on the diagnostic port as per the Haynes manual's directions. and the engine didn't idle up and after 5 seconds the rpms went down further(quite low), removed the clip and the engine returned to normal. I am quite certain now that it is the IAC valve, wasn't able to get the electric connector off to check the resistance, too many other things in the way. Wondering if there is an easier way to get it off.
I have a vacation scheduled to start on the 11th of March I will tacke it then. Hopefully it doesn't start stalling on me.
Last edited by QuietlyThinking; 02-21-2011 at 12:58 PM.
I guess you guys have never heard of an impact driver for removing phillips screws. Its like a large bodied screwdriver that you hit with a hammer to make the screw loosen. I've used them for years on motorcycles.
I guess you guys have never heard of an impact driver for removing phillips screws. Its like a large bodied screwdriver that you hit with a hammer to make the screw loosen. I've used them for years on motorcycles.
-SP
We have, but thats really not needed here. The screws are not tight and they're pretty small, and really not ones you want to snap off.
If they werent that tight you wouldnt be stripping them out! They dont "snap off" with the driver they loosen the screw OR tighten it properly without damage.
It has been a while but, I have made some progress with the issue.
The first thing I did was to compile a list of things to check using this forum and the keyword rough this gave me a nice list of things to check. I also bought a tachometer and a Chilton manual(I didn't really like the Hanes manual), the idle speed was dropping to 500 rpm durring the shift from park to drive. After checking some of the things on the list i found out that the TPS was out of range, I adjusted the TPS and now the idle doesn't drop at all when shifting between park and drive. When I took the car out for a test drive the vibration was completely gone at the first stop sign I arrived at, then it was back. It is not as bad as it used to be, but it is stil running rough at idle in drive.
I am wondering if I didn't tighten the TPS down enough and it moved or if I need a new TPS.
Your idle can also be rough just from wear in the engine. If you want to find out accurately, do a leakdown test. This will tell you the condition of valves and rings. I typically do this test FIRST to make sure it can run right, then do the maintenance. Its a BIG time saver when working on older cars.
KIWI COROLLA, where on the internet might i find a body kit that is the same as your car? it looks great and thanks.
Way off-topic, lol, but the front bumper is OEM Toyota from a JDM AE101 FX-GT and the sideskirts are aftermarket fibreglass ones (only pair I've seen of their kind). You'd be hard pressed to find the FX bumper online, but I can ship one over to you if you've got the cash . PM me if you have any further questions
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1993 Toyota Corolla
1993 Toyota Corolla
. PM me if you have any further questions 
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