Rough Idle in gear 1994 Celica ST (automatic) Options

[Noahwhite2014]

So i have purchased a 1994 Toyota Celica ST Hatchback (Automatic) from a friend a week ago, but he's not available now since he moved to another country (which is why he sold it to me). Ive always been into Celica's but never owned one.

Now that i have it, I'm having an issue with a low idle while in anything except park or neutral. Also, this problem does not happen once i start the car. When i start the car, it will run fine and idle at about or a bit under 1K RPM whether in park, reverse, neutral, drive etc... But once i start driving and bring the RPM above 2k, when i stop and idle again, the RPM drop to around 400-600 (sometimes even lower) and the car shakes when its around this rpm and then smooths out when the RPM gets above 2k

Any idea what the issue with this could be?

I would really love to get this car running well again like when i drove it a year ago or so and it was awesome!

There is a short ram intake on the car. But i don't remember if it was on when i drove it a year ago, i don't know if the intake could cause this problem. It has no brand that i can see, so i can add pictures if you would like.

Thank you all so much in advance!!

[enderswift]

I've seen this issue before. The egr valve might be sticking open and choking the engine with it's own exhaust. This is not an issue at higher engine revs, which is when the valve is normally supposed to open, but the engine won't run properly at idle. Take it off, clean it with carb cleaner, and reinstall. Or buy a new one.

[Noahwhite2014]

Im actually really new to this. So i was wondering, where is the EGR Valve on a 1994 celica? Ive heard of it before but i don't know where to find it... Im fairly hopeless at recognizing things especially since the engine bay is pretty dirty. Could you show me a picture of where it is located? Thanks for the help by the way! As soon as i can find it, ill be sure to clean it out, I've tried cleaning the IAC and it seemed to bring the RPMS up a little bit but still its very low when in gear.

[Noahwhite2014]

Sorry for being so nebbish. Explored my engine bay today, and saw the vacuum line diagram on the car. Easily pointed the EGR valve out. and DAMN that was PITA to get out since the nut that holds the EGR to the pipe from the exhaust was corroded! I replaced that nut and am about to clean out the EGR valve with some carb cleaner. Is there an easy way to get the pipe that connects the EGR valve to the exhaust? It seems i have to maneuver through all kinds of hoses and wires to get to the two bolts holding it on... Then once i got the socket and rachet in there, i had a few millimeters for the upper bolt, and i couldn't even get the lower bolt turned due to the tight space... is it okay to just shoot some carb cleaner down the pipe? Let me know thanks!! Hopefully this works!

[Special_Edy]

The pipe just runs down to an exhaust port in the head, probably best to use throttlebody cleaner and some compressed air, or not clean it out at all. Its tricky getting the nut loose, you obviously need a crescent wrench. You may be able to get it loose if you want without removing the throttlebody or distributor. Remove the distributor and you will need a timing light to reset the ignition advance.
You dont want carb cleaner getting onto your catalytic converter or O2 sensor, and you dont want to knock a bunch of crap loose which will get sucked up into the egr valve and intake manifold.

Carb cleaner will work great in the valve itself though.

[Noahwhite2014]

You dont want carb cleaner getting onto your catalytic converter or O2 sensor, and you dont want to knock a bunch of crap loose which will get sucked up into the egr valve and intake manifold.

Carb cleaner will work great in the valve itself though.

Alright i was kind of thinking it may be dangerous to do this but I'm willing to do anything to help get my car running properly. So the valve is clean and reinstalled now and it idles a bit better (about 30-50rpms higher than before but still low) and it is much smoother now. In gear the RPM also drop about 200... This can't be normal can it? And also when the Air condition is turned on, the car shakes a lot, but not as much as before. The RPM also drops from the AC by about 100.

So:
In gear with the AC on I'm idling around: 200-400
In gear with the AC off I'm idling around: 300-500
In park/Neutral with the AC on I'm idling around: 500-600
In park/Neutral with the AC off I'm idling around: 600-700

I find this odd and so confusing since isn't there a valve that is supposed to bring the RPM up when the AC is on..?

should i try unplugging this valve and seeing if it makes a difference at idle? If yes where can i find the valve/connector to stop it from functioning.

Also just wondering, is it a bad idea to adjust the idle adjust screw just to bring my RPM up a bit? I just want to know as a last resort sort of fix to make sure my engine doesn't die out on me at a stop light on a hot day this summer while my AC is on!

[rentaspace]

My car does this too, in fact sometimes it's so bad I feel as if it's only starting on 3cyl, it actually sounds like a diesel when it does it...
This Video Of The Problem shows when it is terrible. The car will be shaking violently inside and sounds like it's gonna explode...

When it isn't so bad, sometimes a little throttle will be alright... But my car is always shaky in gear at idle...
I have cleaned the EGR but hasn't helped... Might have to replace it




Also with your AC problem, I had that EXACT same problem, there is a valve and I cannot remember it's name but I did post somewhere before about it. I cleaned it and it solved the AC problem.

This post has been edited by rentaspace: Jul 12, 2014 - 5:14 AM

[Special_Edy]

Unplug the efi fuse or disconnect the battery for 30-60 seconds. This will reset the ecu to factory settings so it can 'relearn' the engine.
Maybe clean out your idle air control valve on your throttlebody and check your ignition advance with a timing light if you can get your hands on one.

A 100-200rpm drop when the engine is put into gear is normal. Idle speed is usually measured in Drive on an auto, not in park. Thus the manual idles 200rpm higher since it is measured in neutral.

[Noahwhite2014]

My car does this too, in fact sometimes it's so bad I feel as if it's only starting on 3cyl, it actually sounds like a diesel when it does it...
This Video Of The Problem shows when it is terrible. The car will be shaking violently inside and sounds like it's gonna explode...

Also with your AC problem, I had that EXACT same problem, there is a valve and I cannot remember it's name but I did post somewhere before about it. I cleaned it and it solved the AC problem.

My car only sounds like yours when the AC is on, hopefully mine doesn't get that bad. But yeah my car is sounding like a bus just scaled down...

Unplug the efi fuse or disconnect the battery for 30-60 seconds. This will reset the ecu to factory settings so it can 'relearn' the engine.
Maybe clean out your idle air control valve on your throttlebody and check your ignition advance with a timing light if you can get your hands on one.

A 100-200rpm drop when the engine is put into gear is normal. Idle speed is usually measured in Drive on an auto, not in park. Thus the manual idles 200rpm higher since it is measured in neutral.

I'll disconnect my battery today before going out to brunch since ill be catching a ride, hopefully it helps with the relearning process. Ill try to clean out my IAC again since the first time i didn't do a good job i believe. Im not sure how to check the ignition advance with a timing light, but I'm fairly sure my dad has a timing light since I've heard him talk about it before. I will let you know

[rentaspace]

Idle air control valve is what solved my air con problem, still got the idling problem though

[Noahwhite2014]

So I've let the computer reset at what not with the battery off. And glad to say:

Park/neutral AC off: just a hair below 1k
Park neutral AC On: around 900rpm
In gear, AC off: 700rpm
I'm gear AC on: just below 600rpm

Here's the awesome part though: the shaking is no longer as bad AND my engine starts almost instantly!

Checked out my spark plugs: I'm gonna replace them and the wires with NGK G power plugs and a TE41 wire set.

The plugs I found in there looked pretty old and the gap was huge... Hopefully this wire and plug set smooth out my ride.


Gotta work on that AC though I don't like how the rpm drops ... IAC is next on my list

[rentaspace]

So I've let the computer reset at what not with the battery off. And glad to say:

Park/neutral AC off: just a hair below 1k
Park neutral AC On: around 900rpm
In gear, AC off: 700rpm
I'm gear AC on: just below 600rpm

Here's the awesome part though: the shaking is no longer as bad AND my engine starts almost instantly!

Checked out my spark plugs: I'm gonna replace them and the wires with NGK G power plugs and a TE41 wire set.

The plugs I found in there looked pretty old and the gap was huge... Hopefully this wire and plug set smooth out my ride.


Gotta work on that AC though I don't like how the rpm drops ... IAC is next on my list

Awesome!
IAC is easy as he'll to clean, I just cleaned it in petrol Lol....

But yeah, 5minute job to remove clean and replace.
I might give resetting my ecu another try, but I doubt it's gonna help haha

[Noahwhite2014]

Just gapped by spark plugs and cleaned the IAC and my car is running a bit high now. In park I'm at about 1050 RPM and in gear now its at about 900, When the AC is on, my RPM goes up about 100 then down 100 from the original idle RPM then goes back up to the regular RPM.

So the screw that adjusts the resting point of the throttle plate should be completely blocking air off correct? and the only air should be through the IAC?

[rentaspace]

Just gapped by spark plugs and cleaned the IAC and my car is running a bit high now. In park I'm at about 1050 RPM and in gear now its at about 900, When the AC is on, my RPM goes up about 100 then down 100 from the original idle RPM then goes back up to the regular RPM.

So the screw that adjusts the resting point of the throttle plate should be completely blocking air off correct? and the only air should be through the IAC?

Those figure sound normal, that's what mine runs at when idling alright.
Mine still shakes like crazy thought lol

[rapid36]

So I've let the computer reset at what not with the battery off. And glad to say:

Park/neutral AC off: just a hair below 1k
Park neutral AC On: around 900rpm
In gear, AC off: 700rpm
I'm gear AC on: just below 600rpm

Here's the awesome part though: the shaking is no longer as bad AND my engine starts almost instantly!

Checked out my spark plugs: I'm gonna replace them and the wires with NGK G power plugs and a TE41 wire set.

The plugs I found in there looked pretty old and the gap was huge... Hopefully this wire and plug set smooth out my ride.


Gotta work on that AC though I don't like how the rpm drops ... IAC is next on my list

Awesome!
IAC is easy as he'll to clean, I just cleaned it in petrol Lol....

But yeah, 5minute job to remove clean and replace.
I might give resetting my ecu another try, but I doubt it's gonna help haha

How were you able to remove clean and replace yours in 5 minutes?

[blockustomz]

I had this problem on my 1.8 190k manual. It turned out my intake manifold, throttle body, and egr was all dirty. Pretty bad too, I took off the throttle body and just the top half of the intake manifold. Than cleaned it all with carb cleaner..
Car now starts very smooth with cold starts as well as faster throttle response cruising around.. Wish i did it a long time ago.

[Noahwhite2014]

I had this problem on my 1.8 190k manual. It turned out my intake manifold, throttle body, and egr was all dirty. Pretty bad too, I took off the throttle body and just the top half of the intake manifold. Than cleaned it all with carb cleaner..
Car now starts very smooth with cold starts as well as faster throttle response cruising around.. Wish i did it a long time ago.

Thanks! I'll try that out!

Anything to be careful of when taking the intake manifold apart?
Egr is clean as a whistle (mine had a layer of carbon built up inside)
Throttle body is clean as of a month ago or so

[blockustomz]

Thanks! I'll try that out!

Anything to be careful of when taking the intake manifold apart?
Egr is clean as a whistle (mine had a layer of carbon built up inside)
Throttle body is clean as of a month ago or so

Nothing really to be care full of. Just take you time and don't rush.
Try to clean off all the layers of carbon build up.

I also cleaned my TB a month ago but if you're like me you will have alot of carbon build up inside. You still have to take off the TB to access the intake plenum. Aswell as remove 2 studs out of the Intake Manifold that comes through to the Throttle body.