[aranciaman]

Hi all

I am new to the forum and am running out of ideas. I have the above mentioned vehicle. It is a Jap import into Aus and has the 3S-GE engine in it. Up until the other day it ran like clockwork.
I have only just purchased it and decided in my wisdom that I wanted to give the engine bay a really good pressure clean. I dried it all off and it was ticking over nicely until I decide to put some revs on it. It will only rev to around 2400 rpm and then hunts up and down like a fuel cut is running. It isn't missing and idles just fine. I dried everything off that I could think off or see, igniter, coil, dizzy, throttle pos sensor, air bypass... you get the idea. Either way it still does the same. I took it for a run on the road to try and get some heat into it thinking that this is a water issue. It ran like a rocket until I pressed the overdrive button on the auto and then it started to hunt again. Pressing the button will make it run fine, or not. I thought it may have a failsafe on the auto that sensed low oil level. Checking the auto revealed low oil and I topped it up. Took it out on the road again, same thing. Sitting in the shed, I can plant the boot to the floor and it will hunt.
Went to the local Toyota shop to see if they had encountered this and they hadn't. I am lost, I spent 5 years working as a Toyota Tech and never came across this issue.
Any ideas? There aren't any ECU codes, I have disconnected that battery for hours and tried again. Nothing. I need a fresh approach.
Thoughts?

 

[93celicaconv]

I don't know much at all about the 2.0L 3S-GE engine. I would think that an engine that cannot go above 2,400 RPM would trigger a CEL. Does your CEL light up when you first start the car? Or when the key in is the ON position? I would verify that the CEL actually goes on when the key is in the ON position or is being started first.

Does it exhibit this issue when the engine is cold and first started for the day? Or is it OK then, and only exhibits this problem after it has warmed up completely?

It sounds like it could be the position and/or speed pickup coils in the distributor (but problems here should trigger a CEL). Not sure if you model has a crank position sensor or not, but something wrong there might cause this symptom (but again, it would trigger a CEL). MAP sensor?

It almost sounds like your position & speed pickup coil outputs going to the ECU (through a shielded cable) may have lost the shield ground, so there is induced noise causing these signals to be distorted before they reach the ECU. So maybe check your cable shielding. Also, perhaps the water damaged your ignition condensor, so ignition noise is interferring with the pickup coil output signals.

Otherwise, I'm as lost as you are.

 

[aranciaman]

Thanks for the thoughts. I have checked and cleared codes. All the codes were to do with the tinkering and testing that I had been doing... unpluging things while it was running etc to see if it made a difference. Other than that, no codes. I spoke to one of my old Toyota colleagues from years past and as it turns out he is still working with Toyota and has quite a depth of knowledge. When I mentioned what it was doing he just went, ah yeah, you need to check.... and went on to tell me what should be causing it. Bottom line, he thinks I have either got the TPS wet on the inside or a stepper motor. Either one will cause the issue he tells me and can take a long time to dry out. He told me of a landcruiser that they had found the same issue with only recently which took them 4 days of sitting the stepper motor in front of a heater to rectify the issue. So, I will go home tonight and look for the stepper motor as he is not 100% that mine has one and if not, remove the TPS and have a good look at it. Will let you know.

 

[93celicaconv]

I wonder if what he calls a "stepper motor" is what we call the "idle air control" valve in the United States? I know that valves operates a lot by coolant temperature to adjust the amount of air bypassing the throttle plate to control engine speed, and it has a wiring harness on it for ECU fine tuning.

Good idea about the throttle position sensor (TPS). That can send bad information to the ECU, and the ECU sends out bad information back to the IAC valve that affects idle speed. Hopefully, between these two areas, you will find out what happened. Neither should have been affected by your engine cleaning, as they should have gaskets to prevent moisture from getting inside. But they are old too, so maybe something did get inside.

Let us know what you find out.

 

[aranciaman]

No, we call the air bypass valve the same in Aus. The stepper motor is located on the front of the Air Bypass valve. I have pulled the TPS off and the little stepper motor magnet off as well. They have sat in front of the heater now for three days. I must admit that I was a bit sceptic and didn't think it would do anything but was willing to try anything. I put both of them back on tonight and hit the key. It started and revved freely all the way through the range. No hunting or surging... success. I can now go ahead with fitting the new convertible canvas top. That is turning out to be a real challenge. Slowly, slowly is the key and it is coming together nicely. Soon it will be a nice looking little Celica again.
Thanks for the input and feedback.:thumbsup:

 

[93celicaconv]

Wow. So the fix was drying out the TPS & idle air control stepper motor? I would never have thought to do that. Thanks for sharing - I will have to remember this, as I also like to keep my 93 Celica convertible engine spotless, so it gets an occassional engine cleaning, like you did. If I develop this problem, I now know at least one thing to try to correct it.

 

[aranciaman]

Well change that. It was free revving and running perfectly in the shed the other night. I got home from a weekend away and decided I would take it for a run. Started it and just gave the throttle a tap... same. Hunting, hunting and hunting. Took it for a drive anyway, just because I could and it would come and go. Sometimes good and others not. It seemed to get worse as it got warmer. Came inside, annoyed and stumped. Sat for a while and went back out to the shed to have another look. Started with a good solid wriggle test which produced nothing. Started unpluging sensors while the engine was running, thought what the heck it will only throw codes which I will clear later. Unplugged all the sensors I could see from up top and made no difference. Was thinking that it seemed to be associated with the auto overdrive so I had a look to see what sensors or plugs were on the tranny. One on the inhibitor switch and another three pin plug, the overdrive maybe. Anyway, unplugged the three pin because it was easiest to get to while the engine was running and the idle revvs stumbled a little and then picked up a little. Plugged it back in and they stumbled and dropped again. Unplugged it and gave it a revv, revvs freely through the entire range. Plugged it back in and gave it a revv, hunt hunt hunt. Did this several times and reproduced the same results over and over. So, now am closer to a real solution and will get out in the shed tomorrow night and have a good look at the sensor and see if it is wet or just needs tossing. It looks dry at a basic glance but a good look will tell more. Anyway, you are now more up to date. I will let you know what I finally find.

 

[93celicaconv]

Let us know what you find out. Do you have a 5-speed manual or 4-speed automatic? If manual, I'm windering if that 3-wire connector on the transmission is the speed sensor? Not sure, I don't have manuals.

 

[aranciaman]

I have checked it out and found a manual on the net for it. It appears that the three pin connector is the overdrive solenoid. I found that if I unplug it and then plug it back in, it works fine. I unplugged it and plugged it back in several times last night and it seems to be working well at this point. May just have been dirty, not sure. That is the issue though. I am hoping that I dont have to pull the pan off and replace the solenoid. Oh, obviously I am running a four speed auto.
I tested the ohms reading on the solenoid and it was higher than it should be so it may have to come out yet. Will wait and see.

I am still refitting a new canvas top for it so it will be a little while yet before I get it back on the road. Canvas tops are a real pig to fit. Making sure that everything is just right before I apply glue is taking me ages. Ah well. Better to get it spot on and like it rather than stuff it and be several hundred out of pocket.

 

[93celicaconv]

I wish I could help you, but in looking over the North American version of your vehicle, the O/D solenoid only has a 2-wire connector used here (with a red wire with blue stripe, and a yellow wire with black stripe). And in looking over the North American circuit for an automatic, there is no connection between this circuit and anything to do with engine control. So all I can imagine is that your wiring circuits are different than those used here. You might want to spray that wiring connection (at both ends) with a good contact cleaner, then after letting them dry, reconnect them.

Good luck installing the new canvas top.

 

[aranciaman]

Well, it seems that the issue was a dirty connector on the OD solenoid. Why that would make such an issue I really don't know. I do now though and will be able to rectify it quickly next time it happens.
I have just finished fitting the canvas top, that was a real pig of a job. I got it all fitted up and then couldn't get the lid to close because the canvas was too tight. The instructions said that it needed to stay closed after the top was fitted for up to 14 days to allow it to take shape. The only issue was that I couldn't get it closed. I ended up using a whole heap of pressure, the wife and hydraulics to get it closed. Once it was left overnight it settled down nicely. Nice and firm.
I have just finished taking the Toyota amp out from under the passengers seat and fitted my nice big Pioneer amp. I have a lot more work to do but it is starting to come along nicely. The previous owner has fitted a JVC KW XC770 double din head unit which is quite a nice little unit. I still might replace it with a nice new touch screen system.
Well that is the latest anyway.