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Discussion Starter #1
Greetings All,

Please can someone tell me where the ECU is located.I have searched the internet but to no avail. I have a RHD vehicle, 1990 Toyota Corolla, 1,6 Gli Twin Cam, 5 speed manual.

Thank you
 

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Usually it's behind the center front console. You either get to it from the passenger side footwell or remove what you need to from under the radio area. Maybe both to disconnect the wire harness from the front and remove the ECU from the side.

Are you trying to test wires at the ECU or do you suspect the ECU is bad, or are you doing some other modification?

Usually the ECUs don't go bad but it's possible after ruling out other things.
 

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Discussion Starter #3
Thank you for the reply. I have just had my head gasket replaced as it blew between cyclinders 3 and 4. This was caused by my timing being out and not rectified by the previous technician that worked on my vehicle. My vehicle has power and is running smoothly except for "pinking" every now and then. The technician that worked on my vehicle says he is happy that the vehicle is mechanically sound and I tend to agree with him. I have had this vehicle since new and is 29 years old and has done 806 000km's. I just want to remove and re-connect the ECU just in case there may be corrosion around the connectors.
Thank you
 

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Incorrect cam-timing would also throw off ignition-timing as distributor is keyed to cam. If cam-timing and belt-tension is now correct, ignition-timing should also be correct (assuming distributor adjustment is correct.

ECU connector corrosion is extremely unlikely and would not cause issues with ignition timing (this is digital system).

Multiple causes of pinging:

- incorrect distributor adjustment (measure ignition-timing with timing-light)
- insufficient fuel and resultant lean mixtures, measure fuel-flow on injectors 3 & 4
- hot plugs, may be caused by incorrect plug-range on 3 & 4, or worn plugs
- high-compression, due to carbon-buildup, do compression test on all cylinders
- hot cylinders, can be due to clogged/insulated areas caused by deposits in head. Flush and clear cooling system

Headgasket blowing may also be caused by warped head from previous overheating event. Did flatness of head and engine-block deck get measured during repair?
 

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Discussion Starter #5
Thank you Sir.

Very interesting.

incorrect distributor adjustment (measure ignition-timing with timing-light)100 % happy

- insufficient fuel and resultant lean mixtures, measure fuel-flow on injectors 3 & 4. I need to check this.
- hot plugs, may be caused by incorrect plug-range on 3 & 4, or worn plugs . 100% happy
- high-compression, due to carbon-buildup, do compression test on all cylinders. Need to check this
- hot cylinders, can be due to clogged/insulated areas caused by deposits in head. Flush and clear cooling system. 100% happy
 

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With diagnostic port jumpered, what ignition-timing did you measure? No variations? Steady idle RPMs?

Easy way to measure injectors is pull fuel-rail with injectors attached. Place little cups under each injector and jumper B+ to FP terminals in diag port for 30-seconds. Pour each cup into graduated cylinders to measure exact CC flowed for each injector.

Also, test injector harness:
- disconnect all injector connectors from injectors
- Key ON
- measure for voltage on each injector connector terminal
- one should be +12v battery voltage
- 2nd should be zero volts. If you have any voltage on 2nd terminal, there's short in wirng harness leading to incorrect injector flows
 

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Discussion Starter #7
Thank you.

Your question: With diagnostic port jumpered, what ignition-timing did you measure? No variations? Steady idle RPMs?

What diagnostic port must be jumpered? My ignition timing is set to 15 degrees as I live at sea level. My idle is very erratic when vehicle is hot.

Your question: What ignition timing did you measure? Are you referring to using a timing light?

My head was sent to an engineering firm who cleaned and checked the necessary. All in order.
 

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Jumper Te1 and e1. With engine running this is how you set the ignition timing and the idle speed (if it's adjustable). The specifications are on the sticker under the hood. (I assume there is a sticker like in the USA.) And it should say jumper Te1 and e1. The diagnostic port should be near the strut tower under the hood.

If you only have key ON but the engine not running the check engine light will flash any stored codes in a series of flashes with a pause between digits. If no codes are stores it will constantly flash.
 

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Discussion Starter #12
Thank you. Let me try this. I tried to attach a video of how my vehicle is idle ling erratic but will not allow .mov files.
 

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You would have to upload a video to youtube then post the link here.
 

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Thank you all. Please see video. Apologies for so short. Erractic reving when hot.


I'm tending to think issue is pointing to fuel starvation. My Technician can only look at my vehicle on Monday next week.
Excellent info so far.
 

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Discussion Starter #15
Greetings,

Just another issue. Yesterday my engine management light came on whilst driving to work. When I arrived at work I switched my car off and then started it again and the light never turned on. When I left work the light still stayed off until I reached about 60km and then came on again. As the light came on I felt a small loss in power but the vehicle still kept going. Upon arriving at home, I switched the vehicle off waited about 10 mins and then started the car again and went for a slow drive not past 60km's, the light stayed off. Any ideas please?
Vehicle is a 1990, Toyota Corolla 1,6 GLi Twin Cam 16 valve. 4 AGE engine.

Thank you
Jeffrey Zeeman
 

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Read the stored codes. Jump Te1 and e1 in the check connector with a paper clip then turn key to ON position. Check engine light will blink out the 2-digit codes.

Do a search for info or videos showing how to do this if you've never done it before and don't understand exactly what to do.
 

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Thank you all. Please see video. Apologies for so short. Erractic reving when hot.

https://youtu.be/mbzUxpe4iM8

I'm tending to think issue is pointing to fuel starvation. My Technician can only look at my vehicle on Monday next week.
Excellent info so far.
This is caused by vacuum-leak. Extra air sucked in and engine revs higher. ECU tries to correct by closing IAC, engine slows down. Extra air sucked in leak and engine revs higher, etc. etc. etc.

Vacuum-leak also causes lean mixtures, especially when you increase throttle. Lean mixtures causes stumbling, loss of power.

And... leak has gotten worse and mixtures are lean enough to throw a code... probably 25.
 

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Discussion Starter #19
Greetings All,

I have jumped Te1 and E1 and receive error code 52, which is knock sensor. We replaced and tested the knock sensor and vehicle still pings only when hot and is intermittent. Pinging occurs more often under acceleration and under load. I have also noticed whilst climbing a hill and speed reduces, I then need to change down a gear to maintain speed and pinging is very prominent. I have noticed, when vehicle is cold it does not ping. I have done a bit of research and there seem to be so many variables that can cause pinging. Vehicle is 29 years old and I have done 811 000 km's. Valves were replaced at 750 000 km's. Original bottom end of engine, same pistons, rings, etc.There is a bit of carbon build up on the pistons, but my Technician says nothing to worry about.

The below is a quote from one of the forums on the internet, which I found interesting:

"The pinking/detonation typically occurs at lower to mid-range rpm under heavy throttle, often going up a hill for example. The solution for me has been to install a slightly heavier spring in the distributor that regulates initial advance. Engines are most sensitive to this in mid-range."

Any further suggestions please?
 

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If the ignition timing is adjustable then check/adjust it to proper specification with a timing light. This is where you aim the timing light at the pulley and loosen/rotate the distributor. Lots of how-to info and videos online.

If the timing is advanced too much it will cause pinging.

If you have an EGR system make sure it's working correctly. You can test all the parts: EGR valve, modulator, vacuum switching vslve (VSV). Also check and clean out all the EGR passages as they tend to get clogged over time.

The EGR system lets inert exhaust gases mix with the intake air/fuel and this slows down the combustion speed which prevents pinging.

These are the 2 main things that will cause pinging, assuming you are using proper octane fuel.
 
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