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Toyota Corolla 4AGZE Trigger Questions.

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Hi there,

I have just recently installed a Haltech Elite 750 ecu into my 4agze, it has a reluctor sensor (24 tooth trigger, 1 tooth home) and I wish to get this thing going and hope someone can shed some light for me as to what might be going on.

Now after trying to get this thing to run then cut out often with weird settings, I resulted to calling Haltech directly about this problem.

I was then told that the 24tooth 1home 4agze CAS can be quite a nightmare to receive a home signal often and consistent, and was suggested that I grind a tooth off anywhere on the 24 tooth trigger wheel and run (Generic - Missing tooth - Single Home) as trigger type. So I did just that. (24 teeth 1 missing)

Since then I have not been able to get a consistent Trigger pattern. I have had Haltech on the laptop doing remote help with "guessing" Trigger Arming Voltages and no dice. It seems the "Trigger Synchronization State" reaches "RUNNING" and "Trigger Synchronization Level" reaches "FULL" very intermittently and when hooking up a timing light to cylinder 1 the timing light will only flash a few times or VERY irregular when trying to set TDC Offset Angle.

I have heard that 1 guy in the past has actually grinded another tooth off the 24 tooth wheel OPPOSITE of the tooth already ground off to make a 12-1 and then set to crank but i am not sure how this would help get a consistent trigger.

I am also buying a Oscilloscope in the next coming week and am also wondering if watching the trigger pattern and setting the arming voltage correctly will solve this or not.

I would be happy to pay for a remote session to be done with anyone from HP Academy who could help.

I hope anyone can shred some light on this situation thank you.

If there is any more information anyone needs I will post straight away.

Thanks, Sam.

Oscilloscope should be the first step, you can then confirm voltages, confirm edge setting and confirm the waveform is the correct shape and crossing zero etc. The 24T Toyota is very simple and reliable and should not need to be modified. They sometimes put out quite low voltage at slow cranking speed but generally by 200RPM they are pretty typical distributor level trigger voltages.

Post a scope capture here when you have one if you dont find the problem yourself.

Thanks Adam. I will post a scope capture of the trigger when i can! I am pretty unhappy that i have now destroyed the sensor that was once working with all 24 teeth all because I thought listening to Haltech would be the right way to go. :\

You havent done any harm by making it missing tooth - just wasted a bit of time and not achieved much but the CAS will still be perfectly fine to use with a missing tooth.

I definitely dont see any merit in making it 12-1.

Reflecting Adam@Motorsport's comments.

I had MASSIVE issues on a small diameter (100-120mm ish from memory) 24-1 trigger wheel and reluctor sensor on my 4age. The issues were -

Any gap greater than about 0.8mm resulted in poor starting and the possibility of misfire above about 7500rpm.

Any gap much greater than about 1mm resulted in NO starting and the of misfire above about 7000rpm.

As a result of the above, the stiffness of the sensor mount was also critical. I had to set a gap of 0.5mm and make sure it didn't change significantly.

The slightest poor contact, or moisture in the connector, resulted in poor/no starting and misfire at higher RPM. I ended up triple sealing the connector.

Can you post of picture of your current installation, might help.

Oh, Well that's a relief! Do you think my problem is the Trigger Arming Voltages? do they have to be pretty spot on to get full running sync?

I suppose time will find out when i get my scope connected.?

Do you think my problem is the Trigger Arming Voltages? do they have to be pretty spot on to get full running sync?

Unlikely. Arming voltage just sets the minimum the waveform must exceed for it to be considered a valid tooth, usually not critical and a wide range of settings will work unless there is a large amount of noise. More likely something else like wrong edge setting or not crossing zero due to a ground offset.

Thanks for your input denis, did this solve your problems? if so i haven't changed the trigger sensor location from stock. what your saying is that should it be closer or further away from the teeth of the 24 wheel

Yes it did. However mine was a retrofit, on the early 4age as stock it just run off a sensor in the distributor. Not sure what the setup on your engine is, hence a photo could help.

Please find Images in link below.


Yep...same system. We got rid of it in place of a more typical crank mounted trigger disc and sensor. If nothing else it would be more accurate.

Hmm, was it a universal disc and sensor? and how did you go about mounting the sensor and what not :\ starting to seem like a stuff around tbh :\

The universal disc was bolted to the front crankshaft damper (and then the pulley when the crankshaft damper was removed because it was partly responsible for breaking crankshafts, long story).

The sensor bracket was bolted to two of the sump bolts and tapped hole that was spare on the water pump. Pretty simple fabrication from some ali plate.

On a 10,000RPM full race engine ignition timing was very important so the effort (a day or two) was justified.

I suppose it depends whether it would be easier to get the standard distributor based setup working or spend a couple of days fabricating something that can be guaranteed to work.

Just saw this while searching around, MRP Do a trigger wheel setup i wonder if this will solve my problems for good, Would 24-1 be better or 36-1?


Pretty much what I had, it would be fine.

In theory 36-1 COULD give slightly more accurate ignition timing. On anything below a full race engine the difference would be negligible though.

I ended up setting the arming voltages really low today, also setting trigger to (Generic - Missing tooth - No home) to simplify things and i eventually got the engine to fire on Aerostart after setting the TDC offset properly. Thank you for all your input and support.

I had the engine running today after checking all water and oil leaks and stuff, i started to much around with the idle and afr. I noticed when i try to add any throttle what so ever the engine will idle up then die then idle up and then die over and over and sound really rough all while i noticed that the Wideband was leaning out to 20:1 then back to 14.7:1 everytime the engine cut out. If no one has any idea, i suppose i could upload a Datalog of the engine doing what it's doing. I was wondering if it has anything to do with "Transient Throttle"?

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