4AGE Wiring Question

[Steelies]

cant find much info on 3 wire dizzy wiring. i shortened the dizzy wires but put it together as it was, so if it was wrong to start with would it run funny, if a couple of the wires were around the wrong way or would it not run at all?

[Unclejake]

The way I see it you have the below to eliminate in the following logical order:

1) Mechanical drive to the dizzy shaft

2) Alignment of the rotor to the posts on the dizzy cap when the ignition charge is sent (rotor phasing)

3) The signal from the dizzy (or is it a cam angle sensor?) to the computer

4) The computer

5) The signal from the computer to the dizzy

#3 sounds like a good place to start if you want to jump the que

[Spencer]

Yea maybe try another igniter?

basically the dizzy has 3 wires G-, G1 & Ne. There are two VR sensors in the dizzy G- & G1 are the signal and NE is a common earth. If you only shortened these I cant see them being the issue

The Ecu takes this on board and then sends the signal to the igniter when to fire the coil, The igniter also sends back an ignition event conformation to the ECU ( pins IGT & IGF)

With a scope you could quicky check if all these are correct.

So you set the dizzy up in the correct place, then all I can see the possible faults being

1)VR sensors inside the dizzy

2)ECU

3)Igniter

or the wiring inbetween them is somehow wrong

[Unclejake]

Is the igniter a finned alloy box bolted to the side of the coil?

How does the ECU computer thing know when to advance the timing? Is it connected to some kind of sensor in addition to the ignitor? The reason I arsk (apart from being an ECU noob) is that the igniter is not hanging off the engine so would not be reading engine speed by itself

[Spencer]

Is the igniter a finned alloy box bolted to the side of the coil?

How does the ECU computer thing know when to advance the timing? Is it connected to some kind of sensor in addition to the ignitor? The reason I arsk (apart from being an ECU noob) is that the igniter is not hanging off the engine so would not be reading engine speed by itself

Yup finned alloy box on the coil.

The ECU gets the rotation signal from the dizzy itself there are 2 toothed wheels in the dizzy one is (i think off the top of my head) 24 tooth for resolution, and one maybe 2 or 4 tooth which relative to the 24 tooth wheel gives a TDC position.

The ECU then has a pre-programed igition map which is based on RPM and load (load in these engines is measured by manifold pressure) it then outputs the desired advance for these conditions. (which were optimised on a dyno in the toyota factory back in the 80's)

The ignitor is a 'dumb' device in that its basically just the transistors that trigger the coil. The desired advance is calulated by the ECU & sent to the ignitor as variable square wave which then triggers a spark event on the rising(maybe falling) edge of the square wave

[Unclejake]

^ You rool.That all makes perfect sense. Thanks Spence (the sense).

Steelies: You changed manifold pressure yesterday by adding that catch can and now have a bag of nails.

[KKtrips]

its always done this - even before the catch can..

[Beaver]

fuk you cunts know your stuff

continue helpful advice....

[Unclejake]

The ECU then has a pre-programed igition map which is based on RPM and load (load in these engines is measured by manifold pressure)

its always done this (retarding the timing as the revs increase) - even before the catch can..

Is there a vacuum port on the ECU or was there supposed to be something extra connected to all those vacuum ports Steelies blanked off at the front of the throttle body that connected electrically to the ECU?

[Steelies]

cool thats awesome. i can hook up a scope through work but wouldnt trust i'd be able to use it properly once at the garage.

so first step will be to test wiring and make sure everyhting matches up to spencer the walking toyota bible.

and call toyota parts centre (seedy al) and see if he has a spare dizzy and coil/igniter to try also.

UJ - yeah the bag has been full of nails since it first ran, catch can went on on friday. i'm keen to see how the emissions have changed since putting the can in, even with crazy timing readings.

negatory on the vac to ecu

[Unclejake]

negatory on the vac to ecu

Then you are missing an engine managment component and should stab CDL in the liver for ripping you off before trying different dizzys etc.

[Spencer]

It would run like horse shit if there was no manifold pressure sender, Its just a little black box with a vacuum line going to it. There is a manual for these somewhere on the net that gives the basic voltages and waveforms that should be present on the pins of the ECU/Dizzy, I'll have a look. The factory workshop manuals are an awesome tool for engine management fault finding

[Spencer]

http://files.aeu86.org/manuals/4A-GEManual.pdf

that should be the whole workshop manual for the 4age of your era (100Meg) which should contain a whole section on electrical faults. I wont have your exact problem, but it will have what voltages etc should be on what pins/wires

[Unclejake]

^ good shit. If the manifold pressure sender is present then it could be the fault.

[l1ttle_d3vil]

not sure if this would effect the timing, but if when you rev it it runs like crap but eventually revs up etc, check the TPS is set correct. even swap it over incase just to rule it out completely.

also it has to have a map sensor fitted, should be a black box with vacuum line and a yellow round 3 pin plug, original plug on the loom should be near the injector plugs.

cant find much info on 3 wire dizzy wiring. i shortened the dizzy wires but put it together as it was, so if it was wrong to start with would it run funny, if a couple of the wires were around the wrong way or would it not run at all?

double check these wires are around the right way. did you just wire them up so the wires match their colours between the loom side and dizzy side of the plugs? because these colours definitely vary between models, eg G- signal is red or white, NE signal is red, black or white depending on what model you've got. suss out which pins are the G- / G1 / NE / on the dizzy plug and make sure they go to the appropriate pins on the ecu itself.

I had a few problems with mine ages ago when two wires on the dizzy were around the wrong way, pretty much every time it started it would run differently due to the timing being in a different place, and would advance instead of retard etc. BUT i think when i finally got it running right, the wiring colours didn't match up from the loom to the dizzy plug. also make sure the wires on the dizzy plug you reconnected have a good solid connection, if they don't they can cause similar problems to what you're describing. ah so many possibilies!!

[thegreatestben]

I am removing the Dizzy from my MR2 next week weather permitting if you want to try bits known to work fine.

4AGE timing should be cake

[Spencer]

I wouldnt touch the TPS unless you know some fool has moved it. As long as it sweeps 0-5 volts it wont cause an issue. Only thing you really need to check is that the idle switch in the TPS is engaged when the throttle is closed. I very much doubt the TPS would cause this issue though.

[KKtrips]

how to check this throttle switch??

also MAP sensor is definitetly there..

[Spencer]

There will be 4 wires running into the TPS, 5V (possibly black-red stripe) earth (brown) A variable out put that changes with throttle opening 0-5V (maybe red) and a idle circuit switch which I think goes high when the throttles closed (black i think).

All you need to check is that one has 5V, one changes 0-5v when you move the throttle, and one that latches high when the throtlles closed.

[Steelies]

a dizzying weekend in the wag, now time for more starlet puzzling yay..

does the computer use tps signal to change timing?

the cert guy had a twiddle with the tps and put it 'where its supposed to be' so i'm unsure on the position of that sucker. regardless, this is a problem that has been constant through a few months of fucking with everything. will try test tps to the above specs tonight methinks