It's a bit of a cheeky ask, but I know we have some great guys (& gals) on here, so hoping someone can bail me out!

I have a F reg MR2 4AGE engine in a kitcar - at some time in its life the plugs that connect the loom to the distributor have been discarded & the wiring soldered together, I have strong suspicions that they may be incorrectly connected. Sometimes when you start the car it runs completely normally, absolutely fine, but sometimes it's as tho' it has started in a different "ignition mode" - it sounds as tho' timing is really retarded & if you try to rev, it won't rev out, just sounds really flat, turn it off & restart & everything is fine again, it rarely takes more than a couple of starts b4 everything returns to normal. All other wiring & sensors are standard, hence my suspicions of this distributor wiring. The odd thing is that the wiring colours don't match - from the loom I have 3 wires a black, a white & a red, the black & white go directly to the ECU, (but don't match the pins on a wiring diagram I found!)
unsure at present where the red goes. At the distributor the wiring colours are red, blue & white, the way it's currently connected (dist to loom) is red to black, white to white & blue to black.

Is there any possibility one of you wonderful people could peel a bit of loom back adjacent to the plug (plug is 3 wire plug right near the distributor) each side & tell me which wire is connected to which?

I have tried various combinations &, weirdly it seems to run in each of them, but I need to know which is correct so I can then proceed to set timing up correctly etc.

Checking the wiring to the distributor, I know it has 2 different types of sensors, one of which generates 4 pulses & the other generates multiple pulses (12 or 24 per revolution IIRC), the white wire shows 160 ohms between it & the blue & the same 160 ohms between it & red, so I assume they share an earth & the red & blue relate to the 2 pickups, just to make things more confusing, go inside the distributor itself & the wiring colours are just black & white! no red or blue in sight, they must change colour within the actual moulded connection into the distributor!!!

Any assistance much appreciated, I've looked at the manual & various wiring diagrams but nothing really helps!

I don't have an mr2, but...
it sounds like it is going into a valet parking mode, which when I look it up, some toyota's limit it to 4000rpm

Sounds a bit sophisticated for something of that age?

Ahh it's going back years now to when I megasquirted my 3SGTE of the same era, and the toyota ignition module, if it doesn't get accurate feedback from the cam/dizzy VRs, flat refuses to rev over 5500rpm. It will still start and run, but runs like a bag of spanners.

Ahh it's going back years now to when I megasquirted my 3SGTE of the same era, and the toyota ignition module, if it doesn't get accurate feedback from the cam/dizzy VRs, flat refuses to rev over 5500rpm. It will still start and run, but runs like a bag of spanners.

Ah hang on, not the same ignitor I don't think. Ignore me, I did spend forever fighting a 5500rpm limit due to this but it looks like you don't have the same sensor/wiring setup.

[Edited on 27/8/20 by coyoteboy]

I have a 4age from an MR2. it will use standard injection.
I have taken a picture of the loom side of the distributor connector but can't upload it

I could email it to you

The wiring goes:

Dist Red --> Loom White
Dist Black --> Loom Black
Dist White --> Loom Red

So the wiring is not what you'd expect.

If it helps, I have quite a bit of 4age documentation, PDF manuals and wiring diagrams

[Edited on 27/2/24 by _luke]

quote:

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Originally posted by JonBowden
I have a 4age from an MR2. it will use standard injection.
I have taken a picture of the loom side of the distributor connector but can't upload it"

I could email it to you

The wiring goes:

Dist Red --> Loom White
Dist Black --> Loom Black
Dist White --> Loom Red

So the wiring is not what you'd expect.

If it helps, I have quite a bit of 4age documentation, PDF manuals and wiring diagrams

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Hi, I have sent the photo to your email.
The distributor wire probably is blue - but it was a dark blackish colour.
I'll look up what diagrams I have and get them to you.

ok, a bit more digging.
There is a 4age manual at http://files.aeu86.org/manuals/4A-GEManual.pdf
There seem to be a few different ECU pin-outs.
If you open the ECU, the pins will be labeled in tiny writing
The pins you want will be labeled G, G- and NE
I will send you a simple ignition wiring diagram by email

Hi Jon, not had a proper chance to look at it all yet, but I think that's exactly what I need, particularly knowing if I open ECU can get the pins identified, you defo seem to have a black wire where I have blue, but I'm guessing as the other 2 wires are the same the ble is the same as the black, I think the wiring diagrams you've sent will confirm anyway, much more comprehensive than anything I'd found

I will post findings when I get a look at it Tuesday/Wednesday in case it's of any use to someone else in future

OK, all sorted, many thanks!

In case anyone has similar issues. on my ecu labelled Denso 89661-17140 & 175700-1042

G- is pin 3, loom wire is red connects to the distributor white wire which is common to both sensors
G is pin 4 Black wire in loom connects to blue or black wire at distributor which is the 4 pulse sensor
NE is pin13 White wire in loom connects to red at distributor which is the multi pulse sensor

Totally bizarre system & can't work out how it was even running b4 as the red wire was broken within the loom which you would expect to kill both sensors!

Once restarted & checked timing was a fair way out, but all working fine now!