2JZ misfire. Possible dud ECU

**2JZR31** · 15-08-09, 12:24 PM

So no6 cyl has developed a misfire. Seems worst at idle and comes good at higher loads. Follow my tests and see if you can find an error my logic.

I swapped coil packs and sparkplugs on 5 and 6. Prob stayed in 6. So ruled out spark plug and coil pack as cause.

No6's injector plug has fallen apart. So I smashed all the plastic off and heat shrunk each contact and pushed them back on the injector individually. (well my coil plugs have been going strong like that for years).

Still fucked, so I am still thinking a high resistance join in the injector plug still. So I swapped over no5 and no6 injector plugs. Now the 2JZ is sequential injected, but even so the misfire followed the dodgy no6 injector plug no no5 cyl. Removal of the no6 injector plug from no5 injector caused no difference to the running of the engine. Removal of no5 plug from no6 cyl did cause an even rougher idle. So ruled out injectors and ignitor and cyl itself as cause becuase the fault followed the injector plug (update I even swapped the injector over and it isn't the injector)

Still looking like its the dodgy injector plug. I squashed down the 2 heat shrunk terminals from inside the original plastic plug like I done with all the coil pack plugs with success, and they fit on the injector pins very tightly. So I doubt it is that. But to be sure I stripped back some insulation from the wires of the injector terminals and tested from the stripped section of the wire to the actual terminals and it was continuous. To be even more sure I connected a wire with alligator clip to each stripped section and clipped them to the injector pins. And its still fucked! That ruled out the injector plug.

I unscrewed the large plug from the ECU and sprayed it and its still fucked.

What the hell is left? Its not the injector plug, spark plug, ignitor or the injector. Is it the ECU itself? Dodgy injector driver? FUCK FUCK POS CUNT. Imagine if it was no 4 plug or something? I would have has to remove the plenum for all these tests. I'm glad its not the injector as I would probably need to buy a whole new set.

Who has an Aristo or Supra ECU I can borrow?

**pH@tTm@N** · 15-08-09, 12:38 PM

i have manual supra ecu lying around if needed. north side of brissy tho.

**2JZR31** · 15-08-09, 12:41 PM

Cheers I'm on the Northside, but I probably need a Auto one.

**Sicarius123** · 15-08-09, 12:52 PM

Cost me under $20 to buy all new plastic clips from Toyota. Most of mine were wrapped and just pushed in and fuck it's all a lot smoother after. Much better connection.

**2JZR31** · 15-08-09, 01:02 PM

Yeah I really should get some good clips, but I don't think this is what I causing it ATM. Normally I can watch my digital SAFC rpm meter and the idle stays with in + or - 5 rpm. Thats pretty good for 20% bigger injectors and a bigger cam.

Rz · 15-08-09, 01:06 PM

theres a auto ecu here somewhere

Rz · 15-08-09, 01:07 PM

im going with number 6 cyl being bad

**2JZR31** · 15-08-09, 01:17 PM

Shit dont say that. Hang on, the fault moved when I changed the injector plugs over.

**JayVee** · 15-08-09, 01:20 PM

Do you have a probe to test the pulse at the plug?

Compression test wouldn't go astray.

Rz · 15-08-09, 01:23 PM

ah if it moved with the good plug then its gotta be the plug.
those pins are pretty close together , maybe theres some jumping going on.

**2JZR31** · 15-08-09, 01:23 PM

Yous cunts scared the shit out of me. It never really occurred to me that it would be mechanical. I just done this again to confirm its electrical. 2JZs never fuck up mechanically anyway.

Still fucked, so I am still thinking a high resistance join in the injector plug still. So I swapped over no5 and no6 injector plugs. Now the 2JZ is sequential injected, but even so the misfire followed the dodgy no6 injector plug no no5 cyl. Removal of the no6 injector plug from no5 injector caused no difference to the running of the engine. Removal of no5 plug from no6 cyl did cause an even rougher idle. So ruled out injectors and ignitor and cyl itself as cause becuase the fault followed the injector plug

**2JZR31** · 15-08-09, 01:24 PM

As for the plug itself.

Still looking like its the dodgy injector plug. I squashed down the 2 heat shrunk terminals from inside the original plastic plug like I done with all the coil pack plugs with success, and they fit on the injector pins very tightly. So I doubt it is that. But to be sure I stripped back some insulation from the wires of the injector terminals and tested from the stripped section of the wire to the actual terminals and it was continuous. To be even more sure I connected a wire with alligator clip to each stripped section and clipped them to the injector pins. And its still fucked! That ruled out the injector plug.

I suppose it could be the plug still but after all that I doubt it?

**2JZR31** · 15-08-09, 01:28 PM

Originally Posted by JayVee

Do you have a probe to test the pulse at the plug?

Compression test wouldn't go astray.

I have a multi meter. Whats the best way to test this?

**JayVee** · 15-08-09, 01:28 PM

Got a spare injector you can plug into the plug and see if it's being pulsed?

**2JZR31** · 15-08-09, 01:30 PM

Na I don't have a spare here.

**JayVee** · 15-08-09, 01:32 PM

Test 12V on one pin of the plug but not sure how you could test that it's switching the neg...whack it on ohms and see if you can compare to another injector....maybe the duty cycle will result in the meter giving a resistance reading?

It would if you had an analogue meter

Come to think of it...maybe a dud resistor in your resistor pack? The 12V check should show that up.

**2JZR31** · 15-08-09, 01:37 PM

I will hook the meter up. It might be a resistor. That would be easy.

**2JZR31** · 15-08-09, 02:27 PM

With ignition on and the engine not running. I have the same voltage either side of the resistors. So say 12.2V on the common side and 12.2V on the injector side of the resistors. The makes sense as the resistors should not be dropping any voltage since there is no current flowing when the engine is not running and the injectors are not being pulsed. BUT no6 reads a slightly lower voltage on the injector side, say 11.4V. This points to a current draw on the No6 injector. The resistor reads the same 7 ohms as the rest. Even when running the No6 has less voltage on it than the rest, but as soon as I unplug the ECU side the voltage comes back up.

My ma fuse is fucked on my meter, but on the 10A reading I do seem to read some fluctuating current in the no6 circuit.
If you ask me that points towards a fucked injector driver as it is behaving differently to the rest.

Thoughts?

**JayVee** · 15-08-09, 04:19 PM

With that explanation I tend to agree with you.

You need another stock ECU to check 100%.

Pop the cover off the ECU and look for anything suss...maybe reflow the solder joints upwards fromt he No6 injectors output, might get lucky.

**KDog** · 15-08-09, 04:21 PM

If it's sequential then it could be a dry joint on the circuit board to connector. Also it's transistor driver may be stuffed or the soldering on it.

Take a high res pic of the circuitboard and show me where that injector wire is. I could identify the driver if I had the ECU in my hand but there is no way to tell you from the pic as toyota change there drivers and internal ECU schematics like the wind.

**BMWTurbo** · 15-08-09, 05:13 PM

I've got a spare Aristo ECU if you want to try Dennis.

Can you remove #5 and #6 injector output pin from the ECU end and swap them over and BOTH ends. IE put #5 plug on #6 injector so that you've swapped the runs from the ECU and ignitor to rule out a break or intermitent break in the cabling.

**MRMOPARMAN** · 15-08-09, 05:20 PM

grab your multimeter, and check the continuity from the injector outputs at the ecu plug, and the injector plug.. of the resistance is infinate, check for break in loom. also check from injector plug to earth. and if you are able to back the injector pins out of the ecu plug without damaging them, check power to the injectors plug with the ecu side backed out.

if all thats ok, then it can really only be the ECU

**2JZR31** · 15-08-09, 08:47 PM

I have got my hands on a spare. I will see what happens when I fit it.

**Bozz** · 16-08-09, 08:02 AM

Originally Posted by KDog

If it's sequential then it could be a dry joint on the circuit board to connector. Also it's transistor driver may be stuffed or the soldering on it.

Take a high res pic of the circuitboard and show me where that injector wire is. I could identify the driver if I had the ECU in my hand but there is no way to tell you from the pic as toyota change there drivers and internal ECU schematics like the wind.

If they're anything like the Nissan ones, they frequently lose the triple/quad inline transistor driver array. Easy fix if you have a spare or two.

**2JZR31** · 16-08-09, 08:28 AM

Spare as in you need another fucked ECU? Or are they a generic part?

**Asteroid** · 16-08-09, 12:15 PM

You can usually source components like that easily enough, but without a part number we can't be sure.

**2JZR31** · 16-08-09, 11:14 PM

Runs perfect with the new ECU.

**BMWTurbo** · 17-08-09, 08:50 AM

Good result.

Did you 'retry' the old ECU for confirmation?

**2JZR31** · 17-08-09, 09:31 AM

No, but I did already unplug it, and plug it back in with no luck.

**BMWTurbo** · 17-08-09, 10:01 AM

Originally Posted by 2JZR31

No, but I did already unplug it, and plug it back in with no luck.

If it ain't broke....

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