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Missfire is back - Is it the AEM Injector Drivers?


jevansio

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My intermittent missfire is back, I thought I sorted it by replacing the coilpack connectors but sadly not.

 

Since the missfire seemed to be coming back I thought I'd elliminate some stuff.

 

1st I identified which cylinders, it appeared to be 2 & 5. The missfire would go in a cycle, it would be fine then 5 would drop, then 2 & 5 would drop, then it'd clear. This would happen regular as clockwork every 15 secs or so.

 

So I swapped coilpacks around, problem remained on 2 & 5.

 

So I swapped plugs around, problem remained on 2 & 5.

 

So I swapped injectors around, problem remained on 2 & 5.

 

Does this sound like the AEM injector drivers are going funny?

 

Also my AFRs seem to wander around in exactly the same cycle (even before the miss starts, but also as the miss is occuring), they'rr 14.7 for 15 secs, then swing lean then rich, then return to 14.7.

 

Any help appreciated :D

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Also just been out & unplugged the DLI, still remained.

 

Any chance it could be the injector resistor pack, it look a homemade thing made by Michel when the single conversion was done, not a UK spec one, it's damn hot (it's in the passenger footwell not the engine bay)? Does this tie in with the fact it seems heat related? Does the UK spec pack have that cover on as a heat sink?

Edited by jevansio (see edit history)
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I have my UK pack which I am going to sell, if you want to borrow it you are welcome. It was working well came out of the car last week.

 

Can you log this on your AEM?

Phil thanks for the offer, veyr kind, I will let you know shortly bud

 

Have you got access to a laptop oscilloscope gizmo? Then you can read the waveform at the injectors themselves and at the ecu outputs.

Way beyond my abilities Chris, I wouldn't know what I was looking at, maybe I can ask someone at work as they are that way inclined :D

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OK so I pulled the resitor pack into the open air & went for a run, it stayed coolish to the touch, then it started missing again :(

 

I got home & opened the resistor pack up, it contains 3 resistors each must control 2 cylinders. Is that too much of a coincidence considering I'm seeing a missfire on 2 cylinders?

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I would imagine a resistor capable of handling the current would be wire wound, and either OK or open circuit, I don't see how one could come and go, but electronics isn't my thing :)

 

Is the coil dwell time OK? When it plays up again can you swap the outputs of the ecu injector drivers over? I know that sequentially they won't fire in the right sequence, but you probably wouldn't notice difference. That way you could tell if the ecu was dropping an output.

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Thanks for the input Chris, although I decided to eliminate the resistor pack 1st by moving the injector signals onto another resistor to see if the problem moved from cylinders 2 & 5, and it did, went to 3 (didn't bother checking the other one). I'm pretty sure it's the resistor pack now, I'm getting a one from Phil to try this week so should know soon enough for sure,

 

Thanks anyways

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OK, put the new resistor pack on from Phil, problem was still there :(, back on 2 & 5. I must have been mistaken when it went to 3 as after the the miss degenerated into a worse state which was hard to identify which cylinders were going down (it seemed like all them).

 

Anyway I wondered if the RLTC was playing up, so I cut it out the loom & soldered the injector wires back together, it seems to have sorted it.

 

Not sure whether the RLTC is getting funny abs/rev signals, or it's not grounded/powered properly, or if the box is just fecked, but I will track that one down at the weekend. For now (touch wood) I'm just happy the miss seems to have gone

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Well the missfire is finally gone, it wasn't the RLTC, I had that totally out of the loom & the missfire was still there.

 

I went over Hoidges & he had a look, he noticed that the ignitor that I had relocated to the passenger footwell was roasting, he told me to mount it where it could be cooled, so we tried it & hey presto it was gone. I also tried his ignitor which seemed to behave better than mine so I'm on the look out for a spare one to try incase I have fried mine with too much heat

 

So I'm happy again, many thanks John, much appreciated :D

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