No spark on plug 2 & 3. Not the coil.

[DroopYeyeS]

OK everyone I need help. if you have any ideas on this one please shoot them at me. Ok let me start with the car setup. This is a '95 Eclipse GS 420a, that is for the most part stock in form. It does have a few bolt on upgrades, and I rebuilt the engine about a year and a half ago. Bolt on items are just basics like I/H/E & UDP. About 6 months ago, the car started to stall out while driving. After a few times of this I started to trace the issue. Turned out that the coil had gone bad, so I replaced the coil and all was well again. 2 days later, the same stall out. Upon check, the coil had once again gone out. I marked this up to simply receiving a bad part from the manufacturer, so I returned the part, got a new one, and again all was well. 5 days later the car dies yet again. At this point I headed straight for the coil. This coil tested out ok. I pulled the plugs to verify spark, only to find that plugs 2 & 3 where not firing. To shorten this a bit let me get right to the meat of things. After many hours of testing and retesting, the results remain the same. Plugs 2 & 3 no spark, 1 & 4 are fine. Now before anyone tells me about the layout of the coil, and the primary and secondary circuits, these have be tested to death and are fine. As a matter of fact the issue seems to be that the BROWN wire which comes from the # 41 pin of the ECU is dead. If I switch the lead from the ECU to the 2&3 lead of the coil, those plugs fire, but 1&4 stop. I replaced the ECU with a reman, yet the issue persists. The cam sensor and crank sensor have both been replaced at this point. The cam sensor was done during the rebuild of the engine, the crank sensor during me troubleshooting. The harness has checked out ok as well at each of these locations. Long and short of it is that there seems to be no signal from pin #41 of the ECU. Any ideas here would be greatly appreciated. If anyone knows for certain what tells the ECU to fire a signal on pin #41, please chime in. I would however assume that the same command would be used to fire pin #21 (plugs 1&4) which is indeed working just fine. I really am at a loss here and need more minds with ideas I've not looked at here. As always, thanks for any input, and help on this.

 

[VelocitàPaola]

So you replaced the ignition coil, the ECU, and swapped the ignition coil wires? If so, the only explanation is a discontinuity somewhere on that brown wire. You could try testing it with a multimeter (at the ignition coil and at the ECU plug). If the resistance is higher than a couple of ohms, start tracing the wire and look for breaks or shorts.

 

[DroopYeyeS]

Good thought Paola, but the brown wire is the wire I replaced. I tested it for continuity first, it tested fine. I replaced it thinking maybe it was a random short in the wire (perhaps the EGR pipe was getting to hot), but this proved to not help.

 

[VelocitàPaola]

Good thought Paola, but the brown wire is the wire I replaced. I tested it for continuity first, it tested fine. I replaced it thinking maybe it was a random short in the wire (perhaps the EGR pipe was getting to hot), but this proved to not help.

I don't get it then... (Sorry, your post is a little hard to read. Separating your thoughts into paragraphs makes it a LOT easier) So multiple PCM's aren't sending a signal for just one side of the ignition coil? Both wires to the coil have continuity and you've replaced the two pertinent sensors?

 

[DroopYeyeS]

Allow me to clear it up a bit if I can. The #41 pin of the ECU (fresh reman) is not producing signal of any kind. At this point don't move beyond the ECU itself. #41 produces nothing.

 

[VelocitàPaola]

Allow me to clear it up a bit if I can. The #41 pin of the ECU (fresh reman) is not producing signal of any kind. At this point don't move beyond the ECU itself. #41 produces nothing.

But your old ECU also did the same thing, or no? If the sensors are good, the wiring is good, and there's a spark signal on the other channel, the only possible culprit is the ECU.

 

[DroopYeyeS]

I agree completely. Just considering the odds of 2 ECU's being bad for the same reason. Do you know, by chance, which sensor is supposed to be sending the command for this pin to create a signal? That is at this point what I'm trying to track down. The wiring diagram I have doesn't lay it out clearly. I'm guessing that it will be the cam or crank sensor. I have noticed however, that these sensors share a common lead to the ECU (yellow wire, not sure of pin #).

 

[CODE4]

I agree completely. Just considering the odds of 2 ECU's being bad for the same reason. Do you know, by chance, which sensor is supposed to be sending the command for this pin to create a signal? That is at this point what I'm trying to track down. The wiring diagram I have doesn't lay it out clearly. I'm guessing that it will be the cam or crank sensor. I have noticed however, that these sensors share a common lead to the ECU (yellow wire, not sure of pin #).

That common pin is the +9v feed to power the sensors. The oscillating signal return are on dedicated pins.

 

[DroopYeyeS]

Which pin are you refering to CODE4? The #41 pin (brown) is the wire that is directly connected to the 2 & 3 coil outputs. Pin #21 (black w/ blue stripe) is the 1 & 4 coil outputs. The common power lead that I think you are refering to is the Black w/ Red stripe (sorry don't have diagram with pin in front of me). This lead powers the coil, but not any sensors. Not sure if this is what you're refering to or not.

Edit: Disreguard that. I see you are refering to the Yellow lead for the Cam & Crank sensors the join at the junction. Do you know which of the oscillating leads cause the #41 pin to generate signal?

 

[DroopYeyeS]

Ok, so did more testing today just to make sure there isn't a wiring issue. I noticed that during engine operation, the Black w/Blue strip wire (pin #21), and the Black w/Red strip wire (leads to j/c 3, looks to be common power lead & joins with capacitor on valve cover), are both getting about 11 volts where as pin #41 is only getting .08. Perhaps this will give further help to any more ideas.