Thread: Update on my red car (still need a little advice)

It's been a few weeks, now, the red car is still unstartable and I can't figure out what it is.

Once again, a little rundown:
VQ35 Sentra (individual coil packs), AEM EMS standalone, fully dyno tuned, been running great for over a year and a half. AEM runs a wasted spark, meaning 6 coils run on 3 signals, fires every 2 strokes on opposing cylinders instead of 4. One night, driving late, I took the car up to triple digits for a sec and then decelerated back down to normal speed. During deceleration, engine stalled for no reason. Attempted to pop the clutch to restart, nothing, cranked the starter, still no fire, shut everything off and back on, tried again, still no fire.

All the electronics inside work fine, including the ECU. Starter works fine, batt and alternator are fine, compression is fine. I can connect my laptop to the ECU and read all the parameters, all look normal. Just got new plugs for the hell of it, checked the wires going to the coil packs (3 wires ea, +,-,signal). All check out, I have 12.7V going across the + and -. I took the plugs out grounded and looked at the spark during crank.

The spark varies a lot. Sometimes I'm not getting a spark at all, sometimes I get a very weak spark, sometimes I get a fine spark. I am getting backfiring during the cranking process, every so often, I get one or 2 proper combustions. Followed by a big backfire. I can smell fuel, faintly, in the cylinders.

Here's all the parameters I can see or read:
Crank/cam position sensor: I am reading an RPM upon cranking, an RPM shows on the dash, too, I'm also getting "Sync OK" on screen.
MAP sensor: Within range
Throttle sensor: fine, 0-100%
Coolant sensor: ambient temp
IAT sensor: Ambient temp
Knock sensor: unsure

The ECU outputs to 6 injector drivers, 3 spark drivers, and 2 Variable timing solenoids. All seem to be functioning.

I'm thinking I'm going to be rewiring the entire Engine management, myself; one of the only things I paid someone else to do, originally. I'm thinking there's just a bad wire somewhere. A rewire will also allow me to do a much better wire tuck, so I guess it's for the best. If that doesn't work, the ECU goes back for a diagnostic.

I'm in the process of a massive wiring harness diet and minor tuck while switching to AEM EMS. It's no big deal with the proper documentation (AEM has great docs). Kind of relaxing actually.

The weak spark sounds like it might be the issue. I'm assuming you have 3 GM style coils with two outputs each? Are they MSD brand? The MSD ones are known for their cheap build quality.

i bet its a bumper light wire or somehting stupid of that nature

I've got a friend that's had so many issues with his VQ, that he pretty much knows it in and out. I'll direct him to this thread. He's a member here IIRC, but never on. VQ35 into an A32 Max.

Sounds like the problem is somewhere in the crank/cam position sensor/ one of the coils (since I doubt all would go bad at once). does the spark get weak or off timing at all coils or a certain one?

So you get weak and erradic spark on all the plugs? I would check another just to make sure.

It appears that I wasnt registered... Anyways, I signed on to hopefully shed some light.
I'm Tekkie's friend, and I had some similar issues to this, not sure if its exactly the same issue as mine, but here it goes:
I had an issue to where 2 coils(cant remember which number coil) were misfiring on and off.. and then finally, they stopped completely. After a LONG A** break down(mechanically and mentally), I figured out that the timing was off by a couple of teeth.
My issue was that the UDP completely twisted the dowel key and cut a notch in the UDP caused by a mistake in shifting....
So my assumption on your issue is that it might be slightly off on timing.... and the only way to really adjust this is to drop or pull out the motor and remove the timing cover and match up the yellow links to the arrows stamped on each crank pulley. I have pics, but I need to look for them through all of my usb sticks.

It does seem like its a timing issue....
Are your CKPS/CPS reading right voltage?
You can eliminate your TPS as an issue because even if the TPS was bad, the car would start.

I'm not familiar with the AEM standalone ECU, but does this still run off of a MAF or is it now based on MAP?
A MAF might prevent it to start up... I know because I messed mine up and the MAxx would crank, but not start.

Thanks for popping in Phatso

Pics!!!!!!!

I'm thinking the timing might be off, it sounds similar to how an engine does if the plug wires are on the wrong cylinder. Can you manually check ignition timing with a timing light? Also check the wiring to the crank/cam sensor, if I'm not mistaken it should be an armor/shielded wire. I know that if the shield isn't making a good connection it will cause an erratic signal.