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Old 06-03-2013, 09:24 AM   #1
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So for those that dont know, I've got an 01+ engine in a 94 chassis with an EMS4 and a patch harness from trackspeed for the VVT swap. Saturday I took the car out for its first drive with the turbo in it for a considerable distance. Car was randomly loosing power for a split second and the tach would drop to 0 even though the engine was still reving. After 4 miles the car pretty much died and I could get it to re-start sometimes but it wouldnt stay running. Sometimes I could hear the fuel pump prime other times I couldnt. I've got a universal relay on the fuel pump because mine died last year (new 044 fuel pump at the same time). I just tried hard wring the pump and it stayed running long enough to pull it onto the trailer before it cutout again.

I figured it must be the god damn main relay problem that some people seem to have with stand alones. I wired in a universal relay in place of the main relay. Car started right up. I didnt feel like taking it out again at like 9pm and maybe breaking down again so I just let it sit and idle for like half an hour, no problems, besides stalling the second the cooling fans kicked on, as usual.

I get it out to race, was cutting out intermittently again, but the tach not going to zero. Sometimes the fuel pump would prime sometimes it wouldnt. I got one good run in, car was stupid fast. Next run it died mid course, just was getting no fuel even though I could hear the fuel pump running. I could get it to start but it would immediately die after catching like it just wasnt getting any more fuel injected. Pushed it half a mile back into grid. Did my last run in a 90 civic sedan, jump back in my car, pump primes, starts right up and I drive it over to the trailer like its a perfectly normal street car.

Most times when it dies I loose connection to the ecu with the laptop, even though the car stays powered. And then even after I get the car re-started I wont be able to connect again without waiting a couple minutes with the key off and the laptop unplugged from the ecu. This of course could be an AEM software issue, or a laptop issue, Haltech software does the same thing all the damn time.

:v ash:
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Old 06-03-2013, 10:04 AM   #2
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Somewhere, you have a loose connection.
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Old 06-03-2013, 11:19 AM   #3
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I'm assuming thats the issue. But it almost seems heat sensitive. Since after it dies it doesnt want to start again but let it sit for 10 minutes and it comes right back.
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Old 06-03-2013, 12:51 PM   #4
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Heat builds resistance. There are two possibilities. 1) The heat is in the engine compartment from general thermal load of the engine or 2) the circuit itself is creating heat as the weak connection heats up and eventually fails.

I would start in the engine bay fuse box at and around the main relay. Pull the nut off the main lug off and make sure nothing there has been arcing. You are having a 'big' problem so it probably near something big like the main fuse box.
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Old 06-03-2013, 05:12 PM   #5
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I remembered a few other things that could help the diagnosis. Some random times it'll also fail to crank, like just get 1 click from the starter and thats it. Sometimes it'll crank, but the whole time its cranking the starter relay is constantly clicking.

Possibly unrelated, when I was trying to figure out how to wire in the new relay. So I opened up the stock relay to figure out how it was wired. The power side has a +12 pin and and one that doesnt connect to ground. The signal side has one pin with 2 ohms to ground and one with 40ish ohms. Thinking a bit, that could be a potential problem.
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Old 06-03-2013, 11:46 PM   #6
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How're the battery cable clamps looking? Are they free of oxidation/corrosion? Tightly attached to the battery terminals and wires?
Same for the alternator power wire, check its condition as well.
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Old 06-04-2013, 12:14 AM   #7
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logs?
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Old 06-04-2013, 01:08 AM   #8
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Originally Posted by soviet View Post
logs?
I might have them, I also might have failed at setting the aem up to log.


But yeah the alt and starter power wires are big suspects are they're one of the few things that changed between when the car last worked right and now. Its that, a couple grounds, vics and the clutch switch.
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Old 06-07-2013, 01:51 AM   #9
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The 044 is new right? Could be bad outta the box? Do you have something else that's good to throw in for testing?
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Old 06-07-2013, 02:58 AM   #10
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We got some reports of heat-sensitive failure of the CAM-sensor on the 99-00 and 01+ engines, try swapping in another CAM sensor and see if it helps...
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Old 06-07-2013, 08:14 AM   #11
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We got some reports of heat-sensitive failure of the CAM-sensor on the 99-00 and 01+ engines, try swapping in another CAM sensor and see if it helps...
That was one issue I was thinking of. But theoretically the cam sensor isnt required for the car to run. But I'm really thinking that I just messed up something putting the engine back in or when I wired in the vics and the clutch switch, since the car worked perfectly fine before I pulled the engine to fix the oil leak.
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Old 06-08-2013, 05:42 PM   #12
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So I went though a bunch of ****. Fix the connector for my cam and tps the pins were a little funny the connectors are still iffy and I'm just going to replace them for piece of mind. I found a group of grounds on the under hood fuse box behind a trap door that was about to fall off, tightened that back on. But I found this post looking up something else. ems-4 setup problem Looks like I'll be calling AEM and getting a new ecu.
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Old 06-10-2013, 12:09 PM   #13
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I had a very similar problem in my 01' with a megasquirt and a homebuilt patch harness. I fixed this by hard wiring the grounds from the ECU to the engine ground points. I don't know about you and how you did your patch harness, but I built a secondary DB25 that handles stuff like wideband, EBC, datalogging switch, etc. I also added a whole bunch of grounds (three from front point, three from rear).

Pics in link:
https://www.miataturbo.net/build-thr...6/#post1017483

Fixing my grounds made all the difference.
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Old 06-10-2013, 12:20 PM   #14
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Its a trackspeed patch harness. I literally did 4 things. Tightened the ground behind the trap door on the fuse box. Fixed a loose pin on my TPS (not killing it, just running like crap randomly), fixed the loose pins on my cam sensor and bought the pin lock tab for that connector (didnt realize this was the only oem connector in the whole damn car that used one). Put as password protection on the EMS4. I think some combo of the loose ground and the loose cam connection was causing it to die. And the firmware bug with the AEM that makes it randomly fail to initialize without a password was causing the no-start issue. Seems fine now, drove it for like almost half an hour yesterday without it it crapping the bed.

I still cant get it to activate vics properly or get it to properly read my clutch switch, but those are minor problems in comparison to dying car that refuses to start.
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Old 06-10-2013, 08:49 PM   #15
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Quote:
Originally Posted by Leafy View Post
That was one issue I was thinking of. But theoretically the cam sensor isnt required for the car to run.
Maybe on a batch-fuel car. On your sequential '94, you definitely need the cam sensor.

The NB CAS dies on a routine basis - I carry 2-3 spares at the track at all times.
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Old 06-10-2013, 08:51 PM   #16
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Quote:
Originally Posted by Savington View Post
Maybe on a batch-fuel car. On your sequential '94, you definitely need the cam sensor.

The NB CAS dies on a routine basis - I carry 2-3 spares at the track at all times.
I have a spare on order. I would figure the AEM would be smart and default to batch fire on a cam signal failure, plenty of OEM ecus do this.
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Old 06-11-2013, 01:31 AM   #17
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Have you checked if the alternator pivot bolt is tight? I'm not sure if its true but I've read before that specific connections acts to complete a ground, I remember reading some very similar issues in relation to that.
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Old 06-24-2013, 12:16 PM   #18
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Still had a dying issue on the dyno and on the way there. The cam wiring connector uses a pin lock, that helped once that was on. The coil wiring pins (female) that come from sumitomo are actually too open for the 01+ coil pins so they dont make very good contact, and you can actually see on the +12s where the pin is slightly blackened from arcing. I thought I had it all kicked. But I was wrong. The final piece in the puzzle was the cam sensor, the one that came on my engine is a completely different plastic mold than the 2 known OEM ones I now have had in the car and its been perfect since replacing it.
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Old 06-24-2013, 01:22 PM   #19
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Quote:
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The final piece in the puzzle was the cam sensor, the one that came on my engine is a completely different plastic mold than the 2 known OEM ones I now have had in the car and its been perfect since replacing it.
The older OEM sensors are indeed a different mold than the currently available replacements. The older sensors are a more squared black mold, while the new replacements are a curved-edge blocky grey.
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Old 06-24-2013, 01:27 PM   #20
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Hmm The first one I tried in it was an original piece of a 99 engine, greyish, sharper edges, had an indent rectangle in the nipple that goes in the valve cover. Same with the other replacement that came out of a "large box" full of many old sensors taken from stripped cars. But now I know where there is a "large box" full of used oem cam sensors like half an hour from my house. But the one that was in the car was very black and smooth edges with no sorts of indents or dimples in the tip that goes in the valve cover.
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