gstrudler

Hoping some of the gurus and masterminds around here might be able to help figure this one out...

Strange problem the past few weeks: car dies only on the freeway after cruising for 15-25 minutes or so. I can take back roads to get to the same places and it behaves fine, but freeway cruising kills it almost every time; car runs fine otherwise.

N/A with a fair bit of mods, but basics are: 1997 Prelude SH, eManage Ultimate, M&W Pro 14 CDI (installed 3 months ago), DW200 fuel pump w/ AEM rail & regulator (installed 6 months ago).

Knowns:
During cruise, suddenly goes into engine-braking: no throttle response, but motor is still turning (decelerating); when I throw the clutch in the motor spins down and dies
Electronics stay active, including ECU (still get OBD2 readouts) & ignition (CDI is providing tach readout, which I still get)
Can usually restart immediately, but sometimes will die again; if I let it sit for a couple minutes first I can fire up and drive home
After it has died and I get it going again, it idles high (300-400 RPM above normal) and occasionally hunts for the idle after another 10 minutes of driving
When motor dies, TPS is unresponsive (although the signal passes through the eManage, so unknown for sure where this issue is)

Replaced ignition switch, main relay, cat and front o2 (for code P0420 that popped up; old cat was in sad shape) since it started happening. Checked & cleaned EGR valve; it was only slightly dirty but moved freely. Only thing done to the car before this started occurring was I flushed the cooling system; part of the flush involved the car idling for about an hour.

The high idle afterwards is throwing me off. That seems like a vacuum leak, but I can't imagine a sudden leak big enough to kill the motor, but then just slight enough to raise the idle a little. IAC is probably the closest to this, but nothing I've read anywhere supports a bad IAC causing my issues. I also can't figure out why this is freeway cruising specific, except maybe heat. I can step on the gas at 70mph and it's fine, so it's not systemic fuel starvation. Sensor issues (CKP, MAP, TPS, etc) should put it in limp mode, not kill it (except I guess I don't know how the eManage would respond), but regardless those type of issues should also appear at other times besides just freeway cruising.

Any ideas out there H-T?

holmesnmanny

try a known good distributor

gstrudler

Are you saying you think the cylinder position sensor (CYP) is bad? I'm completely bypassing the ignitor (eManage to CDI), so I know it's not the issue (I had plenty of problems with it before I bypassed it though).

holmesnmanny

I've had issues with ignitors and coils going bad and killing the engine at random times but only when cruising so I would say it's possible either one is bad. Similar to a main relay, they stop working when they get real hot and then work again after it cools off.

Given that you're using aftermarket ignition components, I would probably put it back to stock and see if the issue goes away. Replacing the coil would be where I would start.

gstrudler

Posted this in my other thread, but cross-posting here as well:

Just to update in case someone else runs into this weird issue. I can't say it's conclusive for sure since I don't drive the car much anymore, but it did appear to be a problem with the EMU. Not only would it not stall when datalogging, but I noticed sometimes as soon as I plugged my computer into the EMU the idle speed would change, which seemed really strange. I forced a firmware update to it and also reset the stock ECU for good measure and the problem went away. Hoping it doesn't come back...