ezone

Not quite.
Google how to do a voltage drop test for an idea.

5spdvroom

Another thing that's worth mentioning - if I stall it (let off the clutch too fast) and immediately try to crank, it usually (though not always) sits there cranking and cranking, then lugs for a bit, then comes up to idle and runs fine. (Notice a pattern here? When this car gets bitchy, it cranks and cranks and cranks, then lugs - I can hear it and see it on the tach - and then comes up to a normal idle. Every. Single. Time. Always a lug start when it starts cooperating again. Sometimes with the usual "vroom" as it revs up, then falls back to idle like a normal start.) If I turn it off (even briefly) after stalling, then on, give the fuel pump half a sec or so, it starts immediately. This kinda points to the crankshaft sensor, from what I'm reading. Or does it? Just wondering if bad/loose grounds can do that sort of thing - we're not going to work at all for the next minute or so, and then we're going to work fine and act like nothing happened. Noting that when it flat out won't start, turning it off/on doesn't help; only waiting a few minutes does. (Although now I'm wondering if slamming a door/physically shaking things a little might help, if it's possibly a loose connection.)

Curiously, I found a diagram for an 05, but it's basically flipped. Black relay, nothing, then two identical and lighter relays (page was in black/white). Rest of it looked the same though. I took the above (well, end of last page) pic from my car just now, not off the internet.

And OK, found the page on voltage drop tests. I'll see if I can find time this weekend to play with that.

ezone

TBH, sensors and wiring both can do weird things like that.
Which is it? I can't tell from here.... I'm just tossing out guesses and stuff I'd probably look at if I had it in my bay at work.

My pic is labeled with a black and 2 blues, and another pic shows the AF sensor heater relay in the same location being black also. This is why I always go by wire colors, not relay colors (half the time I can't even trust diagrams showing their positions either)

5spdvroom

Yeah, my concern about taking it in for diagnosis is it's intermittent - this happens every several weeks to every month (I've even gone 5 months without issues, although I wasn't driving during weekdays). 99% of the time, it starts just fine. I'll probably spend the money for the diagnosis, as luck goes, it probably won't act up in front of a tech and they'll have trouble finding the issue. Unless someone gnawed on a wire, and the tech happens to find it.

And, again, never any codes. Only code I've ever seen was for the knock sensor a while back (replaced it, cleared it, haven't seen that since). Although curiously, the CEL came on a few months before - it must've been that, but I didn't have my code reader handy at the time. It then went away on its own a few hours later, and stayed away for a few *months*, I forgot about it, and it came back a few months later (at which point I read the code, fixed the part, solved that one for good). So maybe sensors really can act up that intermittently, with weeks/months between issues?

Only common factor I can find is I last drove the car 30mins to ~4 hours before, each time (i.e. haven't seen it in the morning - takes a little longer to start on a particularly cold morning, like any car, but nothing unusual).

Think I figured it's likely a sensor/wiring/electrical issue, not a fuel system one.


Also... sounds like the crankshaft sensor basically involves 90% of a timing belt replacement. The car is at 107K but had the belt replaced (likely aftermarket) by another shop (that I don't quite trust) before I bought the car. Since this is an interference engine, I'm starting to wonder if I should replace both in one go, so it's one less thing to worry about. And since those sensors apparently fail without throwing a code most of the time. But it could be something else as well, totally different place in the car...

ezone

No evidence for a tech to go on.
Won't act up on command, ever.
And you'll still be charged the checkout fee no matter what.

OTOH those relays are cheap.....I'd at least do that much and see what happens.

5spdvroom

Yeah, the no start bit won't act up on command - you'd need to drive it regularly for several weeks, and it might act up for you. And then you'd need to have all the tools ready for the minute or so you have with it acting up.

The trouble starting after stalling bit is fairly reproducible on demand though - happens at least half the time. Just stall it in the parking lot (repeat as necessary), and you'll probably see it crank away. And those might be related.

Regardless, sure, I'll replace the other 2 relays as soon as I figure out the part number (i.e. is it actually the same relay part as the others, given the multiple blue ones thing, or no?).

And if that doesn't work, I'm thinking it's probably grounds or crankshaft sensor. I can't help but wonder about that last bit...

5spdvroom

Found some more info on the relays: http://www.hondapartsnow.com/parts-l...in.html?PNC=11

Namely, look at 11, 13, and 14.

Points me to this - left one (#13) - fuel pump relay. Blue. Already replaced it. (It is indeed on the left in my case.) http://www.hondapartsnow.com/genuine...bin,2514658,13

ECM relay (#14) - right next to it. Haven't replaced this one, but I'll try that next. http://www.hondapartsnow.com/genuine...bin,2514658,14

Two #11's, more generic: Not sure what these do, and I only saw one in my car - I can go back and look again, but my picture doesn't show a third harness for this. (Thought I saw something about one being for reverse or something, and another is only for automatic transmissions? Not sure how the ECM varies between manual/automatic/what handles the shifting logic.) http://www.hondapartsnow.com/genuine...bin,2514658,11

ezone

Double check the colors of the 4 wires going to the relay you think is it, as I posted earlier. Make sure you replace the correct relay.


The other two relays they show, one can be for reverse lights (not all cars) and the other is the AF sensor heater relay (04-05 cars).

5spdvroom

OK, reverse lights, not all cars - does this having anything doing with the reverse stuff being a bit different in an automatic vs a manual in the first place? I.e. An automatic trans is more electronic and the ECU knows it's in reverse; on most manuals the computer has no idea what gear we're in.

This is a 2005, fwiw. Will check the wires later.

ezone

Manual trans has the backup lights wired directly through a mechanical switch on the outside of the trans.

Automatic and CVT trans use a relay triggered by the trans range sensor (shifter position sensor) in R position.
The range sensor probably isn't designed to handle the high current of the backup light bulbs, so they have the relay handle the high current.

5spdvroom

OK, so I thought about this some more. Looks like the blue relay (left) is fuel pump, the brown (middle/left) is PCM (also feeds the fuel pump relay), blank spot to the middle/right would be reverse lights (if I had an automatic trans), and the one to the right is probably AF sensor heater relay.

Also having second thoughts about it being the crankshaft sensor (even though those sometimes cause this issue), since the tach and speedometer *always* works fine. Even when it's glitching out. Starting to get the sense it's probably the PCM relay (which I ordered yesterday), or a loose ground. Especially since once it's started, it runs fine (relays and grounds seem to do this, but apparently a crankshaft sensor can stall the car? Surely I'd have seen this by now?). The occasional lack of power thing I mentioned, as I realized, is me derping out sometimes and forgetting just how much of the power is at high revs/that I'm on a subtle hill with a headwind (i.e. I have a tendency to try and keep cruising revs as low as possible, sometimes a little too much so).

(Curiously, I mentioned that the speedometer perked up for a second and then stopped there the other day. Normally perks up and then goes back down immediately when it gets power. But, the car glitched again later and didn't. Makes me wonder what would happen if I got the gauge up there, and then cut power to the whole darn thing - will it stay up, or fall back to 0? The former would almost make more sense...)

Also worth noting that, come to think of it, I've never had it fail to start in the morning - it takes longer to crank when the outside temp and engine are cold, then aggressively catches (*ka-ka-ka-ka-ka-VROOM*) and idles at ~1400 at first. Just like any other car, so totally normal. When it glitches, as I just realized, it's always been 1-4 hours since I last drove the car, mid-day, and relays are known for pulling that sort of intermittent crap when they're somewhat warm...

I guess I'll drop that relay in there once it arrives, and if I'm still getting intermittent no-starts, then do the ground tests you mentioned.

ezone

Wire colors!!!

5spdvroom

OK, I got the relay. Confirmed - PCM is the brown relay, same part number, correct wires.

I also noticed something very curious - if I remove the relay entirely and then turn the car on (didn't try to start), the speedometer perks up a tiny bit - like I said happened before. Put the new one in, did a few short start/stop trips, and so far so good, it's running fine and starting up fast (even if I don't give the fuel pump time to run first).

Hmm... I'll keep a watchful eye on it and keep doing the thing that made it glitch before (wait 30min-4hrs, then drive it), but that just might be it...

ezone

Jinkies, is that a clue?
ZOINKS!!