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99 Honda Civic Cutting out - I need your collective brains to help me troubleshoot

I need your automotive brains to help me troubleshoot.

I was driving my 99 honda civic at a steady 65mph on the highway for about 10 minutes. I was not accelerating or anything, when it cut out totally as if I turned off the engine. When I would step on the gas (still moving), it would not even hit/sputter or anything. I pulled off to the side of the road and immediately tried to restart… nothing.

Two minutes later, I try to restart, and it started right up. Get going another 5 minutes, and it does the same thing. This time I only waited about 30 seconds, then it started up again, but it ‘missed’ a couple of times just before it started up. Then it was fine for the rest of the drive to work, and hasn’t stalled since (one week).

However, the check engine light came on the next day after the stalling episode, and has also been on since. The code is P0420 (which says that the O2 sensor before and after the catalytic converter read similar, indicating a bad catalytic converter). I’m not sure if this is, however, a downstream effect/ symptom of a larger problem (that this is not the cause, but the effect of a larger problem?)

Here are some extra facts that may be relevant, or may be totally random:

  • I occasionally catch a whiff of egg like smell (smells like it’s running rich, and maybe it is heating the catalytic converter)
  • It seems to be functioning fine (no loss of power)… the gas mileage even seems OK
    -I filled up with a new tank of gas the night before the drive (I’ve since filled up again)
    -There was an ignition recall, that I did NOT have done (I just found out about it :slight_smile:
    -The car is pretty beat up: 170K miles
    -Gas gage quit working about a month ago… always reads full

I’m open to your thoughts as to what is going on.


First thing to check would be your battery cables. Make sure the connectors are clean and tightly fastened. As you drive down the road, if a battery cable is loose it can expand due to heat from the engine, wiggle around, and eventually lose connection, killing the whole car. Then after you sit for awhile it cools down, restores its connection, and “fixes” itself.

It’s also possible that your cat is plugged, but let’s address that after we check the easy stuff.

BTW, when you first tried to restart it and “nothing” happened, can you be specific? Were there any lights? Did it crank but fail to start, or did it make clicking noises, or did it literally do nothing and everything was dead when you turned the key?

If the ignition recall is the one for the ignition switch…well, then I’d say there’s not a lot of mystery to the stalling. I wouldn’t bother with anything else until that is done. If that is done and it keeps stalling then my first instinct would be along the lines of cables as mentioned by shadowfax.

The P0420 code is probably a completely separate issue, and someone needs to diagnose it. If the converter is bad, then the reasons for that should be investigated as well.

Thank you both! When I would try to restart, the engine would turn over, and I had full electrical, just no ignition whatsoever. Thanks again for your responses and advice. -Joe

I would suggest the fuel pump/ fuel injection relay that is such a wide spread problem on some Honda’s. Just a thought.

The problem might be with the ignition control module.

I just replaced this in my daughters 97 Civic because she complained that the engine would shut off without warning.


I’m going with the most obvious problem areas and it’s the main fuel relay as @PvtPublic suggested and the ignition control module as @Tester alluded to.

Yep, me too. Hondas of that era and a little earlier were notorious for eating main relays. Fortunately, it’s not a terribly hard fix.

Ignition switch, EFI main relay and faulty distributor are your top three suspects. It is very hard to diagnose dies while driving because it’s hard to duplicate in the garage.

You might consider the ignition switch as your model Honda is under a Recall for failed switches. The switch overheats and contacts open leading to bucking and jerking, no starts, or outright stalling at speed.
This repair will be free of charge if it has not been done previously.

The switch carries a lot of electrical load including the fuel pump. The main relay is in the middle of that equation so over time an aged fuel pump can fry the relay.
Since the switch has been a common problem and it’s potentially free of charge at any Honda dealer you might try that first. Just call them, provide the VIN, and they should tell you in a few minutes if it’s covered.