What might cause hesitation/misfire when cruising?

[War_Wagon]

For what it's worth, take the distributor cap off and make sure the ignition rotor hasn't come loose on the end of the distributor shaft. It's happened a few times to me on my Hondas over the years, the little set screw backs off and the rotor gets sloppy. Leads to all sorts of weird random issues. Best part is it's free to check, so hopefully you'll get lucky and that's all it will be!

[California98Civic]

Originally Posted by Ecky

Anyway, without a knock sensor, how would an OBD1 ECU figure out what a safe timing is? What else does it factor in?

I have a 1998 Civic, so I can sympathize with how badly they placed those timing marks. I struggled to get a view for a while. But this really could be the problem, so I'd recommend considering another try. Maybe that mechanic who put the engine in lost patience with the process too and just set timing by what sounded right as he adjusted the distributor? Check other simpler things first, then tangle with those irritating timing marks again. I also think that a couple degrees advance on the timing is no big deal. Just don't get greedy. 2 or 4 degrees won't hurt anything given how easily we drive these engines for efficiency. It'll give you very modestly more torque. When I was doing it, I could see signs of lean, hot burning on my spark plugs. But my engine is off a lot too. And my coolant temps are quite normal.

Good luck!

[Ecky]

So far 30 miles on a tank with injector cleaner + new plugs hasn't improved it, I've not been feeling well so I haven't checked the distributor or messed with timing yet, and the new O2 sensor hasn't arrived.

[Ecky]

Replaced the O2 sensor tonight and took it for a drive, WOW I was missing a lot of power. Runs like a brand new car again.

I suppose it was probably causing the car to run lean?

The culprit:

[California98Civic]

Wow. Congratulations! That looks like an indicator of unburnt fuel, no? If so I guess their could be unburnt fuel in the CAT too? In Cali emissions tests that would be an issue, but I don't know where you are. In any case, aren't deposits like that on a spark plug an indicator of running rich? Do you think just age and time crudded-up the O2 like this, or could there also be another issue, one that could crud-up your new sensor sooner than necessary?

[Ecky]

My car doesn't have a CAT. When I bought it, a previous owner had already replaced the entire pipe. I have no idea how old the O2 sensor was or what it's been through, for all I know the original motor might've had a turbo on it that died, or was running a street tune. This car really was a mess, I'm putting it back together one piece at a time.

I think the car is running right now, but we'll see.