What might cause hesitation/misfire when cruising?

[Ecky]

As title states.

Recently (2 weeks or so) my car has started to hesitate when cruising and when shifting early, such as putting it in 5th at 25mph (just under 1500rpm). I don't notice a hesitation when the engine is more highly loaded and at higher rpm and it still idles fine.

Sometimes when engine braking the fuel doesn't stay cut off, it occasionally fires a few times.

I don't have any engine codes, and it sounds fine even when hesitating, I don't hear predetonation.

Temperatures aren't unreasonably cold here in Florida right now and I haven't done anything under the hood lately other than tighten some bolts in the suspension.

I put in new plugs and wires about a year ago, I want to say they were "30k mile" plugs and I'm at less than half of that right now. The distributor is less than a year old and still looks like it was just pulled out of the box. My O2 sensor's age is unknown but I've had the car for 2 years and out about 35k mills on it. Gas mileage is fine overall. I recently set a trip record but my tank averages seem a bit low lately.

I'm considering putting some fuel system cleaner in with the next tank in case the injectors are dirty, and changing the plugs. What else should I check?

[user removed]

From your information, if it was my car I would probably replace the oxygen sensor if it was not very expensive. Also consider cleaning the EGR system and passageways. The OBD1 systems were not as precise as the 96 and up OBD2 systems. If you feel comfortable doing the work yourself, then clean the EGR passagways and the valve first before throwing money and parts at the problem. If it was my car I would probably do both.

Always price out the original equipment parts versus the aftermarket. if the price difference is not too excessive I would always use OE. You bought a Honda not some cheap imitation from god only knows where. Many will disagree with me on this but when you have to deal with comebacks due to cheap parts it can get expensive very quickly and the first thing you loose is your income and your customers.

regards
Mech

[ksa8907]

Have to agree with old mech here. If the egr is leaking into the intake, you're running with very little oxygen in the combustion=no power.

[Ecky]

So far as I can tell my car doesn't have an EGR. There's a PCV breather box on the back of the block and it has a hose that goes straight to the intake manifold. I replaced the valve on it about 4 months ago because I had no idea how old it was. Turns out it didn't need to be replaced but it was ~$2.

There's also a breather hose from the valve cover to the intake manifold.

Any possibility of failure here causing this?

I'll grab some plugs next time I'm out and price-check an O2 sensor.

[gone-ot]

too lean A/F also becomes more difficult to ignite, so spark plug GAP becomes an issue...meaning it needs to be "reduced" slightly, ie: say from 0.35" to 0.32 or 0.30", etc.

[nbleak21]

Originally Posted by Old Tele man

too lean A/F also becomes more difficult to ignite, so spark plug GAP becomes an issue...meaning it needs to be "reduced" slightly, ie: say from 0.35" to 0.32 or 0.30", etc.

Plug Gapping back to spec or as stated above, or advancing the timing a couple degrees would be my first attempts. Price = Free!

[Ecky]

I replaced the plugs today and put a bottle of some Lucas junk in a fresh tank. On my way home from work I didn't notice the hesitation but it's intermittent so I'm not certain it's fixed yet. I have a new factory O2 sensor on its way.

Was a bit sad when I opened the hood and noticed some oil on the bottom of my A/C high pressure line and also around my power steering pump - those definitely weren't there a few weeks ago. Although the power steering pump will probably be an easy fix, air conditioning never is.

Originally Posted by nbleak21

Plug Gapping back to spec or as stated above, or advancing the timing a couple degrees would be my first attempts. Price = Free!

My timing is already advanced, or at least I think it is. I bought a timing light last year and I was actually unable to see the timing marks at all (though I've never timed a vehicle before). One of the symptoms of advanced timing on my engine is a high rolling idle and I ended up adjusting it until the idle was where it ought to be when rolling in neutral, and then advanced it just a bit from there. I don't get any predetonation even with it fully advanced though.

^ I doubt my timing is the (direct) cause of my recent troubles though as it has been fine for the better part of a year and only recently developed these problems.

[nbleak21]

Originally Posted by Ecky

My timing is already advanced, or at least I think it is. I bought a timing light last year and I was actually unable to see the timing marks at all

Did you jump the diagnostics terminal in order to establish baseline ignition timing? This is a commonly overlooked part of the processes that will net the results stated.

[California98Civic]

Originally Posted by nbleak21

Did you jump the diagnostics terminal in order to establish baseline ignition timing? This is a commonly overlooked part of the processes that will net the results stated.

Adding to nbleak21's comment above, are you sure the car was warmed up when you checked for timing marks. Being completely unable to find the marks suggests a problem with the timing belt, the engine temp, your placement of the timing light, or that the timing is too far off. Also, there is a normal oscillation of the timing a couple degrees plus or minus the stock setting, so if the marks momentarily disappear, that might be why.

[Ecky]

Originally Posted by nbleak21

Did you jump the diagnostics terminal in order to establish baseline ignition timing? This is a commonly overlooked part of the processes that will net the results stated.

Yeah, I did.

Originally Posted by California98Civic

Adding to nbleak21's comment above, are you sure the car was warmed up when you checked for timing marks. Being completely unable to find the marks suggests a problem with the timing belt, the engine temp, your placement of the timing light, or that the timing is too far off. Also, there is a normal oscillation of the timing a couple degrees plus or minus the stock setting, so if the marks momentarily disappear, that might be why.

It was warmed up, the issue lies in that it's obscured by the plastic timing belt cover, for whatever reason it hangs over the crank pulley and I can't see the marks from the top of the engine.

I wasn't the one that dropped the engine in my car originally, and I believe the mechanic I had do it might've reused the timing belt cover from my old B16 or something. If I knew then what I do now I'd have done it myself, I'm still finding stuff he messed up.

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