physSix

I've searched around a bit for a solution to this problem, but all I've been finding are solutions to hesitation under WOT conditions. I recently bought a '91 CRX Si with over 225K miles on it (odometer no longer works, so it could be way higher), and it has its fair share of problems which need to be fixed. The car has the original D16A6 motor and ECU. I took it on a long-ish drive last night, around 45 miles each way, and on my way home I started experiencing some major hesitation and bucking when the car is cruising around 2100 RPM, very light throttle and then trying to increase my speed/RPMs. If the throttle is just lightly applied the car hesitates and bucks, but if I get into it a little bit further, or downshift, it revs up smoothly. I've recently replaced the plugs, wires, cap and rotor. I noticed while doing this I most likely have a pretty badly blown valve cover gasket, as there was quite a bit of oil in the passages to access the spark plugs. Can anyone suggest to a fledgling Honda mechanic where I might start diagnosing this problem?

GCLance

My DX was bucking because of the oil in my spark plug tubes. I'd look into that. If anything, that's just what it is, blown VCG and grommets.

physSix

What is the connection between oil in the spark plug sockets and the hesitation and bucking? Why only at very light throttle? I suppose I can make the connection between the problem and the cause here in my head, but I'd just be interested in hearing a more detailed (and hopefully more correct lol) explaination.

GCLance

The oil filling in the passageway between the spark plug and the chamber must be blocking the spark in a way. Know what I mean? Basically, it causes a misfire. The reason I think it's only during low revs is because everything is moving faster at higher range, so the oil doesn't block it as much. - Sorry it's not coming out as knowledgeable as I would want, lol, I have a hard time phrasing things.

BASICALLY, oil is getting into the spark plug chamber, because of a worn VCG, grommets, whatever it might be. This oil is causing a misfire at because the spark isn't being consistent at the lower range. - At a higher range, the oil is flowing faster, and so is the spark, that way making it more consistent (I'm guessing).

My recommendation is change the vcg, grommets, and tube seals. Hopefully it isn't anything much worse than that.

physSix

A little bit of an update, hopefully I'll get some more feedback...

After changing the plugs, wires, cap and rotor about a week and a half ago, I pulled the spark plugs again this evening. I was going to change the valve cover gasket (and strip all the horrible paint from the last owner off it at the same time). There was zero oil in the passages down to the plugs this time, so I've decided to hold off on the valve cover gasket until the engine gets a rebuild in another 2 or 3 months. I took the car out after re-gapping the plugs to around .042" (they were at about .037"), and had the same problem again as far as the hesitation upon light throttle.

Now that I've been driving the car and paying attention to the hesitation for the past week and a half, it seems that the problem kicks in mostly when the car is either going up or down a hill, or on extremely rough patches of road for an extended period. This could all be in my head, but it definitely happens on one specific stretch of bad road (about a miles worth of road repair where the car is bouncing constantly), and on tonights drive it started happening after going down a short incline and then back up the other side. I've yet to experience the hesitation on a long straight stretch of flat pavement. I'm going to replace the fuel filter next.

Not sure if this makes any sense, but could the hesitation be due to the fuel sitting in the filter at an odd angle and getting caught up somehow? There's a definite "kick" when it transitions from nearly sputtering out, to when I give it a lot of throttle and it "pops" back into running smoothly... Again, if that makes any sense

Thanks again in advance for any feedback.

4drEF

May be something as simple as taking things apart and cleaning them up. Throttle plate dirty, intake valves might be dirty, o2 sensor could be getting lazy, injectors dirty, ignition timing adjustment, TPS adjustment, etc