Hey guys, I've got a 1998 Honda Civic EX D16Y8. I took it in today to have an exhaust leak fixed, (there was a hole in the pipe just past the resonator, before the muffler.) It was running perfect, and has been for a long time, up to the point I drove it onto the lift in the shop. After he finished welding the new pipe in, and I went to start it, immediately, it started missing. I got out onto the main road and it was just running awful. Check engine light immediately started flashing. I made it home, read the codes, and I am getting 4: PO300,301,302 and P1399, all misfire related codes. I called the guy who did the work, and he "assured" me that nothing he did as far as the exhaust goes would have caused misfiring like that. I am not so sure. Does anyone have any idea what could be causing this? I asked if maybe the muffler was clogged, and fixing that hole prior to the muffler maybe has severely restricted the exhaust, but he said no way, there has to be another problem, engine related. Any help, or insight here would be greatly appreciated! Thanks.

 

It may sound counterintuitive, but check if the battery terminals are tight. I had this exact issue 15 years ago and almost went nut to solve it until I realized, much to my embarrassment, the positive battery terminal was a bit lose. It takes literally minutes and it's free, so worth checking.

 

Hey thanks for the idea... I actually have disconnected the battery, and reconnected already to reset the ECU, because on rare occasions, I've seen that fix problems! Battery terminals are both nice and snug.

Update: I disconnected the exhaust, right after the cat, just to see if it might be clogged from there on back, and still the exact same issue. So unless the cat itself has somehow become clogged, I don't think it's exhaust related. I was wondering about the o2 sensors since they are in the exhaust, but I am not getting any codes for the o2's. Also not sure if they could cause a misfire this bad. It also only seems to be about 2.5k - 3k in the rpm range that its missing. Once above 3k, it runs perfect, no misfiring at all.

 

The O2 sensors would give different symptoms.
There are two things I can think off right now that would cause those issues on a D16: timing belt and distributor. If you don't know when the belt was last replaced and/or you have some unknown aftermarket belt installed it may be worth doing anyway. Since it's not expensive replacing the tensioner at the same time is worth doing. These old SOHC Honda engines need timing belts replaced every 60,000miles and a good valve adjustement every 30,000 miles.
The distributor can be tested with a digital multimeter (off the car) but usually it start throwing P1831, P1832 etc. codes before causing misfires.

 

Interesting... I recently replaced the coil in the distributor, as it left me stranded a few weeks ago. Tested the coil with an ohm meter again, and it it's well within specs. The other thing I have heard, is the igniter or ICM might be causing this, not sure if that's a possibility or not. I am tempted to replaced that as well, and see what happens. Although after replacing the coil, and igniter, you're almost better off just replacing the whole dizzy I think. I am going to do a tune up on it today, plugs, wires, cap/rotor, fuel filter, and see if this helps. I have been going to do this for a while now anyway as it's definitely time. I'll report back after the tune up, and go from there. Thanks for your help!