P1300 misfire code, but ignition is new

SW20FL

New Member
5+ Year Member
I got a nice little OBDII scanner for my 97 Civic DX 5spd today to see why my check engine light was on. I have a crack in the exhaust manifold so I knew it would be the O2 sensor or emissions related. I was right, but to my surprise, I found that the ECU also recorded a cylinder 2 and cylinder 4 missfire. Then it shows P1300 which is a multiple cylinder misfire. The car is 100% stock. Not one modification.

That doesn't make sense to me because I replaced every component of my ignition with NEW parts and I reset the ECU by pulling the battery when I replaced the ignition. Not to mention, the car drives and idles wonderfully. The engine has 173,000 miles, but it runs like it has 60,00 miles. It doesn't hesitate or anything to make me even suspect a missfire. Even with the crack in my exhaust manifold I average about 33-36 mpg with 80% highway and 20% city, and 40mpg with 100% highway. I will be fixing the manifold down the road.

I really don't care to fix this problem. I'm just curious why the car would still be detecting a missfire.

I replaced:

Coil
Igniter
Cap
Rotor
Wires
Plugs
New distributor from Honda

I may be guilty, but I didn't set the timing when I installed the new distributor. I just put it in the same position. Would the timing being off have something to do with a missfire?

The previous owner also replaced the first O2 sensor early this year, but installed it in the cracked manifold. Could this have damaged the sensor?
 

Solid_Snake

Te mato con mi VTEC
Registered VIP
5+ Year Member
Well if you didn't adjust the timing right its going to cause pinging/detonation/knocking, and the ECM might be seeing it as misfire. Does the MIL (check engine light) flash when the engine is running?
 


Solid_Snake

Te mato con mi VTEC
Registered VIP
5+ Year Member
DTC P1300 Random Cylinder Misfire can be caused by:
Ignition system, Fuel Supply System, MAP sensor, EGR system (I think only the D16Y5 HX has EGR system), IAC valve, Contaminated fuel or lack of fuel.
 

SW20FL

New Member
5+ Year Member
Well if you didn't adjust the timing right its going to cause pinging/detonation/knocking, and the ECM might be seeing it as misfire. Does the MIL (check engine light) flash when the engine is running?
The check engine light doesn't flash. It just stays on. It did flash once for about 2-3 seconds when I started the car up in the morning and it was idling cold, but never again. The check engine light comes on for maybe 6-7 days, then turns off by itself, and stays off for maybe 6-7 days, then comes back on again, and this is a continuing pattern. I'll set the timing, clear the codes and see if it comes up again.
 


SW20FL

New Member
5+ Year Member
Okay timing is set to 12 btdc.. Codes are all cleared. Drove around for a while and ran another diagnostic. O2 sensor tested good, and no codes or misfires detected. All clear. I know the engine light would come eventually because of the crack in the exhaust manifold, but I'll be checking if there are any more misfires detected. Engine is super quiet at idle and happy =).
 


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