cheggie

Hi guys and gals,

My stock 96 Civic EX w/185k miles recently began running rough and misfiring. It began suddenly at the end of a 35 mile trip, and the car has has zero driveability trouble until now. I have codes P1300, P0301 and P0303 present. I have a copy of the Honda manual and have performed diagnosis for P1300. I have a spare distributor and fuel pump, and I swapped those to rule out fuel delivery and all the parts in the distributor. I'm waiting on an adapter to test the actual fuel pressure, but I'm pretty confident that the pressure is ok. Fuel tank is clean as a whistle, tank was nearly empty when it started, but I filled it up to rule out bad fuel. I saw no water in the fuel or contamination on the pickup screen. Injector screens are clean. Spark plugs are pretty new NGK's, but I doubt all of them would fail at the same time. Wires are good quality replacements, but it's also unlikely they would all fail at the same time - generating a random misfire. I checked valve adjustment, and made a couple of minor changes, but nothing was far out of spec.

During the compression test, I noticed something strange. The pressure seems consistent among all cylinders at around 175, but the reading drops quickly when I stop cranking. I'm used to the compression reading remaining on the gauge for a few minutes. I also noticed that the car seems to run fine when cold, after about 5 minutes the misfire begins. Does anyone have any ideas?

haroldrussi

Pressure dropping on your gauge after you stopped cranking is most likely your gauge leaking down. Warm misfire would usually be ign. related or water in the fuel but you have checked that. Does the dissy cap have any cracks?

cheggie

I swapped in my spare distributor with it's own cap and rotor, with no change whatsoever.

I thought my gauge might be bad, but it worked fine a few months ago. I'll check it to verify it works.

Former User

How old are the plug wires?

cheggie

The plug wires are at least three years old, they are autolite replacements. They were on the car when I bought it. I suppose I shouldn't rule them out.

As a side note, I started the car today from dead cold and timed it. It ran perfectly for five minutes, and then the misfire crept in.


UPDATE:

Found a loose one way valve on the compression tester. New compression numbers with a slightly warm engine are: 1=200#, 2=190#, 3=200#, 4=200# and these numbers held firm after getting out of the car to check - no dropping pressure.

Also, scrutinized the plug wires more carefully and found an ominous mark on number one plug wire...

Yeah, maybe I need to replace the plug wires next...will report back.

cheggie

Well, the number one plug wire was the culprit. I wrapped the damaged section with electrical tape to see if it made a difference, and it did. I cleared the codes and drove into town to pick up the replacements, and no trouble the entire trip. It looks like I took the long way around to find the answer, but I didn't buy any more parts than I needed. I still don't know how misfire on one cylinder can set codes for two cylinders (and then for the random multiple misfire) but it did. Thanks for the helpful insights, I nearly overlooked the most common cause of misfires.

94EG8

I've seen a lot of cheap wires do that. OEM Honda or NGK blue wires are what you want.