soLame

Honda accord 1998 misfire (4 cylinder engine)

Symptoms:
Engine shakes at idle, cold and hot.
Acceleration seems normal, at speed there is no sign of misfire except the CEL comes on.
CEL indicated cylinder 3 misfire. p0303 and p1399

Car:

• 98 accord LX, 150k
• NGK wires, OEM cap and rotor (all 5 yo).
• Original injectors
• Quality fuel used, with seafoam every other month
• Mobil1 oil changes with occasional seafoam oil flush
• Bosh +4 spark plugs (10 years), they work fine in the car, maybe not as good as NGKs, but I had them in this long.

Checks performed:
1. Spark test using in-line spark tester
2. Moved the spark plug around from cylinder 3
3. Moved fuel injector from cylinder 3 to cylinder 2
4. Checked EGR valve, harness voltage as well as 1+3 terminal 12V activation on the valve
5. Disconnected EGR valve, had no effect on misfire, yet threw EGR CEL code
6. Noid light checked injectors
7. PCV valve vacuum
8. Compression test, all cylinders were in 180-170 range
9. Checked spark plug wires resistance, all the same.
+
10. Checked intake and exhaust valve clearance
11. Checked for vacuum leaks with carb cleaner spraying all over vacuum tubes and intake area.
12. Checked mechanical timing alignment.

Replaced:
1. Spark plugs with NGK copper
2. OEM cap and rotor
3. NGK wires
4. Air filter

Next:
1. Need to verify sensor and computer, just need to figure out how.

Any suggestions? I ran out of my Haynes manual troubleshooting steps

soLame

update:
on a hunch, I swapped distributor cap, rotor and wires again last night.
The idle is still rough, I would say there was no change to engine behavior.
I was driving to work today and pushed the car hard up the hill, CEL came on with misfire codes for cylinder 2,3,4 and 1399.
This is getting even more interesting.

should I open up and clean out EGR pathways?

GhostAccord

Flashing CEL is catalyst damaging misfire indication and a P1399 is a random misfire code for all cylinders. Similar to P0300 & P1300.

Sure you could try cleaning out your EGR, it is a possible cause for a random misfire.

I noticed that in your list of things checked you didn't list the ignition coil or the ICM/ignitor and on the fuel side you never mentioned testing the fuel pressure. You could try those as well.

Now moving away from the engine there is the slight possibility that your exhaust is restricted, clogged catalytic converter or crushed pipe?

Other than that you have covered pretty much every thing else. When were your valve clearances checked last... I know your compression test checked out but the valve clearances could be on the loose side.

cptbarkey

swap the Bosch spark plugs back in, its not unheard of that you have one bad new one (or two) or its gapped wrong.

GhostAccord

Why would you suggest swapping back to spark plugs that are 10+ years old in an engine having a misfire issue?

I agree that you might get a bad spark plug, however it is rare. You can test the plugs instead of pulling them. Then if they are not gaped properly you can change the gap very easily.

spoonhatchback2001

Ghost is heading you in the right direction. If your valves are out of adjustment you can cause miss fires and since you appear to have multiple misfire codes it wouldn't be a bad 30 minutes to spend on adjusting your vavles. EGR vavles don't typically cause misfires.

soLame

Thank you for advice.
I took my time and went through the valves today, both exhaust and intake sides checked out within spec. Cylinder #2 exhaust was on the upper range of the norm. 0013, but other than that right in the middle.

soLame

Update:
while working on checking the valve clearance, I noticed that the timing belt is not as taught as it used to be (I think). I would like to eliminate a possibility that the timing belt jumped a tooth.
How would I do that? (checking the forum now).

holmesnmanny

You need to line up the crankshaft to tdc on the lower timing cover notch. You do this by putting a 19mm bolt and ratchet on the crank bolt and turning the engine counterclockwise until it lines up at tdc. Then take off the valvecover and check to see that the cam is lined up correctly. The arrow should be pointing up and there should be two lines on the cam that will line up with the upper timing cover/head . If they don't line up then your mechanical timing is off.

soLame

update:
checked mechanical timing, everything lined up on the dot. Will check timing with the timing light next (now that I replaced distributor cap and rotor, it would not hurt to double check).

How do I check the function of my O2 sensor? should I just clip voltmeter in and see how the voltage is moving? should it be under 1V? I am wondering if the O2 sensor is just getting old.

GhostAccord

Yes it will be between 0-1v, depending on your voltmeter you may not even see the switching voltage.

Best way to see how your engine is running would be to find someone with an OBD2 scan tool with the ability to view/capture live data. That way you would be able to see your short term and long term fuel trims along with your O2 sensor and all the other corresponding sensor data.