AndyFromWI

Hello, I thought I would list a solution about a 4 month journey trying to solve a misfire and then later hesitation / rough idle issue on a 1998 Civic LX.
Hopefully this will be helpful for someone else who runs into this issue.

The car was in great shape and had 246K miles when I bought it.
I needed a car for my son, it had good glass, good tires, everything worked (so I thought) and the timing belt / water pump had just been changed at 236K miles. 200 miles into owning the car, we started getting the flashing engine light and misfires.

Here is a list of the Problem / Solutions:

Problem: Misfire P1399, P0300, P0302, P0304
Solution: Replaced fuel injectors (a spare set came with the car), also mig welded a crack in the Exhaust Manifold

Problem: Hesitation from 1500-2500 RPM and hard start
Solution: Replaced Distributor Cap, Rotor and Coil
Note: The distributor cap was warn to almost nothing, the coil produced a very tiny spark, then later nothing.


After reading many of the forums, I followed the suggested trouble shooting steps: Spark plugs, spark plug wires. My big mistake was that I had assumed that the distributor cap and rotor were new..... This was the one thing I did NOT check, and I should have checked it first. The distributor cap was so worn, that the center nub was 99% worn down, I don't even know how the car ran, after I remove and reinstalled the distributor cap, the car would not start.

Did the previous seller must have know of misfire problem?
After the misfire problem started, I realized the previous seller must have also had this issue, but neglected to mention it. I think this because the when I changed out the fuel filter, it the old fuel filter was like new, also the car had a new set of spark plug wires, and came with a spare set of new fuel injectors. I can only assume that the seller did not get to installing the new injectors. The car would typically run great for 200 miles, then have a problem, I would try something, it would run for 200 miles, and have a problem again.


Suggestions for Misfire:
1: Check spark plugs
2: Check Distributor Cap and Rotor
3: Check that you actually get a good spark.
4: Check spark plug wires
5: Replace Fuel Filter, try some fuel injector cleaner
5: Check/clean or replace fuel injectors. I would suggest first pulling and cleaning the fuel injectors.

Suggestions for Hesitation / rough idle:
1: Check spark plugs
2: Check Distributor Cap and Rotor
3: Check that you actually get a good spark.

History of my trouble shooting:
Basically I got the misfile under control, but then had the rough idle hesitation issue. I raised the idle from 500rpm to 1500rpm to see if that would keep the car running, it helped but the car could be hard to start and did slow to accelerate from a dead stop. At one point I thought I had it fixed, went to the hardware store, tried to start the civic 15 minutes later, and I could barely get it to start or run. At that point I was so frustrated I started thinking maybe I just swap out the engine. Once I finally checked the distributor cap, and changed out the cap, rotor and coil, that fixed the rough idle / hesitation and now the car runs perfect!.

4/17/2016 236,279 Timing Belt and Water pump (before I purchased the car)
1/4/2017 246,233 Purchased car LX 4DR SEDAN, ENGING 1L ni I4 SOHC
1/18/2017 246,464 Fill up, oil looked good, full 10.5 gals gas to full, small overflow. not great mileage 22 (but do not know if tank was truly full when we got the car)
1/21/2017 P1399, 0300, 0302, 0304 Engine missfires, very humid/foggy,
2 plugs were loose maybe 5 lbs, removed cleaned, cleared codes no issue: Maybe humidity? Compression with plugs out: 150, 150, 155, 175 (note engine was cold)
Manual states: Min 135, Max 185
1/22/2017 246,742 8 gals gas, 1/2 can fuel injector clearer, new plugs (278 miles since last fill up)
2/5/2017 Scanned No codes
2/22/2017 248,193 Ignition trouble again, P300, P301, P302, P304 and P1706. Checked spark plugs, torque and plugs looked good. Changed Fuel filter, old filter looked OK, put in the rest of the Fuel Injector Cleaner maybe 3 ozs of cleaner, Cleared codes. Coolant was Low, added 1 pint, reserve was empty, flushed with water, ran rough for a while, went for a 10 mile drive, ran good, but rough if you punch the gas, slow acceleration is fine.
3/25/2017 249,726 Oil full, coolant full, tires full, all good.
4/16/2017 Ignition problem again....
4/17/2017 P1399, p300, p302, p304
4/21/2017 250,330 Welded cracked exhaust manifold, could not find any vacuume leaks, checked spark plugs, Did cold compression test 1: 162, 2: 160, 3: 157: 4: 163
Engine still misses, and idles low, almost did not start at PT, still throwing codes.
4/22/2017 250,330 Swapped out fuel injectors with the extra set that came with the car, running good so far
4/23/2017 250,351 Adjusted idle via mixture screw (remove air cleaner box), cleared P170, P172, ran well, no misfire, no new light.

4/29/2017 250,511 300,301,302, 304, 1399 codes, I cleared them, adjusted the idle stop hex screw to idle at 1700rpm, filled up with 9 gals 1/2 bottle of gum-out fuel cleaner, seems to work.
4/29/2017 250,511 Re-adjusted the idle hex screw, cleaned throttle body, put the idle air screw back to where it was 200 miles ago, with the idle hex screw, adjusted to 800-900 rpm warm, test drove was fine
5/7/2017 250,751 Still running good, no misfires!
5/19/2017 250,945 Running rough around 1500, no codes, just hesitation.
5/22/2017 250,945 Removed fuel rail, double checked it, and blew it out with air, checked plugs, #3 black, 1,2,4 gray on L Compression with plugs out: 163, 160, 153, 160
Changed Oil and Filter, tightened exhaust bolts, checked Weld, looks good, fixed rattle by wiring up heat shield on lower exhaust
5/25/2017 250,945 Distributor Cap was bad, replaced Cap with (Honda cap, and BWD Rotor), coil was very weak, when removed would not spark manually. Replaced coil with BWD coil.
Runs great, no hesitation, manually adjusted idle back down to 800 rpm, AC works but has clinking sound
5/30/2017 251,200 Still running great, no misfire or hesitation.

Attached is a picture of the bad Distributor Cap

Good hunting.
-andy

TomCat39

Thank you for sharing the very detailed log of your challenges and solutions.

I'm confident it will help someone else down the road.