I'm trying to repair my 98 Accord 4 cylinder (auto) and have not had any luck diagnosing the issue. I'm hoping someone will have some suggestions for me. I'm your basic DIY guy who only knows enough to get myself in over my head. I'm also probably a little weak in terminology.

The problem started a little over a week ago. I was driving in-city and the car started to lose power and misfire. The check engine light started flashing. The misfire is happening at idle and at speeds up to 50. At higher RPM with no load, the engine seems to smooth out, but it might under load. Unfortunately, the check engine light was already on due to bad fuel system seal (intermittent over the last couple of months). So, I don't know if any codes happened prior to the engine misfire. I managed to get the car to a parts store and they read the codes P0300 (I think), P0303, and P1259.

Checked oil level and it was very low. It was at about 5K miles, so I did a full change. I did the electrical checks on the VTEC and found nothing wrong with it. I replaced it anyhow. As of yet, the 1259 has not come back, but I don't know if I have run the car enough to have it code yet.

I have put in new plugs and a new ignition module in the distributor (it failed threshold test at parts store). I did a spark test with a 30K gap on the tester and I'm getting a nice blue-white spark on all 4 wires.

I tried to do a fuel system pressure test, but the kit does not have an adapter for this car. I have no reason to suspect fuel, just crossing it off the list.

I performed a compression test and got 185, 180, 180, 180 (1-4) cold and 190, 190, 200, 185 hot. They did not have a leakdown tester.

I pulled the wires off injector #3 and the speed of the engine did not change. Pulling any other caused the engine to almost die.

I now have the codes P0303 and P1399. The engine definitely still runs very rough. When cold, it seems to idle good for a couple of seconds, then bad for a couple seconds, etc. Once it warms up, it seems to just run rough. Driving it definitely still runs rough and has low power.

Could this be a bad fuel injector? Anything else that would cause one cylinder to misfire that has not been covered by my tests? Is there a good way to test a fuel injector?

I'm not sure how hard it is, but I was thinking about swapping injectors and see if the misfire changes cylinders.

 

Swapping injector 3 is a good place to start.

 

Swapped injectors 2 and 3. The misfire stayed on cylinder 3.

 

Is injector #3 firing or not? Listen carefully, feel for vibration, or use a noid light to confirm #3 is opening. Swap w/ no change suggests injector #3 is never firing.

If not firing, first check for constant 12V at the injector (should be if not firing). Then check ground signal path from ECU to #3 for open. ECU should provide a brief ground path to the powered injector to fire it. If not firing, it is likely that ground path is damaged somehow.

good luck

 

Sorry folks. I left that out of my original post. I did a noid test and I was definitely getting pulses. I even built my own so I could see all 4 at once. The signals from the computer looked good.

I just swapped the wires from #3 and #4 and the misfire moved from 3 to 4 as well. I retested both wires (#3 and #4) and I'm definitely getting a spark in the tester. I replaced all the spark plug wires and engine runs great now. It was a bad wire all along.

I'm not sure why it was working in the spark tester but failing in the engine. Maybe I don't have the tester set high enough. Definitely confused on this one...

Anyhow, the car is running great now.

Thanks to everyone that helped me out. I learned something today.
Have a good one

Tim

 

Thanks for followup.

Testing for spark is tricky. We've seen cases where spark appeared strong w/ an in-air test, but failed to ignite compressed air/gas mixture. Compressed air increases resistance for spark to jump gap.

Another spark test is using a timing light to test whether spark is jumping spark plug gap; no flash means no fire. But here we've seen mixed results on occasion also.

good luck