1998 Honda Civic EX: Codes P0301, P1399 Rough Idle & Now Problems with Accelorating

Question

I've had a rough idle intermittently for some time, recently had the check engine light come on, checked codes which read P0301, P1399. These codes have come up twice now (after clearing once).

We checked the spark plugs and all are still in good condition (NGK Iridium), but the plug in cylinder 1 was slightly loose (possibly it was not torqued enough) and we needed to adjust the gap just slightly. Torqued down the plug properly but car would still intermittently start up with a very rough idle, as though it was going to die. Sometimes it will do this when coming to a stop light.

Also, I have been noticing the RPM's taking forever to lower when driving on inclined roads and hills. It will stay at the higher RPM's for what seems like a long period of time.

Now, on initial startup just the other day, car was NOT idling rough - drove out of driveway and went to accelerate up a slightly inclined road and car didn't want to increase in speed. I had foot down on peddle and I thought it was dead, then, all of a sudden it kicked in and jolted forward because I had my foot way down on the gas peddle. Drove it slowly around the block and it seemed OK, but I didn't want to drive any further and came back home. Were talking only 1 mile of driving.

Two other possibly related or unrelated issues happened recently, on separate days. Door locks were acting up, not wanting to lock or locking on their own. They seem fine now and this was very brief. Days later, after startup (not first startup of the day), the car radio would not turn on during drive home. Parked, turned engine off, then turned until ignition light came on, still no radio. Waited a few hours, tried again, radio lights, clock etc on.

Answer 1

Hi there,

These codes indicate a misfire on cylinder 1. Here is a list of possible causes for you.

P1399 HONDA - Random Cylinder Misfire Detected

Read more: https://www.autocodes.com/p1399_honda.html

P0301 HONDA - Cylinder Number 1 Misfire Detected

Read more: https://www.autocodes.com/p0301_honda.html