So over the last few months I have been having CEL pop on with basically all of the misfire codes possible, p1399, p0301, p0302, p0303, p0304. The last time it went on about a month ago it was just p1399 and p0304. So I have replaced all four coils, I did map whack, been putting injector cleaner hoping that may help. I also took my test pipe off and reinstalled the cat hoping that could be the cause. Of course on my way to work today it popped back on, its been about 700 miles since the CEL was on last. I have read the misfire thread and I know I havn't tried everything. I have a mutlimeter but I don't know how to test both the alternator and the TPS, anyone have a link on how I could do this? I searched but I couldn't find any instructions on how to do so. Oh yea and I did a comp test and all cylinders were between 220 and 240.

 

If know one responds I'll check for you when I get home at 6:00 PM ET

 

To check the alt., crank the car and put the multimeter across the battery. if it shows 13 to14 volts, its working.but if it shows12 to12.5, its not working. for tps, turn your multimeter to ohms. disconnect the tps and hook jumpers to the pins of the tps. move the throttle body and see if your ohms reading change. if they do, its possible its fine. if not, than its bad. hope this helps. good luck.

 

Highly unlikely the TPS or Alternator is causing a misfire.

 

yeah i wouldnt even bother checking either of those two...

check plugs, maybe dirty injectors, your compression numbers seem to be ok..

 

Its possible you might have a bad spark plug. do you know what plug is miss firing? are the plugs tight? its possible to have a crack ceramic on a plug internallywhere you can't see it. that would cause it to miss fire. have you determine the codes its giving you?

 

The plugs are pretty new, I replaced them less than 5k ago, also my coils at that time which I thought solved the problem. I had no check engine light for a good 2000 miles, then same thing misfire all 4 cylinders. I then took my tp off, did map whack and started using injector cleaner regulary. Of course then I get another mifire, 1000 or so miles later (only cylinder 4 misfire and 1099 that time), so I got a valve adjustment and regaped the plugs. 1000 miles later CEL back on and its a 1399 and cylinder 4 misfire again. I have a can of seafoam that I will put in next refuel but I doubt that will help. I will check the TPS and alternator and the plugs again tomorow but it sounds like thats not the problem.

 

ur gonna want to connect a manufacturer specific scanner and get the reading for the first code... seeing as how all cylinders are misfiring and there is one manufacturer specific dtc, fixing that code should fix all problem.

p1399(manufacturer specific), p0301, p0302, p0303, p0304

 

I thought that 1399 was just a random misfire code.

 

1 cylinder misfiring can cause the other ones to misfire randomly...take it to honda, the HDS (honda diangonstic sytem) has misfire counter, tells you which cylinder(s) are misfiring and how mny times upon startup..i think its something internal, we did an engine couple weeks ago have burnt exhaust valves...

btw are you using oem plugs???