I have a 99 prelude SH and having problem of my cel. It throws code p300 and found out that code say mulitple missfire. I changed the plugs and still cel is lit. tried to erase the code but it keeps coming back everytime I turn on my car every morning when engine is cold. I dont wanna waste moey of buying spark plug wires cuz seems like it's in good condition. I wonder if it has something to do with the thickness of the oil? or injector since the previous owner installed after market fuel rail? maybe distributor? or ecu? Anyone can help?

 

Is the car even stumbling or hesitating? A code P0300 may mean that one or more of the following has happened:
Faulty spark plugs or wires
Faulty ignition coil
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced.

 

catalic looks good, no oil inside not rotten or something cuz if my catalyic is bad the muffler shop would have told me when they installed my catback and i was there checked the catalyic as well. I also notice though when I start my car when it's cold, it seems like engine have to crack for like 2 or 3 secs before it start and sounds like it's choking man. I also have suspect for my battery cuz i have a loose connection as if the negative conn. can be pull out easily. My first plan is to replaced the wires but i don't know if it's gonna help. That sounds bad when you said possibly burned exhaust vavle that would cost me too much. But i am also panning to changed the catalyic to straight pipe anyway. Thanks a lot!

 

When is the last time you've done any kind of maintenance to your Prelude? A new OEM distributor cap & rotor does not cost very much (www.hondaautomotiveparts.com). First thing first, you definitely need to fix that negative terminal connection - even though a loose battery connection would not cause a misfire CEL to come on, its just something you gotta do.

 

i read the service manual that i got from hondahookup.com and read tha randiom misfire section. I wonder if that broken fuel pressure gauge that attached to my aem fuel rail caused all this? since the SM say also about fuel pressure. Maybe not enough pressure since gauge is broken? maybe some airleak? I am going to shop today and find a fuel pressure gauge and buy plug wires and fuel filter and run a compression test as well. I bought this car last may of 2006 but never drive bcuz of tiitle problem. And now, i just got it registered so Im not really sure when the last owner had service on this. I bought this from small dealership and found out that they took the CEL bulb so I installed one and found thats why cuz it's lit. The only thing i know was when i got this prelude I changed the oil and oil was just really bad as if it won't come out from oil pan and I flushed it before draining it. That was horrible.