I have Honda Civic SI '98 (109,000km)
Recently got CEL (Check Engine Light), took it to honda shop to have it tested
result: PGM misfire codes detected PO302, PO304;
They recommended to start with sprk plugs,
Replaced spark plugs Bosh Platinium

Problem persists, sputters a bit between 2500-3000 RPM and more over 3000.
OK on lower rpm,

Please provide me with the checklist of other potential mulfunctioning components.

Thanks in advance

les_sos

 

was there an o2 sensor code too? I know that honda put out a TSB on a common problem with a wire shorting out on the back side of the intake manifold that was throwing CEL. Do you have access to this info?

 

No, I do not. The only thing on the report is:

"PGM MISFIRE CODES PO302, PO304. REC START WITH SPARK PLUGS and RE ROAD TEST, REST ECU"


I replaced SPARG PLUGS and RESET ECU but problem continues.

r,
les_sos

 

Are Bosch Platinum spark plugs the actual stock spark plugs for that engine? If not, get the correct plug. Your Si is our Ex, correct? Our Ex doesn't use those plugs.

What about the other ignition components? Cap, rotor, and wires? Have you run some injector cleaner through it lately?

Does the car have any mods or did you do any maintenace recently?

 

No, mods;
Yes , Canadian SI is eq. to US EX
The car was for the routine maint .checkup 108,000km (67,500mi) just when after the first ECL showe-d up.

Did not run any injector cleaner nor checked cap, rotor or wires.
The plugs are not the type recommended in owners manual.

I'll need to do it tonight
r,
les_sos

 

use regular ngk, or denso plug, check the plug wires to see if it up to spec. 25k ohms.
check the plug wires order.
missfires at 2 and 4 cylinder.

 

So are the cap and rotor original? As in, they too have 67,500 miles on them? They are way overdue for a service change, if yes. The wires should probably be changed too, but the cap and rotor need some attention if it's original stuff.

 

Yes, Cap & Rotor & wires are original stuff. I get a replacement and recomended s.plugs & see if that helps.

Thank you for recommedations.

R,
leas_sos