: P0300 code....AGAIN!



elby04
10-07-08, 03:01 PM
Ok, this is going to be kind of vague but here's my situation with my car.....I've had the p0300 code coming up for little while now, every once and a while it trips the s.e.s. light on the dash but if I go in and clear the codes it'll go away and not come back for up to a month sometimes. I've changed the plugs and wires and I'm looking for some guidance on what to do next. I believe i heard on here somewhere that the next step would be to do the coils on it but just want to make sure. if it is the coils need to be done next does anyone know if i can take them out myself and have them tested somewhere??? may be a dumb question but its better to ask then waste money changing them if i can find out if there bad or not, right? anyway thanks in advance to whom ever answers.

Submariner409
10-07-08, 03:07 PM
This is usually the problem......wires switched on one or two coil towers. It's critical that the wires are connected according to the diagram.

Click and scroll in.

Take a real hard look at the coil towers with the wires disconnected........any burns or cracks? Make sure the ignition circuits are OK, and if that doesn't cure the 0300 (miss detected) then troubleshoot the fuel injectors.

Ranger
10-07-08, 03:23 PM
Sub, didn't he say that it was intermittent? I would expect a crossed wire to be constant, no?

BTW Elby, I was just down in Missouri this last weekend. Damn, you guys have some cheap gas down there. Filled up for $2.94!

Playdrv4me
10-07-08, 03:32 PM
Sub, didn't he say that it was intermittent? I would expect a crossed wire to be constant, no?

BTW Elby, I was just down in Missouri this last weekend. Damn, you guys have some cheap gas down there. Filled up for $2.94!

Damn, you'll have to let me know where Ranger, it's still 3.29-3.45 in the metro STL area!

Anywho... to the OP... The PO300 code (Random cylinder misfire detected) is not always indicative of an electrical problem. Sadly, a recurring PO300 that happens intermittently or more often when *all* electrical possibilities have been ruled out can be an early indicator of the headbolt issue.

I would give Submariner's suggestion a try, however after that I would not keep pouring money into this problem before closely examining any coolant use you might be experiencing or at some point, a cylinder leak down test.

My White Diamond '98 STS would get that code after an occasional stall, but not nearly as often as you are getting it.

Submariner409
10-07-08, 03:32 PM
If the miss is intermittent then it doesn't sound like crossed wires, but at least he can do a logical progression through wires, coils, ICM, injectors.

This one's a brain teaser.

Ranger
10-07-08, 03:56 PM
Damn, you'll have to let me know where Ranger, it's still 3.29-3.45 in the metro STL area!
It was $2.99 - $2.96 in Monet and Pierce City. I topped off the rental car for $2.94 just outside SGF (Springfield airport).

Raze
10-13-08, 10:34 AM
Do the cheap and easy 'arc' test:

1) at night or in very dark garage
2) get a spray bottle of water
3) open hood and run engine
4) mist plug wires
5) if you see a blue glow or arcing discharge from any wire the insulation is failing and needs to be replaced


Next is chec your plugs, how old are they? what is their gap? what do they look like (coloration)

Injectors, two tests here that are DIY easy and cheap:

1) while running put a flathead screwdriver to each injector body and put your ear to it, listen/feel for a 'click' (though with an intermittent problem this is very unlikely this is your problem).

2) get a volt-meter and check the impedence across each injector, these are high-impedence injectors and should read in the teens for ohms, make sure they all have close to the same values.

Coil-pack, put a timing light on each wire and ensure it's firing consistently (again doubt it with intermittent problem).

Check / replace throttle position sensor ($35), problem here can cause a stall or near stall which will also trigger the misfire code (had this happen to me but also got the stall code).

I would say check your fuel pump but if your car isn't dying every few minutes i'd say you're in the clear there.

MAF sensor may be dirty and need to be cleaned, search around for procedure, not hard but do it the wrong way and you'll be paying for a new one.

Have you changed your airfilter in awhile? (doubt it's a problem but trying to think of any A/F related components that could affect you).

Goodluck...