Cpl Yanni

I just put new spark plugs in my 1998 c5 corvette. It clearly needed them since the old ones are made in japan. I put E3 .54 spark plugs in and now i am having this error code p0300. The old ones didn't do it. Another thing I changed was the oil i put 1 quart of 10w-30 (by mistake) with 5 quarts of 5w-30. My friend said that wont really do anything.

I noticed the car is a lot louder. After about 2 miles it starts to misfire.

ZZOOM06

You probably damaged the wires when you changed the plugs. Get yourself a new set of the red GM performance wires and I bet the miss will go away. Very surprised you put those pricey E3 plugs in,,,,total waste of money IMHO. Best bang for the buck plug is the NGK TR55 at under $2.00 each, or the stock replacements from any Chevy dealer or parts store.

Jimbo

lucky131969

Can't say I've ever heard of E3 plugs before...had to look them up. Not much info on their site, so I assume they do not come pre-gapped. Did you gap the plugs? Not a lot to say here, except go over your work. Make sure you did not crack a plug, and make sure all the wires on on tight. If you did not replace the wires, you may have damaged one during removal.

datsickz06

From my previous experiences with changing spark plugs, and getting misfires is that I used the wrong ones. I once installed those highperformance 4 needle plugs on a 01 impala I had and wow felt the power for a few miles then bammmm started getting misfires so now on my 01 z06 I only use gm approved parts in my engine or I ask the fellow forum members for their opinion

UniqueDoug

Funny just did the same job today! Went with Bosch premium wires, and it is tricky with the plug wires on the coils to make sure they are plugged in all the way!

Op, did you gap your plugs???

Cpl Yanni

i think its safe to assume they are pre gapped. i have no problem preplacing the wires. I heard that i need to drain the power and reconnect the battery because the engine isn't use to the 100% spark.

lucky131969

Oh really? Pre-gapped to what exactly?


I can honestly say, I have never heard such a thing before......

JW Motorsports

Check the plugs. I did this a few months ago and found one cracked in two places.

I got the P0300 code on the DIC, but hooked it up to a scanner and it directed me to the correct cylinder.

onebighitter

taking in all the info louder and misfire. Is it louder in the engine compartment like maybe a plug is loose and that is where noise coming from. Like jw stated find which cylinder is misfiring and start there.

PierEagle

Your best bet is with the AC Delco Iridium plugs, which are pregapped (.040) (if you can still get them) or the NGK TR55 Iridium plugs, and the GMPP RED wires. (Disregard the gap setting shown in the Vette owners manual)

Click on this link and you can doublecheck the work you did re possible misfire problem. Good pictures and text.

http://www.iammoon.com/c5tech/c5_plugs.htm

PierEagle

Whoever told you that has their hat on too tight and it's slowing the flow of blood and oxygen to their brain. Just kidding. If you do it right, the headlights will flip up and down twice to indicate the operation was a success.

vjjack04

Whew. You should get with some folks, locally, who can help you. The comment about "...think its safe to assume they are pre gapped. i have no problem preplacing the wires. I heard that i need to drain the power and reconnect the battery because the engine isn't use to the 100% spark. ...." is goofy. You should get the correct plugs and gap them. Maybe you should have someone who knows check your work. The oil change should have nothing to do with this. You should get a Chiltons or other reference manual.

Cpl Yanni

E3 .54 its right in the name. .54 there pre gaped to .54.

Cpl Yanni

just got back from advanced auto parts and it is #7 that is miss firing. I bought new wires.

dgrant3830

If the new wires doesn't solve it, put back in your original plugs and see if its happy again.

Quicksilver98

And if all the stuff above doesn't help....swap the coil pack on that cylinder to another one and see if the error follows the coil pack or stays with that cylinder. Good luck

Cpl Yanni

bad plug. So I replaced it. Still bad.

So i replaced it with a different brand. Works. wtf?

(Might of been the lack of rubber thingy in the spark plug socket)

cruisemon

C5 plug wires can easily be only partially inserted when plugs are replaced. Couple of tips that work for me.

1. Lightly lube the inside of the boot with hi-temp silicone grease. Do not use regular grease and do not overdo the lube.
2. Put a small wire tie up into the boot with most of the tie sticking out of the boot but not up into the metal part that clicks onto the plug.

Push the boot over the wire. The lube makes it slide on without sticking. The wire tie keeps the boot from sealing on the plug and keeping the plug from seating when pressure builds up in the boot and moves the plug back away from the plug. When you hear the boot click twice, remove the wire tie.

Charlie

K RIPPER

all spark plugs come pre gapped,it is, however, up to the installer/mechanic to check the plug prior to installation for damage either during manufacturing or shipping and at this time check the gap.It is unlikely that the misfire is caused by plug wire not on all the wayas we all know electricity follows the path of least resistance and with the boot on the plug it is significantly harder for the spark to go and travel that couple inches to ground past the boot than it is to jump that small area between the end of the spark plug wire and the top of the plug it is much harder to jump the gap in the cylinder as the cylinder pressure rises it becomes increasingly harder for the spark to jump the gap(supercharged/nitrious cars often recommend close the gap 5 to 10 thou.tighter as cylinder pressure is much higher in these apps.)I suspect you cracked a spark plug (porcelene)they can crack and not be visible to the naked eye and it is much easier for the high voltage to follow that crack to the metal base of the spark plug than to fire the plug in the high pressure enviorment of the cylinder...Don't look for miracles in spark plugs "gimmick " spark plugs are designed to do one thing regular plugs don't do they relieve you of extra cash...from your post I assume you are not experienced auto repair ,thats ok thats what the forum is for to help our less informed,you can use delco plugs or the NGK,NGK outstanding plug ,great price tons of peeps on forum love 'em in your case I recommend Delco'smore $$$ as you can keep 'em in twice as long use silicone dielectric grease on spark plug wires ,with metal end of spark plug wires not securely attached plug wire can come off plug especially w/dielectric greaselast I recommend Never seize compound on spark plug threads as over time ,through heat cycles "SOMETIMES" with the different expansion rates of the alum head and steel spark plug when removing the plug it pulls the threads out of the headw/never seize that will never happen(beware its messy) GOOD LUCK!