My engine check light came on, then after a couple of days the car started running rough. The idle is jumpy and the engine surges when idling. Other than that it seems to drive ok. So I took the car in to get it checked. The code that comes up is C0300 - random misfire, and a code for the knock sensor. I am not gonna worry about the knock sensor since I could change it myself. But I have no idea what the Random misfire can be? Anyone familiar with this code or ever have this problem. Thanks guys.

 

Forgot to mention this a 1999 manual with about 112k miles on it.

 

What kind of spark plugs are installed? How long have they been in there? You need some new NGK pfr5g-11 spark plugs and maybe some coils.

 

how come there is a "C" in front of the code?

there is good info in the stickies about all the codes and what they mean

 

C0300, eh?

Still on the original coils? Ever done any maintenance?

 

I just spoke to my mechanic and he can't seem to find the problem. He says it's not the coils or cat. He recommended that I bring it to the dealer. I've had a tune up done about 5 months ago. So at this point I am gonna go back and get some NGK spark plugs, install a new knock sensor and pick up a code reader at pepboys. I really hope that will clear it up. Going to the dealership is just gonna get me raped

 

How exactly did he determine that it's not the coils?

'99s are notorious for coil pack failure, generally the first indication is running rough when idling under some load.

You could always give cleaning the IACV a shot, see if that helps at all. Also check the harness and connector for damage/corrosion as well.

 

I'm going to say coils. 120kmi+ and a 99? Probably stock coils. I'm going to say it's probably more than one coil.

Unplug and plug back in the coils one by one. If the pitch of the idling engine changes, you know the coil works (at least during idle).