I need some members help. I just recently bought a 1996 Camaro Z28. It was showing the SES light (P0300 code) when I bought it. I picked the car up in Tennessee and drove it back to Missouri about 650 miles. I didn't have any problems and the car averaged 25mpg at 80mph. It seems to have a miss at idle. I was wondering if someone could maybe pinpoint what i should check since it gets such good mileage. The previous owner said he thought the cats were taken off, but I checked last night, and they are still there. Is there a way to tell if they have been hallowed out or are just pass throughs? I figure if its like wires, plugs, or 02 sensors I wouldn't be getting good gas mileage. Could someone help me and give me some ideas?

 

P0300 is a misfire code... hollowed cats wouldn't throw it.

 

if u have a po300 its a good indicater you need a tune up plugs wires air fuel u may not have even noticed the miss the computers are so sensitive just give it a tune up

 

I forgot to add the previous owner said he had just changed plugs and wires.

 

maybe he never cleared the code or he didnt or he fudged it up

 

I also read somewhere where a vacuum line could cause this, and actually my A/C doesn't blow out of my vents, just the defrost and floor. Could a bad vacuum line cause this code?

 

Yes, vacuum leaks can be responsible for misfires.

 

best thing to do is put a scan tool that can read live data
usually a P0300 isnt as random as it says and with live misfire data you can tell which cylinder or cylinders is missfiring

this help tremendously in diagnosis

 

What would be the best way to go about using a live scan tool? Do some shops have them, or is that something you would buy? And if so, which is the best one?

 

Scan tools can be expensive, alot of shops should have them. The GM dealer's Tech 2 can pull up misfire counts as per individual cylinders.

 

Ok on shoeboxes website there is a connector that connects your line to blow thru vents, mine did the same thing look on shoeboxes sight..

 

that connector on shoebox's site is for adapting an obd II cable to work with an OBDI scan tool wont work on OBDII

just about every scan tool can display live data except for the cheapie code pullers at autozone and such

easiest scan tools are the expensive ones that most shops have
any shop that can read check engine lights probably has a good enough scan tool to give you live data
just make good friends with a mechanic, maybe a 20 would help
when you look at the live datae, copy down which cylinders are misfiring and what percent they are misfiring
if none are misfiring while the car is idling you may need to drive the car around to put it under load in which case you need 2 people, one to drive one to look at the data

if you can get the data post it here i'll be glad to give some input
keep in mind it is live data which means the numbers may change while you are looking at them, no big deal

 

Ok I drove it around for about an hour today and noticed the misfire seems to be from 1000 rpm to 2000 rpm after it gets above that it runs great! It will kind of bog down and then when it gets above 2 grand it takes off. Does that help any? I really appreciate all the answers.

 

Sounds ignition related.

 

Like the opti, plugs, or wires?