Couple Questions for you guys

[hammerline81]

Question #1: I had a cylinder 4 misfire on a drive on the weekend so I am assuming it's the plugs and wires(stock ACDelco's). So I'm changing those today, but... I have noticed a huge top end power loss. Going from 140kph and higher seems like it's pulling a huge ass trailer behind the car. I never had any problems goinf faster before but now its terrible. The supercharger is working fine but it seems like the motor isnt performing like it should. Could this be the plugs as well or am I needing to look for something else after?

NOTE: I still have torque and good power from off the line but like I said before, theres a huge power loss in the top end. And I'm getting a O2 sensor bank 1 code so something is going on.

Question #2: I'm getting a Evap. Code popping up once and a while. No idea where to start on that? I clear the code but after like 2-3 days that code comes up.

I own a 04 Comp G for anyone wondering what the car is.

[BillBoost37]

Let's fix the known issues and see what you are left with.

Grab tell us which codes you are getting and their descriptions. That'll give us a good bit of info to help you fix it.

[hammerline81]

I believe it's a P0440.

[Scottydoggs]

thats a evap leak code. try a new gas cap first.

http://www.obd-codes.com/p0440

[hammerline81]

I'll rob the one from my parts car and try that. I looked up the potential causes, never ever had a gas cap issue before lol.

[Scottydoggs]

look at the rubber seal if its got dry rot on it it could be the leak.

[BillBoost37]

Ok..that's one down. How about the O2 code.

[hammerline81]

I'm thinking maybe the O2 is going off because of the plugs.. but who knows

[Scottydoggs]

what o2 code you getting? theres a few of them, all mean something different. could be a lean code bank one, aka vac leak. or low voltage, or no heater.

[hammerline81]

Never got to doing the plugs and wires today. Just got off work and it's almost 9. So I'm hoping to do it tomorrow.

The car will not go passed 180kmh. I used to get to 210 no problems. No idea what the hell is going on..

[Scottydoggs]

thats a heater code for the o2. check the wires first, if they look ok buy a new o2 sensor. rock auto has delcos for rather cheap. thats not a performance hurting code really. it just says the o2 is not heating up as fast as it should be, aka its heater is broken.

tune up should help out the engine issues if its never been done before.

[hammerline81]

Yeah. I'll switch both out when I do the headers. I'm hoping it's the plugs and wires. Doesn't make sense that the car moves like a bat out of hell off the line but calves out when it comes to top end... but who knows

[Scottydoggs]

old plugs will make it crap out when you get on it harder. should fix it up.

get iridium plugs, or copper core plugs only.

[hammerline81]

Yeah, I got NGK iridiums. They worked well for me before.

[hammerline81]

Big difference with the new wires and plugs. But it still a little different. I'll change out the fuel filter and see if I get it all back.