I bought a used 05 cobalt 2.0 sc around 3 months ago, from the beginning I've constantly been replacing parts to get the car up to par. My current battle is agents normal operating temp range misfires and slight engine vibration. You can hear the miss from the exhaust and I've about fully extended my wallet. The cars bone stock except for a typhoon cold air intake. Parts I've replaced would be maf, upstream o2, camshaft position, cleaned throttle body, new head gasket and intake, new timing chain, fuel filter, new plugs gap .32 nkg, new air filter, cleaned grounds, new battery, I've about given the car the whole once over. The only thing I've been able to do that seemed to even it out was to disconnect the pcv hose from the valve cover which connects to the cai and suck air from it. In my opinion I find that quite odd but I'm in uncharted territory for my knowledge. Any help would be greatly appreciated, I also have a snap on diagnostic scanner so I can provide sensor data, I'm just unable to Interpet it. Only code is a p0300 every once and a while

 

300 code is just random misfire. doesn't help much. Some sensor data would help.. o2 b1s1 and maf

Does it tick at idle? If so, it seems like that would be your timing chain tensioner, seeing as how you've replaced just about everything but that.

 

the intake changes how much air is going past the maf and skews the maf reading that could be the cause of the random misfire you may need to put the stock intake back on

the tensioner has nothing to do with his problem

 

He said misfires and slight engine vibration, and he can hear it from the exhaust.. tensioner is right there and it could just be the ticking noise..

 

Swap back to the Stock Intake system. Unplug the ECM for about 30mins. and see from there.

The CAI can cause the Random misfire with a tune.. Some will Argue, But i've seen it happen.

 

i dident know you could hear a vibration from listening to the exhaust the tick could be an exhaust leak could be the injectors making noise could be just some normal valve train noise from normal wear and the tensioner wont make a noise the chain will though

 

simple way to find out is pull valve cover and check to see if chain is loose. have you checked to see if the plugs look good? it could simply be carbon build up on the valves. throw some seafoam in the brake booster hose when she's running and see what that does for you

 

carbon on the valves wont make it mifire

 

if the valve doesn't seat properly it would... i'm having this issue with my girlfriend's l61 cavi right meow

 

Sorry for the delay I can see the motor itself vibrate and hear a miss in the exhaust, as for the stock aircleaner tubing I don't have it, the cai was on the car when I bought it. I will post all my sensor data her in just a few

 

Also everything to do with the timing chain is new, guides and all

 

so it starts to miss after it warms up? have you checked the ignition coils or spark plug boots? If theres any cracks it could arc to the valve cover or if the coils have a lot of miles they can short internally and heat usually makes its worse

 

It doesn't seem to be the coils, I had them tested and I taped the boots just incase. This is a think outside of the box situation lol, my only other true gues is my lower bank o2 because it doesn't fluctuate

 

if your getting carbon on the seat area of the valve you have bigger problems

 

are you refering to the up stream or down stream 02 if its the down stream it dosent do nothing but moniter the cat

you should do a leak down test on your engine

 

I personally went over cleaning the head, so I'm almost certain it can't be carbon buildup. I did mean the downstream o2 but it doesn't matter, when I took it to my local dealer to put a new converter on it they apparently crossthreaded the damn o2 in there soo tight I can't get it out and the washer isn't sealed... I don't know if my car is just too old but I can unplug my scip map and I don't get a check engine and the car keeps running the same, taking the gas cap off also!

 

i wonder if your car had been modded and then put back to stock to resell due to problems

 

I know this is an LSJ, but my buddy has an 09 LNF and he had the same problem with random misfire and he tried everything, took it to the dealership and they said it was bad piston rings. Replaced everything under powertrain and his misfire is gone.

 

Haha I wouldn't put it past piston rings by now, the car originally had under glow, someone painted the motor with a paint brush, real dumbasses!! If I still had a warranty that would be awesome, but I'm sitting on 121,500 miles exact. When you replace the camshaft position sensor does it require a case relearn?

 

Tighten down your exhaust mani for the ticking, bet its loose, had the same problem. Your injectors are gapped too low, stock is .40 i believe (could b wrong) but you have no mods to go down to a 32 thats what im at. And last thing, replace pcv hose, might be clogged.

 

get a tune, your intake is likely causing the misfires.

 

I can't gap my injectors lol but you may be onto something with the gap, I went down just incase they were being blown out. Pcv hose is good, no leaks or clogs and you may be onto something with the tune. My problem is the cost and where a tuner is located in Alabama.. I'd be dipped in **** if it was just a simple cai causing all my trouble!!!!

 

ah i just realized you weren't tuned. Yes that will cause random misfire too. it happened on my LSJ when i had just an intake. also p0172 will pop up from time to time due to it.

 

Almost forgot the manifold isn't ticking, I even left it hooked up when I pulled the head. The only ticking I ever had was the original timing chain when my motor "which it seems all ecotecs have this problem" had the fixed timing chain guide upper bolt break.

 

No I don't have a tune and the only code I get "if I prevailed my motor enough" is a p0300 I'm bone stock aside a k&n typhoon cold air intake.