matt34

Hi! I have a chevy cobalt 2006. I plugged my scanner on it and I get a p0300 and a p0301. That means a general misfire and a misfire on cylinder 1. I get a terrible idle. Car is shaking a lot and Im losing power when I try to accelerate. Almost have to press the gas all the way to get car moving. Its just like if it was stuck on the second gear. I think I get blowby too because at the end of the exhaust it blurp and I get a little bit on oil coming out. When I start the car I get no trouble. After a while, still on idle, I notice the engine turn slowly and headlights flicker a bit, but just after a while. I can see the rpm needle moving a little bit without giving gas. I changed air filter, replaced spark plugs with oem delco, cleaned throttle body, changed CAT and the rest of exhaust is in good condition, changed oil... I dont hear vaccuum leak, cleaned the grounds everywhere with the help of wiring diagram... Battery is a year old (interstate). Fuses seems all good (checked with multimeter for resistance)... I dont know what to look for now. I even tried to put an additional ground on the tcm as seen on youtube... What should be the next step?

matt34

Forgot to mention that on cylinder 1 spark plug and cylinder are wet... 2 3 and 4 are "normal" , I mean they are black caused by carbon, but not in excessive way...

jdbaugh1

iTrader: (1)

Does it feel like it is missing on a cylinder the whole time? Like does cylinder 1 ever actually fire? It seems like you are having problems in cylinder 1 whether it be injector, valve(s), piston rings/ringland, or head gasket is hard to say at this point. Is cylinder 1 wet with gas or oil or both? Do you have or know of anyone with a compression or leak down test?

matt34

Hi! Thanks sir for your answer Ok... First of all, yes it seems to happen all the time, I mean it's constant. Its not happening and disappearing. Its there all the time. The spark plug and inside the cylinder is wet because of "gas" for sure. There is no trace of oil at all. I changed the oil and put it on the side for a night to see prestone go on top or bottom. Nothing... I changed the prestone too with 50/50 oem and no trace of oil at all in it. I found something strange in the computer... I get a g5 myself and I get 8 cal and 8 cal number... On mine I get weird numbers as check number ex: ?2611529 (special caracter) ... 1212111345 (long number). On the cobalt Im trying to fix I get 1 cal number but 7 check number... Are you supposed to get as much as cal number than verification number?

matt34

Forgot to say that prestone never go down at all... oil is going down, I mean maybe a quart every oil change. The milleage is 165000 km

matt34

Sorry got trouble on the cellphone

jdbaugh1

iTrader: (1)

Well if it's wet with gas and you have changed your spark plugs (it's only the one plug that is wet right?)
Someone correct me if I am wrong on this but I think our ignition module shares a coil pack between two cylinders on 180 degree strokes. So if you have spark in cylinder 4 I wouldn't think your ignition module would be to blame as if it's firing in cylinder 4 I would think it is also firing in cylinder 1. That leaves compression. You should do a compression test across the board and go from there.

I have no idea what you are talking about with the numbers on your computer.

matt34

Ok... Yes, cylinder 1 is the only one wet. Cylinder 4 is firering for sure. You are completely right with the thing about the ignition module: its working in pair. 1-4 and 2-3 if I remember well... So if I get fire on cylinder 4, I should get some on 1. And for your information, I already swapped the coil pack and the ignition module without success because I got 2 on hand... So they are not the problem. I think you are right that compression test should be the next step. But, I still dont understand why headlights flicker at idle only after a while... Maybe nothing to see with that? Ok ok sorry... Going to fast I think. Should start with a compression test like you say and start from there... I'll make one and give you the result. What sould be the "normal"? Specific number or almost the same than the other one?

jdbaugh1

iTrader: (1)

I would think your headlights are flickering because the alternator output diminishes with the rough idle when the rpms dip. If they are actually flickering on off I would think that would be an electrical issue of some sort unrelated to the misfire problem. My headlights will dim if the engine rpms drop too low but I'm not sure if yours are dimming or actually flickering like a strobe.

I think it is 180-200 psi for our compression. The important thing is to not have significant variation across the bank of cylinders. My guess is that cylinder one will be really low. If you then poor a bit of oil in the cylinder and the compression raises significantly it is most likely your piston ring to cylinder wall seal to blame. If it doesn't effect the compression level it could be a sticky or non-sealing valve.

matt34

And what about head gasket? You think it would be responsible? For the headlight, the flicker because to see it sometimes I have to fix a point on a wall but not directly where they lit, just a little bit aside... As soon I give a little bit of gas they dont flick anymore... I mean at idle they dont go low and stay steady. They go down and up very fast, just like the oscilloscope you talked about... Do you think not enough compression on cylinder 1 can lead to get the engine not running strongh enough to keep the alternator turning enough to get flickering lights?

jdbaugh1

iTrader: (1)

Could you get a video of the lights? It almost sounds like you could have a loose housing or loose bulb vibrating with the rough idle. I don't know for sure as never experienced it.

It could be your head gasket I supposed. Have you ever had it overheated or anything? Are you losing any coolant?

exninja

iTrader: (1)

If you remove the plug do you get a spark?

rnjmur

Have you done a compression and leak-down test yet? That is where I would start. It could be a head gasket or a ringland. Either way, you are probably looking at tearing into the engine.