Iv got a CEL p0301 cly1 misfire iv changed all Plugs,coils and inj seals and still have a bad misfire anyone have an idea

 

o2 sensor

 

Compression/leakdown test works better than the shotgun approach

 

Most people just don't wanna know the answer to that one.

 

+1. Nice to have another knowledgeable person on the board (again).

 

Ok thank y'all I'm goin to do a leakdown test today but now the misfire is random sometimes the car runs great and sometimes it runs like crap

 

I guess I should have told y'all it only does it at high boost no problems when driving normal

 

Swap the #1 & #2 Injector and see if the misfire follows the injector.

 

Swapping injectors on an LNF can cause issues, you need to replace the seals when you remove an injector. But that is a valid test if done right.

 

before swapping injector do a compression test i have seen the exhaust valves the are burnt and will drop the compression by 20 or more psi in that cylinder and cause issue's... if you drive normal 20 psi low in one cylinder you wont notice it unless you look at a miss fire count on a scanner

 

Just had this code pop up this afternoon when leaving work... I'm only at 54K miles... There was only one code when I checked it with my scan gauge. The car drives fine, so I cleared the code to see if it would come back. If it will, the car is still under extended warranty, I might just take it to the dealer and have them mess with it...

 

My guess is a lash adjuster or two on Cyl 1.

 

Let's hope it was just a quick glitch (the RPMs too low or something), I'm still getting used to the Cobalt after my RX-8, the clutch is way different, and so is the powerband, so I'm testing my limits both at high and low RPMs, almost stalled it today, and then the CEL popped up..

The RX-8 definitely had a higher red line :-) Other than that, my stock LNF is quicker in the straight line.

Edit: the car does run and pull just like before.

 

I had this last weekend. Cleared it and went for a burn up the highway, put some 94 in and It's been fine since. You might of gotten some bad gas. I know up here in Canada we have shitty gas compared to the states.

 

So I replaced the plugs... the old ones looked pretty black, probably been there for a while at 54K, even though they were Autolite XP Iridium as I found out, so probably have been changed. The dealer parts dept was closed to buy the OEM plugs (it was Sunday), so I went to autozone and got some Autolite XP Iridiums and replaced them (NGK Laser Iridiums were special order item, otherwise I'd get them)
So I cleared the P0301 code (it popped up again), replaced the plugs after properly gapping them to .032 (they were set at .050 from the package), double checked the gap on XPs I pulled out of the car, they were set at .040, so that might have robbed some of my performance too.
Took it out for a test drive, got the Low Traction light on shifting from 1st to 2nd (NLS), pulled hard all the way through second and third, no misfire... So I turned around and went back home..
Started it this morning before work, it sounded a little rough, I revved it up a little, and the light came back on... 1st Cylinder Misfire.... At least I know it's not the spark plugs, so I took it to the dealer for troubleshooting.
I'm still under extended 6yr/100k warranty, and my 5yr/100k power train is still in effect, so I'm not too worried about it. So far they cleared the codes, swapped 1st and 2nd coils to see if the problem moves over(I could've probably done it myself, but I'll let them figure it out). They took it for a test drive, but couldn't find anything, so they kept it overnight to try it in the morning when it's cold.
They also said that my fuel system checked out fine, so we'll see what tomorrow brings...
I'll keep you posted.

 

What happened with this?

 

i had similiar issue ended up replacing the plugs twice re gapping them changed cam sensor and finally found my problem in a variable valve timing solenoid right on top of the valve cover

 

Pretty much that... They test drove it again in the morning for about 30 minutes (just started it up and went driving, different loads and everything), and couldn't get the code to pop back up. I was sure it was just them not putting enough load on it (the light usually would pop up at WOT right as I would NLS), so when I got it back from them, I drove it around pretty hard on the back roads, and couldn't get the light to duplicate...

Apparently, that would be covered under my power train warranty, so he didn't bill me, he wants to see if the code appears again and if it has moved cylinders, or if they have to dig deeper. So it seems like properly gapped plugs fixed the issue so far (the one time the light did come on next morning was with only the codes cleared, not fuel maps cleared, I never disconnected the battery, just cleared the codes from my ScanGauge II that's laying around from one of my other cars).

I'll drive it around for a while and see if it comes back, and if it does, I'll take it back, and, according to them, they'll just bill the warranty directly. They seem to be pretty cool. Definitely taking it back.

On a side note, when I replace the plugs again in 10-20K, I'm putting stockers back in, as advised by many folks on here...

 

So the light popped up again (P0301), same cylinder, so the plug/coil is not an issue. I cleared the light as advised by the service assistant manager (it happened yesterday afternoon)... then on the way back from school at night, while shifting at approx 5-6K RPMs, the engine "studdered", followed by the CEL blinking 8-10 times, and the car misfiring badly for about a minute or two... Lost all power to it of course (even for cruising)... After flashing several times the CEL went solid for a few minutes...

After a few miles, the car started driving fine and the CEL went off. I plugged in the ScanGauge to see if the code was stored, but "No Codes Stored" appeared, so it cleared itself after probably completing the drive cycle (way home from school includes some city and highway driving, varying speeds)...

Dropped it off at the dealer this afternoon after work, they'll be looking at injectors tomorrow. If those check out fine, they might need to open up the valve cover.

Will keep you updated. Any input is appreciated.

 

Should I request the compression/leakdown check or should I let the techs follow their check lists and hope it's on there? I don't really want to "request" anything that wouldn't be covered by warranty at this point, but if they cover it anyways, I might "suggest" they do it... Let me know.

 

yes you should request a compression test, it's easy and fast for them to perform, while your at it, you should have them check the valves - for valve gunk build up in the ports.. i'm 50% sure, your misfires could be from the valve gunk.. again 50% sure..

and if they say they've done it, ask them if there is gunk on the valves.. if they say no - then they are not being honest with you.. gunk will build up over time..

and also most likely warranty, is going to cover for the whole job since it's minor diag job..

 

Ok, I will call them tomorrow when they open. Thanks for the info!

 

Called them. They said they have ” check lists to follow”, do they gotta check out injectors first. If those pass, they'll move onto the valve cover, and if their checklist calls for a compression test, they'll do it then.

Sounds just like troubleshooting guides we used on Navy jets...

 

**** the checklist. Tell them checking the injectors is a bigger step than compression test.

 

Mine was an injector I took it to a friend that works at a dealer and nobody in the shop could figure it out they were telling me a weak valve spring but I didn't trust them cause it was only at random it would do it so i put an injector in and it runs like new and I haven't had any problems sence then