knapster6

iTrader: (1)

Well just as titled my cobalt surges in RPM from about 700-1300 RPM when it is cold, as in you turn it over and it jumps to 1300 rpm and immediately drops to 700 then surges back to 1300 and continues to do so until it warms up to around 90* coolant. It is HPtuned, K&N drop-In, catless DP, forge BPV with green spring, 27K miles on car.

Is this at all normal? When its warmed up it doesn't do it anymore, you can park and turn it back on and as long as it is still warmed up it won't have any problems. Seeing if anyone has had the same experience, maybe it just needs a winter tune.

Second thing is that I had 8 codes thrown and all of them were misfire on all every cylinder individually and misfire on all cylinders. I changed my plugs today but was only able to drive 3 miles and when i got home i turned it off and restarted it a few times and didn't throw a code yet. This appears unrelated to my other problem as I haven't thrown a code in a couple thousand miles while I always had the first problem.

mikej

my guess would be because of all the mods and the tune....also I would've gone with the gm stage 1 kit instead because of your low miles...I did it and i dont have the problems alot of these other guys are getting from there tunes....plenty of more power and boost and doesnt change the factory warranty....you are having what is called a random misfire...does the check engine light blink first then stay on when it throws the code? these random misfires are a pain as they can be alot of things but if its every cylinder its not the plugs...sounds more like a coil problem as that part controls all the plugs

Racerdad

I have seen this kind of error on other cars before, and it was a flaky crank position or knock sensors. Something to consider. Do you have a lightweight flywheel, too? That can make the crank sensor touchier, because the speed changes more rapidly than stock.

nobody2u

Mine does this, but according to the dealer it is just in cylinder 3. They replaced the spark plug and ignition coil in that cylinder so far. That stopped the surging but it still misfires. They are going to try replacing the injector next.

umrdyldo

iTrader: (1)

Injector O ring missing ?

bad evap purge selenoid?

knapster6

iTrader: (1)

I bought the car with the mods done so nothing I can do about that. Check engine light just stays on.

There isn't a lightweight flywheel.

The surging itself at cold start up when its cold outside has never thrown a code by itself, as far as I am aware this is not a contribution to the misfires but you never know.

I had the code cleared but probabaly should have taken it in to the dealership, if it throws again I will.

aslo I have never felt a misfire in normal driving or WOT but it shows all these misfires, thinking they are at startup but not sure.

umrdyldo

iTrader: (1)

So was the code set with the CEL? What are your fuel trims like? How many misfires are we talking?

I get a small amount of misfires on cold start but like 5, not that many. Also try variations of having the front and rear defroster on to test with a load on the system.

jran

Last winter my car was doing something similar to that and they ended up replacing the evap purge solenoid at the dealership under warranty.

JacBlackSS/TC

you need someone to read your tune to see if the cat warm-up has been deleted or not as well this could be part of the idle problems when starting the car on a cold start

rukkee

iTrader: (3)

Lol he has a downpipe ....air filter and bypass valve ..... it's not like the car has a ton of mods. If you do some research here you will see all the problems people have had with GMS1 ...... and there have been quite a few .

OP.... does your car still do the cat warmup when you start it cold or was it tuned out ? Do you know who tuned the car ?

If you don't know who tuned it...... your taking a chance that it could have been some guy who bought HPT and started experimenting. You might want to get a hold of BYT... mdub or chevycobalt and have them pull some logs to see what your tune is like.

Nfamous60

iTrader: (11)

having this issue now after getting my car bac i added my tune (PPC/BSR) and it misfires crazy. Shows number 3 cylinder misfires but have new plugs ging to look for a coil pak today for that cylinder and see wut happens.

Chevycobaltss3

iTrader: (2)

with the cat disable on with hptuners if there is the slitghtest leak in the charge system. or a faulty plug. you will misfire. also somthing to keep in mind is winter gas. that along causes more issues then you can think of.

nobody2u

It'll band aid the problem but it won't fix it. Wish I knew exactly what is wrong.

Nfamous60

iTrader: (11)

changed coil pak and added the bsr tune bal car still misfires but not as much so lost on wuts wrong...bout to take it to a tuner to have them run it on a dyno with and without the tune and hav them narrow the problem down $65 but i think thats better then replacing parts off a guess..

donkeyballs

iTrader: (3)

My car didn't like cat warm up disabled and from what my tuner told me some are fine and others idle like **** when cold till they warm up.

FasterIsBetter

Same issue here on cylinder 4. I believe its my mass air flow sensor though. Any time I let it get the least bit dirty from rain being sucked up by my intake, my car will not run hardly at start up. It will even sometimes quit when its really cold out unless I had just cleaned the maf sensor. I can't wait til I put my turbo kit on since it comes with an sri...that will tell me if it truly is my maf sensor but it just seems to always branch from it happening the day after it rained and valvetrain, compression, and boost leaks have all been checked out.

Edit: Just saw all you have is a K&N drop in. Maybe you have some of the oil from the filter on your maf sensor?

AndrewSS/TC

this.

my car sounds cammed on cold starts with cat warm-up deleted.

jaygo7007

exact same problem as well.... except mine were cylinder 1 and 2. me and my tuner swapped to coil packs around and added the cat warrm up feature back on and it seemed to fix the problem.

nobody2u

Exact same thing here. It made it a bit better after plug/coil replacement, but it still misfires sometimes. Like I said the dealer is gonna try replacing my injector in that cylinder. It's all covered under warranty though.

I'll let you guys know if it fixes it.

knapster6

iTrader: (1)

I bought CRC MAF cleaner and cleaned it twice but it still threw those codes, didn't look oily or dirty when I pulled it.

Ya that pretty much describes mine as well

In Michigan so I'm sure winter gas may be partly to blame or brought out a problem a little more than normal. Just changed plugs so we will see, thanks.

Code was set with CEL, AFR is pretty normal 14.6-14.8 most of the time when at idle or constant speed, cruise control. Having a load on the system hasn't made a difference that I know of yet unless it is just at startup, will have to check when I get off duty and get back to my car. I don;t know how many misfire unfortunately, Oreilly auto was kind enough to check and clear the codes but the guy did it wihtout telling me specifics. I need a scan tool.

My tune was done by someone that has been recomended before but I don't know how to get ahold of him, it's 06black(bryan), he tuned it for the previous owner.

Thanks everyone for the responses.

FrossB

iTrader: (6)

My car does this as well...the bad cold start idle, all the misfires, etc. I changed the plugs on my and i did fine for about a day then the CEL came back on

Nfamous60

iTrader: (11)

my car doesnt hav idle problem but with you swapping coil paks that fix your misfire problems or the flucuating idle?

lockdownlegend

iTrader: (1)

any update on this because my car recently started doing this....it starts up fine hits 1500 rpms and then almost instantly coughs/sputters down to 1000-1100 rpms for a couple seconds and then climbs back to 1500 rpms. It finishes that cat warmup cycle and all is good. I just dont like the cold start issue and want to fix it. replaced evap purge solenoid with no luck.

knapster6

iTrader: (1)

Actually I was wrong with the RPM, mine is at 1500 as well during the cat warm up cycle and mine acts the same way, I was going to replace my EVAP solenoid as well because coupled with that problem and a check gas cap light I got when it was on just fine made me think it could be the EVAP system.

knapster6

iTrader: (1)

Took it to the dealer today since they didn't even grease the caliper slide pins and they started sticking to the rotors immediately after they did the warranty work on my rear brakes, they test drove it and I was told.

"Well it's something with your turbo in second gear causing it to misfire"

I said well it is only misfiring on start-up so how can it be misfiring in second gear when I have used a reader just like you did to see the same thing and have no misfires from normal driving or WOT.

He said, "well we would like to think from the factory that it wouldn't have these problems"

To which I said well it has had a MAP Sensor, fuel pressure sensor, fuel pipe/fuel seal done on the high pressure fuel pump, and the rear brake replaced all under warranty because these cars have problems from the factory.

He said it was because of my modifications and I said well that's not causing the misfire, he thinks my exhaust is causing the misfire because they have no clue what they are talking about and I can tell these people which are a very large Chevy dealer in the metro detroit area know less than I do about my car.

Coupled with my other problem it's likely to be EVAP, or a sensor which they are trying to say my mods are the cause and are basically saying it's my fault and they don't even want to look at it further.