Hey all I am relatively new here and I have a couple questions.

My car is a 2007 Cobalt SS/SC with a hair over 30k on the clock the only thing I have done to it is put a cold air intake on it which never threw a CEL by the way I am however having a lack of power and a real nasty engine shake at idle. I had the car run on the dyno today and I the highest of 3 runs was 206.3 the average of the three was 205.4 I also noticed there is a lot of carbon spewing from my exhaust at higher RPMs. Do I have a problem?

(I have cleaned the TB and MAF)

Thanks for the help if anyone has any ideas it is still under warranty but the dealership keeps giving me the run around so I am looking for outside help from other owners.

 

Check the CAT its probably clogged. or maybe ur injectors are shot somehow. who knows.

 

how much are u boosting? have u seen any different psi numbers than usual?

 

I've had the injectors checked with the techII and then cleaned on two different occasions at two different dealerships so I am almost positive they aren't the cause although I would like the extra reason to just go stage 1 LOL.

As far as checking the CAT I have no exhaust experience so am not even sure how I would go about doing that.



My boost numbers hover right around 12psi when it's running full out consistently.



My torque maxed at 182 also which seems real low for the car but I didn't think was relevant to the engine shaking violently at idle and lack of horsepower.


Thank you for responding.

 

Car is probably not that far off. Try cleaning the MAF and see what happens. Boost levels are normal, so exhaust problems are not an issue.

Dyno's differ, but my car did 217/188 stock, so you are in range, if a little low.

 

I cleaned the MAF and the TB when I saw the idle cure post go up on here and it didn't help me out at all.

Thank you though I guess if I am running in range but a little low it's not a terrible thing just kind of annoying since I had my hopes up for a number near 220 with the CAI.

 

Could it be running rich jw

 

its a GM tune. Course it's rich.

his numbers seem within the "stock" numbers.

 

the engine shake could be from your motor mounts... maybe you have a bad one???
and just out of curiosity, do you change your oil on a regular basis?

 

i have an 07 ss also with 56xxx miles at around 50000 miles my engine started makin some rattling type noise as i continued to drive it got worse and progressively it started to sound all gnarly almost like a low grow diesel type sound. one day i as was under my car and i was used my fist to hit along the exhaust to see for any noise and sure enough the cathad a bunch of **** jumpin around inside of it. i had it replaced under warranty and that was all it was. idk if this is ur issue but good luck

 

205whp is right where I've seen most stock ones. You have to remember dyno's read differently. Can you better describe the shake at idle?

 

yea boost levels are good, i was just checking in case for cat issues. but maybe as someone else said it already, could be one of ur motor mounts.

 

I think your fine, dyno's differ and also the fact your in fl and if it was a humid day out when you dyno's the car is gonna dyno a lil low. CAI helps with flow a bit but you only see benefits when you start making more power. Time to go to ottp stg2

 

if its at the same boost level, i would check your intercooler pump...it is a common issue with these cars and can cause massive IATs that make the car hate life

 

Don't go GM Stage 1... USELESS. You'll get 5-10hp at MAX. No noticible difference, GM Stage 2 on the other hand will grant you avg of 30-40hp, and you'll feel a HUGE difference.

 

There is a noticeable difference in the upper RPM range with GM Stage 1. Nothing huge, but enough to know it did something. I know this because I had GM Stage 1 back in the day.

I do agree with you about going GM Stage 2 though. GM Stage 2 gives you more "useable" power throughout the RPM band.

GM Stage 2 produces more on the lines of 20-25 whp on avg.

 

Good call, I didn't think about that.

Bad I/C pumps are very common, and will cost power for sure as the car heats up and pulls timing to compensate.

Stage one, then swap pulley, and you have stage 2. Same difference IMO.

 

If you dont mind, stick your ear up between the injectors and the top of your engine. Do you hear any clicking or knocking? If not, try driving at about 5mph and pop it in 2nd so it kind of bogs and listen outside the window for engine ticking. If so you have a lifter problem. Causes you to run rich and spews carbon out of the muffler and on the plugs.

 

agreed ! that's what I did when I wanted to upgrade to stage 2.

 

Alright sorry all I went to bed last night and had class this morning so couldn't get on here...

I will tap on the cat when it cools enough to touch it again =)

I average 3500 per 80 dollar mobil1 oil change just because it hurts the wallet.


I don't even have to put my head near the engine I can hear the injector click through the hood at least I thought it was injector click and other random sounds but I run 93 in it so I wasn't sure why it would be making noises... eek


Last time I pulled the plugs to check them they were a nice shade of black with white tips so yes running pretty rich I would say haha.


Intercooler pump hmmmm didn't even consider that I will look into that too.


As far as stage 2 goes I will be getting that as soon as I can find the money tree and pick 900 dollars off it... lol


And to explain the shake better when I am watching the engine it rocks back and forth as it should and about every 6th cycle or so it will rock real hard like its missing a cylinder for 2 or three cycles then go back to normal for another 6 and do it again. The RPMs don't fluctuate and the car hasn't yet thrown a code or stalled.


I think that covers everything. Thank you all for your ideas.

 

Pull your valve cover. Have a look in there, its very simply to do and wont hurt anything, just look for broken stuff. Dont unbolt anything but the valve cover on the inside of the engine.

 

now that am reading this post, ive also heard some licking coming from the engine aorund the injectors and motor. but it goes away so didnt pay attenction to it. it has done it a couple of times. so which is the reason for this?

 

if it goes away then you should be ok if you arent noticing a "noticeable" difference in power

 

Could be many things, but I would check the IC Pump as well.

 

If the ticking is that loud, could be a timing chain tensioner as well. Or possible valvetrain problem.