Lperez96

07 Chevy Cobalt SS/SC 2.0L LSJ


Engine codes: P0172 (system too rich bank 1) P0300(random misfires)


So I've been having this issue with my cobalt. Its rough at a cold start with random misfires. Its running rich, Horrible gas millage. It lags really bad when flooring it and when it gets over 5,000-6,000 rpm it just misfires and have no power what so ever, it shuts off on me after I get to a stop so I have to keep my foot on the gas pedal to avoid the embarrassment of my car shutting off. I've check for vacuum leaks with a smoke machine, NO LEAKS. Spark plug gap its good, I run the NGK Iridium spark plugs and when I did a visual inspection they look black from all that extra fuel and you can smell the fuel. last thing I was able to do that gave me a lead but got me stuck was a fuel pressure test. Put in a fuel pressure gauge on my fuel rail and on KOEO it spike to 80 psi then 3 seconds later my fuel pump relay shuts off and the pressure drops to 50 psi. But while the engine is running my fuel pressure stays at 93psi. I think that is a lot of pressure. I check for specs on shopkey and alldata and the only info they gave me was that the KOEO spec is 50-60 psi but they don't give a spec for KOER, So now I'm stuck weather could be my fuel pump throwing fuel to the injectors with too much pressure? is 90 psi the spec pressure for an engine running?. can that reach condition be causing my random misfires?


Mainly everything on the car is stock and its not tuned either. I want to work on this car and fix it up but I want to fix this problem first because is driving me nuts and its no fun when you want to step on it and all it does it just misfires.

ECaulk

iTrader: (6)

How long have you had the car? Its possible someone installed an aftermarkt fuel pump with a return style fuel regulator and then didn't remove the old pump.

Lperez96

I bought it 3 years ago! Ran perfectly fine! Under warranty I had a new fuel pump installed because a line on the fuel pump was leaking! So I got that fix by the dealership, few weeks lates it started to run like crap. I took it back and all they told me was that I had to got back to a stock air intake and stock exhaust headers! And I called BS cuz everything was fine before!

C0balts5

It sounds like the fuel pressure regulator popped a hole. Take the vacuum line off of the fuel pressure regulator and see if you get an fuel dripping out. If that's the case than you found your problem.

Sharkey

iTrader: (1)

our fuel regulator is in the tank, we have a returnless, fixed pressure fuel system.

did you put an aftermarket pump in? i tried to put an aem 320lph pump in my 05 ss/sc when my stock pump died, and i had a similar issue, fuel pressure would go up to around 85psi and wouldnt drop. what i came up with is that the stock in tank regulator cant flow enough fuel through it and thats why the system pressure goes through the roof. i didnt have time to screw around, so i ended up buying a new fuel pump assembly (the whole basket) and dropping it in, fuel pressure is back down to 58psi.

rereading your post i see the dealer put the pump in, so id guess they put in a new basket, and if that is the case its deffective. your fuel pressure should be 58 psi any time the pump is running. higher pressure means a restricted regulator. id take the car back to them and tell them the fuel pressure is at 93 psi and you believe the fuel pump assembly they installed has a problem.