So I've had my 09 SS/TC for about two months now and this problem is slowly getting worse. When I cold start it, it sputters for a few seconds until it finally drops to idle. Then, when I'm driving(especially when the engine's cold) it seems to sputter and have a great lack in power. It was hardly noticeable when I got the car, just slowly getting worse. I'm almost positive it has to do with fuel delivery but I'm not sure if it's the fuel pressure regulator or if it's the pump. All I know is that when I was hooking up my NOS nitrous injection, I tested the fuel pressor and it was all over the place. Anyone have this problem? Any help would be much appreciated...

 

plugs?

 

Just put brand new plugs in it. NGK's that are a stage colder than stock. (For the Nitrous)

 

Well take those out, and put the stock plugs back in. You shouldn't have to go colder for nitrous on the LNF

 

Okay, will do... But the problem started before that. Any other ideas? Fuel filter maybe? Doesn't it have a filter inside the gas tank? I know the 2.2L and the 2.4L have one on the passenger side in front of the gas tank but the 2.0L doesn't.

 

Are you going WOT or more than 1/2 throttle when its not properly warmed up?

I'm also assuming you have a tune for the nitrous?

 

Never WOT when it's not warmed up. And as for the tune, no I haven't. It's still under a custom tune from the previous owner. Until I get it tuned, I haven't and won't use the nitrious. I'm too afraid to spray without a stable fuel supply.

 

Just retune the damn car, and not use nos. It's not needed on an LNF and it's wayy to hard to set up.

 

I would never put nos into a cobalt let alone any other car I'll probably ever own.

 

OP do you have any codes? Even pending codes. Do you have a way to log the car with hptuners to see what lambda your running, timing, map pressure, maf freq, lbs/min air, etc.

How/where did you install the nitrous injector?

You don't know how to tune, so you cannot claim how hard it is to tune for.

 

It's honestly not that bad, you just have to pay close attention to it and use quality parts so a window switch doesnt fail and keep spraying when you let off the throttle. And legally most states you can't have the bottle open on public roads.

 

Okay, let me clarify just in case my situation isn't clear... The NOS kit has zero to do with the problem. Just to answer your question, the kit is a wet shot that has the fuel supply tapped in in the fuel rail just before the Fuel Pressure Regulator. The only reason I mentioned the nitrious kit was that the fuel problem was discovered during the installation. When I was tapping into the feed line, I gauged the pressure to double check for adequate fuel supply. The nitrious kit has nothing to do with the problem, it was happening before. And as for codes, I was pulling one but I cleared it and it didn't return. I think it was a P2106 or something similar. The description was "throttle position not learned"

 

Chill man, most run a dry shot, which could allow for an air leak and mess with all kinds of things. Also did you tap in high pressure side or low pressure side of the fuel system? I could see being high side giving you trouble getting the nitrous into the mix.

The pressure gauge connection on the fuel system is the low side pre hpfp. Without logging or knowing the codes its hard to help out any more

 

My best guess would be vacuum leak, bad map, or bad tune.

 

I don't mean to sound irritated, lol. I'm frustrated with the problem but definitely not with anyones help(:

I ran the pressure gauge on post-HPFP in the same spot I tapped for nitrious so it's on the high pressure side. I'm on my way right now to pick it up(just had a new clutch installed) and I'll see if I can do some logs. Again, I appreciate everyones help very much! This is the best thread i've ever posted on!

 

I never said I knew how to tune an LNF. I said that's it's too hard to set up a kit and get everything working properly with an LNF.

 

Ahh the famous "throttle position not learned" i had that code when i first tuned my car i check everything i could and nothing would come out. I would go into limp mode atleast 2 times every 45 min drive it was super annoying, i had to restart the car for it to go away. I ended up changing my TB and that fixed it for me tho. But seems like you have another problem that that code

 

and you are stating this with what knowledge?

a nitrous kit is not hard to tune in ANY setup. you just gotta have right parts and tune.

 

EXACTLY!! It seems it randomly just loses all of it power and is just starving for fuel. It happens every cold start and then just randomly during each trip. So you just replaced the TB and jt solved the problem?

 

Yup i would go weeks without any problems then i could hardly drive the car sometimes it was weird. And yeah i replaced my TB. I mean i changed my bpv to a forge unit, changed the bpv solenoid, deleted the vaccum tank and nothing fixed it. I changed the tb and that fixed it for me. I checked for resistance if i remember correctly and one of them was off. I think readings where supposed to be one going up and the othwr going down (when moving the butterfly) and i think both would go up (well they would both go the same direction) but i havent had any problems for almost a year

 

Well that will be my first move then. I'll update when I finish

 

Yeah check it first tho i wouldnt want you to start throwing parts at the car since the TB is $100+

 

So I got home today and checked my fuel pressure(i don't have an RPD so it was with a gauge). I hooked into the screw-on port in the fuel rail just before the pressure regulator. Before starting the pressure sat around 32psi. When idleing, the needle rapidly moved between 52psi and 78psi. When applying throttle, the pressure leveled at 72psi. Then, I drove it to see what the pressure was doing when the engine sputters while I attempt to accelerate. Then low and behold, no sputtering. I have a wetshot hooked up to that same port(where I attached the pressure gauge) and therefore had to disconnect it to read the pressure. Think the NOS kit is jacking with the fuel? I'm going to leave it disconnected tomorrow and see if it sputters. Any thoughts? And if anyone else has a wetshot, where did you tap in for the fuel supply?

 

There is potential it is, the port you're talking about is the low pressure side port. The high pressure side post HPFP does not have a connection to determine fuel pressure, there is a sensor that can be logged with HPTuners and I think the torque app or whatever it is (obd2 port plug in to read what the ecu will kick out).

I honestly don't think anyone with an LNF does a wet shot, most run a dry shot with a post TB injection.