Everytime I floor the accelerator I get this nasty hiccup or jerk which has been driving me crazy because the whole car jerks back and forth! You can actually hear the supercharger whine dip in sound when this happens almost like it bogs down.

 

misfire?

try replacing ur plugs

 

No misfire its almost fells like the throttle is confused on what its suposed to do for a second or 2 lol! I replace the TB, but that wasn't it. Anyone have a problem with there pedal sensor?

 

The supercharger changing tone could have something to do with belt slip , or possibly a bypass valve issue. Just a guess.

 

driver error:P

 

LOL driver error? I don't know how anyone can **** up flooring the pedal.

 

plugs...........

 

Nope I tried several sets. This whole problem started after a night of a few races in which i was running my meth kit with boost juice. Maybe it fucked up the map sensor in the manifold?

 

sounds like belt slip, IMO.

 

im new to cobalts, but something similar happened on my 94 z28 my tps was bad and threw no code, i would floor it and it would bog down and sputter

 

Also when your in any gear and you take your foot off the gas instead of a smooth decel like it use to the whole car jerks or bucks. Its weird because it feels like a harsh downshift on an automatic trans. I tried unplugging the sensors one at a time and driving around and it just made the problem worse.

 

What size meth jet where you running?

 

At first I ran an M5, but people on here said untuned thats too big so I went down to an M3 which again untuned ran better. I'm getting rid of the car in a month or 2, but I'm now just on a mission to find out whats causing this.

I'm going to check fuel pressure tommarow. Does anyone know what psi at idle and WOT would be for the Lsj?

 

I'm guessing the TB or MAF sensor is getting confused some how. I used to have a jerk problem when shifting into the next gears, it felt like a bogging issue, It ended up being a result of the design of the cheap ebay CAI (thats why you have to cut the last 2" off the end of it). But i've also heard of people's Electronic Throttle Bodies giving out, probably won't last like a good old mechanical one.

 

is this after coasting or something? or just any time? if you're coasting, and hit the gas, it does that. takes a second for the pump to kick back on.

at any rate, i'm leaving in 1/2 hour hopefully traffic will be ok.

 

I got the same problem with the jerking back and forth....it only does it every now and then but when it does it pisses me off!! Seems like if it starts doin that and you turn the car off then back on it seems to help...just my experience with it

 

Well I did a lot of driving today and noticed that my long term fuel trims are ALWAYS + and never go lower the +8 unless I floor it. I would think I would have unmetered air from somewhere, but no leaks?! Checked every gasket and clamp!

 

I've had a couple little hiccups too. Last time somewhere around the top of 3rd, it stopped pulling for a moment, just enough to make your head nod. I've made sure to pay attention for it, but it shows up so infrequently I'm not really worried.

 

Once I go WOT its ok and doesn't hiccup at all. Its when I take my foot off the gas and decel its like a HUGE JOLT and the car feels like theres an extra drag on the engine.

 

In what gear?

 

The jolt is every gear no matter what rpm or speed. The knock I'm seeing 2nd or 3rd.

 

What happens when you let off the gas real slow?

 

A softer jolt and still decels like its engine braking too much. Now if I VERY slowly ease my foot off the gas with it still in gear SOMETIMES the it doesnt jolt, but its rear.

 

Sounds normal to me. There's always going to be engine braking, and the lower the gear, the more of a jolt you'll get you when you let off the gas.

 

Deffinetly not normal. I've had SS drivers drive my car to verify the problem and all 3 said the same thing when they took there foot off the gas " Bro what the **** is causing that ?" I've done compression and leak down tests and pasted so I THINK internally its ok.