RedfoxTwenty

i posted this in my local car enthusiast forum hoping to get a fresh set of eyes looking in, but havnt had much response... maybe someone here can lend a little info
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Well, the SS is being a little bit of a sporadic beotch. This is all warranty covered stuff, but i just feel like going on a rant

the 10th of July, i bring the SS into the shop i work at...(i'm a warranty administrator and prior to that worked on the line for 4 years at this shop) Every time I've filled the car up with gas in the 2-3 weeks prior, it never hits "Full" on the gauge. Probably hovers 1/8 to 1/4 under full. I took the first filling up as chance- figured "hey, these newer cars have small ass filler necks, probably back pressure clicking off the gas pump" (mind you i've had this car for over a year now). But after it did it the second time (and i made sure i moved the gas nozzle in and out to get those last few drops in) i decided "meh, ill let them look at the sending unit." Surely enough, when i brought it in on the 10th, the sending unit had a problem with the potentiometer, not recognizing anything over 3/4 of a tank. They replace it. (had to order the part so give or take a few days of that week to replace it)
This was addressed in a GM Bulletin #06-06-04-012A and is a known concern

That night, wife is going to work (she works 3rd shift). She calls me up around midnight saying "well, i thought i was being stupid and forgot to fill up and i was calling for you to bring me a gas can, but apparently they didnt fix the sending unit. The gas gauge is basically sweeping back and forth from where the level is, to empty"

Great. I chalked this one up to a DOA bunk part (by no means do i blame any of these problems on the labor... i work at that dealership and i will stand behind most of these guys' work, but you cant be too sure on a part shipped from across the country getting jostled around in a semi truck, especially sensing electronics.) I tell the wife to bring it by the shop on her way home in the morning... and on the way to the shop it sets a Check engine light. I put the Tech 2 on it when she gets in, and its a code for the sending unit. They pull the pump and hook a meter to the unit, and watch as the thing just jumps all around the Ohms for resistance. So basically they had to order another unit, and i got a rental until they put it in (which, in itself is great fun! Enterprise FTW!).

Get the car back on the 20th (friday). The next night i take it to a Cruise in/car show on main street. As i merge onto a highway from an onramp, the car accelerates to 60, then starts sputtering and cutting out. I put my foot down on the gas, thinkin maybe there was some various types of gas mixed in the tank from when they siphoned it out, hoping that opening it up would kinda get it out of its slump. Wrong. Downshifts to 2nd, RPMS jump to 5500, then immediately DIVES down to 500. It did this cycle about 5-6 times within the lengths of 3-5 seconds. I was about to go off... car had a 1/2 tank of gas and there should be no reason for it to act like there was NONE in the tank. Once i got past about a mile up the highway, the car stops acting like a he-bish. I even stomp the pedal a few times to TRY to get it to act up. Nothing.

Alright, so i chalked that one up to possibly bad gas. I top off the tank with some V-power That night(the 2.4 and 2.0 SS models require 91 or above, otherwise we get a horrible spark knock), and again 1 week ago before going out to Lowes (locally all the car guys hang out at the lowes parking lot on friday nights).

Today. Have about 1/4 of a tank of gas in the cobalt. Wife and i decide to head into town, get some shoppin done. By the time we get to the highway, the gauge is reading halfway between 1/4 and 1/8 (mind you we live 4 miles away from the onramp...) Wife is driving, and after we get to the top of the ramp she goes to punch it to merge into traffic. Thing starts sputtering, taching out, then going to about 500 rpms, just like before... It is impossible to go over 60 miles an hour- the car just WILL NOT accelerate due to this.

by now the wife is FREAKING out. My thought is, its the sender again. Figured that its off again, and that 1/4 of a tank really is "Empty" now. So the car is sputtering all the way to the shell station-- We top off the tank, and it stops doing it. Problem is, the 1/4 of a tank thing was accurate. The cobalt holds roughly 13-14 gallons of fuel, and filling it up till it couldn't hold any more yielded only 10 Gallons at the pump. That means (in theory).. we had AT LEAST 3 gallons of gas, enough to make it 90 miles (gm cars dont hit that "low range" light until about 50 miles left.) (3 gallons in a 13 gallon tank is Roughly 23%)

I'm kinda getting annoyed with this crap. If its the sending unit again, why were the fuel levels accurate?? If it low fuel- why was it sputtering with a 1/4 tank of gas in it??? Never has done this before! it cant be a "normal condition" to sputter out at a 1/4 tank of gas... thats just wrong. All i know was it was leanin the A/F mixture out so bad that the engine temp JUMPED to 210-220 degrees (normal is 180-190, and the cooling fans kick on at 195-199 when you are standing still). I've heard of people with aftermarket fuel pumps having similar problems under 1/4 tank of gas-- but this has never happened before in the year i've owned the car. Even if this is a "known concern" why then aren't we advised to fill up the car at 1/4 tank (IE, Low Fuel Light THEN, not at 50-60 miles left)

its been 3 weeks of walking on eggshells with this car. I've had other problems too in the year i've had it, which were addressed in technical service bulletins as "known concerns" for the vehicle. Thank god i have a 60,000 powertrain warranty (and a 60,000 0 deductible GMPP)... If this fuel problem keeps it up, the damn car is going to have one hell of a scorched head/internals before it makes it into the dealership on monday.

(EDIT: 2006 2.4 VVT for the record)

rlinden86

mind you this what im thinking you dont have any mods on the car yet? let them drive the car for like 4 days with different amounts of gas in it tell them to fill it up figure it out. let them idle it for 30 mins. drive it hard. if it blows up they WILL give you a new engine. my car is having rocker or cam problems slightly ticking they cant here when i take it in but i can here all the time. so they said let it go bad or blow up will get you a new engine. so i dont know.

good question though.

ryan.

and you shouldnt run out of gas at 1/4 ive had my 2.4 down to just before the e mark like 1 needle width left. i think it runs out just on the line.

RedfoxTwenty

only mod i have is a megan racing muffler with a custom axle back section scrapped from a magnaflow 2 & 3/4 catback kit.

Boss let me take home a Tech 2 tonight. I'm going to have the ole lady drive it around all night and ill take some snapshots the second it acts up. *crosses fingers*

so yeah, if it does blow up, i've even confirmed from the service manager that a muffler will not void my warranty.

As i said, i've had the car for a year and i've taken it down to redline empty a few times without problems. I think the fuel pump itself is letting go-- possibly debris from pulling the sending unit a few times. Hell ill try to get a free fuel filter out of it too ;-)

rlinden86

your probly more right then i am im not sure. never heard of that problem. but doesnt sound good. tell them to find it and fix it. they always told me if they cant hear it or see it they cant fix it i said thats crap.

ryan.

pjk91

i know you said your sending unit was having issues...but when you floor it around 60 mph and it just dies out like that....sounds like too much fuel in the motor. odd.

SSBOOST

have them try to reflash your ECU back to factory, i know it already was there but try to see if it works because my car had recent fuel problems and i was having similar problems as you and i went back to Chevy and had them reflash it and it was fine, a few hours later i took it to my tuning place and got my performance tune reflashed and its back to normal with all of my horses. Just a suggestion =)

RedfoxTwenty

probably something to look into. I know there are updates to the PCM as far fuel goes. Its being looked at as we speak-- drove it around with the Tech-2 last night and couldnt get it to act up to snapshot it, but i JUST hit 1/4 tank this morning; i told em to take it on the highway and open it up.

will definitely give you all the word on it, so if this happens you know somewhere you can start
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UPDATE

reflashed to latest software updates-- car still stalls/sputters. Does it worse now (at lower speeds as well).

TAC Suggested replacing the entire pump with a somewhat newer design... apparently the strainer element likes to crush in on itself without a full tank of gas- they've said there has been some complaints JUST like this where a the new design pump fixed the problem.

I live in IL, and parts manager said there isnt even one in inventory in this state (Chicago usually has EVERYTHING)... so here i sit with a full weekend ahead of me in an Enterprise rental (time to make some Youtube videos!!!)

will update as things progress.. as usual

calchr2

ive had the same problem. i just had my car into the dealer the last two weekends. the first time the fuel gauge wouldnt read full. they replaced the sending unit with the update piece. i tokk it home, gauge still wrong. brought it back and they reflashed the body control module and put a new gauge cluster (only because i mentioned that it could be the cluster too) in because on the sweep test with the tech2 the gauge would read correctly uptill about 3/4.) so, i have the updated sending unit, new gauge gluster (gauge works properly now) and flashed body control module. i got it back monday of this week. leaving my house, i get on it a little and it wont go past 5500 rpms. i say okay maybe a freak thing. get on the highway and its fine for a little bit. then doesn it again. it wont rev passed 5500. btw i had 1/4 tank of gas. i fill up and its fine. its been fine all week. im passed the halfway mark now, and waiting to see what happens when i get to aabout 1/4 again. first rental was a colorado (not bad for the s10 replacement) second was a hyundai elantra (piece of crap this thing could not get out of its own way even with brake revving). keep in mind i am a tech aswell.

Schultzay

so we have a 99 cavalier that when you fill it up full the gauge says full, but a little bit into the tank the gauge starts to bounce around everywhere. Do you think that would be a broken sender in the tank?? or would it be a broken gauge??

SWmaster

My tank reads at 95% with my dashhawk and full on the gas gauge when I fill it up. When the gauge reaches E it still has about 10% left. I often put on about 20 miles after it hits E or till 5% and have put on a little more without problems. The lowest the sensor seems to read is 4%.

RedfoxTwenty

forgot to mention, got a snapshot of the car with the tech 2 while acting up. I'll get some of the technical data posted here probably tomorrow night after i get it from work.
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heres a good graph of whats happening when it dumps on itself... cant really show fuel pressure without gauges on the rail or whatnot... but its a good representation

PRODETAILER1

im getting random misfires so are other 2.4 owners. with rough idle gm customer service line just gave the ok for the dealership to put in a new tank fuel pump and set coils and plugs and that only because the last 4 times i was in for the misfire they run fuel injection cleaner through and told me to change gas stations.the service manager just told me as i was setting my opp. that gm engineers found out that they have an issue with debry in the fuel tanks my question is , is their anylink between the two problems

calchr2

so mine acted up again tonight. granted i have the 2.0 but i have the same symptoms and have have the new updated sender put in. i was cruising down the highway with about 1/4 tank of gas left and it starts dying out on itself and i cant go any faster. i am in the slow lane doing about 60 and slowly dropping speed due to the engine ccutting out. by the time i get off the highway (about 2 miles) im doing about 40 to 45. i stop at a light, and it seems okay. i startmoving, still okay. i get into 2nd and it starts to die. now my gauge has gone from 1/4 to just over the E line (about 3 miles). i make it to a side street and it completly dies. i try to restart and it starts then dies. i let it sit for a few minutes. it starts and moves a little. i make it to the gass station and fill up. starts and idles fine for 5 minutes. i take it out on the highway and its fine. i drive for about 20 minutes to see if it will act up and nothing. going to the dealer tomorrow and see what they tell me.

in my opinion i dont think and updated part to replace a defective one should not have problems. anyone agree? nothing like this happened before i had the new sending unit put in. also, it could be anything, but never happened before the new sender.

RedfoxTwenty

EXACTLY the same problem i am having. If this new fuel pump doesn't work, i'm seriously thinking about talking to GM about a buyback on my car since this is the 3rd time to fix this repair. You can clearly see it creating a major lean condition, and if it keeps this up much more, its only a matter of time before it smokes the engine. The SS/SC guys, like you, would probably be in a worse situation because GM likes to throw the "Abuse" flag on you, saying you were "tearing it up" when it was under NORMAL DRIVING CONDITIONS.

I work for GM, my father has worked for GM for 30+ years, and my grandfather has as well for 40+ years. I respect the GM brand and believe they have a quality product, but honestly i think we are victims of something without enough R&D before it hit the mainstream. I'd hate to lose my respect for the product over that, but i almost have no other choice when things are getting this crazy. In all the rentals i've had over the last year of owning this car, i've logged probably an ENTIRE MONTH where my car was in the shop and me being in a rental.

i dont mean to pitch a bitch, but we as consumers need to draw the line somewhere. Honestly i believe this is why they extended powertrain warranty coverage.... they knew this **** was going to happen, but rather wanted to just weed it out in the field and not fix it the way it needs to be.

Witt

Log injector pulse width if you can. When it seems to be doing it, its also locking trims to 0 almost immediatly, usually the result of the PCM entering an enrichment/enleanment condition which could be caused by a fault (SES would set after the first or second time) or a protective enrichment.

If pulse width decreases during the condition, it probably isn't the fuel pump. Just something to check if you're bored.

RedfoxTwenty

thats the crazy thing.. because it has NEVER set any codes. No history codes either. No misfire data, etc. the Thing seriously acts like its starving itself for fuel.

i do believe that would be the next step though. If the fuel pump yields no results, ill probably hook up the AFIT machine and see what we can do from there. Maybe swap out a set of injectors for s's and g's.

thanks for the heads up
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edit--- actually had some data that would be relevant to what you said witt


it is dropping, ill talk to the foreman on Monday-- because he hasn't seen the snapshots yet


you can clearly see in the circled area, as engine speed (red) is increasing the injector pulse (green)is decreasing... thats just fundamentally wrong!

again, major thanks!

Witt

Since you have access to a Tech 2, try reflashing the ECM with the newest available calibration. It sounds a lot like a software or PCM problem imo.

RedfoxTwenty

Yeah, didn't know if you saw a few posts upwards-- i installed the latest calibrations last week. Didnt even touch the problem. Service Forums had another cobalt doing the exact same thing, someone was a big enough of a smart A$$ to say "keep it over 1/4 tank then."

But that was were the foreman was pointed to for the fuel module. Its a new design, but it was more meant for a fix on the 2.2's-- they just mimicked it on the 2.0 and 2.4 pumps to solve the strainer issue. Parts came in today... shop is swamped so it might not be till tomorrow till it gets done.

RedfoxTwenty

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update:
fuel module is in... fuel problem is ok for now... but now the fuel gauge is sweeping again and setting the SES light again. Time for repair #5 in 4 weeks