Need some quick advice from the Ecotec gurus...this is my daily driver and I need to fix it ASAP as I need for work and can't fork out the cash for a rental for too long!

2004 Ecotec, 5 speed

Ok, about two days ago on my way to work the problem started. Car ran ran as normal for about 20 minutes, then suddenly whenever I hit the clutch to go to idle the RPMs drop to nothing and I stall. Next morning when I left work the car ran great while the engine was cold..once it was up to normal running temp (194ish) it started again. My first thought was the throttle position sensor...I got home, hooked up my diagnostic reader to see if it was throwing any codes....no codes. I replaced the sensor anyway, car ran good for about an hour, then the same problem occurred.

The next day I thought maybe something in the ECU failed so I ordered a new one and threw that in. Car ran great for about 6 hours..I took a nice long 40-50 mile drive with no problems...then just before I got back home it started stalling again instead of idling. Now here's the weird part...after about 10 minutes, the RPMs only dropped to about 400-500 then bounced back to 1100...then about 10 minutes later it idled normally. I'm thinking this can't be a mechanical issue if it's sometimes correcting itself, right? Electrical issue maybe? If so what...possible ground short somewhere causing the sensor to cut out??

I've checked the throttle body for any blockages and checked for any vacuum leaks, everything checks out ok.

My next thought is DO 2004's have EGR valves (I know 05 doesn't but I remember reading that 03 & 04 did) and if so is there a way I can manually test the valve since the ECU isn't throwing any codes (and I'm using a Tech 2 to check it so I'm pretty sure it's accurate)

Beyond the EGR, any other ideas on what can cause this? Any help is much appreciated, I need to fix this quick!!

replaced the fuel filter lately? check fuel pump? check spark plugs condition and gap? fuel pump relay? pump might be on its way out.

Check the vacuum lines, and fuel filter.

I'd highly recommend checking your oil filter too. Mine was doing that a day or 2 before she died.


-Chris

DJ Beefy:
Fuel filter has about 3500-4000 miles on it, replaced the plugs about two weeks ago and double checked myself that they were gapped correctly (bought the super expenisve pre-gapped sons of bitches that GM recommends because the cheap wal mart ones kept burning weird)...
And I kinda ruled out the fuel pump because normally (and correct me if I'm wrong) but the pumps don't normally cut in and out..or work one day and not the next...once they go, they totally quit out...I had thought about it originally, but then I also started thinking I should be seeing a problem through out the powerband and not just an idle since the fuel pump delivers a constant pressure all the time and not based on engine speed.

IamRascal:
No vacuum leaks...checked them once, then I checked them like 4 more times cause I didn't trust myself the first three times, lol.


Thanks for the ideas though, please keep them coming!! Gotta get her fixed! I'm going to pick up my rental now and I'm praying they give me a Cobalt and not a piece of $&!#% Ford Focus (or Ford anything lol)

do you have an aftermarket volt gauge hooked up to constantly measure the voltage as you drive so you can rule out all grounds and fusable links?

my friends 04 fuel pump died all at once overnight seemingly after a week of his car sputtering at stop signs, hard starting etc.

also the ignition modules tend to go out in the ecos, I have 2 extra sitting here just incase mine goes out along with all the other extra eco parts ive collected jsut incase. now jsut need to start collecting more 2200 parts for my 98 haha.

Yuppers...I run a nice Glowshift voltmeter and the car sits at a nice 14-14.1 volts constantly...though I was starting to think it could be an electrical problem since it sometimes fixes itself after a bit...I wonder if even though the volts are strong and the computer doesn't throw any codes that maybe there is a ground short or something that just isnt being detected...I know it's unlikely, but I've also seen some hard to explain electrical problems in newer engines.

I'll keep an eye on my fuel pressure over the next few days..so far it's been ok.

Would you know off hand if anyone makes a tester for ignition modules? I could try that...I picked up a coil pack tester from my Snap-On guy and that checked out ok, but it unfortunately it doesn't give any reading for the actualy ignition module...I'd hate to eat the $100 on one if it's not the problem...already spent $50 on the TPS and $250 on the ECU and they weren't the problems, lol.

Well at the very least I just got home with my rental (they were nice enough to give me a Sunfire!) so I can at least dig into this a little more and not have to worry about driving it. thanks again for the continual feedback...keep throwing me ideas everyone so I can stop pulling my hair out!! lol

I tested my 2.2 LN2 ignition model at autozone. Call them and see if they can test the ecotech one. Maybe, maybe not.

Idle Air Control Motor/Valve. Mine did EXACTLY what yours is doing for a few weeks, took it to the stealership for warrenty work. They replaced the motor/vavle and have had NO issues sense then.

I'm gonna stop and see if Autozone can test Ecotec ignition modules...i called a few months ago about that and they did not have a tester, but maybe they do now.


I might check the idle air control as well...weird thing is, I can't find a replacement for it anywhere...I checked autozone, advance auto parts, and GM parts Direct, and no one has a listing for one...