[TXTurbo]

After searching through the forums, I couldn't find an exact match for the issue I'm having. My 2007(6spd 9-3 SS) with 52,000 miles on it has developed a weird intermittent stutter on start up. It doesn't happen every time and seems to happen when cold as well as after driving and starting again shortly thereafter. When I attempt to start, it stutters and stalls after a second or two. It takes a couple of starts to get it going, and then it seems fine. Car drives fantastic otherwise and there are no other performance issues whatsoever. I've owned since brand new and this is the first trouble I've had. I pulled the #2 fuse for 30 minutes as suggested on a few threads and noticed an increase in power, but still has the occasional stutter at start. The only other thing that comes to mind is bad gas? I have the 100k powertrain warranty as offered in 2007. Would this issue theoretically be covered? Thanks in advance for your suggestions!

 

[Jonno007]

hey mate,

Check your spark plugs/gaps. What fuel you using? smoky exhaust? How cold is it at your place? CEL on?

when you turn on your ignition, can you hear the fuel pump go on for a few seconds? could be relevant:roll:

 

[TXTurbo]

Jonno,

No smoke from the exhaust at all..forgot to mention that. If it was the plug gap, would it continue at idle or while driving? That's the weird thing, it's only occasionally at start up. Temp here has been 40's at night and in the 50's-60's(farenheit) during the day. I've noticed that it happens even after running the car at operating temp and starting again a half hour later.

Thanks for the tips...I may pull the plugs this weekend and check them out.

I've always used super unleaded, but recently I've bought a few tanks from the Valero station down the street. For the life of the car I've used Shell, Chevron or Texaco exclusively. I'm wondering if it's cheap gas from this Valero convenience store?

 

[JonV]

Valero is not "Cheap" gas, it's a Major Brand.

 

[TXTurbo]

Didn't mean to imply that it was. Just wondering if perhaps I got a bad batch and that would explain the issue?

 

[ctrlz]

I would suspect a small vacuum leak. Check fuel trim with a scan tool.

 

[TXTurbo]

A tech II or some other kind of scan tool?

 

[saabz]

Cold starts and starting after only a short run both imply greater demand on the battery. It could be your battery is undercharged (battery or alternator problem). I recall my starter hiccup like that (and my radar detector chirp in a wierd way) when my battery voltage was below 12V - right before the engine would not turn at all.

 

[Hooah84]

I actually have the same exact issue with my 9-3 Aero (also an '07).

I had run the tank kinda low a few times and the weather had been hot and cold erradically. I had thought that maybe I caught some water in the lines. I ran dry-gas (and my favorite Lucas tune-up in a bottle whether or not it was necessary); seemed to temporarily fix the issue for a number months. But it started reoccurring again this past week. Once again; I had the same conditions: I ran it low and the weather was nuts.

Whenever I experienced this issue before in a different car; it was some sort of water or impurity issue in the gas. I can't say for certain that's the case. I wouldn't venture to say it was the fuel pump/filter, I've had fuel pumps die on me before and it was more obvious than this.

When it happens, I let it go sometimes to see how long it sputters. Generally it works itself out (makes me think a water issue) after a couple of minutes. I did have it stall on me once, but only one time.

If you figure it out, let me know... I'll be heading back to the drawing board.

 

[08manny]

My wife's 93 is doing the same thing... its an 08 2.0T with about 15,000 miles. Its intermittent and has happened probably a dozen times since October.

Since the car eventually goes, we were waiting until next service to mention to svc dept.

We use only Costco premium gas, and the car checked out at its 1st service appt. We'll see what they say about it. We cant reproduce it, but maybe its logged somewhere?

 

[TXTurbo]

Interesting that it seems to be more common than I suspected. I too thought it was bad gas, but I ran a bottle of fuel injector cleaner through it to no avail and have since filled up with Shell premium. I also tried turning the key slowly to make sure I hear the fuel pump start up first...no dice. If it's a vacum leak or low battery, wouldn't there be some consistency to this? I plan on putting my voltage meter on the battery today to see if this is the culprit. If it's a vacum leak of some kind, I'll have the dealer address it when I get my oil changed next week.

 

[mikesul]

I have noticed a rougher start for the first 20-25 seconds with the Vtuner stage 0 tune. I took it out (the tune) for a trip to the dealer and there was no rough start at all. Maybe I need to datalog this start sequence and send it to Brian for a looksee.

 

[jlrdrony]

clutch plate overpressure with flywheel when is cold............?

 

[BF2009]

I have been trying to figure out this problem forever. Been happening for a while. Changed spark plugs and was ok for a bit but then started again. I have it in the shop right now b/c my maintenance man figured out it was an ignition coil through process of elimination. I should have the car back in a couple days but I would check to see if any cylinders are misfiring. I only got the misfires when the car finally gave out...Hope this solves the problem.

 

[Vector-SS]

My car is doing that as well. After about one hour of turning it off and back on, the car stutters, and then this carries on for the next 2 minutes stuttering (while driving) and choking until the car has fully warmed up.

I sent logs to Brian and he said it seems like the o2 sensors are not functioning properly. With the tune, the o2 sensors started operating after about 3-5 minutes, while in stock form almost within the minute.

He however mentioned that he doesn't modify the cold start files, so it's all so confusing and this is driving me nuts.

Second time in 1 month the car is going in for this, and I'm certain they won't find the problem, again.

With my warranty up in one month, this is becoming all too worrying :evil:

 

[Abarth]

Have the same problem on MY07 Aero, sutters then is OK. Happens when it's cold (relative I know) here in Southern California.

 

[EuroStyle]

I have had this twice in the 2 months we have owned our '06 Aero...both times it was the same scenario..drove on the highway, parked for about 1/2 hour and came back out to start it. The first time, it started fine, but then stuttered and fluxuated at idle....I reved it a bit and then it was fine. Second time I shut it off right away and restarted and it was fine. Car was in for the final warranty ends soon check an they found nothing....


Sean

 

[Deli-Llama]

It doesn't happen every time and seems to happen when cold as well as after driving and starting again shortly thereafter. When I attempt to start, it stutters and stalls after a second or two.

This sounds similar to an issue I was having with my car. My research lead me to think there was an issue with the one-way check valve that stops the fuel running back into the tank when the fuel pump isn't running.

The best way to test this theory is to connect a fuel pressure gauge to the test port located in the fuel line near the injectors (you can see it at the front of the engine when you remove the engine cover). The fuel pressure should be 3 bar or 43 PSI when the fuel pump is running. If you leave the fuel pressure gauge connected after you stop the engine then you can see if the pressure drops and this would indicate the fuel pressure is not being held. Possible causes could include a leaking injector or a one-way check valve.

 

[TXTurbo]

Great Info!!! Any chance this would be a warranty issue? I'm out of the 36k bumper to bumper, but the '07's had the 100k powertrain and I'm really unclear what that covers?

 

[curryair]

Exact same problem

I seem to be having the the same problem as TXTurbo with my 07 9-3 2.0T. It didn't happen until it got cold, but it is happening frequently now. Any time I cold start it shutters and dies. If I use the accelerator I can keep it going and after a few seconds it is fine. I checked the plugs and the gaps are within limits. Air filter is clean.

I will try to find a gauge to check the fuel pressure. I assume if the pressure is fine while running that I can rule out any fuel pump/filter issues right?