My car stalls when I push in the clutch while decelerating

[Mr.]

My car(2008 Bullitt with a little over 31,000 miles) has recently started stalling intermittently. It happens while I have the clutch pressed in while in gear. To my recollection it hasn't done it while coasting in neutral. I have been able to duplicate the problem by quickly pushing the clutch in right after accelerating.
The symptoms I'm seeing are:
-Slight RPM bounce at idle(I suppose unstable is a better term than "bounce")
-Right before the car stalls, I will see the RPM's hesitate, drop down to about 500, hesitate/hover + or - 100 RPM's, and then it will drop and shut off. When it does stall, it is very easy not to notice that the engine had turned off especially with the radio on.
-The car is fully warmed up when it happens
-All electrical components still work when it stalls, no CEL, car starts normally even right after stalling at 50MPH, no weird noises/leaks/loose fittings that I could see in the engine bay, etc...The engine stalling is the only thing that seems to be out of normal.

I have tried cleaning the throttle body and that had no effect. I also just ordered a new fuel filter from AmericanMuscle because to my knowledge it's still on the original(I'm the second owner). I will be cleaning the MAF as soon as I buy a can of CRC MAF cleaner.
I've been researching this problem, and the answers thus far from various sources have been:
-Idle air control(our cars don't have that)
-EGR(our cars don't have that)
-Throwout bearing(our cars don't have that, and a bad slave cylinder would have other symptoms)
-Dirty MAF(I'll find out soon enough)
-Dirty throttle body(cleaned it...not the problem)
-Fuel filter(I'm changing it in a couple of days)
-Throttle position sensor
-Tune(I'm trying to rule out everything on my end before I blame the tune)
-Vacuum leak

It has been cold here in NYC the past week which coincides with when I first started having this problem, and maybe that's part of the cause?

The mods I have done are JLT Series 3 110mm cold air intake, Bama 93 race tune, O/R H, and straight through 2.5 inch exhaust(mid-mounted Magnapacks, PypeBomb axlebacks). Every mod was listed in the tune order and the car ran fine with the mods up until last week.
I've also only used 5W20 synthetic oil for oil changes every 3,000 miles, and 93 octane fuel since I bought the car in 2010.

Sorry for the longish post, I just wanted to be as thorough as possible. If anybody has any ideas, solutions, or similar experiences please reply!

 

[UltraKla$$ic]

Try something simple like reflashing. You can go back to stock, then reflash it with the required tune, or I just reflash over the tune again.

 

[Aandf1978]

Yeah man I agree with Ultra, try a re-flash, since nothing has changed, but on a side note I just changed my fuel filter 5 months ago when my Bullitt had 32K and after seeing what came out of it, I will be changing that shit every 15K at least. The filter is cheap, quick and easy to change and cause a world of issues. Just nasty!!

 

[Mr.]

Thanks, I'll try those suggestions. The fuel filter should be delivered in a couple days. Even if that doesn't help the issue, it's still a maintenance thing that's good to get out of the way.
As for the reflashing, I did try re-uploading the race tune and that didn't help. I'll try your suggestion of loading the stock tune then putting the race tune back in.
When I find the solution I'll update this thread...
Keep em coming guys

 

[WarFords]

Mine is doing the same thing right now.

 

[kevinatfms]

i would check to see if the throttle body is dirty, when it gets gummed up at the throttle plate the PCM will "seek" the correct throttle postion by trying to close or open the throttle. if it closes it the car has the potential to shut off. grab a can of carb cleaner and some paper towels and clean the throttle plate really good. disconnect the battery for 15 min and then reconnect and start the car, let it relearn the idle strategy and throttle position and see if it corrects the situation.

i saw a ton of 05-09 GT's for this very issue and its due to the sensitivity of the drive by wire and the percent load calculated during idle. if its off just a hair the computer will start to fiddle with the throttle body to find the correct strategy before setting a DTC code.

 

[SteveP]

If it was running good for awhile then just started doing that, Ide check mechanical like you are doing. Tunes can't just change but I'm sure the guys over at BAMA would help ya as well if you need it.

 

[Mr.]

Hmmm, didn't think to try disconnecting the battery after I cleaned the throttle body. Cleaning alone didn't yield any results which sucked because when I cleaned it I was almost certain that would be the cure. Took the TB off to get the backside as clean as possible too.

i would check to see if the throttle body is dirty, when it gets gummed up at the throttle plate the PCM will "seek" the correct throttle postion by trying to close or open the throttle. if it closes it the car has the potential to shut off. grab a can of carb cleaner and some paper towels and clean the throttle plate really good. disconnect the battery for 15 min and then reconnect and start the car, let it relearn the idle strategy and throttle position and see if it corrects the situation.

i saw a ton of 05-09 GT's for this very issue and its due to the sensitivity of the drive by wire and the percent load calculated during idle. if its off just a hair the computer will start to fiddle with the throttle body to find the correct strategy before setting a DTC code.

 

[Mr.]

Yeah, I'd feel like I'm getting ahead of myself if I were to contact Bama before I tried everything that I could do on my end first especially since there's so many other things that could cause it.

If it was running good for awhile then just started doing that, Ide check mechanical like you are doing. Tunes can't just change but I'm sure the guys over at BAMA would help ya as well if you need it.

 

[SteveP]

ide go back and look step by step and see if you touched anything lately under the hood. As simple as cleaning the motor ya know.

 

[Mr.]

Thanks for the reply. It'd be nice if it turned out to be some overlooked careless thing, but I don't think it is. The last time I messed around with the engine before having this problem was when I installed the intake, which was almost a month before this stalling nonsense started.
I'm going nuts thinking about this...maybe I should believe the DSM forums from my google search - Crankwalk, definately crankwalk

I'll update the thread after I try out all the suggestions tomorrow morning. If anyone else has any thoughts please let me know.

 

[Mr.]

Sorry to quote you again, but I just read in the owners manual about how to make the car relearn the idle strategy. Would you recommend following their outlined procedure of letting the car warm up to operating temp with the A/C on and driving for 10 miles or whatever it says in there?

i would check to see if the throttle body is dirty, when it gets gummed up at the throttle plate the PCM will "seek" the correct throttle postion by trying to close or open the throttle. if it closes it the car has the potential to shut off. grab a can of carb cleaner and some paper towels and clean the throttle plate really good. disconnect the battery for 15 min and then reconnect and start the car, let it relearn the idle strategy and throttle position and see if it corrects the situation.

i saw a ton of 05-09 GT's for this very issue and its due to the sensitivity of the drive by wire and the percent load calculated during idle. if its off just a hair the computer will start to fiddle with the throttle body to find the correct strategy before setting a DTC code.

**just an FYI, I'm going off my(very poor) memory as to what I read in the manual, so anybody looking for info about the idle relearning process should look it up in their owners manual for the correct procedure**

 

[stkjock]

http://www.shnack.com/docs/mustang06.ownersmanual.pdf

some control conditions are maintained by power from the battery. When
the battery is disconnected or a new battery is installed, the engine must
relearn its idle and fuel trim strategy for optimum driveability and
performance. To begin this process:
1. With the vehicle at a complete stop, set the parking brake.
2. Put the gearshift in P (Park) (automatic transmission) or the neutral
position (manual transmission), turn off all accessories and start the
engine.
3. Run the engine until it reaches normal operating temperature.
4. Allow the engine to idle for at least one minute.
5. Turn the A/C on and allow the engine to idle for at least one minute.
6. Drive the vehicle to complete the relearning process.
• The vehicle may need to be driven 10 miles (16 km) or more to
relearn the idle and fuel trim strategy.
• If you do not allow the engine to relearn its idle trim, the idle
quality of your vehicle may be adversely affected until the idle
trim is eventually relearned.

 

[Mr.]

Thanks

 

[Mr.]

ok, so yesterday I disconnected the battery for more than 15 minutes, loaded the Bama performance tune(was running the race tune before), and did the idle relearn process. This didn't help since the car stalled again today on the highway. This time the engine was still cold.

Today the fuel filter came in, so I changed it out. I also disconnected the battery again while I was doing the swap, and followed that by doing the idle relearn process again. I think it's too early to tell if this worked or not. The fuel that came out of the filter had a slight tint to it, and the filter felt harder to blow through than the new one, but I was hoping to see it in much worse condition.

To sum it up, so far I have cleaned the throttle body by removing it from the engine and spraying it down with CRC throttle body cleaner and scrubbing, loaded a different tune, disconnected the battery, did the idle relearn process, and changed the fuel filter. If all this hasn't remedied the problem, the next step would be to clean the MAF. After that I will try putting the stock intake back on and loading the stock tune.

I won't be driving the car for a few days, but I'll update this thread when I have new information. In the meantime, thanks to all the contributors so far, and I'm still open to any suggestions.

 

[das112463]

I have the same problem, mine started after I finished installing shacker hood scoop and conecting to my Steeda CAI. Seems to only be a problem of speeds up over 45 - 50 mph. I didnt notice until I was coming off the autobahn one day went to take the exit and realised I had no power steering cause the car had shut down. scarred the piss out of me.

 

[Aandf1978]

Do you have anyone close to you that you could swap a TB with just to make sure it isn't it. Might be something worth trying and it is pretty quick and painless.

 

[Mr.]

I wish I did. That's a really good suggestion though.

I'm starting to think that it may have to do with the clutch switch(es?). It's as if the ECU doesn't realize that the clutch is disengaged. Maybe someone who knows more than I do can tell me if there is a difference in the map(spark, timing, fuel, etc.) with the vehicle in gear and clutch disengaged vs. the vehicle in neutral also with the clutch disengaged.

Also, does the switch on the clutch pedal only complete a circuit to start the car, or does it serve a dual purpose of also letting the ECU know to drop to the idle RPM?

 

[Aandf1978]

So it only ever stalls with the clutch being pushed in??? NEVER any other time??

 

[Mr.]

only with the clutch in while the car is in gear and moving.

I'm starting to think that it may have to do with the clutch switch(es?). It's as if the ECU doesn't realize that the clutch is disengaged. Maybe someone who knows more than I do can tell me if there is a difference in the map(spark, timing, fuel, etc.) with the vehicle in gear and clutch disengaged vs. the vehicle in neutral also with the clutch disengaged.

Also, does the switch on the clutch pedal only complete a circuit to start the car, or does it serve a dual purpose of also letting the ECU know to drop to the idle RPM?

Does anybody know?