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2006 Mustang GT with Roushcharger setup since '09
The car will lean stumble only when hot and only after startup. the stumble will last approx 8 seconds and correct itself but sometimes kicks the code P0171 and P0174 for lean left & right banks.
I have changed the MAF, Fuel Pump, and recently broke down and took it to a shop where he diagnosed it for 2 hours and determined it needed injectors cleaned which I had professionally cleaned.
None of this changed anything but made me broke.
I can share the snap shot of the data when the code is kicked and can share the live data if anyone might be able to shed some light.
I called the tech back who did the diagnostic and told him the injectors made no change. He said that all he could think was that the flash Roush did to the PCM when I installed it on 09 might have gotten a glitch.
I called Roush and asked them about a reflash and they said they will do it for $100, but almost never need to do that.
All I can think is like the guy said about the PCM, or possible vapor lock but the fuel pressure is like 39# when the error kicks.
I did notice quite alot of vapor pressure in the fuel rail when I was disconnecting it to remove the injectors for cleaning. When I disconned the quick-disconnect, I capped the fuel rail side with my finger and was surprised it had vapor pressure rather than fuel squirting out for the most part. It was like letting the air out of a tire for about 5 seconds.
Any ideas?
Last edited by hotrodjohn71; 03-24-2016 at 09:02 PM.
Do not ever bring your car to a mechanic shop again that does not understand how the supercharger effects your computer tune. All of his fancy diagnostics will tell him all sorts of parameters are way out of wack when he hooks up his machine because fuel trims, cam timing, global timing, air flow, fuel pressure and other variables are different than stock.
If it were my vehicle I would make sure the fuel filter is good, the throttle body is clean, check for vacuum leaks and clean my MAF.
If it still does it, contact a very reputable shop that has an EXPEREINCED tuner on sight and take your car there. The vehicle will need to be datalogged and the log needs to be seen by the tuner so he can evaluate if the tune is the problem and then he can go from there.
Most likely it's not your tune.
And the mechanic that cleaned your injectors sold you snake oil.
Thank you Simon1 for your reply.
Fuel filter new, TB clean,no vacuum leaks detected by the tech or myself, new MAF.
I had a lengthy couple of phone calls with the tech after the diagnosis and he explained exactly what was happening and how all of the components tested and what they were doing. Taking the car to another tech might be a possibility.
The tech has concluded the Roush tune on the ECU as the last variable in lieu of the injectors being cleaned, and he said the components are doing what they are being told to do by the computer, but of course he could be wrong but I would like someone to point to their reasoning from the data I have collected (which I can post).
I also just aquired a live scan diagnostic tool where I can record all data at hot startup trying to get a perfect recording of the 'hot start stumble' in live data and print that out for further analyzation since the code only happens at startup and never when the car is being driven.
If there are sharp diagnostic techs on this forum I would appreciate any consideration. I have the freeze frame of the error code P0171 I can post with all of the trims and 02 data, and I have 2 diagnostic printouts from the tech of the continual rise of fuel trim at idle warmup and also at 3000 rpm if anyone might be helpful and give me an opinion based on the data.
As regarding the ultrasonic cleaning of the injectors, they were professionally cleaned
. Here is a printout of the pre cleaned performance of the injectors, and after cleaning and fine tuning.
Thanks,
John
Last edited by hotrodjohn71; 03-26-2016 at 08:25 AM.
Update:
Finally got it fixed. I hope this info helps someone else with a similar challenge. None of the components themselves were bad, but the location of the Maf sensor was. I took the car to Ford and the tech verified all components good, but relocated the Maf sensor back to the stock air box position from the cold air tube position that Roush designed it to go. This brought the fuel trims back down and the hot start stumble is gone. Been good for 2 weeks so far and looks good.
The cold air tube position of the Maf where Roush designed it to go has the maf on the bottom of the tube and right after a ribbed rubber connector from the air box possibly causing turbulence in that spot, at least that's what we are thinking, but relocating the Maf back into the air box worked.
Last edited by hotrodjohn71; 04-05-2016 at 07:43 PM.
Sounds like it. Moving the MAF after tuning is recipe for bad drivability.
makes sense, we had a gt500 that the customer added a functional ram air hood setup on, every time he passed an oncoming car the change in air pressure over the maf cause the car to stall. best part is he didnt bieleve us that the hood was causing it, we had to tape up the hole and test drive it with him before he would accept it. with maf sensors its location location location, and smooth airflow.
03-24-2016, 08:57 PM
Roushcharger lean stumble at Hot startups
