Failing ECU or? Top tuners chime in.

[maurice05]

Bad/flaky ECU or WHAT?????

I have a 2005 Mustang GT with 87K miles.

At about 76K I installed:
Single chamber flowmasters.
JTL CAI.
Comp Stage 2 cams
Removed the charge motion plates
Steeda underdrive pullies

And had the car dyno tuned by a good Mustang specialty shop.

The car ran great, although it did suffer from the common 05 GT fuel pump air bubble syndrome. Other than that.... perfect.

At 83K miles I had another dyno tune performed by a different shop.
333RWHP!!!! Woo hoo.

Shortly after that the car began experiencing hesitation and cut out at cruising speed. It does not matter what speed, 45MPH... 55MPH... 80MPH... as the car engine changes between load and no load to maintain the speed, you can feel the car jerk/hesitate. Its almost like the engine is cutting off for a split second. It does the same while the cruise control is set... and does it even before the engine is up to operating temperature.

I reflashed the computer back to the previous dyno tune file... but the problem remains.

Since the problem began I have replaced the following:
Fuel pump and filter
Spark plugs
Coil on plugs
Mass air sensor
Upstream O2 sensors

The problem still remains.

No CEL, no pending codes. Flashed and reflashed several times. "Rebooted" the entire ECU. Nothing helps.

I have data logged all sorts of stuff for the local guys to look over.
They see nothing odd. Although when they drive it.... they all say the car does have an issue.

ANYONE with a possible solution post up...... but lets not get stupid and suggest I get a whole new car. I really like this one.

 

[86GT351]

If a shop took your money for a dyno tune and then confirmed there is an issue when driving but can't give you a confirmed diagnosis, I would be scared.

What area are yuou in?

 

[maurice05]

If a shop took your money for a dyno tune and then confirmed there is an issue when driving but can't give you a confirmed diagnosis, I would be scared.

What area are yuou in?

Considering that the problem occurs with tune files from 2 different shops... its clear the problem can not be tune related. So its hard to hold them (the second dyno tune shop) accountable for a problem that just happened to spring up after their tune was installed, but does not go away once the tune is removed.

Both shops have been pretty good about offering up solutions and looking over countless data log files I have sent them.

But so far.... the problem can not be found.

FYI... I live in central NC.

 

[hunter1022]

As stated above a good tuner is going to be able to understand what your problem is and fix it in the tune revision unless it turns out to be a mechanical issue but even then he should be able to tell you what the issue is. If this guy is Dyno tuning your car and says it has issues and can't tell you what they are then you need to find a new shop and not pay this guy a penny.

 

[stkjock]

So it's happening when power is added to maintain speed primarily?

Check the TPS voltage?

 

[maurice05]

So it's happening when power is added to maintain speed primarily?

Check the TPS voltage?

Actually the problem/hesitation/jerk occurs when you let off the gas.... as the car is decelerating.

I data logged the TPS voltages... they were smooth and in alignment with my pedal efforts.

 

[maurice05]

As stated above a good tuner is going to be able to understand what your problem is and fix it in the tune revision unless it turns out to be a mechanical issue but even then he should be able to tell you what the issue is. If this guy is Dyno tuning your car and says it has issues and can't tell you what they are then you need to find a new shop and not pay this guy a penny.

Neither shop is charging me for the additional diagnostics, advice or viewing of the data log info. They would however charge me for actual shop time which i have not paid them for at this point.

 

[BruceH]

Bad/flaky ECU or WHAT?????

I have a 2005 Mustang GT with 87K miles.

At about 76K I installed:
Single chamber flowmasters.
JTL CAI.
Comp Stage 2 cams
Removed the charge motion plates
Steeda underdrive pullies

And had the car dyno tuned by a good Mustang specialty shop.

The car ran great, although it did suffer from the common 05 GT fuel pump air bubble syndrome. Other than that.... perfect.

At 83K miles I had another dyno tune performed by a different shop.
333RWHP!!!! Woo hoo.

Shortly after that the car began experiencing hesitation and cut out at cruising speed. It does not matter what speed, 45MPH... 55MPH... 80MPH... as the car engine changes between load and no load to maintain the speed, you can feel the car jerk/hesitate. Its almost like the engine is cutting off for a split second. It does the same while the cruise control is set... and does it even before the engine is up to operating temperature.

I reflashed the computer back to the previous dyno tune file... but the problem remains.

Since the problem began I have replaced the following:
Fuel pump and filter
Spark plugs
Coil on plugs
Mass air sensor
Upstream O2 sensors

The problem still remains.

No CEL, no pending codes. Flashed and reflashed several times. "Rebooted" the entire ECU. Nothing helps.

I have data logged all sorts of stuff for the local guys to look over.
They see nothing odd. Although when they drive it.... they all say the car does have an issue.

ANYONE with a possible solution post up...... but lets not get stupid and suggest I get a whole new car. I really like this one.

First you have to let it all hang out. Who did all the work? Name the shops. Many things can affect tip in, a qualified shop will be able to fix it. You are only hurting other Mustang members by not naming the shops who can't fix it.

 

[maurice05]

First you have to let it all hang out. Who did all the work? Name the shops. Many things can affect tip in, a qualified shop will be able to fix it. You are only hurting other Mustang members by not naming the shops who can't fix it.

And I see it exactly the opposite.
How many times have trained tech's at the stealership been unable to make a fix... or fixed stuff that wasnt broke... or fixed stuff only to have it break again? REALLY.

At this point slamming good shops with good technicians just because they have been unable to pin point the cause of my cars problem, which may or may not be their fault, and could in fact be an intermittent ECU issue that would be difficult at best to diagnose even with proper input and output signals being mapped at the slow datalog speeds is quite premature. I have used both of these shops before... over a 10 year period. I trust them. But some issues require more time and perspective to nail down.

I have no issue posting up on poor performance by a tech or particular shop.
But until the problem is found... there is no point to bad mouth anyone.

If I do find out it is something simple and should have been seen quickly... I'll be certain to name names.

 

[BruceH]

And I see it exactly the opposite.
How many times have trained tech's at the stealership been unable to make a fix... or fixed stuff that wasnt broke... or fixed stuff only to have it break again? REALLY.

At this point slamming good shops with good technicians just because they have been unable to pin point the cause of my cars problem, which may or may not be their fault, and could in fact be an intermittent ECU issue that would be difficult at best to diagnose even with proper input and output signals being mapped at the slow datalog speeds is quite premature. I have used both of these shops before... over a 10 year period. I trust them. But some issues require more time and perspective to nail down.

I have no issue posting up on poor performance by a tech or particular shop.
But until the problem is found... there is no point to bad mouth anyone.

If I do find out it is something simple and should have been seen quickly... I'll be certain to name names.

If you already know all these things then why would you ask us? Are you one of the paid contributors to this forum who direct threads?

 

[maurice05]

If you already know all these things then why would you ask us? Are you one of the paid contributors to this forum who direct threads?

Simple. Because there is a chance someone on this forum might have had the same issue.

How in the world would I be "directing" this or any other thread?

I have presented my issue with the car, and would like for someone to offer up advice for an actual fix. NOT advice on how to deal with a particular shop or turn the thread into some sort of tech bashing/my tech is better than yours sort of thing.

I dont have the time for it.

And when the issue is resolved... I'll post up the fix for others to benefit from.

Life is simple.

 

[irishpwr46]

so it happens as you release the pedal. almost as if the throttle blade is closing completely and killing the engine in the process? did either tuner mess with the traction control at all?

 

[maurice05]

so it happens as you release the pedal. almost as if the throttle blade is closing completely and killing the engine in the process? did either tuner mess with the traction control at all?

Yes I would describe the problem as occurring just as the gas peddle is being released. It can really be noticed while traveling downhill.

It "feels" more electrical than air starvation... but maybe air?

Data logging of the throttle position and electrical output/inputs of the TB show normal operations.

I would ask though.... what action do the cams take once you lift off of the gas pedal? (ANYONE????)

Also... Yes, one of the tunes does have the traction control turned off... the other did not touch the traction control function.
Both tunes have the issue described.

 

[irishpwr46]

the cams arent going to react to the gas pedal, they will react to the oil pressure. you didnt lock out the VCT i am assuming. i doubt it is air starvation, im just trying to clear up exactly when the problem will occur.

 

[05gtowner]

If you already know all these things then why would you ask us? Are you one of the paid contributors to this forum who direct threads?

Does this post seem odd to you as well? I know I got a gut feeling that this isn't what it seems. No introduction, no, background, yet I get the sense he knows more then the average newbie yet can't figure this out. OP why don't you find a ecu from a junkyard and have it flashed by the dealer then drop your tune in there and see if your issue still exists? Did you use a Ford fuel pump when you replaced it? Have you replaced or serviced the injectors? What about the cops, are they ford or aftermarket?

 

[maurice05]

the cams arent going to react to the gas pedal, they will react to the oil pressure. you didnt lock out the VCT i am assuming. i doubt it is air starvation, im just trying to clear up exactly when the problem will occur.

The VCT is not locked.

However, I'm pretty sure the cams react not only to variation in oil pressure, which is how they are moved, but also information from the ECU. (Engine load, RPM's and such) through the cam solenoids.

I'm just curious if the cams go to a certain degree when the throttle is lifted.

I do know Ford cuts off the fuel injectors when the pedal is lifted to save gas, and that this "feature" has caused issues for some cars... but not mine.

 

[maurice05]

Does this post seem odd to you as well? I know I got a gut feeling that this isn't what it seems. No introduction, no, background, yet I get the sense he knows more then the average newbie yet can't figure this out. OP why don't you find a ecu from a junkyard and have it flashed by the dealer then drop your tune in there and see if your issue still exists? Did you use a Ford fuel pump when you replaced it? Have you replaced or serviced the injectors? What about the cops, are they ford or aftermarket?

Unsure why all the paranoia on this forum.

Well I'm no noobie for sure. This is my 3rd 2005 GT. My first was ordered back in September of 2004. It died in a car crash three years later. My second 05 GT only lasted a year before dying in a crash as well.
Both caused by red light runners with cell phones.

This is my 3rd 05 GT.... I have plenty (40 years) of car mechanical experience down to rebuilding of engines and tracing electrical wires.

So there is my intro.

As for your concerns about my car issue.
1. Swapping out the ECU is not a simple plug and play considering the cars mods, handheld tuner, and of course the car key security system programming. Your idea is on my list of things to try... but there are costs, and I'll wait for a few more folks chime in.

2. I did not use a Ford fuel pump. However, the problem existed before the swap... and after. The pump was more to correct the air bubble issue common with 05 Mustangs which it did. I've data logged the fuel pump voltages and shirt/long term fuel maps. No one sees anything.

3. The injectors did get a Ford servicing just prior to me buying the car.
Not sure why they would only act up on deceleration though. They seem fine around town and at 130MPH on the back strait at VIR.

4. The COP's were aftermarket. Now I find out that the vast majority of aftermarket COP's are garbage. However, I have access to HV testing equipment at work... and the factory ones checked out OK. The problem was present with the aftermarket COP's... and now with the tested factory ones.
Running the OEM ones now.

Further... the upstream O2 sensors and MAF sensor are both Ford OEM.

I do appreciate your ideas. Thanks.

 

[maurice05]

Just noticed my membership info shows I recently joined.

I actually joined shortly after purchasing my first 05 back in December 04.

I posted more than a few times for a couple of years... then dropped off as my focus went from cars to my children.

I had to re-register.... using my old user name.
Maybe inactivity?

But hey.... I've been around, and found this a good forum for my technical needs.

 

[irishpwr46]

so youre saying you joined this forum in 2004? hmmm

 

[stkjock]

so youre saying you joined this forum in 2004? hmmm