Anyone have any ideas on this problem? FINALLY SOLVED

[Leigh_bullitt]

Hi Guys
Happened again today.
went for a drive and for about an hour it was ok but just felt off. Couldn’t make any smooth gear changes and it was hard to hold a constant speed, like surging and then hesitation when applying the throttle lightly.
after having some lunch, it started rough again but smoothed out amazingly while it was driving.

one thing I did notice….
When it runs rough if I accelerate slowly at around 2k rpms the active exhaust valves suddenly close and then open again.

im thinking could my problem simply be a bad tps sensor?.
I mean the one that’s in the throttle pedal.
The throttle body is clean and running perfectly.
the reason I ask this is because the active exhaust is relied on RPM, Gear and Throttle input.

I think mechanically the car is fine. Maybe I just have this gremlin ??

is their any way to service the throttle tos sensor ??

cheers

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[sk47]

Couldn’t make any smooth gear changes and it was hard to hold a constant speed, like surging and then hesitation when applying the throttle lightly.

When it runs rough if I accelerate slowly at around 2k rpms the active exhaust valves suddenly close and then open again.

is their any way to service the throttle tos sensor ??

Hello; let me first say I do not have good answers. Let me tell a story. I restored a 1963 Oldsmobile Cutlass F-85 a few decades ago. Got it running fairly well except it would "hunt" (surge and then slow down) when i tried to cruise at a steady speed on level roads. Was smooth on hills or accelerating. Long time trying to figure this out. Turned out to be a problem in the old type distributor. They (distributors) used both a mechanical and a vacuum motor timing advance/retard systems. The vacuum motor had a small hole in the diaphragm inside. The hole would not let the vacuum motor hold steady. The arm would constantly move and so change the timing slightly. Found a new vacuum motor and the problem was solved. While this sounds very similar to what you describe there was not any engine missing as you have reported.
I go back to a suggestion about checking for vacuum leaks. I do not have any confidence in this suggestion, but it appears at some point you will need to form a strategy. One part could be to make sure there is not a simple mechanical fault. I get most folks tend to look at the electronics of modern cars, but there still are a lot of mechanical aspects to an engine.

I do not know why the exhaust will do as you describe. Does seem a clue especially if the exhaust and rough running clear up at the same time.

There are websites where common problems of particular car models & years are listed. I have found the general community to show these common issues. My Chevy pickup has had problems that I search and then find it is a more common issue for the whole population of that year truck.

 

[cerbomark]

Hi Guys
Happened again today.
went for a drive and for about an hour it was ok but just felt off. Couldn’t make any smooth gear changes and it was hard to hold a constant speed, like surging and then hesitation when applying the throttle lightly.
after having some lunch, it started rough again but smoothed out amazingly while it was driving.

one thing I did notice….
When it runs rough if I accelerate slowly at around 2k rpms the active exhaust valves suddenly close and then open again.

im thinking could my problem simply be a bad tps sensor?.
I mean the one that’s in the throttle pedal.
The throttle body is clean and running perfectly.
the reason I ask this is because the active exhaust is relied on RPM, Gear and Throttle input.

I think mechanically the car is fine. Maybe I just have this gremlin ??

is their any way to service the throttle tos sensor ??

cheers

I do not understand the active exhaust as you described. I don t think it changes other than with the active exhaust mode change (if equipped ) manually . If this has happened since new then I d guess a bad sensor, part or pinched wire somewhere during the manufacturing . Hey, did you try getting with someone that can live data the car?

 

[Leigh_bullitt]

I do not understand the active exhaust as you described. I don t think it changes other than with the active exhaust mode change (if equipped ) manually . If this has happened since new then I d guess a bad sensor, part or pinched wire somewhere during the manufacturing . Hey, did you try getting with someone that can live data the car?

Yes the active exhaust has preset tables that can actually be altered when tuning.

particularly quiet mode…. It will read back info based on Rpm and throttle position and open and close according to this position.

it weird it’s like I can’t hold the throttle in a single place as it surges when rough it’s like the revs hang more and gear changes are not the smoothest.

however when running good no surging no slight hesitation and it seems to be engine braking less strong as when it’s rough. Both could be contributed to the throttle body and the tps in the pedal.

 

[Leigh_bullitt]

I may take off the throttle pedal and take a look at it. Can’t hurt to see if I can open it and see if something is wrong.
I don’t think it would make a cel either because I think it would only say if it’s working or not, not if it’s intermittently doing something off.

it would cause issues everywhere because the throttle body won’t be working well and also the IMRCs wouldn’t know where to be if the TPS is doing something funky.

 

[Leigh_bullitt]

Also I forgot to mention that I sent two data logs to my tuner when running good and running rough and he could not see anything that was off.
but this was because the Pids he asked me for wouldn’t show this as being a problem.

also mine is the Bullitt so it has the GT350 throttle body etc ….

 

[Mike Pfeifer]

Do you by any chance have the ability to post a video of the car running poorly?

 

[Leigh_bullitt]

I’ll try. But I think you would only notice it if you was driving. But I can send a video of the dash and what the Roma are doing.

you know when you drive a cold vehicle in traffic and it seems to be well a little off till it gets warm. That’s what mine is like all the time and then I either leave it and it’s good again or like today while driving it just suddenly went from rough to super smooth. And I was in traffic again and it’s night and day difference

 

[cerbomark]

puzzling , and going on so long. I might be tempted to change the fuel pump. I don t know, it's just throwing parts at it but it is a mystery.
Spark, fuel or air, take your pick.

 

[cerbomark]

https://www.mustang6g.com/forums/threads/gas-particulate-filter-on-new-18-19-gt.110634/

id go back to this too. You have about 6 things to go over just here in this thread. I d start with the cheapest . Consider some of it maintenance anyway.

 

[Leigh_bullitt]

Yeh I have considered the fuel pump as well to be a potential problem.
it’s my bad cause I always run the tank almost dry so it could be something with that you know ..

 

[Leigh_bullitt]

To be honest a faulty fuel pump would affect the sound of the exhaust to making it sound weak I’m guessing lean?. And strong and healthy when running Rich ? Or at perfect Stoic

 

[Leigh_bullitt]

Just out of curiosity where are the TPS sensors on these cars ?.
are they both on the throttle Body and the accelerator pedal?.

 

[sk47]

t’s my bad cause I always run the tank almost dry so it could be something with that you know ..

Hello; This is a bad idea. One reason being the fuel pump needs to be bathed in fuel so as to keep cool. Low fuel levels can allow the pump to run hotter than normal and so shorten life.

Another reason is to prevent water from forming in the gas tank. Not so much of an issue in the USA as most fuel has around 10% ethel alcohol (from food grains). I did, decades ago, add alcohol during cold weather to help get rid of the water. Water will mix with alcohol and so will be burned during combustion. Of course, if you run pure gasoline water can still be a problem. Some stations in the USA do offer pure gasoline.

Condensation of water in a fuel tank is much reduced in modern vehicles. Tanks and fuel systems are sealed some better. Many are plastic. Even so during cold weather i like to keep half a tank or more. Preferably 3/4 or more. That reduces the chances of inside the tank condensation of water.

I do get some folks rarely drive a Mustang and so the problem of old fuel can arise. Regardless running a tank low can lead to problems. Leads me down another, likely fruitless thought path. I do not recall if you told of your driving habits. If you only put few miles on the car a year and it sits a lot, then perhaps a long drive might help. Say 200 or more miles. Fill it up with fresh fuel and run that out. Maybe add some fuel system cleaner. Push it some. A few weeks ago, I went to look at a new car about 100 miles away. Deal fell thru. On the way back home, I decided to take I-81 from Bristol to Morristown TN rather than a shorter back roads route. I ran with traffic at near 80 MPH (maybe more) for many miles. Had been a while since such a run. I noticed better fuel economy the next few fill ups.

Anyway, I might add to that idea to run in the rain a good distance. In the old carb days, I would dribble water into the carb of a running engine at fast idle. The water cleans out the carbon some. Picture popcorn. A tiny bit of water in the popping corn gets hot enough to phase to steam. Volume increases suddenly about 1700% (?) and pops the corn into popcorn. Same idea in a combustion chamber. The water vapor goes to steam and the sudden volume of steam loosens the carbon deposits. Just have to be very careful when pouring water down a carb. Much safer to run in 100% humidity rain.

Wouldn't it be nice to have a reason to drive more? Anyway, that you often run the tank near dry gave me an idea. Might be getting some water condensation in the tank. If your gas station fuel is not regulated to have alcohol in it as mine is, then perhaps a clue? Water in the gas could fit some of your symptoms.
Maybe change fuel stations. I tend to use high volume service stations as they replace fuel often. Many, if not most, underground fuel tanks here are now composite and not metal. I used to drive a school bus which ran on gasoline. Had to fill up at the school systems service garage pumps. Their tanks were old and leaked. They would put a red dye in the tank which colored the water at the bottom of the tank under the gasoline. I have watched a mechanic pump out gallons of red colored water.

Just some more WAG's. Feel free to ignore.

 

[cerbomark]

Hello; This is a bad idea. One reason being the fuel pump needs to be bathed in fuel so as to keep cool. Low fuel levels can allow the pump to run hotter than normal and so shorten life.

Another reason is to prevent water from forming in the gas tank. Not so much of an issue in the USA as most fuel has around 10% ethel alcohol (from food grains). I did, decades ago, add alcohol during cold weather to help get rid of the water. Water will mix with alcohol and so will be burned during combustion. Of course, if you run pure gasoline water can still be a problem. Some stations in the USA do offer pure gasoline.

Condensation of water in a fuel tank is much reduced in modern vehicles. Tanks and fuel systems are sealed some better. Many are plastic. Even so during cold weather i like to keep half a tank or more. Preferably 3/4 or more. That reduces the chances of inside the tank condensation of water.

I do get some folks rarely drive a Mustang and so the problem of old fuel can arise. Regardless running a tank low can lead to problems. Leads me down another, likely fruitless thought path. I do not recall if you told of your driving habits. If you only put few miles on the car a year and it sits a lot, then perhaps a long drive might help. Say 200 or more miles. Fill it up with fresh fuel and run that out. Maybe add some fuel system cleaner. Push it some. A few weeks ago, I went to look at a new car about 100 miles away. Deal fell thru. On the way back home, I decided to take I-81 from Bristol to Morristown TN rather than a shorter back roads route. I ran with traffic at near 80 MPH (maybe more) for many miles. Had been a while since such a run. I noticed better fuel economy the next few fill ups.

Anyway, I might add to that idea to run in the rain a good distance. In the old carb days, I would dribble water into the carb of a running engine at fast idle. The water cleans out the carbon some. Picture popcorn. A tiny bit of water in the popping corn gets hot enough to phase to steam. Volume increases suddenly about 1700% (?) and pops the corn into popcorn. Same idea in a combustion chamber. The water vapor goes to steam and the sudden volume of steam loosens the carbon deposits. Just have to be very careful when pouring water down a carb. Much safer to run in 100% humidity rain.

Wouldn't it be nice to have a reason to drive more? Anyway, that you often run the tank near dry gave me an idea. Might be getting some water condensation in the tank. If your gas station fuel is not regulated to have alcohol in it as mine is, then perhaps a clue? Water in the gas could fit some of your symptoms.
Maybe change fuel stations. I tend to use high volume service stations as they replace fuel often. Many, if not most, underground fuel tanks here are now composite and not metal. I used to drive a school bus which ran on gasoline. Had to fill up at the school systems service garage pumps. Their tanks were old and leaked. They would put a red dye in the tank which colored the water at the bottom of the tank under the gasoline. I have watched a mechanic pump out gallons of red colored water.

Just some more WAG's. Feel free to ignore.

I asked him earlier about his fuel quality. He s in another country and I don t want to assume. BUT again, he said it s been like this since new so.... pump?

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