• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


stumbling/sputtering under heavy throttle

Messages
26
Likes
5
Location
Richmond
#1
Hi all! I bought a FiST yesterday. It's a salvage/rebuilt. On the drive home I went to pass on the highway WOT in 4th and it stumbled bad. I tried again in 2nd after taking an exit and again it fell on its face. It seems any throttle input greater than 50% causes this. Otherwise it drives fine.
Mods disclosed were Cobb RMM and whoosh sound symposer delete. Also the seller installed a stock muffler as it came with aftermarket. When the weather gets better I will be looking it over more thoroughly.

Things I'm considering :
Bad gas from sketch station
Plugs/coils
Original owner tuned and did not return to stock(seller did not tune and is not aware of any tune)
Bad catalytic converter?
Exhaust leak? Would effect be this bad??
Bad air or fuel sensor
Some other unknown mod yet to be found



No CEL and I've checked for stored and pending codes using a Bluetooth reader + torque

If the car is tuned how does that work? I'm going to get an accessport (wtb thread coming soon) but will it be able to overwrite the tune that is possibly on the ecu already?



Sent from my Nexus 6 using Tapatalk
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,495
Likes
7,986
Location
Rich-fizzield
#3
I'm leaning towards a fuel related issue from what you have said just now..... no codes... do you have an AP3 to check Air fuel ratio? To see if it runs lean under throttle? IF YOU SEE IT START TO LEAN OUT DO NOT GET INTO THE THROTTLE AS IT CAN DETONATE! This is not good .....Motor go boom if it happens. Until it can be verified id stay out of boost.[nono]
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #4
I've sent an email to Cobb support asking if a new accessport would marry and function on an already tuned car

Sent from my Nexus 6 using Tapatalk
 


TyphoonFiST

9000 Post Club
Premium Account
Messages
11,495
Likes
7,986
Location
Rich-fizzield
#5
I've sent an email to Cobb support asking if a new accessport would marry and function on an already tuned car

Sent from my Nexus 6 using Tapatalk
Do you have the stock tune still?



Sent from my SM-N950U1 using Tapatalk
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #6
Do you have the stock tune still?

Sent from my SM-N950U1 using Tapatalk
I have no idea what tune is on the car. I'm working with limited knowledge based on what the seller told me about it. It's like a really expensive but fun puzzle [emoji16]

Sent from my Nexus 6 using Tapatalk
 


kivnul

1000 Post Club
U.S. Army Veteran
Messages
1,193
Likes
710
Location
Deer Park, WA
#7
With the car running and cruise control turned off, hit the cruise control cancel/resume button. If your tac needle moves to exactly 1k (or 2k or 3k etc) regardless of throttle input then you currently have a Cobb style tune. Hit the cancel/resume button again to go back to normal. If it does nothing then you do not have a Cobb style tune loaded. (but you may still have a diablo or other style tune loaded)
 


Last edited:
OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #8
With the car running and cruise control turned off, hit the cruise control off button. If your tac needle moves to exactly 1k (or 2k or 3k etc) regardless of throttle input then you currently have a Cobb style tune. Hit the off button again to resume normal. If it does nothing then you do not have a Cobb style tune loaded. (but you may still have a diablo or other style tune loaded)
Thanks! It definitely does not have a Cobb tune. I did some more inspecting and am curious how the stock vacuum lines are ran. Is there a diagram somewhere? One of the lines going that is connected to the intercooler pipe is crimped Here are a couple of pictures from mine.

IMG_20180725_162526.jpg IMG_20180725_162436.jpg IMG_20180725_162415.jpg
 


kivnul

1000 Post Club
U.S. Army Veteran
Messages
1,193
Likes
710
Location
Deer Park, WA
#9
I need to amend my instructions as they were in error. Instead of the Off button you need to use the cancel/resume button. I apologize.
 


Messages
106
Likes
22
Location
Lawrence
#10
Thanks! It definitely does not have a Cobb tune. I did some more inspecting and am curious how the stock vacuum lines are ran. Is there a diagram somewhere? One of the lines going that is connected to the intercooler pipe is crimped Here are a couple of pictures from mine.

View attachment 18047 View attachment 18048 View attachment 18049
In your first pic, what line is that with the kink in it?
 


felopr

Senior Member
Messages
815
Likes
370
Location
JD
#11
Thanks! It definitely does not have a Cobb tune. I did some more inspecting and am curious how the stock vacuum lines are ran. Is there a diagram somewhere? One of the lines going that is connected to the intercooler pipe is crimped Here are a couple of pictures from mine.

View attachment 18047
Need a more pan out shot to make where that hose is from

View attachment 18048 View attachment 18049
apart from being dirty , everything looks ok, also you have a aftermarket cold side charge pipe. more photos of it.

Also check the air filter
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #14
Willing to bet it's the coils/plug gaps.

Sent from my SAMSUNG-SM-N910A using Tapatalk
Coils look good. Plugs were .031 .030 .031 .030

Pic

IMG_20180726_181314.jpg

Air filter looks good too. I should have included in my original post that the car only has 18K miles.
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #15
AP is on the way. Does anyone have any thoughts on how those plugs look and if they should be gapped closer? I'm thinking about putting a new set in just to rule it out

Sent from my Nexus 6 using Tapatalk
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #17
plugs look ok to me.
maybe a little rich but hard to tell
they are gap correctly
Thanks. Any thoughts on the kinked line? I've been looking on tasca and I think it may be part of the evap system? Trying to find a part number for it. Would it being kinked cause the symptoms I'm seeing?
 


felopr

Senior Member
Messages
815
Likes
370
Location
JD
#18
Thanks. Any thoughts on the kinked line? I've been looking on tasca and I think it may be part of the evap system? Trying to find a part number for it. Would it being kinked cause the symptoms I'm seeing?
yes is part of the evap fuel lines
i would like to take a better look at the kink to see and where in the line is that kink to see if it is ok
would it cause the symptoms? no, dont think so imo.
 


OP
2
Messages
26
Likes
5
Location
Richmond
Thread Starter #19
yes is part of the evap fuel lines
i would like to take a better look at the kink to see and where in the line is that kink to see if it is ok
would it cause the symptoms? no, dont think so imo.
It's about midway in the line, right next to the airbox

IMG_20180727_184525.jpg
 




Top