Semi Jake Brake - Say What???
02-28-2010, 09:11 AM
#1
2nd Gear Member
Thread Starter
Join Date: Jul 2009
Location: canada
Posts: 408
Semi Jake Brake - Say What???
Why does my 03GT sound like a semi flipping on a "Jake Brake" under deceleration? When lifting off the throttle at, say 3000rpm's, exhaust sounds like normal engine braking until around 2500rpm's, then it gets all loud until roughly 1500rpm's. These are rough guesstimate rpm's. Keeps reminding me of a semi "Jake Brake".
Why is this and is there a way to eliminate?
Just curious...
Why is this and is there a way to eliminate?
Just curious...
02-28-2010, 09:46 AM
#3
1st Gear Member
Join Date: Nov 2008
Location: Rockland, NY
Posts: 83
I thought thats what the PCM "dime mod" was for. There's a gasket with a smaller inlet for air getting into the PCM valve, that's supposed to stop hanging RPM's at idle and the conditions OP described.
?
?
02-28-2010, 09:47 AM
#4
2nd Gear Member
Thread Starter
Join Date: Jul 2009
Location: canada
Posts: 408
Just ordered an SCT tuner. Could it be deactivated with this?
02-28-2010, 09:51 AM
#5
2nd Gear Member
Thread Starter
Join Date: Jul 2009
Location: canada
Posts: 408
02-28-2010, 11:30 AM
#8
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
This modification has been discussed to death on this forum, just search for "IAC mod". That said, using a 1/2" copper pipe cap, drilled and inserted into the IAC air feed tube is much easier than making a custom gasket, and does not require dismounting and remounting the IAC while experimenting to get the hole sized correctly.
========================================
With regard to the OP's issue adding restriction to the IAC bypass will generally exacerbate the popping during deceleration.
One thing that might be causing the OP's engine to pop during deceleration (not a normal issue) could be a sticking/sluggish IAC that is not passing sufficient air.
The decel fuel cutoff has a number of conditions that must be met before it kicks in, and required to keep the injectors off. The Coasting Fuel Shutoff Time scalar (4 seconds in the OEM tune) sets the amount of time at closed throttle before the injectors shut down, and the Decel Fuel Shutoff/MPH value (25 in the stock tune) is the minimum speed at which the injectors will be kept off.
The OP did not say what gear/speed this was happening at, however if the IAC were sluggish/sticking and the speed dropped below 25MPH, the injectors would fire up in an overly rich condition due to the IAC being stuck = popping in the exhaust...
02-28-2010, 07:41 PM
#10
2nd Gear Member
Thread Starter
Join Date: Jul 2009
Location: canada
Posts: 408
I think you meant to say the "IAC" (Idle Air Control) mod, and "IAC" valve.
This modification has been discussed to death on this forum, just search for "IAC mod". That said, using a 1/2" copper pipe cap, drilled and inserted into the IAC air feed tube is much easier than making a custom gasket, and does not require dismounting and remounting the IAC while experimenting to get the hole sized correctly.
========================================
With regard to the OP's issue adding restriction to the IAC bypass will generally exacerbate the popping during deceleration.
One thing that might be causing the OP's engine to pop during deceleration (not a normal issue) could be a sticking/sluggish IAC that is not passing sufficient air.
The decel fuel cutoff has a number of conditions that must be met before it kicks in, and required to keep the injectors off. The Coasting Fuel Shutoff Time scalar (4 seconds in the OEM tune) sets the amount of time at closed throttle before the injectors shut down, and the Decel Fuel Shutoff/MPH value (25 in the stock tune) is the minimum speed at which the injectors will be kept off.
The OP did not say what gear/speed this was happening at, however if the IAC were sluggish/sticking and the speed dropped below 25MPH, the injectors would fire up in an overly rich condition due to the IAC being stuck = popping in the exhaust...
This modification has been discussed to death on this forum, just search for "IAC mod". That said, using a 1/2" copper pipe cap, drilled and inserted into the IAC air feed tube is much easier than making a custom gasket, and does not require dismounting and remounting the IAC while experimenting to get the hole sized correctly.
========================================
With regard to the OP's issue adding restriction to the IAC bypass will generally exacerbate the popping during deceleration.
One thing that might be causing the OP's engine to pop during deceleration (not a normal issue) could be a sticking/sluggish IAC that is not passing sufficient air.
The decel fuel cutoff has a number of conditions that must be met before it kicks in, and required to keep the injectors off. The Coasting Fuel Shutoff Time scalar (4 seconds in the OEM tune) sets the amount of time at closed throttle before the injectors shut down, and the Decel Fuel Shutoff/MPH value (25 in the stock tune) is the minimum speed at which the injectors will be kept off.
The OP did not say what gear/speed this was happening at, however if the IAC were sluggish/sticking and the speed dropped below 25MPH, the injectors would fire up in an overly rich condition due to the IAC being stuck = popping in the exhaust...
Thread
Thread Starter
Forum
Replies
Last Post
Matt's 95 Stang
5.0L (1979-1995) Mustang
2
10-05-2015 07:16 AM
MustangForums Editor
General Tech
0
09-25-2015 06:42 PM
