Engine 1986 5.0-GT- Idling/bucking Problems

QuickFox86

Member
Sep 22, 2020
11
7
13
Mesa
#1
Hey guys. So I'm having running problems with my '86 GT. Sometimes the car runs great, but sometimes it will have a bad idle and buck really bad when you attempt to drive it. It also sounds like it's backfiring sometimes. I know this is probably an ignition/timing issue, or maybe I have a vacuum leak somewhere. It also might be a TFI module, but I am not sure. Anybody have any suggestions? Thanks.
 
#2
Many things come to mind as possible causes but rather than poke here or jab this do this checklist step by step,

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...
forums.stangnet.com
 
Reactions: 1 user
#4

Ok I'll run through it. Thanks.
 
#7
So, is your '86 completely stock? If not, what modifications?
 
#8
As far as the engine goes I know the speed density system has been replaced with a mass air system, and the EGR has been deleted, as well as aluminum heads, msd box, and a tubular intake manifold off a 1st gen lightning.
 
#9
QuickFox86 said:
As far as the engine goes I know the speed density system has been replaced with a mass air system, and the EGR has been deleted, as well as aluminum heads, msd box, and a tubular intake manifold off a 1st gen lightning.
Click to expand...
Do you have an aftermarket cam by any chance? I have an original '86 converted to mass air, plus E303 cam, aluminum heads, roller rockers, 24lb injectors, equal-length headers, etc., as well as deleted smog pump and EGR. At low speeds (under 1,500 RPM) I frequently get bucking, which I'm told is likely the cam. But my idle is great. I did take it to a tuner for some work.
 
You must log in or register to reply here.

Similar threads

Car idles good, then VERY SUDDENLY dies
Replies
25
Views
2K
Fox 5.0 Mustang Tech
Vulpes5.0
W
Resolved Loss of Horsepower After Base Idle Reset??
Replies
8
Views
1K
Fox 5.0 Mustang Tech
WTW
W
Engine Help hard/no start runs rough.
Replies
25
Views
2K
Fox 5.0 Mustang Tech
CAMTWO1070
D
Engine Wont idle and light backfire
Replies
3
Views
890
Fox 5.0 Mustang Tech
General karthief
T5 with no neutral gear switch on top of case
Replies
13
Views
1K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Noobz347
Menu
Log in
Register