1991 F150 4.9 loss of power
03-18-2008, 06:35 PM
#1
Junior Member
Thread Starter
Join Date: Mar 2008
Location: SW MO
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
1991 F150 4.9 loss of power
I just bought a pretty nice 1991 Ford F-150 with the 4.9l . It has auto Trans and when ever you are light on the gas . after a shift it bogs down and misses . really when its going around 30-50 mph . like when ot going in to O/D and the Rpms go down to 1 k and its stats missing and losing power . if you give it some gas it will ussaly drop down one gear and be fine . also it accelrates fine does not miss . but seems the low rpm range is very slugish .
Thanks any advise would help .
Thanks any advise would help .
03-18-2008, 06:46 PM
#2
Member
Join Date: Feb 2008
Location: Torrance, CA
Posts: 43
Likes: 0
Received 0 Likes
on
0 Posts
Assuming all the basic tune up stuff is checked and there are no obvious problems (nothing floating around the airbox, wires, plugs etc) you could hook up a timing light, tape the trigger on and tape the whole thing to the windshield with the wires running out of the hood. Watch the consistency of the light when the problem happens as you drive (be careful!). If the light breaks up there is an ignition issue, if not, get a propane bottle that you can place in your lap, run a long hose out the window, under the hood and into the air intake. Drive the truck and when the problem happens bleed in some propane. If it helps you have a lean/fuel delivery condition at lower speeds. If the problem stays the same or gets worse you know it's not lean. This is all down and dirty old school stuff but it helps to eliminate systems pretty fast.
03-21-2008, 03:38 PM
#3
Junior Member
Thread Starter
Join Date: Mar 2008
Location: SW MO
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
i ran some seafoam thru the brake boaster hose today . and cleaned up the injectors and vavles . and now its almost runing perfect . Iam thinking i should also replace the speed sensor . because now it only does it in 4the gear and in OD. right at 45 mph .
question how do i know if i have dealer or factory installed cruise controll ?
where is my speed sensor at in either location ? i thought in was above the Rear diff . or is it inside the diff ?
also how do i know if and what type of trans i have ? is it electric or mechanial controlled ? and would replacing the speed sensor affect anything on a mechanial controlled transmission ?
question how do i know if i have dealer or factory installed cruise controll ?
where is my speed sensor at in either location ? i thought in was above the Rear diff . or is it inside the diff ?
also how do i know if and what type of trans i have ? is it electric or mechanial controlled ? and would replacing the speed sensor affect anything on a mechanial controlled transmission ?
Last edited by SplF150; 03-21-2008 at 03:51 PM.
03-24-2008, 09:23 PM
#4
Senior Member
The speed sensor is mounted on the differential,front side towards the top with a 10mm bolt,you will not have a speed sensor with a non-elec. trans. Your trans is comupter controlled,i'm pretty sure.As far as the cruise control,if you have controls on the steering wheel then it is factory,aftermarket cruise for the most part will be vacuum controled only.