Miss at light throttle
Thread Starter
|
Trailering
Joined: Mar 2021
Posts: 22
Likes: 0
Miss at light throttle
92 F150
5.0
Hello,
I'm trying to figure out why i have a miss at very light throttle while cruising. At least I'm assuming its a miss. Give it more throttle it goes away . It will also just die randomly while I'm cruising at low speed, Maby10mph or so. I cant make it die it just does it when it wants to.
I have changed tone of stuff,
Egr
Purge Solenoid
Throttle Body
Idle air control valve
Coolant temp Sensor
Intake air temp sensor.
Distributor
Coil
Fuel Pressure Regulator
Timing is at 10 deg
Tps
I sprayed carb cleaner everywhere looking for vacuum leak found none
Wires
Plugs
Map
I unpluged the Sprout and drove it it acts the same
Air filter is clean its a K&N if that matters
I took the filter out and drove it no change
Injectors
Brake booster check Valve
The Coffee Cans are not rotted
I had the compactors on the computer changed
Both of the tanks it seems to run the same.
I have 2 codes 542 and a 634. The 542 leads me to believe the pumps are bad but both of them. I don't know about that. I dont have a fuel pressure gauge or id check that.
Im stumped.
Thanks
5.0
Hello,
I'm trying to figure out why i have a miss at very light throttle while cruising. At least I'm assuming its a miss. Give it more throttle it goes away . It will also just die randomly while I'm cruising at low speed, Maby10mph or so. I cant make it die it just does it when it wants to.
I have changed tone of stuff,
Egr
Purge Solenoid
Throttle Body
Idle air control valve
Coolant temp Sensor
Intake air temp sensor.
Distributor
Coil
Fuel Pressure Regulator
Timing is at 10 deg
Tps
I sprayed carb cleaner everywhere looking for vacuum leak found none
Wires
Plugs
Map
I unpluged the Sprout and drove it it acts the same
Air filter is clean its a K&N if that matters
I took the filter out and drove it no change
Injectors
Brake booster check Valve
The Coffee Cans are not rotted
I had the compactors on the computer changed
Both of the tanks it seems to run the same.
I have 2 codes 542 and a 634. The 542 leads me to believe the pumps are bad but both of them. I don't know about that. I dont have a fuel pressure gauge or id check that.
Im stumped.
Thanks
Logistics Pro
Joined: Nov 2013
Posts: 3,928
Likes: 1,198
From: Mojave, Ca
First thing to do is get your hands on a fuel pressure gauge. Major auto parts stores loan them out for free with the correct adapters. Or you can buy a fuel pressure gauge kit on eBay/Amazon for a few dozen dollars.
Without knowing the condition of your fuel system, you're just gunna be throwing parts at the problem and hoping you get lucky.
Without knowing the condition of your fuel system, you're just gunna be throwing parts at the problem and hoping you get lucky.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Verify the firing order is correct and the plug wires are routed to reduce crossfire.
corrected image for 1993 and earlier 5L truck engines
https://www.supermotors.net/registry/media/72380
corrected image for 1993 and earlier 5L truck engines
https://www.supermotors.net/registry/media/72380
Cargo Master
Joined: Mar 2003
Posts: 2,333
Likes: 296
I have a 93 F150 w/ the 5 L.
Bought it new and from the day I bought it it has had a very slight miss/ shaky idle and goes away with just a slight increase in throttle.
With less than 30k miles I had changed the plugs/rotor/cap/wires, wire routing, resealing the intake, new injectors and iac, all at different times, hoping to find the culprit.
Fuel pressure within specs.
It did often die when stopping and changing gears like when backing out of a driveway into traffic. New iac solved that but the erratic idle remained.
While under warranty, Ford even had no idea what was causing it.
Now at 230k miles / 30 years later and with a new engine and computer with new caps installed and it still does that same thing.
I am quite certain that it is something in the electronics causing this.
Just one of those things that I chose to live with -vs- dumping tons of cash into with the hopes of fixing the minor issue.
Bought it new and from the day I bought it it has had a very slight miss/ shaky idle and goes away with just a slight increase in throttle.
With less than 30k miles I had changed the plugs/rotor/cap/wires, wire routing, resealing the intake, new injectors and iac, all at different times, hoping to find the culprit.
Fuel pressure within specs.
It did often die when stopping and changing gears like when backing out of a driveway into traffic. New iac solved that but the erratic idle remained.
While under warranty, Ford even had no idea what was causing it.
Now at 230k miles / 30 years later and with a new engine and computer with new caps installed and it still does that same thing.
I am quite certain that it is something in the electronics causing this.
Just one of those things that I chose to live with -vs- dumping tons of cash into with the hopes of fixing the minor issue.
Cargo Master
Joined: Aug 2021
Posts: 2,258
Likes: 742
From: Maryland
When's the last time the fuel filter was changed?
Here's a thread on ground points. https://www.ford-trucks.com/forums/1...nd-points.html
The fuel pumps are grounded near the windshield washer bottle and the cable from the negative battery terminal, to the engine block and frame, can cause a lot of symptoms with these trucks.
Here's a thread on ground points. https://www.ford-trucks.com/forums/1...nd-points.html
The fuel pumps are grounded near the windshield washer bottle and the cable from the negative battery terminal, to the engine block and frame, can cause a lot of symptoms with these trucks.
Thread Starter
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Trailering
Joined: Mar 2021
Posts: 22
Likes: 0
Fuel pressure is 30 psi at idle and while driving.
Not sure when the fuel filter was changed had the truck a few months. When i looked at it it was shiny like it was new that's why i didn't change it.
Not sure when the fuel filter was changed had the truck a few months. When i looked at it it was shiny like it was new that's why i didn't change it.
Thread Starter
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Trailering
Joined: Mar 2021
Posts: 22
Likes: 0
I guess my firing order is 1,5,4,2,6,3,7,8. It wont run any other way. I even found tdc and re stabbed the distributor. Does this sound right?
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Hotshot
Joined: Jun 2015
Posts: 12,830
Likes: 2,436
Unfortunately unleashing the parts cannon has made diagnosing the problem more difficult.
Although it was aimed at the distributor mounted ICM, wasn’t random stalling a sign at a failing ICM?
Although it was aimed at the distributor mounted ICM, wasn’t random stalling a sign at a failing ICM?
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Logistics Pro
Joined: Nov 2013
Posts: 3,928
Likes: 1,198
From: Mojave, Ca
Seems suspicious. It should raise to 35-40 while you're driving. Low fuel pressure will cause a lean-miss. What happens when you go full throttle on the freeway?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Fuel pressure should increase to about 40psi with vacuum removed from the regulator(engine idling), and it should never drop below the vacuum attached reading at any time.