Suddenly stumbling
Thread Starter
|
Freshman User
Joined: Sep 2014
Posts: 31
Likes: 0
From: Lake County, Florida
Suddenly stumbling
Scratching my head with this. My '84 F150, 351W Truck has run great since I bought it nearly two years ago. Always starts right up. Couple of days ago after about 15-20 minutes of driving, she started stumbling. When I took off from a stop, the stumbling is really bad. What puzzles me is that last night I went for drive and it didn't stumble at all. This morning I drove to the grocery store about 10 miles down the road. She ran perfect, but right out gate heading out of the parking lot the stumbling started again. I was thinking maybe bad gas. this all started shortly after I filled up the main tank the other day, but today I switched to my saddle tank, which I didn't put any gas in the last fill up and it still stumbled. Anyone come across this issue?
Thanks in advance.
Thanks in advance.
Thread Starter
|
Freshman User
Joined: Sep 2014
Posts: 31
Likes: 0
From: Lake County, Florida
Once the hesitation starts, I can still feel it stumbling, even when cruising. It is a four barrel , stock intake with an Edelbrock 1406. All the emissions stuff had been removed when I bought it. When I bought it, it had a Holley 4180, but it had a blown power valve, so I put a new Edelbrock on it. Never had an issue. I'm gonna go through it tomorrow and check the plugs, wires, cap and rotor..etc
Lead Driver
Joined: Apr 2002
Posts: 5,240
Likes: 1,222
Once the hesitation starts, I can still feel it stumbling, even when cruising. It is a four barrel , stock intake with an Edelbrock 1406. All the emissions stuff had been removed when I bought it. When I bought it, it had a Holley 4180, but it had a blown power valve, so I put a new Edelbrock on it. Never had an issue. I'm gonna go through it tomorrow and check the plugs, wires, cap and rotor..etc
From your description of the issue it seems your motor runs strong from cold to warming up but after the motor has been at operating temperatures for 10 or 20 miles the stumbling begins. This indicates that your fuel and ignition are working properly.
Sometimes as the exhaust system heats up portions of the inner wall of dual wall exhaust pipes can collapse blocking or partially blocking the exhaust flow. This will produce a loss of power. Could also be a heat induced issue in the cat or the muffler.
Lead Driver
Joined: Apr 2002
Posts: 5,240
Likes: 1,222
Another reason I thought of a collapsed dual wall exhaust pipe was that it ran fine going to the store. Then presumably you spent enough time shopping that it cooled down some. The heating and then cooling can contribute to the collapsed exhaust. It's hard to check the back pressure but can be done. If your exhaust pipes are old dual wall have a muffler shop put on some oversize single wall pipes and let that v8 breathe.
Freshman User
Joined: Jul 2020
Posts: 39
Likes: 0
Have you replaced the fuel filter?
I've had a similar situation. Once I thought about what was happening and when.
I realized when it was sitting, all the seidament in the tank was dropping to the bottom. When I drove it that seidament was getting stirred up. The filter was only allowing a little gas through it.
I replaced the filter and the problem went away.
Later I dropped the tank to find out it was full of rust.
I've had a similar situation. Once I thought about what was happening and when.
I realized when it was sitting, all the seidament in the tank was dropping to the bottom. When I drove it that seidament was getting stirred up. The filter was only allowing a little gas through it.
I replaced the filter and the problem went away.
Later I dropped the tank to find out it was full of rust.
Trending Topics
More Turbo
Joined: Feb 2019
Posts: 563
Likes: 4
From: Wolfsburg
Have you replaced the fuel filter?
I've had a similar situation. Once I thought about what was happening and when.
I realized when it was sitting, all the seidament in the tank was dropping to the bottom. When I drove it that seidament was getting stirred up. The filter was only allowing a little gas through it.
I replaced the filter and the problem went away.
Later I dropped the tank to find out it was full of rust.
I've had a similar situation. Once I thought about what was happening and when.
I realized when it was sitting, all the seidament in the tank was dropping to the bottom. When I drove it that seidament was getting stirred up. The filter was only allowing a little gas through it.
I replaced the filter and the problem went away.
Later I dropped the tank to find out it was full of rust.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Thread Starter
|
Freshman User
Joined: Sep 2014
Posts: 31
Likes: 0
From: Lake County, Florida
The filter is fairly new. I think that I did figure out the problem. It's so simple,but it didn't cross my mind until today. the engine is misfiring, so it has to be the coil. That"s the one simple thing that I have failed to replace since I purchased the truck. I'll get back to ya'll on that. Thanks for the input.
Lead Driver
Joined: Nov 2013
Posts: 7,155
Likes: 1,166
Is the idle okay? Does the engine only act up above that?
If so, my hunch is a leak in the vacuum advance system, either in the line or the bellows itself. Vacuum for this system is typically taken from a port just above the throttle plate. This means there's no vacuum present at idle, so you only get the leak and lean condition above that.
If the vacuum advance isn't working (for any reason), you may not even notice it. But if a vacuum leak is present, that can cause poor running. It's easy to test. Disconnect the line from the carb and put a cap on the carb fitting. Go for a short test drive. If the engine runs okay now, you have a vacuum leak in the advance system.
If so, my hunch is a leak in the vacuum advance system, either in the line or the bellows itself. Vacuum for this system is typically taken from a port just above the throttle plate. This means there's no vacuum present at idle, so you only get the leak and lean condition above that.
If the vacuum advance isn't working (for any reason), you may not even notice it. But if a vacuum leak is present, that can cause poor running. It's easy to test. Disconnect the line from the carb and put a cap on the carb fitting. Go for a short test drive. If the engine runs okay now, you have a vacuum leak in the advance system.
Thread
Thread Starter
Forum
Replies
Last Post
78Ranger_GARedNeck
1973 - 1979 F-100 & Larger F-Series Trucks
24
May 6, 2008 08:30 AM
Ogriv
1987 - 1996 F150 & Larger F-Series Trucks
6
May 25, 2006 11:23 AM