engine stumbling on acceleration - F150online Forums

Go Back   F150online Forums > Powertrain & Mechanical > V8 Engines
Log In 

engine stumbling on acceleration

Thread Tools Search this Thread
Old 04-02-2001, 07:57 PM
Junior Member
Join Date: Apr 2001
Location: San Rafael, CA. USA
Posts: 3
Unhappy engine stumbling on acceleration

I just posted a message where I stated that the engine on my 1979 F-150 Lariat missfired.

To clarify, it actually is more of a stumbling at about 1700 rpm. The speed is irrelevant when this happens. Also, a tuneup was done - new spark plug wires, distributor cap etc.

Mechanics haven't been able to find the problem. Since it has 93,000 miles, I wonder if the fuel pumps are worn - since I believe there is one for each of the two tanks. However, since this happens regardless of which tank I am running on, it would really be a coincedence if both are giving out at the same time.

Thanks for any input.
Reply With Quote
Old 04-02-2001, 08:12 PM
Senior Member
Join Date: Feb 1999
Vehicle: 2001 Ford F150
Posts: 2,233

Does this happen only at 1700 rpm or at all higher rpms?

Try changing your ignition coil if that wasn't changed. It could be on the verge of burning out. It's cheap and probably due to be changed anyway if you haven't done it yet. When they get old, they don't put out enough voltage to produce enough spark at higher rpms.

If it's a fuel pump problem, it's highly unlikely that it's the pumps in the tanks. They are very dependable since they're constantly cooled and lubricated by the gasoline. Of course if you run out of gas often, then they'll poop out much sooner, but to have both go at the same time is quite improbable.

It could be the main engine fuel pump giving out. I think your engine still has the "old fashioned" engine driven mechanical fuel pump. If the diaphram is going bad, then you'd most likely have gasoline leaking into the oil pan which will raise your oil level, so check to see if your oil level is rising.

Try changing the fuel filters. I don't remember where the main fuel filter is on the older trucks. There might also be a filter at the fuel transfer valve that could be clogged. There should also be a filter where the fuel line goes into the carburetor. It's probably a bronze filter and if it's clogged, you can easily remove it and clean it out. This one only comes into play when the main filter media fails.

Reply With Quote
Old 04-02-2001, 10:04 PM
Junior Member
Join Date: Apr 2001
Location: San Rafael, CA. USA
Posts: 3

Thanks Dennis - I think it may be the primary fuel pump, since it hasn't been burning any oil - haven't had to add any for the last 10,000 miles or so. I will check it out. Thanks again.
Reply With Quote


Similar Threads
Thread Thread Starter Forum Replies Last Post
5.4 issues - misfire Chalk V8 Engines 14 11-03-2015 12:50 PM
2005 5.4 "Project" data_engine V8 Engines 2 08-06-2015 10:52 AM
2004 5.4 Air/Fuel mixture off??? silver fx4 5.4 2004 - 2008 F-150 3 08-05-2015 07:55 PM
Stopped shifting normally delu Transmissions 3 07-27-2015 06:20 PM
Rough Idle while in gear, surging under heavy acceleration kolik 1997 - 2003 F-150 7 07-10-2015 11:04 PM

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off

All times are GMT -4. The time now is 08:50 PM.

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Fordé is a registered trademark of the Ford Motor Company