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Bronco stutters and backfires.

badkarma

Jr. Member
Joined
Aug 16, 2010
Messages
167
While driving sometimes at shift points or a bump it seems like fuel pump or ignition shuts off. It has a Holley avenger efi and there are no exhaust leaks as installed a new exhaust 3 days ago and I am looking good on that end. Idles fine and this is intermittent issue but frustrating.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Interested to see what kind of answers anyone might have.
To start the ball rolling though, what else is attached to it? New wiring, or original? New fuel lines and tanks, or old? External or internal fuel pump, or remote reservoir?
What transmission and engine?

Did it do this all along, or start more recently? Did you buy it with the EFI installed, or was it done while you owned the vehicle?

Paul
 
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badkarma

badkarma

Jr. Member
Joined
Aug 16, 2010
Messages
167
External pumps still dual tanks. I have a c4 and it is a 347. Sometimes it runs like a top this vehicle was a complete build. 1500 miles on Odometer since completion.
 
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DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
New gas tank by any chance? Maybe the fuel filter is plugged?

Flat tappet cam in the new-ish engine? If so, was it broken-in properly at the first fire-up? If a roller cam, not an issue.
Also, if a cam problem it would run poopy all the time, so likely not an issue.

Fuel injection? (you said pumps) If so, what type?

Paul
 
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badkarma

badkarma

Jr. Member
Joined
Aug 16, 2010
Messages
167
Great questions which force me to look at it. It is a roller. Will ID pumps? When it stutters the speedometer completely drops then resets so I am seeing a shutdown or loss of connectivity. When I look at the voltage meter on a separate gauge it shows constant no fluctuations. Thank you for your time
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Haha! Good one. Probably insensitive and politically incorrect to someone somewhere of course. But two of my best old buddies used to stutter pretty badly, and would probably laugh out loud seeing that.

Paul
 

1strodeo

Squirrel Watcher
Joined
Sep 15, 2016
Messages
3,596
Loc.
Wisconsin
Haha! Good one. Probably insensitive and politically incorrect to someone somewhere of course. But two of my best old buddies used to stutter pretty badly, and would probably laugh out loud seeing that.

Paul

Humor is usually all I have to offer in the Tech section %)

Good luck badkarma! (Hopefully those don’t cancel each other out) ;D
 

Mikesimp70

Full Member
Joined
Jun 20, 2017
Messages
341
While driving sometimes at shift points or a bump it seems like fuel pump or ignition shuts off. It has a Holley avenger efi and there are no exhaust leaks as installed a new exhaust 3 days ago and I am looking good on that end. Idles fine and this is intermittent issue but frustrating.

Sounds to me like you are losing ground. Do you have battery ground to engine, frame and is frame tied into the tub?
 

B RON CO

Contributor
Bronco Guru
Joined
Jun 29, 2016
Messages
2,412
Loc.
Statesville, NC
Hi, if you have a tach on the coil lead I would unhook it. A bad tach could cause your ignition to cut out. Good luck
 

Master Chief

Contributor
Bronco Guru
Joined
Nov 24, 2006
Messages
1,199
I ran into this issue on mine at about the same mileage that you have on yours. Are you running a stock Duraspark distributor by chance? If so, pull it out and see how much play (lateral and up/down) you have in the shaft. Mine was a NAPA reman and had movement in all directions. Not sure how the engine continued to run because it was so bad. Anyway, a new distributor solved my problem.
 
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badkarma

badkarma

Jr. Member
Joined
Aug 16, 2010
Messages
167
Sorry for late response.I was on the road for a couple of weeks. I appreciate the responses. I have the msd 6 al. I posted wondering if speed sensor going bad could cause this or bad 02.I am going to try to see how to data log this weekend as it will hopefully point me in right direction. P.O. is no help and I did not receive handheld tuner for it.thanks frustrating to say the least
 
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badkarma

badkarma

Jr. Member
Joined
Aug 16, 2010
Messages
167
Looking at the tach issue and will look at all my grounds. I was thinking that may be a strong possibility
 
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