• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Bronco dies when shifting into drive or reverse

YNOTBOB2007

Full Member
Joined
Oct 2, 2007
Messages
207
Help. 69 Bronco, automatic with Ford 2 bbl. carb. This is an issue I've had for 4 months now and can't drive it. Idle is set at 900 (high I know but trying to keep it from dying). When I shift into reverse or drive, idle drops to 600 and idles rough, then dies. Hard starting after. I've since replaced fuel filter, most gas lines, installed a new performance distributor, plugs/wires, timed it, blew out the fuel/air mixture screws on the carb, and no change. Is there another idle screw besides the big spring-loaded one on the driver side of the carb? This issue is holding me hostage from driving it! Thanks.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
If you have a stock carb there are 2 idle mixture screws under the front of the carb they are hard to see but they are there. Even if you dont have a stock carb all 2 and 4 barrel carbs have at least 2 idle mixture screws. The big one on the side of the carb is the idle speed screw. You might also have a internal vaccum leak on the intake manifold might pay to check the torque on the intake bolts.
 

66fora69er

Contributor
Sr. Member
Joined
Dec 9, 2006
Messages
479
I had a problem like that a couple of years ago and it was all timing related. would idle fine but put it in gear and it died. worth re-checking
 

reamer

Contributor
Bronco Guru
Joined
Mar 20, 2008
Messages
1,249
Timing chain replacement time! (or if new out of allignment)
 

Packham25c

New Member
Joined
Aug 31, 2010
Messages
34
Loc.
Dover, DE
Maybe your Transmission is jacked. Had the same problem, dropped the tranny and found out why...
 

Attachments

  • ImageUploadedByTapatalk1306115985.440887.jpg
    ImageUploadedByTapatalk1306115985.440887.jpg
    192 KB · Views: 92
OP
OP
Y

YNOTBOB2007

Full Member
Joined
Oct 2, 2007
Messages
207
I contacted the previous owner and he thinks it may be the fuel pump....been in there forever. I'll do a pressure test next time I'm up there. This morning it idled fine, then got worse when I put it in gear, then died. Then hard to start, and wouldn't even hold idle, even as I increased the idle screw. I had to keep my foot into it to shift gears to get it back in the driveway. By the way, what should the fuel pump pressure be at the gauge? I'm assuming I install the gauge before the fuel filters (I have 2, one clear in line, and one on the carb). Thanks for all the input. Hoping it's this and not the timing chain.
 

Explorer

Bronco Guru
Joined
Mar 2, 2008
Messages
4,390
Loc.
Raphine, Virginia
Wasn't kidding about plugging off the vacuum advance. My 76 did the same thing. Would idle and rev fine, but soon as you dropped it in gear couldn't take off. Never did figure out exactly why that fixed it, but it ran so good pluged off I quit looking.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
IF it is idling at 900, it will idle in gear, it isn't the fuel pump.

And X2 (or X3?) on the vacuum advance. If itis hooked up wrong it can do exactly what you describe. Try unplugging it and capping the line.
 
OP
OP
Y

YNOTBOB2007

Full Member
Joined
Oct 2, 2007
Messages
207
O.k. I'll try unplugging the vacuum advance at the carb. I assume I will then cap the inlet at the carb where the line was going into? It's strange this would be the problem as it's always been connected and has run fine until recently.
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,316
It's strange this would be the problem as it's always been connected and has run fine until recently.

Ding.

"What is the phrase every Bronco owner has uttered when trying to track down a problem, Alex?"
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
"installed a new performance distributor".........this here be ya problem!
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
Ok a real one fer ya whens last time you checked out ya neutral safety switch?? Some times i have to cycle mine through the gears then alls well!
 
OP
OP
Y

YNOTBOB2007

Full Member
Joined
Oct 2, 2007
Messages
207
Interesting about the NSS...I actually did cycle through all gears backing out of the driveway, then forward, then, blap blap blap, dead. Was able to start it & get it back in the driveway, where it idled even worse, than wouldn't even hold the idle. This problem started months before the performance distributor install, so that is not the culprit. I actually have incredible response and great higher, smoother revving as long as my foot stays in it. I just don't get it. Ran great until I put it in semi-storage last November. Added fuel stabilizer, and started it once a month. That is when the trouble started. I've since went through almost half tank of new, fresh gas thinking too much stabilizer, or bad gas/sediment at the bottom of my tank. I have 2 fuel filters that I've since replaced, along with the fuel lines (except for the one off the main tank).

My plan when I get back up there (Sierra foothills where it is in storage) next week is to 1.) remove the vacuum advance and see what I get. 2.) check fuel pump pressure as it's very old. 3.) remove carb and clean. It's a motorcraft from a 73. 4.) triple check timing. Thanks for all the help on the diagnosis...just miss driving it and can't get to my favorite camping spot until I figure this out
 
Top