86 Bronco II stuttering on hills, 55 mph - Ford Forums

Redfoot · 08-03-2004, 12:46

Howdy all.

Proud new Bronco II owner here. Please excuse my ignorance about this vehicle, but I am looking forward to learning it inside and out. The engine is a V-6, and the truck has 168,000 on it. A tune up was done 8 months ago. Here is the issue.

At idle, the Bronco is surprisingly quiet, and is responsive up to about 45 MPH. Then, when either on the highway or a hill, the truck will begine to stutter at 55 on flat, lower speeds on hills. The loss of power seems to be hit or miss on hills, but on flat ground it almost seems like there is a govenor at 55, and it causes the engine to slow down. Pumping the gas pedal has an effect, only minor though. The truck does this with 1/4 tank of gas, or full. Apparently the truck has been doing this for some time now, and the original user just avoided highway use, instead of fixing the problem.

I did a search on the site, and I ran into this thread.

I messaged headstand with no response so far, but I was wondering if there was anything else I can check. I was planning on swapping out the fuel filter, and a guy at the hobby shop on base unfortunately tells me that the closest reliable place to do an engine diagnostic is an hour away (i.e. a place that will not rape me

), so engine codes will be a no go for now. I have a Chilton's and a lift will most every tool I can think of, I just need a little giudance here.

Thank you very much for your time!

-Redfoot

laminge · 08-04-2004, 04:37

Welcome to the forums

I am sure someone can help

Redfoot · 08-04-2004, 08:06

Thanks laminge, I can't wait to get this guy roaring down the road!!

-Redfoot

laminge · 08-05-2004, 04:09

Too me it would seem to be a couple of issues

1) fuel delivery system
2) Air intake/furl mixture

89F150 · 08-06-2004, 01:35

I would also go with the fuel filter first as well. Also what are the plugs and wires like. Would they have been chagned recently?

laminge · 08-06-2004, 01:39

Just trying to relate it back to my experiences, would a faulty fuel pump be the cause? Could it be running out of fuel under those load and revs?

release · 08-06-2004, 04:37

It might be the fuel cap not letting air into the tank to replace the fuel pumped out Try driving it with the cap off or loose

cheers maca

Redfoot · 08-06-2004, 16:43

Thanks Guys, I will pick up a new fuel cap as well. The wires and plugs were changed about 8 months ago when the beast could not pass the strict Colorado emission laws. What brand are they? I do not know. Could the stuttering be caused by the plugs/wires change? In the realm of possibility, yes, for I do not know exactly how long the issue had been occuring prior to me owning the vehicle.

A bud of mine and I are going to spend some time on the lift on Tuesday.

From what I have read, we will be addressing the following.

-Air Filter (due anyway)
-Fuel Filter
-Fuel Cap
-MAP sensor
-Fuel Pump (s)

In regards to the fuel pumps, if that is indeed the problem, does anyone have a walkthrough on how to troubleshoot them to find out which pump it is? From what I have read there is more than one, a low and high pressure. Rulling everything else out, should I just replace the both of them to be safe. Also, dropping the tank sounds like a bitch of a job. Any tips?

Thanks again for all of your help!

-Redfoot

laminge · 08-06-2004, 16:48

Sorry

Carnt be of help with that

Redfoot · 08-07-2004, 16:00

Alright,

I broke down and had a fuel filter installed because I really wanted to get this baby going, and the lifts were full.

Basically, the hesitation is about 90% gone. I drove about 40 miles on the highway right after the install, and a few miles in the city after this install. I got her up to 85 on the highway, and I thought I had it licked, but then on the hill returning home (3 miles on 8 degree gradient) I got hesitation at 35 MPH. Pumped the gas, got to the top, made a u turn, went back down. Got up to 65 on a straightaway, floored it on said hill again, this time no hesitation, no problem. This was with a newly topped off tank of gas.

I am wondering if I I am still burning off some crud that may be in the line from the past filter, or if the pumps need to be checked out.

I am going to try to burn down a tank of gas with STP injector cleaner to see if that helps, and before I start dumping more money into parts that may not be an issue.

Thanks for your help, and I will keep you informed.

-Redfoot