Hi all,

I have a 1986 F350 4x2 with a 7.5l engine.

I recently replaced the ignition control module on this truck after It would not start. It fixed the problem however after doing so the truck started to sputter when trying to accelerate after a complete stop. It was also doing this while driving at low speeds 10 -15 mph. The other day it was doing it and backfired REALLY loud. Actually scared me cause it caught me off guard.

My first thought was that it was carburetor/fuel related. It seemed to get worse the other day while sitting in the drive idling. It was acting like maybe the timing was off or it was missing.
Ok so I thought one of the wires might be bad and started checking, one seems to be slightly loose at the spark plug but I did not check anything else. YET
My first thought was to check the timing. Its not running THAT bad just not as smooth as it was prior to changing the module.
I was trying to find the marks ON THE HARMONIC BALANCE but cannot seem to locate them. I did find a mark on the front side (facing the radiator) but after putting a dab of white on the mark and the timing light on it, its way way off the pointer. Way retarded. with the light on (on cyl wire 1) the mark shows way to the left (passenger side) almost at a halfway point on the balancer at about the 9:00 position. How can this be? I must have marked it wrong? but the mark I highlighted is the only one I can see.

Anyone have any thoughts?

 

Are you taking the vacuum line off the dist?

 

Hi,
Yes I also have the air filter assembly off and that line plugged as well

 

The 460s in these years are famous for the harmonic balancer turning on the rubber. You most likely will find replacing the balancer will fix your problem. If the rubber gets to bad the balancer will come apart causing possible bad damage. That was one of the first things I had to do on my 86 after I bought it in 1998.

Craig

 

X2.....The balancer spun on the rubber.
Try some sandpaper on the outside circumference of the balancer to make the marks show up.
If the truck backfired you likely blew out the powervalve in the carb and it is now running WAY rich.

 

Thanks for the replies. So what I would like to do is have someone confirm where the marks are on the balancer or pulley because as I stated I could only see one. Until i confirm the placement of these marks I will not know for sure if that reading (9:00) is a result of the movement or just out of time.
Honestly I haven adjusted a vehicles timing in so long I don't THINK its running consistent with it being that retarded but I certainly could be wrong. This morning it was running (idling) fine a tiny bit rough but very good. I'm going to drive it later this morn and I will post the results.
My feeling is that those of you may be right about the slippage. I'm assuming that if it did slip this WOULD NOT effect the performance of the vehicle like in my original post.? Really all that is happening is the balancer has rotated and is giving me a false reading on the timing light. Is that a fair understanding.
Thanks again for your help.
J

 

Assuming your car was set right and the balancer slipped, it shouldn't affect performance (unless it slipped off!)

What kind of cars are you used to timing? One problem I had when I First timed the truck is that #1 is on the right side of the motor. On Chevy's it's on the left, and that's all I ever timed. So I thought my timing was WAY off...

 

Yea good point Jim. The 4180s do not have backfire protection unless someone installed it. Holley didn't start installing them from the factory until 1992. To determine if the timing marks are on. Pull the dist. cap turn the motor to #1 & the timing marks should be right there at the pointer. If not the dist is off or the balancer has spun. While your at it. when you turn the motor by hand to check turn it backwards & see how much play you have in your timing chain. If the crank turns more than about 3/4" before the dist. moves you have a wore timing chain also.

Craig

 

^^^^
Good point.
The stock timing gears have nylon teeth and as these wear the timing gets sloppy (under 60k in my experience)
The plastic bits also clog the oil pump pickup!

Another way to tell is to hook up the timing light and rev the engine then let the throttle snap closed.
If the marks jump around, instead of retreating smoothly, you are witnessing the chain flailing around inside the timing case.

 

Wow lots of options. Thank you all for the replies. Yesterday I went ahead and played with the timing a bit just to see how the truck would run when i got close to the proper time settings.

It was not that much different just slower. By that I mean it was idling slower (duh) I couldn't get it all the way to 8 degrees but I got pretty close and it was, again running about the same just slower rpm. I didn't tweak the idle cause I couldn't remember when in the process of timing that should be done if you timing is off. I did make sure to check and set the idle to 650 as the truck says before reading making any changes. I don't know..now Im getting...

KERM wrote: "To determine if the timing marks are on. Pull the dist. cap turn the motor to #1 & the timing marks should be right there at the pointer. If not the dist is off or the balancer has spun."

Isn't this the same thing I'm doing only with the timing light? I'm not trying to be a smart @#$ but..hmm wait..you may have something here.. no I don't think this will work. cause either way, out of time or slipped the marks are not going to line up with distributor.

Juts wanted to remind everyone, I recently replaced the ignition control module on this truck that's when all this started. It NEVER HAD ANY OF THESE SYMPTOMS BEFORE.

This might be something..when I turn key to start, initially it sounds like the battery is very low as its starting to turn over and then starts just fine. This is all in the same key turn. I don't know how else to describe it. Its like it labors at first from lack of power in battery and then kicks over. It feels and sounds just like RIGHT before you try to start your car and the battery is low..next key turn you get clicks..only with mine its starts ..hope this makes sense.
I replaced the solenoid switch about 5 months ago.

I'm going to check some other things mentioned. At this point I'm leaning towards it being distributor related..Cap-rotor-plugs-wires if not at least I can eliminate them after closer inspection. The truck has 83,000. orig miles at this time, was leaking oil from a loose valve cover but this thing runs like well... a well maintained truck with 83,000. miles on it. This is the first issue I have had with it since purchasing it last year.

Thanks again I will be back with updates..

 

No, this will tell you whether or not there is an issue with your timing chain or harmonic balancer.

Make a mark on the dist base where the center line of the #1 post is, take the cap off and spin the motor until the rotor is lined up. Your timing mark should be reasonably close to 8*.

If it's not, you'll know there's either a problem with the timing chain or with the balancer itself. Timing chain would be off a few degrees. Balancer...could be anything.

 

The truck will labor to turn over on the starter if the timing is too far advanced, this is why the DSII system has ignition retard while cranking.

 

Hey guys,

I had a long post ready and the power went out here (Bakersfield, CA) we had 40mph winds and plenty of rain. so it was lost.

I was going to apply the suggestions but had to drive the truck yesterday so just put everything back and started it up. I did find a vacuum hose that was not connected and another that was going to the wrong place so put those right.

Thing is they were like that before all this started so Im at a loss about that. I will post details of what they are later. But yesterday whey I drove it it ran pretty much like before all this started. ABSOLUTELY NO HESITATION, started easy ran great.. Its still idling slightly rough..very slightly.

Oh and I did end up finding marks on balancer I highlighted them and put the light back on. They are showing up almost directly behind the water pump almost dead center of the motor? I know to do a proper timing adjustment there are other things to tweak but I can never remember what sequence that is. If someone could direct me to a thread that outlines this I would appreciate it.

Im gonna leave things as they are for now. I will try again next week to tweak it further. My daughter is away for a visit with grandma so Im gonna be busy remodeling her room. Hey its raining and wet so cant work anyway.
For now its running fine that's good enough for this next week to go back and forth for materials.

Thanks for all of your help. I will get back on it next week.

 

To set the base timing, warm your truck up until it's no longer on the fast idle, and pull/plug the vacuum hose for the timing advance can.

Then set the timing as normal.