Random hesitation at high speeds (1 Viewer)

[iptman]

Hey guys,

I made my annual Daddy Daughter trip out to Skyline Drive today in the 40 and on the way home on 66 I had a random loss of power while going 55-60 MPH. I drove out 66 this morning any didn't feel anything like it. Basically it felt like either fuel or spark totally went out for only about a second which wouldn't have been that bad had I not been going 55-60 on 66 while everyone else around and behind me was going 75-85. After it happened a handful of times over 15 miles I jumped off 66 and took 55 (which turns back on to 66 for a few miles ) to Gainesville before taking 4 lanes wide and lit up 66 the rest of the way to Fairfax County Parkway. The hesitation happened again 3-4 times in the 15 miles of 66 before jumping off and once more on the parkway. Anyone have any thoughts on this? The only thing different between before and after, except ~100 miles of Skyline Drive is I topped off the tank with 8 gallons of Non-Ethanol Liberty 87 in Front Royal. I don't know if I've ever experienced bad gas but I wouldn't think only slightly more than half a tank full would effect it this much. The 40 ran fine this morning on 66 then 35-40 MPH the rest of the day down and up Skyline Drive.

 

[Stumpalama]

Throw some seafoam or drigas in the tank and run it. It could be bad gas.
Also, check your dizzy and rotor and plugs and plug wires. You could be trowing spark around the dizzy.

Check your battery connections and grounds, battery and engine grounds.

Was it like a dead pedal or a buck and hesitation?
Did you get any after fire, like a pop from the muffler at all?

 

[John Smith]

In addition to the above. Check your fuel filter for rust debris. When it does the stutter thing, pull over immediately and shut down the engine and check the fuel level in the carb sight glass. It sounds fuel starved related to me. When I had my old rusted tank, it would run fine at low speeds with partially clogged fuel filters. Yes, I ran two filters to keep rust particles out of the carb. But when I tried to hit 55 it would stutter and start to cut out.

 

[iptman]

Was it like a dead pedal or a buck and hesitation?
Did you get any after fire, like a pop from the muffler at all?

The feeling was as if I had completely let off the gas petal. No backfiring or popping out of the exhaust that I noticed. The fuel filter is the OEM metal can version so out of luck checking it for debris. I did put a new one in when I bough the truck 2+ years ago.

 

[emorth]

If you think it might be an intermittent ignition circuit, I have a device to detect momentary power loss. One less variable to consider.

 

[Stumpalama]

Check the coil for ground arcing as the coil goes bad, it starts to find other paths to ground since the resistance gets so high inside it.
There could be evidence of arcing from the main plug wire to the negative post on the coil.

 

[Stumpalama]

The feeling was as if I had completely let off the gas petal. No backfiring or popping out of the exhaust that I noticed. The fuel filter is the OEM metal can version so out of luck checking it for debris. I did put a new one in when I bough the truck 2+ years ago.

How long were the episodes in duration? You can cut a steel filter open and check for debris. Just do it over a bowl

 

[Devilmans Hand]

What type of ignition system are you running?

The power supply side to my coil would sometimes come unplugged and kill the engine.

I'm thinking that rust and crap from the tank would cause a weird surge or bucking instead if immediate loss of power.

Sometimes if I'd lay in the throttle under load then heavy brake in neutral the engine would die completely, but that went away when I properly adjusted the power valve.

I'm thinking electrical.

 

[iptman]

How long were the episodes in duration? You can cut a steel filter open and check for debris. Just do it over a bowl

It was really only a second or two before getting back to normal. Not even enough time for me to let off the gas.

 

[iptman]

What type of ignition system are you running?

The power supply side to my coil would sometimes come unplugged and kill the engine.

I'm thinking that rust and crap from the tank would cause a weird surge or bucking instead if immediate loss of power.

Sometimes if I'd lay in the throttle under load then heavy brake in neutral the engine would die completely, but that went away when I properly adjusted the power valve.

I'm thinking electrical.

I'm running the stock 77 ignition which is a coil with igniter and a points distributor. I replaced the cap, button and wires when I got the truck. I did get replacement points but I didn't/don't understand how to install them.

I haven't had time to drive it or look at anyhing since Sunday. Hopefully I can this weekend.

 

[iptman]

If you think it might be an intermittent ignition circuit, I have a device to detect momentary power loss. One less variable to consider.

I think I'll take you up on that. I'll text you if I can "work from home" one day this week.

 

[emorth]

Ok, let me know.

If the coil is old I would replace it. As Stump mentioned, they fail from old age (I can relate), the insulation breaks down on the high voltage wire inside the coil and on the cone on top of the coil. The condenser can also fail from old age. Had personal experience with both crapping out, at different times, on my 1974 Cougar. Also had the rubbing block break off of the points on my dad’s 1973 International pick up on I-81. Oh the joys of pre-electronic ignitions.

Suggestion, Take a spray bottle of water and with the engine running in the dark spray a light mist of water on the ignition coil, distributor and wires and look/listen for arcing.

Did the power loss occur when the engine was under load (accelerating or going up a hill)? The ignition system works harder when the engine is under load (more fuel in the cylinder, higer resistance at the spark plug gap) and thus it is more likely to fail because the arc finds an easier path to ground.

 

[Stumpalama]

Do yourself a favor and ditch the points. I have a small cap electric dizzy on the shelf...

 

[Blue77FJ40]

The feeling was as if I had completely let off the gas petal. No backfiring or popping out of the exhaust that I noticed. The fuel filter is the OEM metal can version so out of luck checking it for debris. I did put a new one in when I bough the truck 2+ years ago.

You can grab two hose clamp pliers as shown and pull off the filter and see through enough to spot rust build up. If you don't have a spare fuel filter on hand (something all FJ40 owner should have), then extend the old filter's use by tapping the inlet side down to jar loose some of the buildup. And by all means, follow John's suggestion an add a second fuel filter. One of those glass units with replaceable inner filters are ok if you can find them. Otherwise, employ google for alternatives.

 

[John Smith]

I didn't realize you still were running points. It's the points. They are easy to swap out, and if you are going to keep running them, you should always keep a back up set in the glove box.

 

[iptman]

Did the power loss occur when the engine was under load (accelerating or going up a hill)? The ignition system works harder when the engine is under load (more fuel in the cylinder, higer resistance at the spark plug gap) and thus it is more likely to fail because the arc finds an easier path to ground.

I do recall it happening when I was accelerating to keep up with the flow of traffic or going up the slight inclines at the beginning of 66.

 

[iptman]

I didn't realize you still were running points. It's the points. They are easy to swap out, and if you are going to keep running them, you should always keep a back up set in the glove box.

There's no adjusting or setting the gap or anything like that? It seemed like there needed to be some precise measurements done to make sure they worked right. I do also have a NOS coil I found on ebay a while back but it'd be nice if this was just the points acting up.

 

[Jakes40]

There's no adjusting or setting the gap or anything like that? It seemed like there needed to be some precise measurements done to make sure they worked right. I do also have a NOS coil I found on ebay a while back but it'd be nice if this was just the points acting up.

You adjust it with a feeler gauge. But I would take Stump up on hid offer! Get rid of the points dizzy. Go to electric.

 

[Stumpalama]

There's no adjusting or setting the gap or anything like that? It seemed like there needed to be some precise measurements done to make sure they worked right. I do also have a NOS coil I found on ebay a while back but it'd be nice if this was just the points acting up.

You should keep a coil handy anyway. Easy to swap in, but a show stopper when it goes out in the middle of nowhere... I know from experience.
Throw some points and some fine sandpaper paper in the glovebox with a feeler gauge too.
It looks like points need to be checked and reset about every 5-8k miles... They can be filed or sanded as well to extend their life.
Though, again, I would just go electric for reliability and ease of maintenance. Keep your old dizzy and coil in a box in the garage, if you are concerned with keeping it "original".

 

[76FJ40]

If you stay with points look for a dwell meter on ebay or CL. Easier to use than a feeler gauge unless you have developed "the touch".