1978 20R, de-smogged, Weber 32/36 just over a year old, plugs wires cap & rotor new 2,000 miles ago, distributer 2 years old, coil one year old. Timing at around 8, set a couple months ago, valves adjusted two months ago right after rebuilt head was put on with a new head gasket.

I know the fact that all the above stuff is new doesn't mean it can't be malfuntioning, but...

Out of nowhere, I got serious hesitation one morning. From a stop, it jerked a lot trying to go forward. A feeling like running out of gas. Did that a little for a few minutes but still got to highway speed and was fine.

Since then it's been a little sputtery on & off, with an occaisional miss at idle. Getting worse as of today. It actually stalled, though it started right back up.

I think I notice it being a little jerky driving down the road, but it's always hard to tell what's the road and what's the engine.

Yesterday I put a new fuel filter in it, and sprayed the carb with cleaner. I checked all the spark plugs and they all look the same, and look good. I thought that helped, but then today, after washing it and getting the oil changed, it was there again, and it's been bad all morning. High rpms don't seem to cause it, but don't seem to cure it, either.

Any ideas?

 

Sounds kind of like a bad ignition relay. Had that issue on an old BMW would stall while driving, sometimes it would take a while while cranking to start, and hesitate under load. Replaced lots of fuel related parts and symptoms still there, then i tapped the relay and it would die. Replaced it and drove like a dream.

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The fuel pump relay?

 

Is there a way your timing chain stretched a little bit? I've done a lot of the same stuff you've done recently to my 81 22R with no change in hesitation. I think I've narrowed it down to the timing chain. I'm a broke college student right now, so I'm holding off on doing anything there for a while.

 

I have no idea. I have the dual-row chain, so I'm guessing it's not likely. But the fact that it isn't constant makes me think it's not a timing problem. A whole day of driving can go by with no issues.

But yesterday it seemed to be getting worse.

I had someone tell me that if it happens at idle, and not just under load, that it's more likely to be an ignition problem than a fuel problem. That make sense?

It definitely will happen at idle.

 

Get a visual inspection on your plugs and distributor innards. Look and feel for loose wires and cracks. Get back when convenient. See if there are any sooted out or fouled plugs or cracked insulators.

If you're still travelling through western Washington I might be able to hook up with you.

 

Plugs looked good. Distributer cap and rotor looked good.

Drove from Moab to SLC and it drove great. Might have been acting up a little once I got to town, but drove great on the whole trip up.

Thanks! I got a job in Montana for the summer so that's the direction I'm headed now.

 

Well, improper jetting can also cause issues like this. Last summer I'd have my truck purrrfect and out of nowhere it would randomly start missing and jerking at cruise. My jetting was off just one size. Keep us informed of any further problems.

I'll be in Butte for Folk Fest in July. If you're around let me know, I'll buy you a beer.

 

Ha! Nice. I went to that every year the first 3 or 4 years. Missed it the last one or two. I might make it over. I'll let you know.

 

Does it seem to happen more when it's humid out? Do you get a lot of suction when unscrewing the fue cap? Are any engine grounds lose or weak? Any way for you to replicate the exact conditions it does this?

 

The wet thing has been on my mind, since last weekend was really rainy, and it was happening really bad after I washed it.

But it was running kinda crappy yesterday around SLC, and it was dry then.

Engine grounds should be good, but I'll re-check.

No suction when I take off the fuel cap. It doesn't really even seat all that well, so I'm not sure there would be any.

So far I haven't been able to figure out a specific time it happens, but I'm payin attention trying to.

I'm still thinking that with how good it tends to run out on the interstate and under load, that maybe it's not a fuel issue, but on the electrical side, but I just don't know. It seems to be holding steady for now. Got me from Moab to SLC no problem, so I'll just wait till I'm situated up north and look further into it then.

But keep the ideas coming, if you have any. I'll look into all of it later.

 

Has this all been on one tank of fuel? Believe it or not I once had a similar problem on a 20R I had with Valero gas. It takes exceptionally poor fuel to make a 20R run poorly.

 

Nope, it's been happening over probably 7 tanks of gas so far.

 

These intermittent spasms can be a real bear. There are so many things that can cause something like this but taking shots in the dark on guesses might only confuse the issue. Hopefully some tell will present itself in due time.