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Not 100% sure this belongs here and not under ENGINE (in fact I'm very much hoping it doesn't!) but looking for a little advice troubleshooting a new problem I've been having. I'm seeing a noticeable (50% or more) loss of power from the pedal to the wheels, which seems to be getting worse. At first I noticed this only in the lower end of 2nd gear (I generally skip 1st gear entirely on-road), but yesterday I saw it expand into at least 1st-3rd gear. There is an occasional surge where it either temporarily or more permanently seems to regain normal power to the wheels, but without that I was craaaaaawling up the hill to my house with almost no acceleration even down in 1st/2nd with the pedal to the floor. The engine was NOT over-revving in that situation, btw.

All of this is pretty consistent with imminent clutch failure that I've experienced in other cars, but I'm hoping there are other diagnosable answers because that's pretty much my worst-case I think in terms of cost/my own ability to fix it. Carbs were cleaned not that long ago and the fuel pump was replaced (by me, so maybe borderline incompetent).

If the engine isnt revving up while you lose perceptible power, then it isn't a clutch slipping. Sounds like an engine issue to me. Fuel delivery would be the place to start. Fuel tank (red death), fuel filter (check for red flakes of tank liner), pump, cracked lines, and go from there to air issues, etc.

Good point. Not sure if they're a culprit or not but the lines probably do need replacing. The other stuff (other than the tank, haven't dealt with that) is easy enough to quickly check.

I don't think I would over look the braking system. Check to make sure a shoe has not come off or that the parking brake is not hanging up a bit. I had a parking brake put my pinz into a terrible slide on the freeway after feeling like it lost all sorts of power, then as the pads expanded from the heat it just locked up. the parking brake was only slightly engaged but it caused the pads to heat up and expand enough to stop the truck completely.

I've definitely experienced that before -- horrifying at highway speed! -- so I'm pretty damn careful about making sure the brake is disengaged before I go anywhere. But it is a bit finicky.

I had the throttle linkage under my calf go bad (don't remember if it was rust, or just why) but I remember that I was only getting partial power with the pedal floored and I had to replace the rod between the pedal lever and the hand throttle linkage to fix it. First check if the linkage is working right (simple and easy to check), then go on to more advanced possibilities. Check for brake dragging by temperature of drums or parking brake housing. Check carbs and spark. If you get good idle but poor power/performance with lots of missing then check the 4500 rpm box.

Do you get high rev's in neutral e.g. no load? That would at least
eliminate a linkage issue.

If it comes down to, it ain't fuel delivery or Red death, etc etc etc,
then a good check of the vital signs would be in order -- Spark, advance,
and a compression test.

For instance when was the last time the valves where adjusted?
Exhaust valves wearing into the seat could hang open slightly
and there goes all your power -- been there done that

I'll have to look into that. For some reason it seems I always end up posting these things right before I leave town or get insanely busy and have no time to immediately check into it.

Bizarrely, the problem seems to have disappeared. I put about a mile on it just now to try and diagnose, and had nothing like the issue I had the other day (which was about 8 miles). Weather today is maybe 10 degrees cooler, otherwise no real changes. Took some steep hills as well as getting it up into 3rd and 4th.

I guess this lends some credibility to the parking brake theory, but like I said I'm usually pretty attentive to that these days.

I suppose the disc linings could be coming apart and causing it to bind... even with the handle all the way released?

I wasn't going to chime in until you said it resolved itself...

My 4500 limiter did eventually go bad, but the issues I had would come and go at random, might be something to look at it the gremlin comes back...

My 4500 limiter did eventually go bad, but the issues I had would come and go at random

Usually when the rpm limiter box goes bad, the biggest symptom is heavy missing as the throttle is opened. This does result in greatly reduced power but the missing can be so bad that you think it won't be able to keep running - but usually it idles just fine. Didn't sound like these were his symptons, though.

Problem is, regrettably, back.

I guess the best way I could describe it is very much being like overgeared. It happens most prominently uphill. Even on a very gentle hill, there's a noticeable bogging of power. Unfortunately, I live on a fairly steep hill, and last night had to throw it into 1st gear to get up it -- which promptly died out. Typically, I have been able to climb this hill without trouble in 2nd gear.

I was able to start it back up and get over fine. Interestingly, resetting the gas pedal seems to temporarily fix the problem, a lot of the time. Let foot off, put foot back down... power surges back. Sometimes.

No smoke, no smells I can detect. Makes me think it's a fuel issue. The truck does have trouble starting when pointed uphill, and none while downhill. To me that makes me suspect the fuel pump. I replaced that about 6 months ago with a compatible VW Type 1/2 one, but it was off ebay... maybe it's just not cutting it? Unfortunately I also replaced my clear fuel filter with a solid metal one, which means it's not easy to see at a glance if I've got red death or something going on. But, aside from the lines themselves (which I may replace just to have done so) and the tank, the whole fuel system was basically replaced within the last year.

Same with a lot of the ignition components, which also seem like they could be part of it. This may make me bite the bullet on the PinzSSI, although I bet that's not all of what I'm dealing with.

Possibly carb bowls draining too quick? Need to check levels

If you are in the LA area would suggest you contact Jim at Goatwerks and have him look at the situation. Don't know if he does house calls but if you want your truck up and running and a general look over there is no one better in Southern California. Very knowledgeable and reasonable. Your problem will be diagnosed quickly and resolved. His knowledge and experience is deep but not free.

Cheers,

Scott