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Peppy La Few

1645 Views 8 Replies 4 Participants Last post by  KAHruzer
Just looking for ideas here.

Can't complain, the truck's really been running good, stable.
Even getting something around 20mpg. It's become my daily driver to-from work an hour away.

The odometer's broken at 136,000 so don't know the real mileage.

I'm presuming it to be age/miles at this point, but the engine seems to lack the pep one might expect at certain points in the range, like for passing. Almost nothing there. And, after slowing down at highway speeds, I have to ease it back up to speed. Pressing the pedal more does nothing, perhaps even prolongs the acceleration.

Once I reach around 70-75 mph, it acts like it's topped out.

Otherwise, at lower rpm, it feels good, has torque et al. But, the high end is lacking.

Any ideas on what might improve that situation?

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Over the past year, it's gotten a Distributor, cap, rotor, wires, plugs, oil change, oil filter, air filter. No throttle body work at all.

Can it be cleaned in place, or are you speaking of a removal tear down? Spray-in, or fuel additive?
I guess Sea-Foam, or such, is what I mean.

I do run 87-octane real fuel, however. Really poor performance on ethanol, both mpg and pull.

I might try a tank of 91-octane just to see what happens.

And, will try a compression test when I have some time. At least a few cylinders to see what it's like.

Come to think of it, I did add some AutoRX to the oil this time. And, it's about time to change again.

Oh, one other thing. I had a one-into-two exhaust of some kind (with some throat, so it's not OEM) and one leg broke off just past the "Y", before the muffler, and has yet to be replaced. Could back-pressure be an issue here? It's a bit louder than normal right now.
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Thanks guys.

Conceptually, I'm a fan of getting more back to stock than customizing in most ways.
If the engine ran like OEM, I'd be perfectly happy. In most ways, it does. Just that aged feeling on the top.

Odd part of this, to me, is the difference in the two trips, going and coming. In the morning, cool air, the thing runs just great. Coming home in the evening, it's like a entirely different vehicle. Temps approaching 100, driving into south wind, all the hills seem higher, longer grade. Going, I never have to downshift, but coming home, I have to to get up the hills.

And, since I'm also filling up twice a week now, I can tell distinct differences in each tank of fuel. So, suspect the quality of fuel varies at least some from tank to tank. I've started narrowing my source of fuel to only two stations now and am getting improvement there.

Anyway, I suspect this truck has well over 200K on it, so age would tend to be factor today.

If I could get it to run like it does in the morning all the time, I'd be fine. Actually, I am fine, I really drives pretty darn good for a truck its' age. And, 20 mpg isn't bad either.

You could have a good point, though, on the o2 sensors. They do tend to go bad well before they show.
That could be affecting top end performance as well. But, tell me, I understood CATs do not typically ever ware out. I did just put a new exhaust system on the truck last week, but from the CAT back.

One thing. My other car, it's been sitting most of the winter since I did a major tune up on it, new plugs, wires, dist cap, rotor. Maybe 1000-2000 miles since last June. Last weekend, I found 4 of the 6 plug wires arcing out to the block (engine would barely run). All 4 of those had cracks in the heavy insulator need the plug end. The only conclusion I could arrive was that our unusually harsh winter (-15F at times) caused freeze fracturing of the insulator material. It surely wasn't from use.

Anyway, the reason I tell this story is that I think I put the same brand plug wires on my truck last year, too. So, think I'll plan to replace those again with some good ones. That should help.

Probably cheap foreign-made parts where climate wasn't well considered in material selection.
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It could be as simple as the hills being mostly down going, and up coming back.
But, I have considered that and felt it to be pretty much an equal situation both ways.
Since then, though, I do think the return trip has more longer grades than going. So, that could be much of what I'm experiencing.

I ordered new plug wires and await them. After I install them, I'll re-evaluate.
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