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| Truck Stumbles at Full Throttle, But Not Part Throttle?? https://slantsix.org/forum/viewtopic.php?t=15210 |
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| Author: | Mooosman [ Tue Nov 29, 2005 7:16 pm ] |
| Post subject: | Truck Stumbles at Full Throttle, But Not Part Throttle?? |
Man, the little "quirks" of this truck are really starting to annoy me! The latest one is this stumbling. When you leave the light, or are trying to get up to speed, there is a point that you reach in the throttle position where the truck stumbles and farts really bad, but when you back off the throttle, say to 1/4 open, the engine smoothes out and accelerates normally. Even when you are cruising and "get on it" a little, the truck will hesitate and stumble badly. It almost feels like what would happen if the choke were getting sucked closed or something, but I wired the choke open to see if it was that, and the stumble was still there. Ideas? I don't think this is ignition, it feels like a carburetion problem to me. The truck is an 81 D-150, 225 slant six, auto, 1 barrel carb. The truck doesn't have lean burn, but it does have Electronic Spark Control, and a couple solenoids hooked to the carb. Thanks for any help! Nick |
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| Author: | SlantSixDan [ Tue Nov 29, 2005 7:22 pm ] |
| Post subject: | |
Faulty power valve in the carburetor is the most likely cause. Go through the carb with a rebuild kit (or toss the piece of junk Holley 1945 in the trash can and put something better on.) |
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| Author: | volaredon [ Tue Nov 29, 2005 7:23 pm ] |
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Electronic Spark Control IS Lean burn! Same thing, they just changed the name. Sounds like a dead accelerator pump in carb. |
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| Author: | SlantSixDan [ Tue Nov 29, 2005 7:36 pm ] |
| Post subject: | |
Quote: Sounds like a dead accelerator pump in carb.
Dead accelerator pump: vehicle gasps and hesitates immediately upon application of the acccelerator from a standing start. Applying the accelerator gradually, reduces the hesitation. Applying the accelerator suddenly, worsens the hesitation.Faulty power valve: Vehicle starts forward on application of the accelerator, but as soon as the accelerator pump shot is used up, the vehicle stumbles and hesitates due to the power valve not supplying enough fuel. Can also manifest as a stumble/hesitation at or above any particular throttle opening. |
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| Author: | CStryker [ Tue Nov 29, 2005 8:45 pm ] |
| Post subject: | |
Quote: Electronic Spark Control IS Lean burn! Same thing, they just changed the name. Sounds like a dead accelerator pump in carb.
Actually I have been told by several purists that it is /not/ lean burn, it's a succesor to it. ESC was worthless even on stock engines, and they frequently broke. From what I have been told, lean burn was actually much more durable set-up that was much more reliable on a stocker, but still hampered "tweaking" performance.-Chris |
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