Weird Driveability problem

[k20]

Ok, weird problem was wondering if anyone had an idea. First the specs, 496 with a Speed Demon 850, a th400 with a 2000 or 2400 stall (honestly cant remember). Truck idles at 700 in gear 1100 in park/neutral. Now for the symptoms. Running down the road its fine, great throttle response. Regular stop and go its fine. Normally the temp runs about 185 and the trans temp is 120-140 depending on how hot it is outside.

Now here is where it starts getting odd. Sitting in 5 o'clock traffic the engine will heat up to almost 200 but no higher (not really weird). The transmission will heat up to almost 180 (that is being read at the pan btw). After sitting in this traffic, if you hit the gas, there is nothing as far as power goes. Wont rev past about 2200. Pop it in neutral and it revs loud & proud, pop it in gear and there is nothing, even starting off with the shifter in 1 it doesnt wanna pull past that 2200 mark. Also in D it seem to shift sooner than normal.

The tranny fluid is at a good level and isnt brown or burnt at all, still nice & red. Am I losing th400 #4, or is it just overheating the tranny causing these weird symptoms.

I would think vaporlock but it revs good in neutral and I have a bypass fuel system (electric fuel pump).

Any ideas?

 

[Thunder]

Distributor Module or pick up coil?

 

[dremu]

Distributor Module or pick up coil?

Mmm, especially when you say heat I think thermal issue, like the module isn't gooped to the dizzy enough, or something like that. Thermal issues in electrical systems are nasty

-- A

 

[k20]

Thats a thought, cause it has been acting kinda weird to start lately if its sat overnight. Especially if its a damp morning. *sigh* always something. But if thats the case wouldnt it stumble during a neutral rev? I mean it acts normal in neutral, blip the gas and itll zing to 4000 in a heartbeat, but drop it to D and it wont go over 2500.

 

[4X4HIGH]

These are classic symptoms of a plugged Catalytic convertor (assuming it has one).

 

[tRustyK5]

I've found dist problems can be like that. In neutral there is no load on the motor at all so it'll rev and whatever even if spark is weak or poor. Put a load on the engine and it dogs...

I'm curious about your timing too. With a stall convertor and an 1100 rpm idle I'd think if everything was tuned right and working right that in drive it'd be at a solid 900 rpm. I could always tell when my timing was too retarded in my older cars because there'd be too much difference in neutral idle and Drive idle. To lose 400 rpm putting it in drive, especially with a stall convertor seems wrong.

Rene

 

[Mike D]

I bet you are on the verge of overheating and the fuel is boiling in the carb. I would try to shift into neutral when stuck in traffic. Excess heat generated by the torque converter is adding to the problem. Check your clutch fan, it could be going bad. If it is replace it with a thermostatic type. That means as the clutch fan feels hotter air it fully enguages the fan blades rpm. This extra air volume should reduce the engine temp and allow satisfactory engine performance.
With the engine stopped, grab the fan and try to wobble the blades. If you see or feel any slop of the clutch on the shaft it is bad and should be replaced.

 

[k20]

well the problem was a broken throttle cable, the only way the throttle was opening was the plastic sheath was twisting and binding pulling slightly on the throttle. I was able to do 60mph with the throttle open 2% by a piece of binding plastic....excellent. I guess it got worse when hot b/c the plastic got stretchy.