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Stalling on hard acceleration - UPDATE 13DEC (post 7)

longbedder

longbedder

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Vehicle: 1994 Burb, TBI 454 with Whipple blower

Problem: Very infrequent backfire/stall when I'm already at speed and punch it. It's happened three times.
  • The first time I was cruising at 60mph, and pushed the pedal about halfway down to get around someone on the freeway. It backfired, belched a puff of black smoke out the tailpipe, and stalled. While I was coasting, it caught again and ran fine.
  • The second time, I was coming down an onramp, accelerating, and it backfired and stalled. I had to pull over and crank it to start. It then ran rough for about 10 seconds and smoothed out.
  • The third time I was doing 40mph, and punched it. Backfired, stalled, and I had to stop and crank it to start again. It ran rough for 10 seconds and smoothed out again.
It goes weeks in between episodes, and is therefore tough to diagnose because I can't recreate the problem easily. Any ideas? I had replaced the O2 sensor in between episodes 2 and 3 (not to address the problem, just routine maintenance) - otherwise nothing has changed.
 
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How long have you had this set up? Did you do anything to increase the amount of fuel that would be required to run the whipple? Im not sure but more air would require more fuel right? Sounds to me like it is leaning out when you hammer down.
 
The Whipple has been on there since I've had the truck, and this is a new/recent problem. The blower system comes with a replacement PCM chip, which changes the fuel map to accomodate increased airflow.
 
My first thought, is the tps has a dead spot, and only shows itself when the throttle is right on it.
 
longbedder said:
The Whipple has been on there since I've had the truck, and this is a new/recent problem. The blower system comes with a replacement PCM chip, which changes the fuel map to accomodate increased airflow.
Click to expand...
I would start by checking for the obvious vaccum leaks then the voltage that the tps switch is putting out. A good repair manual should tell you what the reading should be. Just check it with your voltage meter and make sure that it steadily increases as you move the throtle. There may in fact have a "dead spot" like mentioned above. I've never seen one but I don't see why that couldn't be the case. I've seen them freeze up and stick in one position. Then I would check for a clogged fuel nozzle. I do beleive that your problem is fuel related.
 
I would agree that it's probably a fuel delivery issue. I guess I'll start with some TPS diagnosis and go from there. The only down side is the blower makes it a relative PITA to get to the throttle body hardware (small price to pay for the benefit, I s'pose...).

Anyone know the symptoms of a weak/dying fuel pump? Is it all or nothing with them (i.e.: I wouldn't be able to restart)?
 
I'm still having the same problem, with a brand new TPS and O2 sensor.

Is this the sort of thing that WinALDL would help me out with, if I was running a log while the problem occurred?

Any thoughts/experience on ignition issues with 94 TBI?

This is a b!tch to diagnose, as it happens fairly infrequently (but almost always on the freeway) - decidedly NOT COOL!
 
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