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Random power loss - rpm limiting

jtrux

jtrux

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Jan 14, 2007
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San Antonio, TX
So, yesterday I was driving in from out of town in my '91 V1500 (TBI 350/NV4500) and traffic started to slow so I down shifted to third and when normal speed resumed, I began to accelerate and it had nothing. I was probably going 25 and it was struggling to get to 35. I exited and was going to pull over and investigate but decided to stay on access roads the rest of the way home.

As long as I didn't lean on the go pedal too hard and kept RPM's down, it was OK. Still struggled a little and I could feel something off but couldn't place it.

I parked it and haven't looked at anything. Was gonna start with fuel filter, but that seems unlikely since it just happened instantly, but I'll check anyways.
 
You could check the spray pattern of the TBI as well.

What's the fuel level?

At this stage there are a ton of things it COULD be. Checking fuel pressure (visual via spray pattern is somewhat of a way to do this) would be one of my first checks though.

Check engine light works, and functions properly?
 
Half a tank of fuel.

Pump is putting out 15psi.

Not a single other indicator.
 
My V3500 had a clogged fuel filter years back. Started fine, ran fine but would not rev very high. Had to short shift each gear. New filter, ran perfect since.
 
Could be water got in the gas tank and is clogging the fuel filter,or there is enough to dilute the gas and not supply complete combustion..

Another possibility is if you have a catalitic converter,it may have had its guts come loose and is restricting the exhaust flow..
 
Cat came to mind as I was typing my original post. I will snake my cam down there and see I can see anything.
 
Check out the ignition. A cracked wire (or one that has gotten intimate with the exhaust) can run OK at no load and fall flat when the speed/load increases. Other parts of the ignition can do similar.
 
Yes,I remember my dad's '68 Chevelle wagon refused to pull a load one night,I stopped for gas,and it started right up,ran perfect--but when I put it in drive and tried to pull away,it just snuffed out!...

I found the distributor rotor had burned thru,under the spring,and the spark would jump to ground to the distributor shaft when you put a load on the engine..luckily my dad kept an old cap & rotor in the car for spares,it ran great again after I swapped the old rotor on it..felt like it had a lot more HP too,it must have been failing for awhile..

A bad ignition coil can do that too,usually after it heats up..
 
My truck did something like this and it was the ignition module inside the HEI distributor. Don't know if you're running that setup or not.
 
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