Loss of RPM after revving engine

[sds292]

First let me say THANKS to all the great people and information found on this site. I can not imagine owning a vehicle of this type without the access to this information. Now the problem: Truck starts great and easy, idles fine, but if I rev it up and let off the pedal quickly the bottom falls out and usually stahls. This can even happen on the road if I put in the clutch with the RPMs above 2000. Clean fuel, no leaks (that I have detected). Thoughts?

A special thanks to Barrman. Thanks to him I was in and out of the DMV in less than 15 minutes. His info on Texas titling was excellent.

 

[glcaines]

I would recommend changing all fuel filters before trying anything else. Make sure the in-tank fuel pump is working when bleeding air out of the vent. I suspect you are starving the engine for fuel due to clogged filters.

 

[sds292]

Thanks. Fuel pump is working. I have the filters and was going to replace this weekend, but was looking for confirmation. When i got her the pump was not working. The fuse had been wrapped with foil from a gum wrapper. I did a direct wire and added in line fuse. Pumps starts right up with the power switch.

 

[Heavysteven]

I agree new filters, I'd open the drain valve on my primary with the engine not running to confirm my pump is running.

The primary was easy loosen the bolt leave the wrench on the bolt and spin I off from below.

The secondaries work same way loose bolt on top remove canister.

One more thing Baldwin filters are the way to go. I don't care for the napa's.

Hopefully this will fix it, if not post back there are some experts on this website

 

[cranetruck]

So, when you let go of the pedal after revving it, the rpm falls below idle and dies.
I'd take another look at the linkages around the IP, how is the shut-off mechanism working?

 

[sds292]

Loss of RPMs

Yes, if you let off quickly it dies more often than not. I did check around the pump and did not see any signs of leakage or potential air gaps. The shut off works great. A slight outward pull shuts it right down.

 

[cranetruck]

Yes, if you let off quickly it dies more often than not. I did check around the pump and did not see any signs of leakage or potential air gaps. The shut off works great. A slight outward pull shuts it right down.

Yeah, shutting it down doesn't seem to be the problem.
It's what the lever does when the engine is running that's the question, does it stick in the "off" position more or less?

 

[sds292]

Loss of RPMs

Sorry No it seems to go back flush to dash with a quarter turn. but it is something I will definetly check more closely. Thanks.

 

[mhassett]

sds292;
What is your idle speed?
Try turning it up a little, say 700 RPM.
I have one that I had to set at 800 RPM to prevent stalling on relerase of throttle.
Hope this helps.

 

[stumps]

Yes, if you let off quickly it dies more often than not. I did check around the pump and did not see any signs of leakage or potential air gaps. The shut off works great. A slight outward pull shuts it right down.

It should take more than a "slight outward pull" to shut your engine down. You should have to pull the cable out a little more than 1 inch. There should be significant spring tension.

-Chuck

 

[AceHigh]

So, when you let go of the pedal after revving it, the rpm falls below idle and dies.
I'd take another look at the linkages around the IP, how is the shut-off mechanism working?

That is what happened to me to cause this. A quick (and free) fix cured it- the shut-off had jumped out of place.

 

[Barrman]

Glad you got it titled and on the road.

As stated above, idle speed, fuel filters, air filter and the shut off all need to be right. Mine when I got it would go great until I had it at speed for more than 30 minutes. Then it would die if I pushed in the clutch. Fire right back up if I gave it throttle though. I had to turn my idle up just a little and that problem went away. Did all new filters as well.

However, I still have to give mine 2 clicks on the hand throttle or just a toe wiggle to start it hot or cold, every time. You just need to learn the personality of your truck.

 

[jonesal]

I have this same problem. Any chance of helping me locate where in the TMs the adjustment procedures might be? Both for idle speed and how the shut off is supposed to be adjusted ("just so") in the IP? I have a picture in my head, but some more info from the TMs might prior to diving in.

Thanks,
Allen

 

[sds292]

Loss of RPMs

Thanks to all. The idle is about 850-900 +/-. I will check the shut off cable tension. It pulls out about 1 1/2 - 2 inches and locks into place. I really like free fixes! You are definetly right about the personalities, but I wouldn't want it any other way.

 

[pyrogod117]

I know this doesn't belong in here, but my car does the exact same thing. It just about stalls then recovers. Fuel filters?

 

[stumps]

I know this doesn't belong in here, but my car does the exact same thing. It just about stalls then recovers. Fuel filters?

Gasoline? Diesel? Fuel injected? Carbureted?

-Chuck

 

[pyrogod117]

Gasoline? Diesel? Fuel injected? Carbureted?

-Chuck

Gasoline fuel injected.

 

[stumps]

Fuel filter problems usually result in poor operation when high fuel flow is required, such as during high speed operation. Even a very clogged fuel filter will allow idle speeds.

Modern computer controlled fuel injected engines are very complicated things. Since it is pretty certain that the manufacturer got all the bugs out of the computer program before the car was sold... except for maybe sudden acceleration problems ... something has probably changed since the car was made.

One common cause of poor return to idle characteristics is all of the ethanol the gas companies to put in gasoline. I have seen TSB's describing these problems, that tell the mechanic to tell the customer that it is just the gas, and won't cause any harm.

A clogged air filter will exacerbate the problem, because the computer will be forced to reduce the fuel mixture to prevent catalytic converter failure.

Is your Check Engine light lit?

-Chuck