For some reason my truck often idles very low (maybe 300 rpms?) yet other times it idles fine. When it happens I have to keepd my foot on the go-go pedel to keep the engine from practically stalling. It seems to happen more often when ambient air temps are higher. Even when the problem happens, the truck runs fine once off idle.

Anyone know what might be wrong?

 

Mine did that too, i replaced my fuel return check valve and Lift pump at the same time, and it went away dont know for 100% which it was, but i serriously suspect the fuel return check valve not holding enough pressure to pop off injectors. But thats just a guess since im no expert

Dusty

 

Most likely the overflow valve is shot. 5 minute replacement job with one wrench.
Best price here-

Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349
$22 + $5 shipping and handling.

 

Are you both describing the same part... Is the fuel return check valve and the overflow valve the same thing?

Thank you for your help!

 

Pinch your return fuel line closed and see if that helps the idle when it drops. If it does then the overflow valve (fuel return valve, same thing) is popping off too easy and needs to be replaced.

Easy fix.

 

Yes we are my bad it is the Overflow valve

 

Mine's been doing kinda the same thing, in the morning usually, when it's cold. Idle drops to around 650-700. Sometimes it does it when the motor is warm, in the middle of the day. I though maybe it was beacause of the improved fluid coupling in my new TC, 'cause it didn't do it before I put the new trans in.

Overflow valve, huh? Didn't think of that one......

 

I had the same problem with a 97, took to the dealer and they adjusted the idle on it.

 

One other thing to check on the '97 is the throttle cable. If it starts to fray, the idle may well drop.
Jiust a thought

 

I never did replace this back in 2004, I just called them and the part is now $40! How's that for inflation???

Are these guys still the cheapest place to get the valve from?

 

Got mine about two weeks ago from TST for about $60, so $40 looks good to me. Have to say though, that the part from TST was not the stock part-it WAS Bosch, and there were two numbers. One was the same and the other was different. The hole on the end of the bolt was smaller on the one from TST. Maybe to create more pressure in the pump?