Engine/Transmission (1994 - 1998) Stumble

[JMichelson]

I took my 98 12-valve in for emissions testing the other day. The test required an idle to full throttle, hold it for a couple seconds and back to idle. When I revved the engine up it felt like It stumbled about half throttle, just for a split second. I had never noticed anything like this before since I don’t make a habit out of revving my engine form idle to full throttle. The engine seems to run fine, with no power problems and was up to normal operating temperature. The truck passed the opacity test with 36 on a maximum of 40. Anybody have any ideas? Thanks, Jeff

 

[rholcom2]

My guess is it doesnt like things sniffing its behind . Sorry I cant be of any help. Just a little comic releif

 

[JMichelson]

Originally posted by rholcom2

My guess is it doesnt like things sniffing its behind . Sorry I cant be of any help. Just a little comic releif

Thanks rholcom. I guess I should rev it up with out the test probe shoved up it's tailpipe and see if it still has the problem.

I didn't realize that a Cummins could be so sensitive.

 

[HEMI®Dart]

A guess



Possibly the overflow valve is getting old letting fuel go through at less pressure than it should.



Possibly the lift pump is at the the low end of the pressure spec (at idle) causing a momentary lack of fuel until the pump can start pumping faster.



If the truck runs good and has good torque the above 2 things are probably fine.

 

[Smokin Dodge]

What is your timing set at that may have a little to do with it.

 

[rholcom2]

I dont know if this is relavent at all since mine is a 24V. But, mine had a "stumble", in it when goign from no or low throttle to wide open, or even getting on it from a stop light. I couldnt figure it out for the longest time, no light came on in the dash, didnt seem to be predictable by me buying fuel at a different station or anything, so I got a fuel pressure guage and found that the lift pump was dead. Once again, I dont know if this will help what so ever, but I did experience what could be called a "stumble"