Engine stumbles after small throttle inputs

[ASJT3]

Hey guys, recently I've been having this problem with my '90 C1500 305. The engine stumbles after holding down the throttle slightly for any time longer than 5s and then releasing, like if I apply the gas lightly to slowly roll up to a light. When i let off the pedal, it will stumble then recover after a second. Sometimes its so bad it almost stalls.

There is no stumbling after heavy throttle inputs. Not sure what causes this. Any ideas?

Thanks,

Alex

[j cAT]

Originally Posted by ASJT3

Hey guys, recently I've been having this problem with my '90 C1500 305. The engine stumbles after holding down the throttle slightly for any time longer than 5s and then releasing, like if I apply the gas lightly to slowly roll up to a light. When i let off the pedal, it will stumble then recover after a second. Sometimes its so bad it almost stalls.

There is no stumbling after heavy throttle inputs. Not sure what causes this. Any ideas?

Thanks,

Alex

could be a bad EGR spring. these over time get weak, then they open too much . at idle EGR is off. when the throttle is increased then the egr opens a small calibrated amount. having excessive exhaust back pressure could also increase this effect . more exhaust pressure more egr exhaust gases get into the intake to reduce emissions and combustion temps. too much and then you get all this. block off egr ports. that means remove from engine and plug up those two holes. then see if the problem goes away. you may notice the engine will ping this is normal with the egr out.

[danielsatur]

If you suspect the EGR system, you can put a tourniquet on the EGR system for the short.
Yes - It will throw a DTC, but did the stumble go away?

[ASJT3]

Thanks for the replies fellas. I blocked off the EGR between the EGR valve and the solenoid. "The Beast" ran great! Drove it around a little and exhibited no stumbling, and the idling seemed smoother. Hooked the EGR back up and guess what, stumbled an coughed like an old man.

Question is, is the valve bad or the solenoid bad? Don't have much experience with this system. What do you all think?


Thanks,

Alex

[j cAT]

Originally Posted by ASJT3

Thanks for the replies fellas. I blocked off the EGR between the EGR valve and the solenoid. "The Beast" ran great! Drove it around a little and exhibited no stumbling, and the idling seemed smoother. Hooked the EGR back up and guess what, stumbled an coughed like an old man.

Question is, is the valve bad or the solenoid bad? Don't have much experience with this system. What do you all think?


Thanks,

Alex

read post #2 again. ya replace the EGR they don't last forever.

[ASJT3]

Was looking thru my old posts and realized I forgot to post the fix:

EGR replacement solved the problem, runs great now.

Thanks!