Stumble when warmed up

[lkfldredneck]

When my truck starts and is idling cold, you can hit the throttle and it wont stumble, but once it warms up, it stumbles like an irish guy on st patty's day. itll bog down then itll rev like normal. i replaced the TPS (60 fvcking dollars later) as i needed it and it helped a little, but it still stumbles. we've narrowed it down to either the IAC or Coolant temp sensor. i read that it could be the EGR fvcked up and stays open or doesnt open enough but when we did the heads we cleaned the egr ports on the heads and intake. i wouldnt think its the egr cause that wouldnt cause idle or throttle problems. youd think.. any help if someones had this problem would be great! thanls

 

[SCOTTYINWV]

Remove, clean, reinstall and relearn the IAC and replace the coolant temp sensor. It's $15 and a big ***** when it goes bad. Remove and clean the egr also.

 

[lkfldredneck]

Remove, clean, reinstall and relearn the IAC and replace the coolant temp sensor. It's $15 and a big ***** when it goes bad. Remove and clean the egr also.

Thanks man! and the egr is clean as far as i know, threw it in the parts wash for a day when it was off. im getting a new throttle body so if non of that works ill throw the new TB on and hopefully thatll fix it. whichever one i dont use ill build it for performance. if it doesnt fix it ill blame the fuel pump and see if anythings wrong with that

 

[SCOTTYINWV]

Is it throwing any codes? Care to post a video of it? It could be bad gas also. Did you flush the tank after it sat so long? Was timing set to spec? I would plumb up a fuel pressure gauge before I changed the pump, but changing it wouldn't be a bad idea for preventative maintenance while the box is still off.

 

[NacIK]

Not to thread jack but is there a tread on here for cleaning the IAC? I found a YouTube video once but can't find it now.


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[lkfldredneck]

Is it throwing any codes? Care to post a video of it? It could be bad gas also. Did you flush the tank after it sat so long? Was timing set to spec? I would plumb up a fuel pressure gauge before I changed the pump, but changing it wouldn't be a bad idea for preventative maintenance while the box is still off.

Itll throw a code but then go away after a minute more then wont show when i go to test it with a paper clip. And i think i have a video somewhere, id have to look. We flushed the tank then poured 20 gallons in it. And then some more after we ran through all that. Its had a stumble since we got it running so i dont think its the gas. Timing is perfect, right on. Tested many times, forward and then back and we have it spot on. Idk how many times we've replaced the fuel pump in this thing but its been atleast 4 times since bought.

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[lkfldredneck]

guy that i work with that has a 96 350 vortec said he had the same problem a while back, replaced the IAC since he had an extra one and it didnt help, replaced the egr and it didnt help, then wanted to replace the fuel pump until he realized it could be the temp sensor, replaced it but it didnt help so he replaced the temp switch and it fixed it. hoping to gawd that thats what it is, cause its just a $15 part. think i might be gettin it in the shop on saturday so we'll check it out.

 

[qukon 95]

test the egr valve it may not be holding vacuum

 

[great white]

Egt sensor is a high probability based on your description.

The one for the ecm, not the gauge.

You might be throwing another 15 bucks away, but your description does seem to point to it....

 

[Hood93z]

I have to say I wanna know what's wrong if you find it I have a 94 I've changed fuel filter, map sensor, coolant temp sensor, rotor button, dist. Cap, ign. Coil I've unpluged the EGR sensor and blocked the vacuum lines to them. Runs great as Long as it's cold but when it gets to running temp it stumbles spits sputters I'm running out of options here...


1994 Chevrolet Z-71 ext. cab white 2001 chevy truck wheels 305/70/R16 all terrains HIDS color matched mirrors, and marker lights, glass packs