1st what causes the engine to stumble as you lower the idle? is it fuel pressure ? or volume? if i increase the pressure at a lower idle-could i possibly turn my idle down to almost barely there? poss 300? but have no stumble?
CK5
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fuel pressure-is it possible-tbi?
- Thread starter only 31s
- Start date
I'm not 100% sure by any means, but a lower idle may not have anything to do with fuel pressure or volume. Probably mostly because an engine just starts having a hard time making enough power to overcome the internal resistance and friction, and the concentration of combustible mixture is so small the ignition might have a hard time igniting it.
vortec
1/2 ton status
why would you want to do that? just curious.
6.2blazer has a good idea about the engine having to fight it's own internal forces. along that line, i'm thinking it might simply not have enough rotational inertia to properly compress the mixture at rpms that low.
6.2blazer has a good idea about the engine having to fight it's own internal forces. along that line, i'm thinking it might simply not have enough rotational inertia to properly compress the mixture at rpms that low.
Thunder
3/4 ton status
Your ECM is programed to keep the idle around 650-750 RPM depending on application. Forcing the idle below the programed RPM really screws things up. Tne ECM will try to increase idle speed by adding more air thru the IAC. Which wont work so then it trys adding fuel. It is constantly switching back and forth between rich and lean. Causing a surging idle, stumbling, ECT. The only proper way to lower idle speed is to reprogram the chip.
you are aware you can reset your idle speeds on your ecm and not hurt it -it will adapt[im not saying you can drop it 3 or 4 hundred rpm] im just trying to understand the workings of the fuel itself-and its effects on the idle.
only 31s said:
wow.... You ask for help, then chastise the people giving said help... I'll have to remember to never help you.....
Not sure why you even ask a question if you know more than everyone else...
(by the way, OP, you are wrong)
(by the way, OP, you are wrong)
Pad
no - this is what happens most of the time out here-i ask a specific question ,hoping for an answer from someone with a factual answer,and get commentary from guys who want to[hear ] themselves on screen-i was lookin for info -not conversation,if i wanted that -i would be in a different category in this forum.
You didn't like this answer or you don't believe it's fact?
thats the norm
i do agree with that answer! but there is a way to reset drive idle and then reset iac to accept this new position to [learn ] again. unfortunately i have a really screwd up tbi set up on an edelbrock intake on a block from? and possibly a 383 stroked motor w/all 1990 accs and wiring[the motor has a different balancer+the flywheel is weighted-also has old style valve covers w/world heads under them] while researching how to idle this beast prperly a mitchell book or chilton service manual has instuctions on how to reset idle speeds in the event of the tbi overhaul. not that i ever dont appreciate any info i get from this site but look how long it took me to answer your counter question without trying to show an attitude - this type of explaining drives me insane[im not comp savvy an i hate to type]-but i wanted to explain it this time, cause i dont want to seem ungrateful for any and all info i have ever gotten at this site.
i do agree with that answer! but there is a way to reset drive idle and then reset iac to accept this new position to [learn ] again. unfortunately i have a really screwd up tbi set up on an edelbrock intake on a block from? and possibly a 383 stroked motor w/all 1990 accs and wiring[the motor has a different balancer+the flywheel is weighted-also has old style valve covers w/world heads under them] while researching how to idle this beast prperly a mitchell book or chilton service manual has instuctions on how to reset idle speeds in the event of the tbi overhaul. not that i ever dont appreciate any info i get from this site but look how long it took me to answer your counter question without trying to show an attitude - this type of explaining drives me insane[im not comp savvy an i hate to type]-but i wanted to explain it this time, cause i dont want to seem ungrateful for any and all info i have ever gotten at this site.
I'm not sure how good Chilton's and Mitchell's is for the idle setting, but thirdgen.org has an idle air reset article, (been awhile since I glanced at it, might be called minimum air adjustment?) it's what many here have used to reset idle.
Even if you could get the idle speed down as low as you said (300) the velocity in the runners would suck, which would tend to cause all sorts of fueling issues. On a port injection setup, it wouldn't be quite as bad because the fuel is sprayed on the valve...with TBI, as with carb, velocity and heat are the only things keeping fuel atomized, cold engine with RPM's that low wouldn't run good, if at all. Regardless, the ECM would be trying to get it back to it's target idle anyways.
That sucks if you don't know what the engine is(not sure I understood your statement right)...fueling and timing are going to be wrong if it's a 383 with 305 or 350 TBI, and that can lead to some problems of it's own.
Even if you could get the idle speed down as low as you said (300) the velocity in the runners would suck, which would tend to cause all sorts of fueling issues. On a port injection setup, it wouldn't be quite as bad because the fuel is sprayed on the valve...with TBI, as with carb, velocity and heat are the only things keeping fuel atomized, cold engine with RPM's that low wouldn't run good, if at all. Regardless, the ECM would be trying to get it back to it's target idle anyways.
That sucks if you don't know what the engine is(not sure I understood your statement right)...fueling and timing are going to be wrong if it's a 383 with 305 or 350 TBI, and that can lead to some problems of it's own.
you said it !
my concern with my idle and fuel issues have driven me insane!!! if i cant justify having the beast-[7 mpg] i will have to sell it - no one in my area has a truck like it -and its still almost factory clean![bought it from texas]-pics are in the burban section-thanks for your info and patience-Rob
my concern with my idle and fuel issues have driven me insane!!! if i cant justify having the beast-[7 mpg] i will have to sell it - no one in my area has a truck like it -and its still almost factory clean![bought it from texas]-pics are in the burban section-thanks for your info and patience-Rob
Did you check thirdgen's tech articles? The procedure is there.
From what I've heard others say here, (and seen in one case) their excessively undersized injection setups still idle and run fine, they are just lean under load.
From what I've heard others say here, (and seen in one case) their excessively undersized injection setups still idle and run fine, they are just lean under load.
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Your a more patient man than me... 
Tho I was told today by a bystander watching me train a new shrinkwrap grunt, what an outstanding instructor I was....
Now, if he would have bought me lunch, that woulda been something! 
Tho I was told today by a bystander watching me train a new shrinkwrap grunt, what an outstanding instructor I was....
Now, if he would have bought me lunch, that woulda been something! 
