You may have covered this, but what are you measuring engine speed with? It's not a tach set for a 4 cylinder is it? Just thought I'd throw that out there.
CK5
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TBI throttle
- Thread starter carpeonnel
- Start date
carpeonnel
1/2 ton status
No it's just a small autometer tach ive been running for years. Trust me, you really don't even need the tach to tell it's idling too high, especially with the open headers 
carpeonnel
1/2 ton status
I just gotten get this beast idled down so I can drive it to get my new exhaust done. It's kind of hard to drive it 30 miles when you can't shift it cuz it's idling too damn high
Thunder
3/4 ton status
Here is a good how to about setting the idle.
http://s-series.org/component/option,com_tech_article/Itemid,/item,63/task,item/
http://s-series.org/component/option,com_tech_article/Itemid,/item,63/task,item/
carpeonnel
1/2 ton status
thanks for the link. So from what I read, I'm gonna need to remove the cap over my set screw. I can't just reset it, but rather have to unplug the IAC and set it manually then reconnect the IAC to get the idle where I want it? Ya follow me
Yes but the IAC has to be fully seated first and that is done by jumping the A and B connector at the ALDL connector and then turning the key to the on position and wait for 30 seconds then disconnect the IAC connector then you can remove the A/B jumper and start and readjust the base idle.
i suggest spraying around the TB with some brake cleaner just to be sure... brake clean is a vacuum leak finders best friend
It is also highly unlikely that your high idle is caused by a misadjusted base idle screw adjustment if the plug is still there. Have you pulled the IAC motor off and carefully cleaned any carbon deposits off the pintle and also from inside the TBI unit? If not i suggest doing that first.
carpeonnel
1/2 ton status
no, TBI has never been messed with since I bought it 5 yrs ago. Besides putting the throttle body spacer in. I'll be home tomorrow and work on it Friday. I'm just gonna take the TBI off and thoroughly clean everything I can clean, clean all the connections and replace the gaskets under the TBI and spacer. Truthfully I don't think I'm gonna find anything that would drop my idle that much but I'll feel better checking everything I can before resorting to resetting it. I'll let you know. Thanks
So when you re-connected that vacuum line (in the 3rd pic) the idle didn't drop at all?
1300-1400 is pretty high - quite possibly out of the range of the idle screw.
I would go around everything with brake cleaner or propane before turning any bolts (although you may need the air cleaner and snorkel for this to work right). Checking with a stethoscope would be nice, too (a piece of rubber tubing to your ear usually works, too, but maybe not with open headers).
Then check out the throttle blades and IAC pintle to make sure everything is clean. The throttle bushings could be worn as well, not letting the blades close all the way. It's also possible the IAC motor is broken or stuck. When you go to reset your idle, you could take it out and measure the length before and after just to make sure it moves.
1300-1400 is pretty high - quite possibly out of the range of the idle screw.
I would go around everything with brake cleaner or propane before turning any bolts (although you may need the air cleaner and snorkel for this to work right). Checking with a stethoscope would be nice, too (a piece of rubber tubing to your ear usually works, too, but maybe not with open headers).
Then check out the throttle blades and IAC pintle to make sure everything is clean. The throttle bushings could be worn as well, not letting the blades close all the way. It's also possible the IAC motor is broken or stuck. When you go to reset your idle, you could take it out and measure the length before and after just to make sure it moves.
carpeonnel
1/2 ton status
When I replaced that line in the pics it dropped maybe 100-200 rpms. Not much. I sprayed carb cleaner all around the spacer, TBI, and the gaskets while it was running. I actually cleaned the TBI fairly well when I did it. I went thru the whole damn can of carb cleaner and sprayed everything from the blades to the air cleaner bolt with no result.
I just really think that it's not a vacuum leak cuz wouldn't that have to be a HELL of a vacuum leak to make my K5 run up 1400rpms at idle? Seems like the K5 would run like crap and my brakes would be pretty crappy too if it was a big vacuum leak, but they're solid. I dunno. It's just funny that it's been running this exact same way for 5-6yrs with no change. Seems that if it was a leak it would have changed at some point and the truck would have ran like crap, but it runs smooth as glass (just really fast in park
)I got called into work tomorrow so it'll be Monday before I can get to it (gotta work 72hrs straight
)But I'll let you know what I find. I'm gonna go thru every I can before trying to reset it, but I'm afraid that's what I gonna have to do
Have you had the vehicle scanned, see if there is anything obviously going on?
Did we cover the basics...check engine light comes on with engine off/key on?
Did we cover the basics...check engine light comes on with engine off/key on?
carpeonnel
1/2 ton status
no check engine lights. Jumped AB with paper clip and I have no codes. Haven't checked it any other way though
Bro in law had something like this with his TBI S10 a few years back...I'm thinking it was something with the blades of the TBI. He actually got a whole junkyard unit and whalla, problem gone.
Remove and plug off the vacuum hose for the brake booster. You could have a bad booster that leaks. I've had that happen years ago and fought looking for the problem for some time before thinking to do that.
carpeonnel
1/2 ton status
that's a damn good idea.
carpeonnel
1/2 ton status
well the Blazer is running and idling perfectly now. Idles at about 950 in neutral. A friend of mine came over and scanned it and said that my IAC was having issues. Said it was slow basically, but also said that my system was "open" and that it should be "closed" but wouldn't do it b/c of air/fuel ratio problem. Well we couldn't find any leaks after checking again but when I took the TBI and spacer off to replace the gaskets and clean the TBI I noticed the back side of the gasket under the spacer was all degraded. So I hosed down the hole TBI with carb cleaner and scrubed it pretty good. Went ahead and replaced the IAC and the gaskets. When I initially put it all back together and ran it, it still idled really fast still but evidently the computer has to relearn the crap again and sure enough a few minutes later it quieted down and purrs like a kitten now. Thanks for all the help
Good to hear man!
