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No idle then 2grand idle, help?

ryanf413

ryanf413

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91 k5. I did a tune up, and sea foam down the tbi recently and it was idling steadier than ever at 1000-1100 then we got some snow and some cold and one day it didn't want to idle, would stall out without the gas pedal. So i held it to idle for a bit then did a bunch of donuts in the driveway and had some fun, then it was back to normal, figured the cold got to it was all. Today I fire her up and same deal, didn't want to idle then I move her around the driveway and it seemed good but then was jumping to 2grand at idle and staying there. After running for a little while now, she's idling at 1000 again but doesnt sound smooth (sputtery). And a few minutes ago she was at 2000. Someone wanna point me in the right direction?
 
ryanf413 said:
91 k5. I did a tune up, and sea foam down the tbi recently and it was idling steadier than ever at 1000-1100 then we got some snow and some cold and one day it didn't want to idle, would stall out without the gas pedal. So i held it to idle for a bit then did a bunch of donuts in the driveway and had some fun, then it was back to normal, figured the cold got to it was all. Today I fire her up and same deal, didn't want to idle then I move her around the driveway and it seemed good but then was jumping to 2grand at idle and staying there. After running for a little while now, she's idling at 1000 again but doesnt sound smooth (sputtery). And a few minutes ago she was at 2000. Someone wanna point me in the right direction?
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TPS sensor? Have you checked it for codes? Is the check engine light on?
 
4xfrankie said:
TPS sensor? Have you checked it for codes? Is the check engine light on?
Click to expand...
I'm just gonna parrot the 91 service manual; ENGINE IDLES ABNORMALLY(TOO FAST OR TOO SLOW) 1-idle speed misadjusted 2-throttle linkage or throttle shaft sticking or binding 3-air leaks atintake manifold gasket,vacuum hoses disconnected or routed wrong 4-ignition timing misadjusted 5 distributor mechanical advance malfunction 6-restricted air cleaner . check the linkage. Love the 91, I'd kill to have the last k5 !
 
4xfrankie said:
I'm just gonna parrot the 91 service manual; ENGINE IDLES ABNORMALLY(TOO FAST OR TOO SLOW) 1-idle speed misadjusted 2-throttle linkage or throttle shaft sticking or binding 3-air leaks atintake manifold gasket,vacuum hoses disconnected or routed wrong 4-ignition timing misadjusted 5 distributor mechanical advance malfunction 6-restricted air cleaner . check the linkage. Love the 91, I'd kill to have the last k5 !
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OK, here is more-ROUGH ,UNSTABLE ,OR INCORECT IDLE/STALLING-check 02 sensor/throttle position sensor/coolant temperature sensor/manifold absolute pressure sensor excessively rich or lean condition(use scan tool), evap. emission control system,leaking fuel injector,ignition system est,ignition timing.
 
4xfrankie said:
I'm just gonna parrot the 91 service manual; ENGINE IDLES ABNORMALLY(TOO FAST OR TOO SLOW) 1-idle speed misadjusted 2-throttle linkage or throttle shaft sticking or binding 3-air leaks atintake manifold gasket,vacuum hoses disconnected or routed wrong 4-ignition timing misadjusted 5 distributor mechanical advance malfunction 6-restricted air cleaner . check the linkage. Love the 91, I'd kill to have the last k5 !
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Thanks man. Gotta get a service manual next time I'm out. And hell yeah I love it, they're all great but 91 is a favorite.
 
it's probably a sticky IAC.... that controls your idle... some of the seafoam may have gotten in it and loosened a chunk of crud on it....

and 1000 to 1100 is not correct.. it should be idleing down around 700 once warmed up....
 
ryoken said:
it's probably a sticky IAC.... that controls your idle... some of the seafoam may have gotten in it and loosened a chunk of crud on it....

and 1000 to 1100 is not correct.. it should be idleing down around 700 once warmed up....
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It's still in project mode but I'm pretty sure it doesn't come down to 700 so I'll have to double check that then go from there.
 
it's just another indicator that the IAC is cr@pping out...


you could try cleaning it with carb cleaner and a soft toothbrush, but it isn't usually recommended... sometimes it works, but it often leads to the quick demise of it shortly after... I think they're usually in the $40 range...
 
ryanf413 said:
It's still in project mode but I'm pretty sure it doesn't come down to 700 so I'll have to double check that then go from there.
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Have you ever accessed the assembly line data link (ALDL) under the dash before? Pretty easy to do.IAC trouble code is code 35.
 
ryoken said:
it's probably a sticky IAC.... that controls your idle... some of the seafoam may have gotten in it and loosened a chunk of crud on it....
Click to expand...

This, that IAC chokes off a small air bypass to control idle speed. you can pull the iac off and clean out the passageway usually (haven't been in this particular engine) The IAC stepper motor itself is usually considered to be unserviceable.
 
ryoken said:
it's probably a sticky IAC.... that controls your idle... some of the seafoam may have gotten in it and loosened a chunk of crud on it....

and 1000 to 1100 is not correct.. it should be idleing down around 700 once warmed up....
Click to expand...
It's warmed up so I started it back up today and and it was actually idling around 750 for a bit but the service engine light was on and a few times when I'd give it a little punch on the gas it would sorta belch almost like it was gonna stall on me. Heading to advanced to grab a service manual and probably an iac. Anything else you think I should be looking for? I appreciate it
 
well, check codes first... off idle stumbles are often EGR which could very well be your CEL...
 
dyeager535 said:
A little late, but calling anything from a parts store a "service manual" is more than a little incorrect lol.

Download the proper one from here http://67-72chevytrucks.com/vboard/showpost.php?p=5621043&postcount=1

Check codes, don't replace parts. Unless you enjoy wasting money.
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In this instance a Haynes manual would be better than nothing , esp. if looking up just basic info like trouble codes. I agree that a GM service manual is the way to go. There is nothing "incorrect" about the info in a parts store manual,just not as comprehensive as GM, sheesh
 
Put a Haynes back to back with any '87-91 R/V service and wiring manuals, then get back to me and say it's better than downloading the GM manuals for free.

You don't need a Haynes to check GM TBI trouble codes, you can find those for free everywhere. Heck, those and the GM charts are here already https://ck5.com/forums/threads/tbi-trouble-codes.240425/
 
dyeager535 said:
A little late, but calling anything from a parts store a "service manual" is more than a little incorrect lol.

Download the proper one from here http://67-72chevytrucks.com/vboard/showpost.php?p=5621043&postcount=1

Check codes, don't replace parts. Unless you enjoy wasting money.
Click to expand...
dyeager535 said:
Put a Haynes back to back with any '87-91 R/V service and wiring manuals, then get back to me and say it's better than downloading the GM manuals for free.

You don't need a Haynes to check GM TBI trouble codes, you can find those for free everywhere. Heck, those and the GM charts are here already https://ck5.com/forums/threads/tbi-trouble-codes.240425/
Click to expand...
youre right
 
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