LT1-LT4 Modifications 1993-97 Gen II Small Block V8

surging on idle

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Old Oct 2, 2006 | 08:16 PM
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Default surging on idle

i checked all over for vacuum leaks but none came up. whenever i sit and idle when warm or semi warm i get a surge from 1000rpm idle to 1400rpm then either back down to 1000 or it does it back to back. i cleaned my IAC motor still has a little carbon on it but im thinking i need to replace it.

anyone have any other ideas?
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Old Oct 2, 2006 | 09:46 PM
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if you made no recent mods,id say its still a dirty iac. have you also tried to clean the little maf wires?
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Old Oct 2, 2006 | 09:47 PM
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maf wires to the maf? well i ran it on speed density map un plugged and it still did it.

would the IAC make it surge above 2000rpm? i think it may be plug wires but who knows.

Originally Posted by juicedimpss
if you made no recent mods,id say its still a dirty iac. have you also tried to clean the little maf wires?
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Old Oct 2, 2006 | 09:52 PM
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actually i was talking about the little tiny sensor wirs inside the maf,but if you are on a s/d tune,it wont matter.
as for surging above 2k,it does that sitting still at idle?
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Old Oct 2, 2006 | 09:54 PM
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sitting still at normal temp itll surge up to about 1500rpm for 1 second and drop back down or repeat it 2 or 3 times in a row.

im thinking ICM now. elec ignition.

itll surge holding the gas steady above 2000rpm. itll also give me a hesitation/misfire while cruising in 2nd or 3rd around 3000rpm.
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Old Oct 2, 2006 | 10:02 PM
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cold startup is good?if it has to crank a while it may be a bad fuel pump causing a lean surge
if it is misfiring,id look at the opti plugs.make sure they are not corroded.
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Old Oct 2, 2006 | 10:08 PM
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cranks great.

it has the power it should all the way to 5500rpm. it spins 2nd like all hell. its just a little hickup. between 2000 and 3500rpm. not all the time its more random.
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Old Oct 3, 2006 | 12:14 AM
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it doesnt do this all the time, its periodical
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Old Oct 3, 2006 | 12:23 AM
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do you have access to a datalog? it might help to see what the iac is doing.
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Old Oct 3, 2006 | 02:21 AM
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yea ill try to see if i can use it. i checked a little earlier and my ignition coil is loose on its platform or holder or whatever it is. i can move it when wiggling the coil to opti wire.

Originally Posted by juicedimpss
do you have access to a datalog? it might help to see what the iac is doing.
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Old Oct 4, 2006 | 12:30 AM
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ok today i held the car at 3000rpm and saw the tach jump 200rpm every few seconds. and a popping in the exhaust when it surged. im thinking ICM now and plug wires.

it didnt do anything on idle today until i beat on the car to get the seafoam out of the engine. i unplugged the IAC and it ran great except a few bounces up to 1100rpm.

just for the hell of it and well money's sake, who thinks its the opti?
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Old Oct 4, 2006 | 09:11 AM
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check the connector in the top of the opti.
look for blue/green growing in the pins.
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Old Oct 4, 2006 | 10:30 AM
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the car is on its rag i think. LT1 PMS. i tapped the ICM on idle and i get no more missfiring at 3k. the idle is doing good since i unplugged the IAC and ran it then let it sit overnight unplugged.

ill check the connector
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Old Oct 4, 2006 | 07:22 PM
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bump*

found the boot going from the opti to the ignition coil torn 1/4" on the coil boot.

its arching out onto the block i bet. and im replacing the IAC valve. i did a resistance test on it and it came out less than 40 ohms. normal is 40-80 ohms.
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