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IAC "idle spider" passage mistake ?

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1.6K views 12 replies 4 participants last post by  Brizo  
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#1 ·
Hi everyone, I have the intake off of a 5.7P in a
'95 Impala SS with all the pipe plugs out of the bottom. All of the air holes under the plugs going into each intake port are 1/4" in diameter except the hole to #1 cylinder which is only about 1/8th inch! Is that a mistake? If it's supposed to be smaller, does anyone know why?

We are searching for the cause of a 4 count ? misfire and then intake backfire anytime the throttle is floored suddenly after its warmed up. Thanks for any help
 
#2 ·
They are all like that .
Even through revisions of the intake.
One can only assume the flow- length and proximity to the TB dictated a different hole to balance the amount of total idle air that runner saw.
Pretty much would all go out tge window with cams , air flow mods , idle speeds.
I would doubt it to be a cause for your issue.
 
B
#3 ·
Thanks Marky, We suspected something like that since it was the passage closest to the TB .

On this '95 SS , after it goes off fast idle if you punch it more than half throttle on take off it will shake / misfire several times, backfire 2 -3 pops in the intake and then take off like normal. Otherwise it drives perfect. Never had any codes and we've tested and replaced everything . Any ideas?
 
B
#4 ·
Still fighting this miss. tried another Opti spark and tried disconnecting the knock sensors this week but still no change. Open the throttle fast and the engine misfires about 4 times, then usually pops back 1-3 times then takes off.... entire event takes 1 second. Will also do it standing still but never misfires on acceleration. Idles a little rough in gear after cold start and smooth out as it warms up but I think all the 5.7 P's did that . Thanks for any ideas, Dan
 
S
#5 ·
Try cleaning your MAF and your injectors, and replace the Throttle Position Sensor (TPS) - it is a wear item.

Do you have access to a programming cable like this one?
 
B
#7 ·
Sherlock, All those parts have been replaced. I am a retired tech working part time at a Chevy dealer on all the "older cars". I'll have to look for the cable next week. The replacement ECM we installed was said to have the latest GM programming. And if we have the cable?
 
B
#10 ·
Sherlock9c1, The owner has ordered the OBD-1 12 pin to usb cable from OBD Diagnostics so should have it in few days. Meanwhile, I assume I need to load Flashhack to our shop laptop? Thanks so much for your help on this, Dan
 
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