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dawdaw
06-29-2012, 11:42 AM
96479648So did a routine tune up on the motor today and ran intosomething odd. My rear 4 cylinders are running pig rich, (plugs are black andsaturated in fuel) while my front 4 cylinders seem to be burning just fine. Themotors is a 12.8 to 1, 383 with oem rails, 42lb injectors, twin walbro's, andit is running on 93 octane. Any clues as to what could be doing this? Is it the fact that the rear cylinders are fed fuel first as opposed to the front? I'm clueless as to what this is and i've heard of this happening before but can't recollect as to what the cause was? Thanks!
95ImpySS
06-29-2012, 03:59 PM
Do you have an aftermarket throttle body?
dawdaw
06-29-2012, 04:25 PM
Do you have an aftermarket throttle body?

Yes Sir 58mm
popo8
06-29-2012, 04:33 PM
Are you running a stock intake?
95ImpySS
06-29-2012, 05:06 PM
Is it a BBK by any chance? There is a vast problem with BBK throttle bodies. Most were marketed as LT1 TB's but in fact were just TPI throttle body's. If so, check this out. http://para.noid.org/~lj/PCM%20Tutorial/SplitBLMinfo.htm
popo8
06-29-2012, 05:17 PM
Sounds to me like the IAC circuit for the air to go to each hole is not working properly. Not enough air getting to rear runners and hence they are fat.
dawdaw
06-29-2012, 05:44 PM
Are you running a stock intake?

No, it is a factory fully ported intake...


Sounds to me like the IAC circuit for the air to go to each hole is not working properly. Not enough air getting to rear runners and hence they are fat.

Hmmmmm can you give me a little bit better translation/remedy for this problem if that's what it would be


Is it a BBK by any chance? There is a vast problem with BBK throttle bodies. Most were marketed as LT1 TB's but in fact were just TPI throttle body's. If so, check this out. http://para.noid.org/~lj/PCM Tutorial/SplitBLMinfo.htm

Negative, Professional products
popo8
06-29-2012, 05:48 PM
No, it is a factory fully ported intake...



Hmmmmm can you give me a little bit better translation/remedy for this problem if that's what it would be



Negative, Professional products


Does your TB have an IAC hole in it or not. Should be a hole between the blades.....
dawdaw
06-29-2012, 05:57 PM
Does your TB have an IAC hole in it or not. Should be a hole between the blades.....

Ahh man I can't remember... I'll tear into it tomorrow and let you know. What would be the problem if it did and if it did not have the hole?
popo8
06-29-2012, 06:40 PM
If it doesnt then its the same problem I went through with my monoblade. Without being able to direct the idle air into the proper route to all of the runners, then the air will not make it to the rear runners. The path is very small, and can also easily get gunked up in the rear runners.

One step at a time though, take a pic of the front of the tb, and let us see if there is a small hole.... then we will work from there.
dawdaw
06-30-2012, 10:13 AM
If it doesnt then its the sameproblem I went through with my monoblade. Without being able to direct the idleair into the proper route to all of the runners, then the air will not make itto the rear runners. The path is very small, and can also easily get gunked upin the rear runners.

One step at a time though, take a pic of the front of the tb, and let us see ifthere is a small hole.... then we will work from there.


Well Sir it appears that I have 2 IAC hole in my throttle body..... I'm goingto check the resistance between the IAC coils (A to B) and (C to D).... Andalso make sure there is no continuity between my B to C and A to D Coils andmake sure thats working.... If the resistance in the IAC is out of spec (40 to80 ohms i think) or there is continuity between the (B to C) or my (A to D)coils then I take it my IAC is junk? Also i have PCM communicator where I couldlook at the IAC counts i'm pretty sure and see how it's functioning.... what isthe # of counts the IAC should be reading upon initial start up and fully warm?I'm pretty sure it's 30 to 35 for fully warm but want to double check
dawdaw
06-30-2012, 10:13 AM
Anc can someone please tell me why my text is gray lol
firebird_1995
06-30-2012, 10:40 AM
If I'm not mistaken, the top hole is where the ventilation air from the passenger side valve cover is reintroduced. The bottom port is the iac port. The important part of the iac system on an aftermarket TB is on the back side where it bolts to the intake. The port on the TB needs to match the port on the intake, otherwise the idle air will be dumped into the front of the Plenum instead of being directed into the iac channels that exit near the injectors at each runner.