As far as mentioning BLM's at idle I added that because My BLM's were getting way out of wack at idle. It was running real lean on one side and rich on the other. I thought the two might be related. Carl is adjusting his throttle stop with success for idleing. According to my Haynes manual the resistance on that little step motor(IAC), should be between 40-50 OHMS. OHM readings between the a and b and c and d terminals. That is only to measure the resistance of the motor windings. BTW, My pintle was stuck and wouldn't move.
Fred

 

Hey DR. As odd as it sounds, as i stated earlier, the IAC counts at idle affect the idle split BLM'S. I know where ya are coming from w/ the idle air passages thru the intake. All i can say, the shutting down of the throttle plates and having all the idle air going thru those little holes at the mouth of the intake manifold runners, has never worked for me.

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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.

 

Well, you do have a 396 and I have a 350 so who knows, but with my cam and 40ish counts, I figure anyone can do this, and I didn't open up my 58 much more than stock.

Here are some goodies, compliments of Christian:

Quote:

<font face="Verdana, Arial" size="2">I'd say the split BLM and IAC are LT1edit issues for sure, never be afraid to share stuff, because you're rarely alone.

The actual IAC passage that needs to be opened is the very small hole pictured here:
http://carprogrammer.com/Z28/PCM/TB/DSCF0706.JPG
I opened it to look like this:
http://carprogrammer.com/Z28/PCM/TB/DSCF0699.JPG

Don't mess with the actual IAC passage. Several other stock pictures here:
http://carprogrammer.com/Z28/PCM/TB/

You basically want to get the air flowing through the triangle pictured here:
http://carprogrammer.com/Z28/PCM/TB/DSCF0704.JPG
And less air in the intake plenum, since rumpy cams introduce reversion like a ****.

Keep me posted,
-Christian

Check out Als' updated page on the IAC passages- really good!
http://members.***.net/chipsbyal/idle.htm
</font>

[This message has been edited by Dr.Mudge (edited August 12, 2002).]

 

Ooooooh, ok. If you've got a 'biggy cam', this is why many people give up on close loop idle and run PE up to 1200 RPM in the PCM, then make sure the AF is good on the dyno and you have closed loop operation like a normal rig the rest of the time.

 

Fred,
The car I've been working on that has split blm's at idle does the same thing. For about 30 seconds the blm's will be within 3-4 of each other and then one will start to drop and the other will rise. MAP, idle rpm, and timing doesn't change but the blm's start to go crazy. On one side the long term will drop to 108. About 10 seconds later the short term will rise and go over 128 and then the long term will start to head back to 128. At the same time the other bank will be rising up to 140 or higher and after 10 or 15 seconds the short term will drop below 128 and the long term will start to drop again.
Then they'll both sit at 122-126 or so for about 30 seconds and the process will start all over again.
I guess we're going to try and drill out the passage that Dr. Mudge shows in the post above and see if that helps at all.
Then try to adjust the IAC again.

 

well at least you know your sensors and PCM are working correctly from the standpoint that the short term and long trerm fuel trims are trying to do what they need to do. I had that issue and in my application it turned out to be slow O2's and/or the non-GM O2's. i replaced w/ GM O2's and that swinging back and forth stopped. FYI...the electrical tests of the O2's were fine. scanner really did not show a slow condition.
Dr mudge, if you get a chance, email me about your mods and cam you use. thanks!
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'97SS, More Performance 396, AS&M cold air, Grotyohann LT, SLP 2ODL muffler, Magnacor, PCMFORLESS PCM, LS1 twin piston calipers, KVR crossdrilled and coated rotors, SLP stage II w/ KYB AGX, 6M, Star Stage II.

[This message has been edited by carl97ss (edited August 13, 2002).]

 

These are GM O2's. The car is a 93 and we converted it over to heated O2's using all GM parts. Sure wish I could figure out why it does this.
Not sure if it hurts anything or not though. I guess I'll just adjust the idle stop screw until the O2's are about as even as they can get.

 

Dan, I dont imagine stock speed density cars have that problem, do you have any mods though that might explain it?

Carl, pretty simple, Heads, SLP shorties, K&N intake cutout, proprietary cam similar to cc306 but better lobe profile, without getting into every single part thats it.