Car is a 93 w/ an 11.8:1 396, has ported LT4 heads and intake, custom cam 236/242 114lsa, hooker longtubes, 42lb Lucas injectors, and a 58mm BBK tb.
The original programming came from Ed Wright, but wasn't quite right so I bought TunerCat and we've been messing with it here and there. The idle blm's to start were 108/120. The short term on the 108 side was between 40-60.
We've drilled the hole in the tb per these 2 websites: http://para.noid.org/~lj/PCM%20Tutor...litBLMinfo.htm and http://members.***.net/chipsbyal/idle/index.html
No change.
We've also tried taking out timing at idle. Originally the closed TPS spark advance was 30*, I bumped it down to 25, then 22, now about 20. Still nothing. The idle seems quite a bit smoother, but the blm's haven't changed.
Then we reset the IAC and started messing with the throttle stop screw and "adjusting" the IAC valve while trying different timing. Nothing. Blm's we're still 108/120ish. They didn't move at all.
Then I decided I was going to start lowering the VE table and idle rpm and map and try to lean the idle out about 5%. That started to help. The blm's changed to 108/130 with the short term on the 108 side rising to 70-80. Then I took 8% out of the VE table at idle map and rpm. This helped more. 108/140 with the short term on the 108 side bouncing from 100-120. I thought that if I started messing with the IAC now that maybe they'd start to close up together. Nope. They wouldn't change at all.
So I'm thinking it might be an ignition miss or a vacuum leak maybe?
Can anyone explain what either of those would do to the idle blm's on each side? It doesn't sound like it has a miss. Would a miss show up in the blm's at part throttle/WOT?
Exhaust leak before the O2?
I just need some more ideas since the 2 usual fixes didn't help.
Also, you guys with similiar cams, how much vacuum do you pull at idle and what does your car idle at?
Anything I forgot let me know, as these splits are making the car go into cell 18 at WOT and it's adding fuel.

 

First I would use a can of carb clean to look for intake leaks. Not that I really expect a lean condition on the 120 side because its still showing rich, its just the easiest thing to try so why not.

Maybe check the plugs now just to make sure there's spark at idle and the plugs in tight.

Next easiest thing is to switch wires on the 02s (make extensions) to simulate swapping those (the sides will switch readings if that's NOT the problem).

Then I would try swapping injectors side to side (maybe a leaky one).

Then I would start worrying its something freaky.

Hal

[This message has been edited by Hal Fisher (edited August 26, 2002).]

 

Split BLMS, are 95% the result of an aftermarket TB. I see you have a BBK 58mm.

The IAC passage, needs to be enlarged. These are the only details I have gotten into, but there is much more out there.

In the computer programming forum of this base, is information on it.

Ciao.

Cam.
DR.ZED

 

Try swapping the old tb or a stock one back in.

Hal

 

Tonight we found an exhaust leak on the sh!tty Mufflex y-pipe. I'm pretty sure that's what is causing it. The leak is on the same side that is showing rich. Is that what should happen?

 

Please scan it and tells us if things change.


Hal

[This message has been edited by Hal Fisher (edited August 27, 2002).]

 

I believe most people just give up and go with PE idle, because the lower the RPM the worse the effects of the cams EGR is going to hit you, and its just going to drive the O2s nuts.

 

Last night we took the torque converter out of the car to send it back to have it re-stalled so I can't scan it for a couple of weeks. Once it's back together I'll scan it again and see what's going on with the exhaust fixed.

Dr. Mudge - I've thought about using a PE idle. I just figured I'd let this drive me totally nuts first, then try it.
Heck, I'd like to do a totally open loop tune for it anyways.