95Blackhawk

yeah, as stated above, take the intake off and look at your idle air plenum for blockage.

blown94

I bet some of your idle air passages in the intake are carboned up and partially or totally blocked off. I had the same problem b4 and could never figure it out. When I pulled the engine apart I noticed some of the idle air passages had a gummy tarlike carbon buildup in them. You might be able to clean these passages from the outside with a throttle body type cleaner or better yet combustion chamber cleaner but you need to direct it through the IAC port in the throttle body, not through the blades as this will not reach the passages. If they're totally blocked this may not work as theres no air moving through them at all and the cleaner won't reach the blockage. Best way is to remove the intake and soak it down with combustion chamber cleaner then blow the passages out.

cause4panic

i bet your rockers are too tight

95Blackhawk

I also took everything off the intake manifold and shot high pressure water through the passages. Even after many minutes of doing this, there was still carbon coming out.

wrd1972

I once had splits but not that severe.

My tuner managed to eliminate them simply through the tune. Most of the time my idle BLM's are 128/128. Seriously. My idle timing is around 25 degrees.

All my other BLM's ( and occasionally idle) are plus minus 5 points as well. Therefore, my motor is very happy in closed loop at all times. BTW I have a 224/230, 57x lift, 107 LSA cam very similar to yours.

IMHO, through my experience, compared to a good dyno tune, a mailorder tune is crap. You need to find a good dyno tuner that knows the LT1 and have him tune it.

If you are confident there are no intake air leaks, exhaust leaks (pre O2's), then that leaves ill effects from the cam (which poses s small problem) or maybe damaged valve seats that may be causing leakages and reversion.

HardcoreRM125

UPDATE:


Pulled intake. Noticed all idle air passageways were clean. But #1 cylinders idle air passage is half the size of the rest. Looked at my spare intake manifold and it is also like this. Designed this way for some reason (that is being my technical background as I am sure it gets into turbulence and air distribution and crazy engineering ...)

I think perhaps on cammed cars this can hamper their breathing at idle.

Back to the drawing board. It seems more and more to point towards the nature of the cam, and a poor mail order tune.

I slowly am learning tuning and really enjoy it so hopefully I make some progress with this. I plan to try WS6T3RROR's Individual Cylinder Fuel Trims ...


Joe

As always I am open to suggestions though!



Joe

95Blackhawk

Have you closed your TB blades all the way to force all idle air into the idle air plenum? You have not indicated this was done.

HardcoreRM125

Yep did that a while ago. One of the first things I did ...

I will play around with it more this weekend for sure.


Joe

HardcoreRM125

UPDATE - I noticed a slight misfire only really prevalent at idle. The plugs/wires have less than 200 miles on them. None are burned.

So ...

I replaced the Opti. It now runs stronger and smoother. My BLM Split is still getting worse. It no longer is a closed throttle thing and is now prevalent across all cells.

Most recently - I have replaced the distributor, pull & inspect & replace intake gaskets & seal with The Right Stuff, and swap left injectors to right after soaking the pintle end in a quality jet and injector cleaner.

All injectors are ticking. All Ohm out the same. All have 12V source

FWIW - The car ran STRONG until it relearned its Split BLM's.

They are prevalent at all times now though. Idle, Part Throttle, Mid Throttle, WOT ... Its so ****ing frustrating.

To date I have done the following to try to fix it:

-Plugs
-Wires
-Opti
-Intake Manifold Gasket (And used The Right Stuff)
-O2 Sensors
-Closed TB (stock TB) as far as screws allow before blades (clean) stick
-Tested Manifold, TB, and Elbow for vacuum leaks after the MAF

The exhaust gaskets, I can't hear, smell, or see a leak at the flange. At the collectors there are ZERO leaks.

I am absolutely out of ideas!


I may swap to the stock injectors, reflash, and see what happens...?


Can anyone help me? The car ran very strong until it learned its Fuel Trims ... At some points it is the full 108/160 split. Part throttle usually is a 20 split in BLM. The minimum split is at least 8.

I can send anyone my FreeScan CSV datalogs that can be read in Excel.


Joe
___________

zmike

any updates? I have been tracking down the same conditions as you.

HardcoreRM125

I got a wideband, switched to an Open Loop tune, and have never looked back.

The car runs much better. No bucking at low RPMs in parking lots and such. It was really easy to dial her in on an open loop tune. Took me maybe 3 reflashes and logs to get her right.

I think with my tight LSA, 108, and it being a big lift cam, .600, .600, a lot of unburned fuel was going through the exhaust. The 02's would try to correct it and lean it out too much. The car just couldn't compensate for it.

When I went to an open loop tune, it instantly ran significantly better. The more I richened the mixture (based on my wideband readings), the better she drives on under normal driving. I think I cruise in the mid 13's AFR (versus 14.7), and WOT at around 12.8-13.0

Bottom line, my 02's were robbing my car of fuel. Open Looped her and it has fantastic driveability.

zmike

Never even thought or considered that. What all is involved in doing this? Just using the wideband O2's for programming?

ByByC5

Hardcore,

I did the same thing initially with my set up, open loop tune and wide band and had great results too.
However, I recently found injector offsets for my 36 lb SVO's and reflashed my pcm with those and the change in idle and part throttle drivability was amazing!!

Worked so well I am working towards a closed loop tune again. I am running a closed loop tune now, and it's really good. Just not as smooth as the open loop tune I had.

I also changed the "Fast O2 Rich/Lean mv VS CL Mode" settings to help smooth out the lean 14.7 the pcm is looking for in CL.

Great sticky thread here:
https://www.camaroz28.com/forums/com...ts-lt1-770192/

And your 30 lb. offsets here (if using Ford SVO 30 lb injectors)
http://www.fordracingparts.com/parts...-9593-b302.pdf

HTH

Keith