Guys, I'm having an extreme split BLM issue here, my mods are in my sig, my left o2 shows 160 at idle & right one around 120 or 128, than the pcm adjusts the injectors & both sides will shows 128/128, but my injector pulse width on left is 4.4 & the right one 2.2 or something, that means my left side is pushing 2 times more fuel through, seems to happen only at idle & crusing below 2000rpm & needs some load to stabilize than its 131/128 which is pretty good. anything lower & it splits big time, or 2000 & no load.

This is what I did to try to resolve the problem:

Swaped the o2's from one side to the other. Result: No change
Swapped the injectors from one side to the other: Result: No change

I'm thinking its the big single patter cam spilling the fuel back into the intake? someone help on what you think the problem is LMK thanx guys.

 

If its truly a 'big cam' then go open loop idle, most of the time its done to 1200 RPM but sounds like you may be going higher than that, since you cruise 2k or better most of the time I'm sure thats not much of a problem.

Just make sure the idle is sufficiently richened not to suck, so if your visiting the dyno any time soon it may be a good time to play with that. I verified my open loop tables as being very close to 'true' AF, and ran the whole setup open loop, for several reasons not really by choice though.

 

do you think it is? can I email you some of my scans later on? I have to get them out of my laptop but I don't know here I just checked

TPS 18% Map 86.7, rpm 1200 BLM long term is 128/116
TPS 12% Map 72.0, rpm 1300 BLM long term is 132/112
TPS 8.2% Map 60.7, rpm 1325 BLM long term is 132/109
TPS 3.5% Map 48.0, rpm 1375 BLM long term is 133/128
TPS 25.9% Map 83.8, rpm 1875 BLM long term is 130/116
TPS 0% Map 32.9, rpm 1650 BLM long term is 159/124 speed 58 decelerating slowly
TPS 24.7% Map 88.2, rpm 1600 BLM long term is 130/117
TPS 12.9% Map 70.1, rpm 1425 BLM long term is 134/109


Seems like the more throttle I give it, the more the left side goes normal/richer & right side rich/richer, less gas the right side goes leaner back to normal & the left side leaner to real lean like 160

 

Also, when I pointed my lazer gun at the primaries this is what I got:

cyl #2 297*C
cyl #1 289*C
cyl #4 330*C
cyl #3 340*C
cyl #6 328*C
cyl #5 337*C
cyl #8 198*C
cyl #7 204*C

what is with the back 2 cyl's? too rich?

 

Those 2 cyl are running reaal coooool!

 

TTT

 

There have been a lot of posts on the split BLM problem in the past. Most are a direct result of the throttle body..... I see you have a Holley. To eliminate the most likely culprit, put the stock one back on & try it. This will eliminate a major variable for a 20 minute effort.

A big cam will give some intake flow reversion & upset the idle mixture. Most aftermarket t-bodies do not use the individual idle ports in the lower intake, they instead bleed air to the plenum for idle air control. This allows the small quantity of idle air to be diluted by the "reversion" air in the intake & not reach all cylinders equally. The bleeds put an equal amount at each cylinder to lessen this problem. Try it & keep us posted.

Hope this helps.

 

So far as I recall, the Holly is the "good TB", not like the BBK etc which requires modding. The back 2 cyl usually run the leanest, so its odd that they are showing up cool here.

 

why do you want to get it flowing through the triangle? I thought you want everything directed through the IAC passage? Also, my Holley is as far back as the screw will let it go when adjust for idle, no difference ? I'm gonna try putting the stocker back on I guess, & modify it like those pics, but would like to know why.

 

Bunker, the stock TB has no gouged out passage other than a STRAIGHT shot to the IAC passage, some aftermarket TBs have a hole which leaks air, this would be the "triangle" I believe you are refering too, you do NOT want it leaking air in this fashion.

I had thought that Holley, was designed just like the stocker. Most of this problem will show up as a car not wanting to idle at all, even with maxed out IAC counts, because the air is not going where it should. Someone that supposedly spoke with some aftermarket companies said that this improved driveability, which is a load of crap. I had to make a small bleed hole, and close off this leak, on my BBK 58mm TB.

Again, last Holley I looked at did not have this issue, but they are $$$.

 

Just a side note. Holley is the second worse designed TB next to the BBK/Edlbrock.

I run a LPE and have never had a split BLM problem even with my tiny 234/242 .575/.565 cam

 

Holley a bad design? I agree I didn't like the way the throttle felt & the amount of travel for WOT that it has, I didn't look to see if it was like the stocker, but even with my stock TB I had this split blm issue.

 

Ps. Ellis, wouldn't you normal BLM's also be because your cam has a big split? 234/242 where as mine is 236/236?

 

What exactly do you mean by the preceding statement? Are you in Cell 16 at the time you are looking at the BLM's? What do you mean when you say "then (what I think you meant) the pcm adjusts the injectors and both sides will show 128/128"? How would the pcm "adjust the injectors"? Why would the BLM's change from 160/120 or 128 (which is it - 120 or 128? They shouldn't be jumping around like that) to 128/128.

The data you put in the 2nd post is OK, but it would be easier to plot with a Cell reference. What is the MAP value at idle? What is the idle RPM? Do you have a complete data log, rather than just the data you posted?

 

Yes I have a complete data log, I need to get a floppy from a friend for my laptop so I can transfer the stuff, idle its cell 16 & 58-60.5 for map, what I meant by the BLM is its 160/120 for long term but than the pcm adjusts & short term becomes 128/128 & long term 151/128, but the left side would be 2.8 & right would be 2.3 for duty cycle.