What would be some things to look for in regards to low blm's on one bank. Driver side bank is always between 125-135, but passenger side is anywhere from 108-115. car Idles crappy , almost a shudder. took it to a shop and they said my injectors are too big. I dont buy it. I am running racetronix 32lb injectors. low sped driveability sucks too. feels like a miss. The cars seems to clean out and pull pretty good over 2800 rpms. It has new plugs, wires, o2's. any advice would be appreciated. thanks.

 

As long as the pcm is tuned for the injectors they can't be "too big". An intake leak or exhaust leak prior to the O2 sensor could cause it. Also what causes it most of the time is a bad O2 sensor. If it sits around 108 for too long your plugs will be fouled and your O2 sensor will be a gonner before too long. How do I know been there and done that. The pcm is adding a ton of fuel on that side which is probably a false lean condition. Switch O2 sensors and see if the problem follows the sensors. If so then it's the sensor and I'd change all 4 spark plugs on that side.

If you get tired of blowing money like I did you could always tune the O2's out, if your tune is close to the correct A/F. Yes this is a bandade fix but it works(recomend getting a wideband or confirming data on a dyno if you go this route). Main thing is that you will have to change your spark plugs because they are probably fouled out on that side.

 

Split BLMs at idle are a common issue with a cam of any size to it. If your BLMs even up in other driving conditions, then it's probably just the cam.

 

thanks for the replies. i get the split in almost every cell. I used to get the split in the opposite direction untill i resealed the the passenger side flange. It used to be 128 on driver side and 150 on passenger side. i sealed the flanges by the o2's on both sides. nowi get 128ish on driver side and 108-115 on passenger side. the car has a noticable drivability problem down low. It idleswhat i would call rough. I have had this cam in the car for quite a few years now. when the thing is running right it idles pretty smooth. The intake has been resealed. has a fairly new opti, 5000 mile or so. I did take the opti off the other day and the rotor screws were loose. I just tighened them back up. I was kinda frustrated that it was coming apart so soon. its a gm opti. I am just looking for some ideas as to why its consistently pulling fuel from that bank in all cells. I adjusted the rockers at varies stages of preload. It has new wires,plugs, o2's. Anyone in the midwest want to work on this thing? I am convinced That there is a correlation to my running problem and my split blm's. If it was a vacuum leak wouldnt it affect both banks? I sprayed carb cleaner to the intake with no change. Would a flat lobe on the cam do this? I am seriously out of ideas. I am tempted to pull this thing and tear it down, but i am not convinced that this isnt a FI problem. it seems to run ok when i first start it. runs progressive worse the warmer it gets.

 

Might be of some use... seems related:?

I did an mod to my 02's, connected one Wideband 02 with "Simulated Narrowband Output" to both PCM 02 inputs... you would expect identicle Lterm/Sterm/BLM corrections right? For the most part that is true except when my setup was in Fuel Trim Cells 5 and 6.. read below for all the info...


Well I finally connected my Wideband output to the PCM, it seems to run alot better, overall much less cam surge down low... cruising in 1st and 2nd is much better, but I need to get some miles on it. One major change with wiring this up is one 02 signal feeds the two PCM inputs. This might be the reason for the smoother low RPM power... not totally sure.. I guess I could wire up one stock 02 to both inputs and see what happens.
Couple things I noticed:
the low rpm (900-1100rpm) slight load "chug" is totally gone.. I blamed the chug on bank to bank rich/lean that occurs because the stock 02's cant sense accurate AFR at very low idle with bigger cam, one side is weak, one side stronger and ends up feeling like a very slight missfire? Hard to explain or notice.

I datamastered it and noticed I had to run VE Master again since the fueling was different now so maybe that means the WB is reading better than the stock 02's?

The WB02 sensor is in my left pipe only, not both like I originally thought so one day I'll have to add a port to after the y and see what happens.

Something strange happens with the BLMs at a cruise with slight accel .. very slight accel... ~1350rpm and 35kpa only at certain RPM and MAP.. in my case it's around with both 02 mV reading the same voltage since wired from the same sensor, Lterm BLMs end up split with 110 on one side and 138 on the other.. injector flow rate also shows the split 1.74 and 2.15ms with 83lb injectors.. this is quite a bit. , also noticed most or all of this happens in FUEL TRIM CELL 5 and 6. It runs ok when this is happening (better than with 2 stock 02's). How can this be happening? Same 02 mv inputs create split BLMs?? This split also goes the other way at around 1500rpm and 31kpa... mostly crusing at that speed, any increase in load makes it go away. Lterms are within 1 of each other when this happens anywhere in the log. Again, it runs good.. little cam surge but maybe it's actually right/left bank rich/lean creating the slight chug (reason why it feels smoother in open loop than closed loop)?

BTW, wiring right to the PCM wires is much easier than crawling around under the car.