Split BLMs with closed throttle
Thread Starter
Teching In
Joined: Jun 2011
Posts: 3
Likes: 0
Split BLMs with closed throttle Hi guys,
First post here. I have been fighting an issue with the BLMs being split in
low load, 0% throttle conditions. I probably had this when I got the car, didn't notice it until I logged it.
* At idle(Cell 16) in neutral the MAP is 47-50 KPa. Driver side LT BLM: 115-118, Passenger side BLM: 145-155.
* At idle(Cell 16) in gear with foot on the brake MAP is at about 60 KPa. Driver side LT BLM: 128, Passenger side BLM: 140-142.
* Low speed / <3% throttle(Cell 18) MAP is around 55 KPa, Driver side LT BLM: 120, Passenger side LT BLM: 140.
* Decel at 65 MPH(Cell 1) MAP is at 30-35, Driver side LT BLM: 108, Passenger side BLM: 135.
In normal driving both sides are between 122-132 and the split is 0-4 BLM's.
This is my current setup:
- Stock bottom LT1
- Ported alu heads
- LT4 hotcam kit w/ 1.6RR
- #30 Bosch III Injectors from FIC
- Edelbrock AirGap intake
- Tri-Y headers, 2,5" exhaust, hiflow cats
- CAI
- Stock 48mm throttle body
- Opti was replaced about 2 years ago by previous owner.
This is what I have done since I first found out about the BLM's being split:
- Replaced the stock injectors with FIC Bosch #30's
- Installed headers + exhaust.
- Replaced MAF with a new one.
- Replaced FPR(old one didn't hold pressure).
- 2x new Delco AFS75 o2's, later swapped them side to side with no difference.
- Closed throttle blades with stop screw as much as possible and adjusted TPS to 0,67v.
- Installed new MSD plug wires + new spark plugs.
- Checked / replaced intake gaskets.
- Adjusted valve lash to zero lash + 1/2 turn preload.
- Triple checked for vacuum leaks.
- Checked for exhaust leaks, can't find any.
It runs great IMO. I'm not sure how smooth idle should be with the hotcam though, it sure is a bit rough.
This is getting frustrating to say the least. Thanks a lot for spending your time reading this,
First post here. I have been fighting an issue with the BLMs being split in
low load, 0% throttle conditions. I probably had this when I got the car, didn't notice it until I logged it.
* At idle(Cell 16) in neutral the MAP is 47-50 KPa. Driver side LT BLM: 115-118, Passenger side BLM: 145-155.
* At idle(Cell 16) in gear with foot on the brake MAP is at about 60 KPa. Driver side LT BLM: 128, Passenger side BLM: 140-142.
* Low speed / <3% throttle(Cell 18) MAP is around 55 KPa, Driver side LT BLM: 120, Passenger side LT BLM: 140.
* Decel at 65 MPH(Cell 1) MAP is at 30-35, Driver side LT BLM: 108, Passenger side BLM: 135.
In normal driving both sides are between 122-132 and the split is 0-4 BLM's.
This is my current setup:
- Stock bottom LT1
- Ported alu heads
- LT4 hotcam kit w/ 1.6RR
- #30 Bosch III Injectors from FIC
- Edelbrock AirGap intake
- Tri-Y headers, 2,5" exhaust, hiflow cats
- CAI
- Stock 48mm throttle body
- Opti was replaced about 2 years ago by previous owner.
This is what I have done since I first found out about the BLM's being split:
- Replaced the stock injectors with FIC Bosch #30's
- Installed headers + exhaust.
- Replaced MAF with a new one.
- Replaced FPR(old one didn't hold pressure).
- 2x new Delco AFS75 o2's, later swapped them side to side with no difference.
- Closed throttle blades with stop screw as much as possible and adjusted TPS to 0,67v.
- Installed new MSD plug wires + new spark plugs.
- Checked / replaced intake gaskets.
- Adjusted valve lash to zero lash + 1/2 turn preload.
- Triple checked for vacuum leaks.
- Checked for exhaust leaks, can't find any.
It runs great IMO. I'm not sure how smooth idle should be with the hotcam though, it sure is a bit rough.
This is getting frustrating to say the least. Thanks a lot for spending your time reading this,
Considering you have a stock TB, TB related splits should not be happening. Check the passenger side plug wires for opens or high resistance and the plugs. Incomplete ignition will cause the BLMs to climb and go badly split. Sounds like an ignition issue to me.
Thread Starter
Teching In
Joined: Jun 2011
Posts: 3
Likes: 0
Thank you for your help. I have removed all the plugs(which are new NGK TR55ix) and they at least looked okey. Plug wires are new, I will however go and check the resistance as you suggested next time I'm out in the garage.
