BLMs at 108; HELP!!!
05-25-2004, 09:18 AM
#1
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Thread Starter
Join Date: Jun 2001
Location: Fuquay Varina, NC USA
Posts: 96
BLMs at 108; HELP!!!
My BLMs (left and right) are relatively low in every cell. They are at 108 in cell 06 (most used cell in normal driving).
In cell 10, they go to about 110 - 112.
The car runs fine and the O2 sensor response is rapid (as displayed on the Scanmaster). I changed the O2s anyway and the car seems to be slightly smoother and the readings respond just as quickly as the previous sensors, although over a narrower band.
The fuel mileage has been low (in my opinion!) since I bought the car 3 years ago. It struggles to break 20 MPG on a trip. This is with a M6 and 3.42 gear. As far as I know, the car is stock except for the headers, electric water pump and cold air intake I have added. Even my 03 GMC Sierra Ext. Cab truck (5.3, A4, 3.73.gear) does better on fuel!
What's going on?
In cell 10, they go to about 110 - 112.
The car runs fine and the O2 sensor response is rapid (as displayed on the Scanmaster). I changed the O2s anyway and the car seems to be slightly smoother and the readings respond just as quickly as the previous sensors, although over a narrower band.
The fuel mileage has been low (in my opinion!) since I bought the car 3 years ago. It struggles to break 20 MPG on a trip. This is with a M6 and 3.42 gear. As far as I know, the car is stock except for the headers, electric water pump and cold air intake I have added. Even my 03 GMC Sierra Ext. Cab truck (5.3, A4, 3.73.gear) does better on fuel!
What's going on?
05-25-2004, 06:46 PM
#2
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Join Date: Dec 1969
Location: Calgary, Alberta, Canada
Posts: 324
Looks like you are running rich.
Might be a leak somewhere, bad plug, missfire something is telling the computer to subtract fuel, no telling exactly what. You might want to try and get a tune up first or put it on a scope.
If the car is in real good condition you might experiment by increasing the injector constant size, let's say from 24# to 26# and see if that doesn't set you on the right path. The computer will still use what ever fuel map it has in it, but it will cut back on the injector pulse width to compensate overall for the "larger" injectors. Thus perhaps allowing you to get towards the 128 BLM # that is optimal.
If you don't get a good result from a minor change in the injector constant ... then look somewhere else before you do damage.
Hope this helps
LWM
Might be a leak somewhere, bad plug, missfire something is telling the computer to subtract fuel, no telling exactly what. You might want to try and get a tune up first or put it on a scope.
If the car is in real good condition you might experiment by increasing the injector constant size, let's say from 24# to 26# and see if that doesn't set you on the right path. The computer will still use what ever fuel map it has in it, but it will cut back on the injector pulse width to compensate overall for the "larger" injectors. Thus perhaps allowing you to get towards the 128 BLM # that is optimal.
If you don't get a good result from a minor change in the injector constant ... then look somewhere else before you do damage.
Hope this helps
LWM
Last edited by LWM; 05-25-2004 at 06:56 PM.
05-26-2004, 06:52 AM
#4
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Join Date: Jun 2001
Location: Fuquay Varina, NC USA
Posts: 96
The headers are shorties and I've had the low BLMs since before the header install.
I'm beginning to wonder if a previous owner changed injectors to a larger set or possibly reprogrammed the PCM.
I've been over the fuel and ignition systems looking for clues. I've even run it with the MAF disconnected and the BLMs will still get back to the 109-110 range in 100 miles or so.
I have a low mileage Opti with Accel 9000 wires (OVC).
I've checked for vacuum leaks and even pulled the Carbon Cannister to check it for leaks or fuel saturation.
My MAF reading is 6 GPS at idle and about 20 GPS at 60 MPH.
MAP readings are 10 (approx. 20" vacuum) at idle and 15 (15" vacuum) at 60 MPH in 6th gear.
I haven't checked the fuel pressure yet (I don't have a fuel rail connector) but the regulator looks like the stock one.
I didn't worry too much about the BLMs at first because I figured the PCM was just doing it's job. Then I found out that 108 was pretty much the bottom of the adjustability range (I used to think the range was 0-256; 128, +/- 128) and I still think I may be rich, based on my fuel economy. So now, it bothers me.
I'm beginning to wonder if a previous owner changed injectors to a larger set or possibly reprogrammed the PCM.
I've been over the fuel and ignition systems looking for clues. I've even run it with the MAF disconnected and the BLMs will still get back to the 109-110 range in 100 miles or so.
I have a low mileage Opti with Accel 9000 wires (OVC).
I've checked for vacuum leaks and even pulled the Carbon Cannister to check it for leaks or fuel saturation.
My MAF reading is 6 GPS at idle and about 20 GPS at 60 MPH.
MAP readings are 10 (approx. 20" vacuum) at idle and 15 (15" vacuum) at 60 MPH in 6th gear.
I haven't checked the fuel pressure yet (I don't have a fuel rail connector) but the regulator looks like the stock one.
I didn't worry too much about the BLMs at first because I figured the PCM was just doing it's job. Then I found out that 108 was pretty much the bottom of the adjustability range (I used to think the range was 0-256; 128, +/- 128) and I still think I may be rich, based on my fuel economy. So now, it bothers me.
Last edited by Tommy'Z 6speed; 05-26-2004 at 06:58 AM.
05-26-2004, 07:55 AM
#5
Registered User
Join Date: Dec 1969
Location: Calgary, Alberta, Canada
Posts: 324
Originally posted by Tommy'Z 6speed
The headers are shorties and I've had the low BLMs since before the header install.
I'm beginning to wonder if a previous owner changed injectors to a larger set or possibly reprogrammed the PCM.
I didn't worry too much about the BLMs at first because I figured the PCM was just doing it's job. Then I found out that 108 was pretty much the bottom of the adjustability range (I used to think the range was 0-256; 128, +/- 128) and I still think I may be rich, based on my fuel economy. So now, it bothers me.
The headers are shorties and I've had the low BLMs since before the header install.
I'm beginning to wonder if a previous owner changed injectors to a larger set or possibly reprogrammed the PCM.
I didn't worry too much about the BLMs at first because I figured the PCM was just doing it's job. Then I found out that 108 was pretty much the bottom of the adjustability range (I used to think the range was 0-256; 128, +/- 128) and I still think I may be rich, based on my fuel economy. So now, it bothers me.
That's a possibility, stock injectors are black and nondescript.
SVO 24#s are baby blue on top = to 25# GM style
SVO 30#s are red on top = 32# GM style
SVO 42#s are green on top = 45# GM style
108 is indeed the bottom of the range, your PCM is pulling out all the fuel it can and it is still convinced it is "rich".
Your idle GPS at 6 is about right.
Vacuum looks good.
Hope this helps
LWM
05-27-2004, 09:46 PM
#7
Registered User
Join Date: Nov 2001
Location: Kansas
Posts: 3,517
Since you checked your MAF already then it really sounds to me like the previous owner either added an adjustable fuel pressure regulator and cranked the fuel pressure way up or added some 30 lb injectors. Many aftermarket performance parts sites advertise those pressure regulators as easy hp but the PCM for 94+ F-bods always ends up compensating for the extra fuel by decreasing the fuel trims like you are experiencing... I think a lot of ppl get duped into buying them. Simply increasing your injector constant in a new program for your PCM would take care of the problem OR if there is definitely an aftermarket fuel pressure regulator on the car then you can try messing with it till you see your BLMs start climbing back up.
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