Running Rich
06-18-2007, 06:23 PM
#1
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Thread Starter
Running Rich
My 90 vette is runnig very rich at idle. I read on the forum that I might need a custom chip or else the car would run rich if I have bigger injectors.
The specs of the car are:
Comp cam
ported heads and plenum
Edelbrock Hi FLo TPI Intake and Runners
24lb injectors
stock throttle body
No cats, 3" dual exhaust
Right now the fuel pressure is at about 47. It was at 55psi before but I lowered it to try to elimate the car from running rich. The timing is at 7 degrees, new 02 sensor, TPS and IAC valve. Any ideas?
The specs of the car are:
Comp cam
ported heads and plenum
Edelbrock Hi FLo TPI Intake and Runners
24lb injectors
stock throttle body
No cats, 3" dual exhaust
Right now the fuel pressure is at about 47. It was at 55psi before but I lowered it to try to elimate the car from running rich. The timing is at 7 degrees, new 02 sensor, TPS and IAC valve. Any ideas?
06-18-2007, 11:12 PM
#3
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06-19-2007, 10:14 AM
#4
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St. Jude Donor '10-'11-'12-'13
BLM = Block Learn Mode. These numbers (which you get from the ECM) will tell you how the ECM is adjusting fuel delivery at various loads and rpms in an effort to hit a 14.7:1 air / fuel ratio. OEM BLM numbers range from 108 to 160, with 128 being right on. I like to think of these numbers as multipliers.
If you were scanning during normal engine operation, you would hopefully see BLM numbers at or very near 128, indicating virtually no fueling adjustments are needed.
If you were to see a BLM number of 110, this would indicate that the ECM is reducing the amount of fuel normally injected at a given load / rpm / airflow situation. The O2 sensor has told the ECM that the engine is running rich and fuel needs to be taken away.
If you were to see a BLM number of 155, this would indicate that the ECM is increasing the amount of fuel normally injected at a given load / rpm / airflow situation. The O2 sensor has told the ECM that the engine is running lean and fuel needs to be added.
BLM numbers only update when the ECM enters closed loop (getting O2 sensor feedback). Accurate O2 sensor functioning is critical for this process.
There is a little more to it, but that is basically it
If you were scanning during normal engine operation, you would hopefully see BLM numbers at or very near 128, indicating virtually no fueling adjustments are needed.
If you were to see a BLM number of 110, this would indicate that the ECM is reducing the amount of fuel normally injected at a given load / rpm / airflow situation. The O2 sensor has told the ECM that the engine is running rich and fuel needs to be taken away.
If you were to see a BLM number of 155, this would indicate that the ECM is increasing the amount of fuel normally injected at a given load / rpm / airflow situation. The O2 sensor has told the ECM that the engine is running lean and fuel needs to be added.
BLM numbers only update when the ECM enters closed loop (getting O2 sensor feedback). Accurate O2 sensor functioning is critical for this process.
There is a little more to it, but that is basically it
06-19-2007, 01:45 PM
#5
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Thread Starter
Wow thanks for the explanation.
I called a few tuning places around here and they all said they dont want to reprogram the chip. They said the older vette chips are hard to erase and reprogram because they tend to not take the programming. I remember reading that a forum member can program the chips. Who does it? Is it worth it to buy the programmer and do it myself? Thanks!
I called a few tuning places around here and they all said they dont want to reprogram the chip. They said the older vette chips are hard to erase and reprogram because they tend to not take the programming. I remember reading that a forum member can program the chips. Who does it? Is it worth it to buy the programmer and do it myself? Thanks!
06-19-2007, 03:40 PM
#6
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St. Jude Donor '10-'11-'12-'13
There is definitely a learning curve w/ DIY tuning, though once it all "clicks", it is a lot of fun (and some headaches too 
). You will need a solid understanding of the EFI system and how all the components work together, as well as the tuning hardware & software. There are several options out there.
You didn't specify the cam specs, but if it is not too radical, there are a few tuners on this forum (Azzato Chips, PCM For Less) who could certainly set you up quite easily, and for about what you'd spend on basic tuning equipment. If this is just a one shot deal for you with this engine, it might be worth it to have someone else do it. If you plan to upgrade a little bit at a time or build something a little more radical down the road, you might want to consider doing it yourself.
). You will need a solid understanding of the EFI system and how all the components work together, as well as the tuning hardware & software. There are several options out there. You didn't specify the cam specs, but if it is not too radical, there are a few tuners on this forum (Azzato Chips, PCM For Less) who could certainly set you up quite easily, and for about what you'd spend on basic tuning equipment. If this is just a one shot deal for you with this engine, it might be worth it to have someone else do it. If you plan to upgrade a little bit at a time or build something a little more radical down the road, you might want to consider doing it yourself.
06-20-2007, 09:40 PM
#7
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Thread Starter
You didn't specify the cam specs, but if it is not too radical, there are a few tuners on this forum (Azzato Chips, PCM For Less) who could certainly set you up quite easily, and for about what you'd spend on basic tuning equipment. If this is just a one shot deal for you with this engine, it might be worth it to have someone else do it. If you plan to upgrade a little bit at a time or build something a little more radical down the road, you might want to consider doing it yourself.
Thanks for the help!
Last edited by jimmers; 06-20-2007 at 09:57 PM.
06-21-2007, 08:25 AM
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St. Jude Donor '10-'11-'12-'13
That's a nice cam; not too radical at all. Either you (after some learning / trial & error) or a tuner would be able to tune for it easily.
06-21-2007, 01:02 PM
#9
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Thread Starter
I called Alvin at PCM but he wasn't in today. I'd love to play around with it and try it myself. I just need to find a good cheap programmer. Thanks for all your help.
