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My idle seems a little rough. I finally got tuner pro running after much aggravation with ccm issues. I read that the iac should be about 30 steps or so while idle and mine is like 10-15? Can someone look at my data and tell me what they think? Now that I have tuner pro working I can record data if that would help! I appreciate any help or advice? Also, how does my blm look?
Currently new:
bosch 3 injectors
iac
plugs and wires
opti (petris)
Your injector pulse width seems awfully high for idle speed. Up over 8 milliseconds. For reference, my 383 idles around the same manifold pressure and am only getting about 2.3 millisecond pulse width.
With that much on-time with the injectors, I'd expect pig-rich fuel trims and O2 sensor readings, but curiously I'm not seeing that.
What injectors did you get? How is your fuel pressure?
I purchased refurbished Bosch 3 injectors from fic about a month ago. I didn't check the fuel pressure as I don't have a gauge but the pump and regulator are new.
Hmmm.... you might want to confirm what the flow rate is on those.
Unless FIC modified them to be 24 lb/hr (factory LT1 flow rate), those are only rated to about 18 lb/hr according to published data. So if they really are only 18, the ECM is going to have to increase the on-time to get the correct amount of fuel delivery.
Also, you might want to ask them if they have the voltage offset data. What's published online is very different than the factory values. That can also mess with the final pulsewidth and fuel trims.
If he had an exhaust leak upstream of the O2 sensor(s), it would fool the O2 sensor into thinking he was running lean. ECM would then dump a lot more fuel in unnecessarily which would likely cause his BLMs to drop to the 108 minimum value (I've seen that kind of thing happen before).
But his BLMs are 133 on one side and 115 on the other. Not ideal, but not horrible either.
As it stands, the ECM is driving the injectors very hard just to maintain close to stoich 14.7 (at idle speeds!)... which leads me to think his fuel pressure is very low, or the injector flow rate is very low.
That does seem low. I think you should be up at ~42 psi connected and ~45-46 disconnected.
If your regulator is non-adjustable, then it's probably bad... less likely might be a bad fuel pump not delivering adequate pressure in the first place.
I assume you were able to positively confirm what injectors you have?
so to close the loop, it seems my new ac delco fuel pressure regulator was bad. I installed my original one and it is idling so much better! Fuel pressure at idle without the vacuum line is now 43psi and about 36-38 at idle under vacuum. I will run the tuner pro in the near future and see if the ms of the injectors has changed.
ULTM8Z - I did reach out and they told me the injectors have been proven in the field with loads of c4's running them. They also led me to the fuel pressure issue and gave me some tips on how to check if it's the pump or regulator. Thanks again for your help! I may reach out again after I run tuner pro again and ask you to take a look.
did you ever take any additional data? Curious what happened with your injector pulse widths. There's another guy in another thread I'm helping who has high pulse widths too and similar fuel pressures. I'm curious what effect your new regulator had on the injector pulse widths.
1993 C4 Chasing Idle Issue Have Tuner Pro 5 Data!
