85C-4

I have been searching this forum and was hoping that someone could point me to some expected or normal values for MAF, BLM, IAC and etc. I understand that these change depending on conditions but I am hoping to find a range of normal values or even a detailed review in a publication for my 1985 C4 with the 4+3. Some example questions that i have a re what is a normal MAF value for a given RPM, the same for IAC and how to interpret BLM values. Thanks

byebyeL98

Another forum member (Morley) had posted this link in a thread a few months back. It is a page he created, and IMHO gives a very well rounded and easy to understand overview of GM EFI tuning.

(I don't want to speak for him, but I think it is still a work in progress)

http://home.comcast.net/~khiester200035/index.html

It answers a lot of the questions you are asking. The stickies on this page over at Thirdgen.org also carry a lot of information:

http://www.thirdgen.org/techboard/diy-prom/

Morley

MAF values are very hard to give an answer for, there are many variables that will affect a MAF's reading. I can say that at idle your MAF should be reporting around 9-12 gms/sec flow.
For BLM's you want to see 128, but 125-134 is very acceptable. As the BLM goes lower it indicates you are running on the rich side, and as they go higher you are running towards lean.
The IAC counts really only come into play at idle and you'd want to see them as low as possible, but here again there are many variables that will affect the IAC counts (ie. fan request, alternator load, A/C clutch engaged or not....)

85C-4

Gentlemen- Thanks a great deal for the information, this will certainly help answer my questions and is appreciated!

N0DIH

I have numerous data logs of my LT1 if you want to look over them to see what mine runs for typical data.

I see around 7-8 GM/sec idle air flow, which ends up around 1.9 to 2.0% calculated duty cycle (rpm*PW/1200 for calculated duty cycle), MAP around 40-42 (0.4 to 0.42 as Freescan logs it), 4 mS PW on the injectors, around 29-38 for idle IAC counts.

Again that is for an LT1, which shouldn't be very far off.

If that helps any.

Morley

Except that you are MAP and he is MAF, the two have no common relation in readings.

85C-4

Thanks for the offer, for now I am just researching trying to get a better feel for the numbers. As noted there are differences between MAF and MAP systems. Anyway, the car runs well at this time and I am going to scan again soon to see how the long term fuel trims (BLM) change with the pink top injectors that are in it. That's the only non-stock thing about the car-

Alvin

Maf is going to vary with how much air the engine is pulling in.

BLM's should AVERAGE around 128. That doesn't mean they will sit there.

IAC should read around 30-50 counts at a fully warmed idle in gear.

95BlueBomber

What about fiding whether or not your injectors are overworked? My INJ DC goes red after 5900... does this mean anything? The numbers are in the lower 80's.