liquidh8

Hey all, me again, I was wondering if anybody had this problem. When I am driving down the road the IAC opens up to 160, but after I come to a stop and idle, it'll stay there. Sometimes lowering to 130 or so, but always high. Guess I have a bad IAC. It doesn't really surge or anything, but I still haven't got the idle thing figured out yet. SOooo, this could be a new problem to compound my existing idle problem. hehe. BTW, would anybody happen to have the pinouts for a BBC IAC and for the SBC IAC??? I hooked the BBC IAC with a GM pigtail, and as you all know, the GM pigtails have ALL white wires. The BBC is a rectangle connector, and the SBC is a square one. Need to know what ones are a+, a-, b+,b-. thanx in advance.

JP86SS

iTrader: (1)

Square IAC on 87' SBC = A+, B- & C+, D- Thats running from 730 E3, E4 & E5, E6 respectively.
You'll probably have to confirm the direction of travel and reverse both sets if needed.
don't know on the BBC.

RBob

iTrader: (1)

Which ECM, mask?

RBob.

JP86SS

iTrader: (1)

This was just posted a few days ago.
Might help as well.
https://www.thirdgen.org/techbb2/sho...hreadid=331784

liquidh8

sorry, 747 ecm, $42 mask.

RBob

iTrader: (1)

IAC control on the '747 is bad. First thing is to hit the Tuning Guide sticky and the '747/'846 section. There is an article on the IAC control. The end of the article is the most important.

What happens is that there isn't a controlled (closed loop idle) idle speed until the engine is up to temperature. Until then there is only the lower limit (don't want the engine to stall), then upper limits.

These upper limits can be quite high. This causes a high floating idle speed until the engine is up to temperature. Only then wil lthe idle speed vs coolant table values be used.

RBob.

liquidh8

thanx rbob, I used a stock 5.7 bin today to see if my changes have hurt me, and I believe they have. If I leave the c/l idle speed @ 600 rpms, in the table, then the IAC counts will go to 0 when I stop and idle, If I move them up to when the car is REALLY idling at, about 750-800, the the IAC count come up to lie 130 or so and the car runs a little worst, though the idle doesn't go up, just starts to surge. I have read the tuning guide, but I am going to go back and read some more to see what I must have missed. Now that it is cold here, (PA), I have to figure out the cold stuff. After 3 tries it starts in the morning, then runs like crap till it warms up. I pops and almost stalls off idle, till it warms up (72 C). from there it has been getting the blms closs and trying to get the timing straitened out. As I said in a different post, The knock sensor isn't working. Today I got it to ping and the knock sensor didn't register any counts. Damn Vortec heads. Sorry for babling.