Wingnutt

Background...after installing a Holley TBI, I had an extremely rich cold start until my Blazer (350/700R4) reached C/L.

I started things off by leaning out my O/L AFR to get rid of my extremely rich cold start. This was accomplished setting all of the values in the O/L AFR vs. Temp to 13.00. Then I used the Cold ARF vs. Vac to refine things. I also significantly lowered my IAC vs. Temp counts based on an old thread that I found doing a search.

All of this got me down to a reasonable AFR during O/L, but it’s still a tad rich. I am getting some popping in the exhaust when I let off the throttle, but I can live with that until I get the following problems ironed out.

Tonight I had the Blazer hooked up to ALDL and noticed that the MAP was giving all kinds of screwy readings, so it got replaced. This helped a bit along with fixing a tiny vacuum leak that I found.

Now here’s where the fun begins.

When I start it up and let it idle until it goes into C/L, everything is fine I have 700 RPM idle, steady BLMs, IAC counts, and O2 readings.... until I put it into drivethen back into park. That's when things get wierd. It will idle around 1100RPMs and after about five minutes it settles down.....sometimes. Other times it will continue to idle around 1100 RPMs with what I can best describe as a burbling sound in the exhaust note (it almost sounds like a miss). The IAC counts are elevated (around 17 or so) for a long time then settle down to around 4 with a nice smooth idle, again sometimes.

Now for the really weird part, the BLMs are rock steady at 128, no matter what the idle is doing (I have a new O2 sensor, I replaced the old soot filled one Friday night).

I raised the IAC vs. Temp counts back up about 5% tonight, which helped the idle quality a little bit, but after doing that, I am getting a really rough engine deceleration when I goose it, then it settles down to either an 1100RPM or 750RPM idle.

Does ANYBODY have any ideas on where to begin to clean the idle up so I can start on screwing up the rest of the bin? As always, TIA!

91L98Z28

1) did you change the injector size when you swapped the holley TB? If so, my *GUESS* is that you need to go back to the original BIN, and change the injector size constant (or base pulsewidth or whatever equivalent your BIN has). I guess I should state that I'm not familiar with any TB apps and as such I'm not sure how your BIN deals with injector size.

2) Do you get O2 crosscounts? Does your INT move at all? While I guess a perfect 128 BLM is possible, .. if you never see it change, it makes me suspicious.

3) did you change the fuel pressure regulator/is it integrated with your TB? could the fuel pressure be different now?

RBob

iTrader: (1)

Check out this thread:

https://www.thirdgen.org/forums/show...hreadid=308613

Up in the sticky's, the prom tuning guide book, there are links to several good posts on the '747.

RBob.

Wingnutt

I forgot to mention it is a 7747 with the $42. Yes the Holey does have larger Deplhi injectors, and I will look for something that controls the pulse width or injector constant tonight when I get home. As for the regulator, it is whatever is in the Holley, and I haven't messed with it....yet. Also what is an O2 crosscount and INT? As you can probably tell, I think I'm on a vertical learning curve here.

I've searched but somehow missed that thread you linked to, I skimmed over it and it looks like what I need.