Hey guys. Ive been having trouble trying to get the idle tune down on my 350 TBI with ZZ4 cam. Ive tried to tune the BLMS in idle cells 40KPA & 50KPA(switches back and forth) at 800. Car starts up fine idle is decent not great. O2 kicks on then slowly creeps up 850mv and sticks there till the BLMs start drop to 104. As the blms drop car wants to die out but catches itself till the blms settle. Ive taken so much fuel out of those cells mostly the 50KPA its starting to get pretty low. No matter how much ive taken out the blms are not dropping at all. Am I missing something.

 

Incorrect valve adjustment, possibly a couple may be too tight? Any codes? MAP hose on? Map passages clear? Timing close? Sounds like ECM is trying to control the rich issue. Recheck all the mechanical pieces first.

 

Air leak, bad o2 sensor.

Also https://www.thirdgen.org/techbb2/sho...hreadid=310130

 

I did get code 45 (o2 rich) recently and the ongoing code 43 that Im trying to figure out how to disable because my ecm can't get my motor to knock. Ive just noticed that I am getting the "Forced to Open Loop" flag at idle. What is that all about???? I cant seem to find a vacuum leak anywhere but I will check again. Base timing is at 10 degrees in the chip and my IAC counts at idle are around 30.

 

Code 45 is no surprise, you are indeed rich so code is correct. Code 43, in my exp most times its a bad or mismatched knock sensor. Don't disable, the engine knocks, the ecm doesn't "make" it knock (too deep to worry about right now). Sounds like you have chip burning tools, if so make a stock bin and retry. Headers? If so a grass roots test for dead cylinder; fire engine for approx one minute, I will wet my fingers and touch each header pipe near head, cold pipe=dead hole. You have a dead cylinder or are way overfueling all cylinders. My guess is one or more cylinders aren't making power, so the injected fuel is pumping down the exhaust. You'll get it. Check mechanical stuff first.

 

Does the O2 stay rich (850 mV ish) if you rev it up a little, or drive it around? Or is it just at idle? Does it ever go below 400 mV?

I'd adjust more than just 2 cells when fighting a rich problem. I'd get the whole area around idle (1 RPM breakpoint above and below, and several MAP breakpoints). The idea being that if it's way too rich, then the MAP will be falsely high, and you might overlean the higher maps, and not get the lower MAP, and then the engine will basically oscillate around the lean "hole." When in the hole, it falters and RPMs drop and MAP goes up and IAC opens, this gets it to a place that at least has fuel, which shoots it over to the lower MAP slightly higher RPM, which is too rich, so then it starts to pull out fuel, hits the hole again, and it just gets rediculous. But, I would make sure the O2 signal is accurate first, otherwise you're chasing a ghost.