355 and I just cant seem to lean it out, so I started over again from scratch and heres what I've done and the order I've done it and I keep arriving at the same result... Sooty rich!

Changed cylinder volume constant to allow for additional 5 cu/in.

The stock 350 motor idled at at 30 map or so. The new 355 idles at 60-64 Map. To initially rough things in, I took all the stock fueling tables and rearranged them to my 60 map idle. eg. I selected the stock 30 Map column and pasted those values in my 60 Map column. I did this for all the fuel tables to get things close.)

I did this exact same thing for my open and closed spark tables also.

I totally removed all startup choke fuel by zeroing all values.

I added 100 rpms to all entries to keep it running.

and finally as suggested on here, I opened up the butterflys and readjusted the IAC. this seemed to help big time but not totally. Its still rich and it just idles higher than I'd like it to.


I keep trying new things, spark tables, lowering and lowering the fuel tables, playing with different injector sizing (inputting different values) and I just cant seem to get it to stop fouling plugs. It runs nice after a new set of plugs but slowly and surely gets worse and worse as the plugs become more and more fouled.

Is there accell enrichment going on here? not allowing it to go any leaner? I dont know whats going on. Maybe someone else can shed some light on this of what they might think it is. (the obvious has been gone over...several times) plugs, wires, rotor, cap, vacume leaks.

16168625 ecm E6
355 cu/in 10.5 cr
Good sized cam but dont have the specs handy. Installed 6* advanced.
GM 202 cast iron heads massaged slightly.
All the stock goodie were bolted back on the new motor, Intake / TBI unit, sensors, exhaust ect. Just the block and its internals are new to this vehicle with the exception of the heads as I mentioned.

I datalogged a while back and the consesus was everything looked pretty close but the timing was off a bit. it idles around 30* now.

This issue is definately caused by my cam, but I dont know how to go about correcting it.

 

What's going on is lots of fresh air is getting into the exhaust because of the overlap in the cam. The ECM thinks lean and adds a bunch of fuel to compensate.....then you have your rich condition.

I suggest going open loop at idle, I'm not sure how to envoke open loop at idle only with that particular ECM, but I'm sure Fast will be along to help. In the mean time you can just try locking out closed loop by setting the enable temperature to a high point. Now go in and tune the idle by smell and feel and see what it likes. I bet you'll find that it's much leaner than the BLM's would have you think. In my experience a 218/226 110 ls cam is right on the verge of being able to run closed loop, in my case I was using a 747 ecm so it may be possible with the newer PCM just by offsetting the O2 rich lean thresholds.

You'll quickly find that a WB is indespensible when it comes to tuning big cams. Most big cams just don't like running at 14.7 to 1 AFR.

 

Set $48D1 to the max allowed value of 150 dec C (255 decimal). This is (or I think it is) the cool temp threshold for open loop idle in the $E6. When this is set, the PCM will always idle in open loop. You can also use the open loop idle AFR table to dictate the lean limits for the AFR while idling. I think thats at $4B9C in your PCM. The PCM wont allow the engine to idle any leaner then whats in the tables.

Also, be careful if your using AIR. IIRC, the open loop idle also envokes the PCM to direct air into the manifolds, which could cause issues with a cat if you have one. The extra air and fuel could result in a melt-down. Id have to check and see if this is really the case, or if it just bypasses the air. If youve tossed the AIR, then no worries.

 

Mine is a big block app, but may be applicable. With the new cam, it went from 35 kpa idle to about 55 kpa idle.

I had to go to an open loop idle, about 12.5 to 13.0 on the WB. Bumped the idle rpm up about 100 to 150 rpms.

 

Dimented. No AIR and No Cat. Now when you say set $48D1 what table does that corrospond to? With tunercat I can set a constants for open loop / closed loop, but I think changing that value would either keep it in or out all together, and from what you seem to be saying, I can keep it open loop just during idle conditions. Which I really like that idea.