I8AStang

I am doing a chip for a friend of mine who has swapped in a steathram/zz4 combo. The car is using a t56 six speed. When I first logged the car, the BLMS were way rich, and as I did chips to change that, the idle got worse, chip by chip. I tried raising the idle timing, playing with stall saver and so one. As soon as the car goes closed loop the idle gets bad. Open loop the idle is fine. I took this as meaning it needs to be richer at idle. Is there anyway to force an open loop idle? I tried setting the tps PE tables to 0 in the 400 and 1200 ranges, but it still runs closed loop. I haven't messed with the chip stuff in a while (been tuning Motec on fsae car), but my intuition tells me it wants to idle rich of stoic. More timing doesn't seem to help, and I have raised the idle speed to 925. I worked on it all day and it seemed to get no better. It runs good everywhere but idle. The BLM's are also acceptable, I can tune those right, but this idle thing is bugging me pretty bad. ALso, I didn't think the zz4 cam was really large enough to not idle at stoic with "normal" timing. Any help would be greatly appreciated. Sometimes out of the blue it will idle fine for a few seconds and then die. It is especially bad if you abrubtly blip the throttle and let it idle down, it seems almost as if the IAC doesn't even try to catch it.

funstick

remember that thing about 02 sensor reading the amount of oxygen in the exhuast ??big cam lots of oxygen in the exhuast. well youll have to lower your cl/ol thresholds for idle to command openloop.also to prevent from getting codes you may want to change the value for the code ine the code area.

I8AStang

IT isn't getting codes, and I didn't think the cam was that large. ALso, the o2's read rich, and still read slightly rich (blm's were 109 when I first noticed problem, now that blm's are in the 120's at that point the problem is worse), additional oxygen would be lean. I am willing to give anything a try, I can't acces the cl/ol tables with tunercat can I? I din't see anything like that and I thought I looked. The zz4 cam is something like 208/220 on a 112 lsa, not that large. It seems to like to idle rich. I may try more timing, but over 25 degrees at idle seems a little much. Thanks for the quick reply. I would really like to be able to access that closed loop o2 table, how do I do that?

funstick

no the sensor would read rich. its a false rich youve got there. replace the sensor but im betting on a ton of oxygen content in the exhuast. when you have a lean condition HC goes up and drowns out oxy. when your your rich hc co stay up but oxy comes up as well. without a 4 gas or a wideband your shouting in the dark here. when your overich ton of o2 makes it out the exhuast pipe. try adding some timming to the idle area.

I8AStang

What do you mean by trimming? Also, I know it likes more fuel at idle, as in open loop it does fine, how do I give it more?

Grumpy

A false rich.
I gotta remember that one.

Grumpy

Give the engine what it wants.
Increasing the overlap with a cam change, increases the self ERG'ing of the engine since at low rpm, more exhaust can be sucked back into the chamber. Like any EGR strategy it takes more fuel and timing to burn this poor mixture (ie the **inert** EGR).

Might just be easier to run Open Loop. Stoich is only the **perfect** mixture due to having catalytic converters, it has nothing to do with keeping the engine happy.

JAY87GTA

I'm experiencing a similar problem with my CC305 cam. It's to the point now that I'm getting knock counts at idle. Then that in turn is giving me bad driveability problems. I'm wondering what the consequences of changing the stoic measurement in the prom would be?

I8AStang

Is there anyway I can just make it run an open loop idle? I thought power enrichment was open loop, so I made the 400 and 1200 rpm vs. tps tables 0 % throttle, but it still ran closed loop idle. I may keep trying timing and see if it likes it, if I have no option I will run it open loop, but I am reluctant as this force me to get it the VE tables that much closer to right. Thanks for the replys. I understand the effects the camshaft has on reversion, and how it makes the engine act like the egr is stuck on at low engine speeds. It is just surprising me because of how much timing I added, with seemingly no difference in performance. It seems it just needs more idle fuel. Too bad I can't just set Lamda to .9 and hit the "Q" key (motec joke).

Grumpy

NO there is a difference between Power Enrichment and Open Loop. PE is a seperate and total mode all unto it's self.

If you want to get a hot rod'd engine really right, you ought to consider getting a WB, so then you can do something other then Stoich, which again is just for the converter, not the engine.

I8AStang

It was my understanding that PE was a form of open loop, with "special" timing and fuel for max power. I am gonna try to go the other way with timing and see if this helps (don't think it will) thanks again for ideas.

I8AStang

I think I have found other issues. The BLM's showed the car was way rich (like 1000+mv o2's, with the blms's pegged) and it wasn't that rich (acutally smelled leaner than my laser). I don't think the O2 is reading properly. ALso the car was idleing at 60kpa, which didn't seem like enough vaccum, but I didn't think much of it. When driving I noticed you can't get it to drop below 60kpa, even if you let the car coast at 3000rpm (it is a stickshif). Every other car I have ever seen this would result in 20-30kpa readings. I guess I need to get these sensor issues sorted out. Right now I made an open loop file so the engine can at least be broken in.

87400tpi

false rich condition caused by exhaust leak....

JAY87GTA

Mine idles at 53kPa and will see about 25 at the lowest, in gear on decel. You sure you don't have any vacuum leaks? I know the first time I put mine together one of the gaskets between the plenum and base had slipped.

I8AStang

It was a vacumm leak going to the map sensor, so the sensor was reading much higher (lower vacumm) that it should. The car will not run at all now, I have no clue why. Everything checks fine, all sensor readings are normal, it has spark, and it is VERY unlikely it jumped time. Pulled it in the shop, ran fine, now it run start. The only thing I can think of is running excessively rich with the high map value may have fouled the plugs.

JAY87GTA

Go back and start over with a stock bin. Likely you've got it all goofed up now since you were chasing the vacuum leak. Easy to try anyway.

87400tpi

good luck