I am new to the 730 ECM and installed one an engine with the following specs (It was orignally 650 cfm carbed). It idled great with the carb at 600 rpms.

355 ci
LT1 intake (converted)
fresh stock 882 heads
1 5/8" headers
730 ECM
24#/hr injectors at stock LT1 fuel rail pressure
(I checked the flow of all injectors before installing)
new small base disributor set at 6 degrees with timing light
Cam specs:
crane 280H
.454 lift with 1.5 rockers
duration at .050; I = 216 deg. , E = 216 deg.

idle map = approx. 43kpa at idle
idle spark = approx. 20 degrees at idle

IAC (min. idle) is set for approx 3 counts at idle in park
idle PW are approx. 1.6 ms

Checked throughly for vaccuum leaks......none

The engine runs decent everywhere except for idle. In general,
it was tuned using a DIY WB-O2 and scantool (thank you Grumpy).

Upon startup and in open loop at about 900 rpm (cold) it runs with the idle fluctuating between 800 to 1000 rpm. Once warm and in open loop it fluctuates between 550 to 850 rpm. It is very erratic. I had the target idle set for 600 rpm in the prom. It would fluctuate and then stall. I then set it for 650 rpm in the prom and it does the same wild fluctuation thing. This is all open loop.

I have been searching and reading for the past week about the throttle follower thinking this might cure the problem. I haven't tried modifying that yet. Will it help??? I have read many different ways to start (some older and some newer theories). Which is the best?

I set the spark change vs. rpm error to zero for advance and retard. It helped a little. I am using 20 degrees in the idle spark table for 35 to 50 kpa (where it idles). With the idle flucuating so much the kpa are all over (average is 44 kpa)

I am at a loss.....been tuning idle for two weeks and just end up re-starting over with a new bin after about 15 burns. I have about 50 burns just trying to get the idle better.

Once it enters closed loop at idle it gets REAL BAD. It runs between 500 to 1000 rpm and then stalls after about 10 seconds.

This 730 is truly showing how bad of a tuner I am. The easy way out I guess is upping the idle to about 750 rpm. It is still erratic but not as bad. It idled at 600 rpm with the carb. I just don't get it. Any comments are welcomed.....including bashing.......tuning idle for two weeks deserves some.
Going to try messing with the throttle follower stuff tomorrow night.
Tuning the fuel and spark was much easier on this 730 than the 165s I have used in the past. But the 165s all had rock solid idle, but this 730 is all over the place.

 

A carb uses a wet manifold so there is lots of *background* well vaporized fuel available at idle. You just lose that *advantage* with EFI.

Try an open loop chip, ie set the C/L enable to 255, and see if that helps. IF that helps the maybe tighten up the rich lean O2 parameters.

Throttle follower only happens as the throttle opens, and as it closes, once open or closed it's a pretty much a constant adder to the IAC.

 

The extra fuel makes sense. When I riched up the idle a whole lot it would idle better. As soon as it hit closed loop, the ECM started pulling fuel and it would start running bad in a hurry. I am really leaning toward running open loop like you mentioned.

I am not sure how the O2 values work quite yet. If they are for idle only or all of the time. If they are idle only then I will run closed loop in general and open loop at idle. I will check them out.

It just seems strange to me. It is a tiny cam with tiny headers and tiny heads and an LT1 intake (overkill). I know this isn't a great part match up but I wanted to learn how to tune the 730 before installing a HSR with a 730 ECM on a 244/244 degree (108 centerline) cammed 327ci Camaro I have had forever. The best I could ever get out of it carbed was 13.3 in the 1/4. But I always wanted to see at least high 12s....hoping the 730 and the knowledge I get this summer from tuning it will get me there. Plus it is a new ECM to learn and that is always a good thing.

Your comments are appreciated. I will start looking into the messing with the O2 thresholds and wait on messing with the AIC stuff for better throttle response.

 

I added even more fuel at idle to see what happened. It ran much much better. It idled good enough that I added the spark change vs. rpm to the original values in the table.

With 24#/hr injectors and the prom constant set to 24#/hr and the prom operating temp. idle at 750 rpm (in drive....park adds another 100rpm) it has PW of about 2.4ms. Originally I had 1.6ms pulsewidths and it idled bad.

Adding any more fuel at the idle (43kpa at 750 rpm) area in the lower VE table did not help the idle. I am running a value of roughly 70 in this area. It seems like a whole lot of fuel at idle. But that is what it likes. lowering to 65 and the idle was not as good, 75 and it idled no better than the 70 value.

Seems like a lot of fuel to idle, but that it what is likes. Also added 2 degrees of spark in the idle vs. spark area.

So now I had a park idle of 850 rpm (at 43kpa) and drive of 750 rpm (at 48 kpa) with approx 2.4ms PulseWidths. This was all done open loop so far.

Warmed up the exhaust and let it go closed loop. It started pulling fuel and idled rough. Set the Idle slow O2 min value at .7 and the max. at .9 and the fast idle O2 at .8.
It idled on the lean side (2.0ms) pulsewidths.

Set the the Idle slow O2 min value at .8 and the max. at 1.0 and the fast idle O2 at .9. Bad thing to do Idled way too rich (3.5ms pulsewidths)

Set the the Idle slow O2 min value at .75 and the max. at .9 and the fast idle O2 at .75. Idled decent with these values.

It seems most people have found that they needed to lower the O2 idle theshold values. I needed to raise these. I checked for exhaust leaks around the new FelPro header gaskets and didn't see or hear any.

I learned that the 730 ECM is very touchy to the Idle O2 thresholds even though they seem like a bad way to tune when far from .5 volts.

I also noticed that using these values and staying closed loop is ONLY good if the PROM is already dialed in need perfect.
I revved the engine to about 1500 rpm where I new I was still lean (BLM of about 122). This was in park at BLM cell 4. So the ECM adjusted for this lean by moving the BLM from 128 to 122. Now when I returned to idle it had the 122 BLM value which pushed the idle pulsewidths up to about 3.0ms. Too rich again. If the PROM was perfect, then the BLM would have been at about 128 and it would have idled fine............but it didn't because of the 122 BLM.

Anyway, it is a good learning experience and I need to mess with the O2 thresholds a lot more. Thank you for the help with the idle. It is much better and stays pretty stable now with the extra fuel.

Still seems like a lot of fuel at idle, but it wants it. Off idle and up to 1500 rpm the PWs are at about 1.6ms with a BLM of 128. Idle is a weird thing.

 

more tuning.........changing idle (closed throttle vs. spark advance)

I looked over the logged data last night and noticed how quick the engine was to respond to the quickly changing MAP values. On the LT1 intake the MAP is mounted direct with no vacuum line. It sees a change in MAP very quickly (there is no line delay / filtering). With the extra timing I added at idle the engine was quick to respond to the changing MAP values. It needed to be "lazy".

So I changed the closed throttle timing from the stock 20 degree value to 16 degrees at 600 and 18 degrees at 800 rpm. Huge difference, the idle stabilized a lot. It removed a lot of the idle surge.
To further reduce it, I set the idle spark advance and retard values from the stock 5 degrees to 0 degrees. It idled slightly better, almost no difference, but better.

This allowed me to reduce the fuel at idle from 2.4ms pulse widths down to 2.1 ms pulsewidths. Result was less fuel consumption and a less stinky exhaust.

I added fuel at the 1200 to 1500 rpm area where it was slightly lean and set the O2 idle threshold to .65 (lower) and .75 (upper).
This allowed closed loop idle to maintain the open loop pulsewiths that I had desired.

End result, idles in drive at 700 rpm and neutral at 800 rpm with lower MAP values (higher vacuum). It is very close to what the carb idled at now and the idle is stable. In the beginning it surged from 600 to 1000 rpm and would stall.
I am still narrowing in on the closed loop idle but I have found that numbing the ECM at Idle helps to stabilize it.

 

hmm i just did some work on a 383 with a 622 lift cam tha has 265 at 50 and 106 lda. this was not a fun adventure. wass running TPIS miniram with 1000cmf throttle body. it has all of about 4-5 inches of vacum at idle. things ive found that work. Dont trust a damn thing your wideband says at idle. there som much air mixing cross feeding of cylinder self egr and Internal intake plenum reversion that its impossiable to even think that youll be able to trust what the wideband says.

for this particular engine its idleing around 1200 rpm and it still sounds way way way choppy up there. yeah you get the raw fuel smeel to.
Things that helpped. leaving the spark adder to negative rpm values seems to help. i disabled the idle overspeed retard. i locked the ecm into open loop. youve got be nuts to even try to run this engine under 4000rpm in closed loop. its got huge headers and a 4 inch exhuast to bot.

flattening the VE table in the idle areas. did make AE tunning difficult without the add in from the delta map AE ader.

but it was doable.

Also flattening out and running 25-28 degrees of spark really seemed to help it out.

there alot to do but mostly youll have to experiment.

 

From what I have read and you confirmed is that O2 sensor are not good at idle. I haven't even looked at the WB-O2 readings at idle yet. It sucks that the ECM is looking at the NB-O2 at low rpms.
If I get off idle in closed loop the ECM goes into the off idle O2 thresholds (I think) and starts pulling out a lot of fuel. At 1000 rpm to 1500 rpm it runs good. Once closed loop kicks in it starts reducing the PWs and it you can hear the lean pop start in the exhaust.........and it just keeps getting louder and louder as the ECM reduces the PWs to try to keep the NB-O2 happy.
It seems strange because the cam is only .454 lift and 216 degrees Int. and Exh. I think the overlap is about 10degrees at .050. This is a very mild street engine. Nothing fancy, just enough to learn the 730 ECM on.
Now that the Idle is pretty close, the next thing to jump into is working the DFCO and throttle follower to minimize the big startup flair (up to 1900 rpm right now).

 

I agree with you that the ECM should have no problems using closed loop during idle. With an idle manifold pressure of 43 KPa and the mild cam, something else is wrong. Just don't know what though.

The (too) obvious would be the O2 sensor is bad or it isn't a heated one.

It could also be the ECM. There is an O2 sensor amplifier between the sensor and the ADC.

Could also be a wiring problem. There is a dedicated ECM ground reference for the sensor. Maybe something is wrong there.

With as high as you set the idle state O2 thresholds that engine should be running very, very rich. But it isn't.

Another may be that the O2 sensor is silicon poisoned. It will report rich and drive the engine lean when this happens. Pull the sensor out and look for a white fluffy substance on it. That is a sign of silicon poisoning.

RBob.

 

**** Problem Solved ****

The distributor was set at approx. 30 degrees retarted. Man, do I feel like a fool. Wasted a lot of timing trying to fix a broken car with a ?good? chip.

To find it I did this:
Pulled the O2 sensor and checked as RBob suggested. It looked black with no spotting. Installed a used spare O2 sensor. It still ran at idle.

Re-checked all the plug wires were on correct for the tenth time. All looked good. Wipped out the timing light and re-checked again. It looked good. Got under the car to make sure the dampner marks were correct. Ooopppps, I was timing it off of the sticker that had been painted over. Sanded the balancer to highlight the correct marks. It was off by about 30 degrees.

Adjusted timing the timing with the correct marks, set min idle, set the IAC, set the TPS. Threw out all BINs and LOG files I had made so I wouldn't grab one by accident. Started with a fresh stock BIN. Made a documentation file of what I learned and what not to do.

It runs excellent now. Idles better than the carb. The idle is set to the stock 588 rpm at a 58 kpa reading in neutral (about 60kpa at 588 rpm in drive). Pulled out a bunch of fuel at idle with the lower VE table. Now down to about 1.7ms PWs. Left timing at stock settings. This all open loop. During closed loop the O2 now sees it as lean and adds a slight amount of fuel. Now I can start doing some real tuning.

Thank you for the help on this one. At first I thought the 730 was going to take me forever to learn. Now I am thinking maybe just 5 years or so to get it tuned for peak performance. All good stuff.

 

I like the pun, "Wasted a lot of timing trying to fix a broken car. . . "

RBob.