Open loop idle. idle commanded to 675. idle throttle stop screw sets to 800 rpms. IAC is non functional for now and inlet plugged. spark is 20 ADV all around MAP 40 and RPMS it surges through. surge is not severe just a constant 650-900 up down. WB shows 13.6-14.3 and OL tables I have set AFR/CTS/VAC to 13.6 all around surge. I understand that table is VAC not MAP so those values stated are 60 VAC area. VAFPR. I do see DC changing 1.5 to 2.5 during event. Proportinal gains reduced twice (10%-10%).
Cat chasing tail? Any more settings needed in .bin?

 

Well my understanding of this is you have the main spark timing table set at 20*. What about the idle spark compensation high and low. Do you have these set to 0? If not you might consider it.

 

I will check that thank you.

I set all the cells in VE1 that it idles in to a common value. That seemed to help this am ride. I dont know if AFR/CTS/VAC uses VE values to calc commanded A/F ?????

 

Basic injector PW calculation:

PW = BPC * VE% * ~AFR * ~T * MAP

The ~ means inverse, so a smaller AFR creates a larger PW.

Note that the proportional gains are inactive in open loop.

RBob.

 

idle spark compensation was zero'd out in .bin.

I might add it comes and goes. There are time I will come to stop sign and it is rock steady but generally it pulsates slightly.

In WP the SA stays at 20 never moves

Since my IAC is plugged non functional should I adust any of the throttle follower tables? Or would that affect off idle TF. I can see the DC change with the pulsation as well as map changing. Could that be TF adding fuel?

Is the cam 224/230 @ .05 114 LSA causing a fluctuation in VAC causing the VAFPR fits?

 

Items like this are tough from a distance. However, if the IAC is unplugged, the IAC opening PW should also be zero'd. Otherwise the ECM will add some fuel whenever it commands the IAC to open. Which the ECM doesn't know that it is unplugged.

And if the IAC isn't opening, then the fuel pulse can cause an issue.

"AE - IAC Opening fuel"

RBob.

 

Seems like this is a common problem. Thought I'd share a few tidbits on correcting this in the .bin (chip) after engine modifications.

If you have a stock engine, things to check would include varying battery voltage at idle, low fuel pressure, EGR malfunction, and vacuum leaks. Make sure to check for ECM/PCM codes. This may help to narrow down the problem.

Okay, assuming your engine is modified, in good shape, and you've ruled out the above conditions, here are some other suggestions. If at all possible, try to datalog when the condition is occurring. You can then see if stall saver is active, MAP values, battery voltages, spark advance, etc.

1. Stall saver settings: You may also need to lower the stall saver thresholds. Often missed. The target idle is controlled by the PCM, not mechanically at the TB. At temp and in "Park", set the idle screw so your IAC steps with your scantool are between 10-15. You may need to adjust the TPS after this so that voltage output at idle is 0.53-0.58V. TPS% is self-adjusting, just cycle the ignition key on and off waiting a few second in between. Your scantool will report TPS% now at 0% again. Reducing IAC steps allows for maximum adjustability and lessens controlled "air leak" that can cause idle problems in all driving conditions (cold/hot weather, warming up, etc.). Make sure to remove the throttle cable slack from the throttle linkage adjustment screw after doing this procedure being careful not to put tension on the linkage.

2. VE/Main Spark tables: Find out the MAP value at idle at normal operating temp. If you've replaced your camshaft, your engine may have a higher MAP value (less engine vacuum). For a stock engine, idle MAP is usually between 30-40 kPa. With a larger camshaft, you may now be idling at 50-60 kPa. You will need to smooth/flatten out the cells in the VE table AND main spark table around where your engine idles.

3. Coolant spark compension table: If your idle varies only when the engine is cold or after a few minutes after engine start-up, you may need to smooth/flatten the cool/coolant spark compensation vs load/vac table. The table adds timing during cold engine operation only. If your modified engine has less vacuum at idle, this table is often out-of-spec and contributes to the out-of-spec main spark table for a double-whammy.

4. Varying battery voltage: Usually not a problem but if your alternator is subpar or if you've installed underdrive pulleys, you may have low voltage at idle that can cause a whole host of problems. Think about re-installing your stock pulleys if this is happening to you. Underdrive pulleys don't contribute that much to power anyway. Install an electric fan instead and you'll remove the biggest resistance factor on the accessory drive system.

Hope this helps. I had this problem and it has now disappeared using the techniques I outlined above. Been one of the most frustrating issues to solve for me. I'm sure others share my frustration. I also think my EGR was contributing as well, since things improved when I physically replaced the EGR with a block-off plate. Just disabling EGR in the .bin was not enough.

My only other advice is make one change at a time and re-test. I wasn't able to identify which change fixed the problem as I was impatient and did multiple changes to the .bin at the same time (i.e. VE and spark table(s) smoothing). Maybe you're more patient than me. In the end, my idle is rock solid stable and I've changed heads, installed a larger camshaft, and running Edelbrock's MPFI with the '7427 in PFI mode. My idle is set at 650 RPM. My IAC is functioning perfectly with no changes to the stock settings. Now on to tune something else...

 

Good Stuff. Thank you. Other members may benefit as well.

Just about all mechanicals are up to date. All very new. No vac leaks. Checked header collecctor to ext pipes a month ago on lift. Bolts tight. I have copper gaskets on that fit. I WONDER IF ADDING A SECOND SET WILL HELP? Maybe they are not lining up correctly causing a hairline leak as ext is custom welded?? May not be flush? Manifold/TBI unit no leaks as well. Checked that too. I really think it is a tuning issue. Possibly compounded by VAFPR resonse to changing MAP as well. EBL-no codes. I have been datalogging event and only items I see are the evident ones (rpm/map/dc/spark). Nothin I can point to. I see WB move 13.6-14.3/1 during surge. Maybe that is DC change?.

Stall saver is active BUT no IAC control(plugged at TB). I did experiment yesterday by lowering stall saver and that worsened it. I will raise stall saver speed to about what I had B4 I lowered and check the result. Thus idle speed is set by throttle stop screw. Commanded well under to remove ECU control. TPS is nonadjustable on 1995 unit. It is smooth in logs.

All VE cells and Spark are already flattened. However CL BLM Learn may intervene. OL idle. Cam 224/230@.05 114 LSA. Issue is better cold. Issue when warm CL. Coolant spark comp I suspect is zero at warm temps. Will verify. Thanks fo tip. Should idle 40 MAP. Moves to 40-50 or 60 during surge.

Stock alternator replaced recently and battery is new this year. I will verify Volts after weekend as car is not driven. Electric fan. No EGR. No underdrive pulleys.

 

Ron,

You said you're running O/L Idle. RBob, correct me here, but Prop Gains work in C/L, right? So reducing PG will not bring about the desired results.
I think RBob should write a book on "How to love Closed Loop E ngine Control"

 

[quote=Ronny;3803115]Good Stuff. Thank you. Other members may benefit as well.

Just about all mechanicals are up to date. All very new. No vac leaks. Checked header collecctor to ext pipes a month ago on lift. Bolts tight. I have copper gaskets on that fit. I WONDER IF ADDING A SECOND SET WILL HELP? Maybe they are not lining up correctly causing a hairline leak as ext is custom welded?? May not be flush?



My luck with those type of gaskets over the years was never good. You should try a nice set of ceramic gaskets (watch your bolt length they are thick gaskets) for the headers and at the collectors a good ball socket connection is worth every penny. But the copper either on head or collector often leak you really need to allow for exhaust movement via engine twist and torque. I good set of Felpro steel core gaskets on collectors and ceramic on the heads with stage 8 header locks (use antisieze on the bolts!) work great... always torque headers center bolts to outer two... not that they need a real torque reading just hand box wrench tight then stage 8 after you heat cycle em about 3 times works best... Another good tip is the Dupli Color header/engine paint with ceramic... clean the connection points and paint them with this stuff really last on a rust free hot surface... also on steel heads works nice to paint them just plug the holes with paper and tape over the bolt holes or use old bolts in the holes first... Copper or steel gaskets on alum heads well thats a no no... to much expansion and changes... and the steel will mark the alum heads and leak in time...
Also a great trick for the 3 bolt collectors is to double them up if you can and use all good stainless hardware, oh also paint the gasket with ceramic as that helps a whole bunch, I have a 77 G-20 van that allowed all the stuff to rust headers exhaust and all then cleaned and painted with this stuff and after 1000's of miles water and all, this dang paint is as good as a set of ceramic or stainless or chrome headers... it just works...