Engine stalls when coasting to stop
Engine stalls when coasting to stop Engine is a LQ4 with T-56 in my 1970 Chevelle. It's got drive by wire. I am working on tuning it and have it running pretty well while driving. However, it tries to stall every time I push the clutch in or shift to neutral while coasting to a stop. I can rev the engine in the driveway and it'll return to idle before stalling. I'm thinking it has something to do with the throttle cracker/follower but I haven't had any luck after adjusting them. Does anyone have any suggestions?
The included log has a couple stalls if that's any help.
Thanks,
David
The included log has a couple stalls if that's any help.
Thanks,
David
Staging Lane
Joined: Nov 2015
Posts: 96
Likes: 0
Try setting your Throttle Cracker Disable Speed to just below the Enable Speed and put some airflow into the 400rpm cell of your Cracker Table.
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There's kind of a lot going on in there.
1. Looks like not enough base running airflow. I plotted ECT VS dynamic air at idle, and it was much higher than your tune. Between 10 and 10.5 g/sec. I think you need to command more air. Start with 10 g/cyl at 80 degrees and in gear in the RAF table. 12.3 at 32 degrees is close, so interpolate between them to fill in the table. Above 92, use 10.5. Make your PN values 1-g/sec lower than in gear.
2. You're getting these random 41 degree spark advances at idle. Your peak idle torque is probably occurring near 30 degrees. Any more advance than that and you're losing torque, which becomes counter productive.
3. You're stalling even without moving. Cracker settings won't touch that.
3a. In your idle regions, from 0 to 1200 rpm and up to 0.3 g/cyl, set all those cells to 22 degrees in both idle tables and both high and low octane tables.
3b. Your idle under speed and over speed spark tables. Make your maximum correction 8 degrees and no more. At 25 rpm error, spark should move 1 degree, 2 at 50, 4 at 100, 8 at 200 and beyond. Interpolate between those values for the rest of the tables. Make sure you use negative numbers in your over speed table.
4. Your derivative tables - from 0 to 0.5, make those zero. Leave the rest of the table alone. Both high and low tables.
Save all of that as a different tune. Do a write complete to clear all your trims and start her up. It'll have to learn idle, so be patient. Should idle high and then trim down.
I couldn't tell if you're running cable throttle or fly by wire. To fine tune some other items, we will need to know what size throttle, cable or wire, etc.
1. Looks like not enough base running airflow. I plotted ECT VS dynamic air at idle, and it was much higher than your tune. Between 10 and 10.5 g/sec. I think you need to command more air. Start with 10 g/cyl at 80 degrees and in gear in the RAF table. 12.3 at 32 degrees is close, so interpolate between them to fill in the table. Above 92, use 10.5. Make your PN values 1-g/sec lower than in gear.
2. You're getting these random 41 degree spark advances at idle. Your peak idle torque is probably occurring near 30 degrees. Any more advance than that and you're losing torque, which becomes counter productive.
3. You're stalling even without moving. Cracker settings won't touch that.
3a. In your idle regions, from 0 to 1200 rpm and up to 0.3 g/cyl, set all those cells to 22 degrees in both idle tables and both high and low octane tables.
3b. Your idle under speed and over speed spark tables. Make your maximum correction 8 degrees and no more. At 25 rpm error, spark should move 1 degree, 2 at 50, 4 at 100, 8 at 200 and beyond. Interpolate between those values for the rest of the tables. Make sure you use negative numbers in your over speed table.
4. Your derivative tables - from 0 to 0.5, make those zero. Leave the rest of the table alone. Both high and low tables.
Save all of that as a different tune. Do a write complete to clear all your trims and start her up. It'll have to learn idle, so be patient. Should idle high and then trim down.
I couldn't tell if you're running cable throttle or fly by wire. To fine tune some other items, we will need to know what size throttle, cable or wire, etc.
There's kind of a lot going on in there.
1. Looks like not enough base running airflow. I plotted ECT VS dynamic air at idle, and it was much higher than your tune. Between 10 and 10.5 g/sec. I think you need to command more air. Start with 10 g/cyl at 80 degrees and in gear in the RAF table. 12.3 at 32 degrees is close, so interpolate between them to fill in the table. Above 92, use 10.5. Make your PN values 1-g/sec lower than in gear.
2. You're getting these random 41 degree spark advances at idle. Your peak idle torque is probably occurring near 30 degrees. Any more advance than that and you're losing torque, which becomes counter productive.
3. You're stalling even without moving. Cracker settings won't touch that.
3a. In your idle regions, from 0 to 1200 rpm and up to 0.3 g/cyl, set all those cells to 22 degrees in both idle tables and both high and low octane tables.
3b. Your idle under speed and over speed spark tables. Make your maximum correction 8 degrees and no more. At 25 rpm error, spark should move 1 degree, 2 at 50, 4 at 100, 8 at 200 and beyond. Interpolate between those values for the rest of the tables. Make sure you use negative numbers in your over speed table.
4. Your derivative tables - from 0 to 0.5, make those zero. Leave the rest of the table alone. Both high and low tables.
Save all of that as a different tune. Do a write complete to clear all your trims and start her up. It'll have to learn idle, so be patient. Should idle high and then trim down.
I couldn't tell if you're running cable throttle or fly by wire. To fine tune some other items, we will need to know what size throttle, cable or wire, etc.
1. Looks like not enough base running airflow. I plotted ECT VS dynamic air at idle, and it was much higher than your tune. Between 10 and 10.5 g/sec. I think you need to command more air. Start with 10 g/cyl at 80 degrees and in gear in the RAF table. 12.3 at 32 degrees is close, so interpolate between them to fill in the table. Above 92, use 10.5. Make your PN values 1-g/sec lower than in gear.
2. You're getting these random 41 degree spark advances at idle. Your peak idle torque is probably occurring near 30 degrees. Any more advance than that and you're losing torque, which becomes counter productive.
3. You're stalling even without moving. Cracker settings won't touch that.
3a. In your idle regions, from 0 to 1200 rpm and up to 0.3 g/cyl, set all those cells to 22 degrees in both idle tables and both high and low octane tables.
3b. Your idle under speed and over speed spark tables. Make your maximum correction 8 degrees and no more. At 25 rpm error, spark should move 1 degree, 2 at 50, 4 at 100, 8 at 200 and beyond. Interpolate between those values for the rest of the tables. Make sure you use negative numbers in your over speed table.
4. Your derivative tables - from 0 to 0.5, make those zero. Leave the rest of the table alone. Both high and low tables.
Save all of that as a different tune. Do a write complete to clear all your trims and start her up. It'll have to learn idle, so be patient. Should idle high and then trim down.
I couldn't tell if you're running cable throttle or fly by wire. To fine tune some other items, we will need to know what size throttle, cable or wire, etc.
Staging Lane
Joined: Nov 2015
Posts: 96
Likes: 0
I wasn't able to see your IAC counts, but I'll take another look when I get home from work. Have you drilled your throttle blade? Not a bad thing if you did, just need to know.
I really appreciate all of the help!
glad it seems we're making some progress. What I saw in the scan is a lot of idle timing at 18 degrees. Sure enough, in the idle tables, there is some 18 degree stuff in there. What I'm going to do is attach a dummy tune to give you something to reference, and you'll be able to just copy stuff over.
The basics are that we will raise the idle timing to 25 degrees to give it some more torque. We will use derivative air to sort of set a floor on air flow and keep the idle from dipping too much. We will also lean out your idle a smidge, as bigger cams like leaner idle - or rather they read false lean and run overly rich if you're not careful.
In the end, you do have a larger cam in a 5.3, so there may be a need to bump up the idle speed. What clutch are you using, by the way? Is it very light?
I'll get backa bit later with the dummy tune.
The basics are that we will raise the idle timing to 25 degrees to give it some more torque. We will use derivative air to sort of set a floor on air flow and keep the idle from dipping too much. We will also lean out your idle a smidge, as bigger cams like leaner idle - or rather they read false lean and run overly rich if you're not careful.
In the end, you do have a larger cam in a 5.3, so there may be a need to bump up the idle speed. What clutch are you using, by the way? Is it very light?
I'll get backa bit later with the dummy tune.
glad it seems we're making some progress. What I saw in the scan is a lot of idle timing at 18 degrees. Sure enough, in the idle tables, there is some 18 degree stuff in there. What I'm going to do is attach a dummy tune to give you something to reference, and you'll be able to just copy stuff over.
The basics are that we will raise the idle timing to 25 degrees to give it some more torque. We will use derivative air to sort of set a floor on air flow and keep the idle from dipping too much. We will also lean out your idle a smidge, as bigger cams like leaner idle - or rather they read false lean and run overly rich if you're not careful.
In the end, you do have a larger cam in a 5.3, so there may be a need to bump up the idle speed. What clutch are you using, by the way? Is it very light?
I'll get backa bit later with the dummy tune.
The basics are that we will raise the idle timing to 25 degrees to give it some more torque. We will use derivative air to sort of set a floor on air flow and keep the idle from dipping too much. We will also lean out your idle a smidge, as bigger cams like leaner idle - or rather they read false lean and run overly rich if you're not careful.
In the end, you do have a larger cam in a 5.3, so there may be a need to bump up the idle speed. What clutch are you using, by the way? Is it very light?
I'll get backa bit later with the dummy tune.
OK, here is the dummy tune. Most of this file is crap, so don't just upload it and go. Here is a list of what to copy over:
1. Idle-RPM. Rolling idle table, and all adaptive idle tables and settings, and the stall saver tables. Pretty much everything on this page that doesn't match your tune already should be copied over.
2. Idle-Airflow. Adaptive idle tables and settings, rolling idle tables and settings. For now, don't grab the follower and cracker stuff. if you are having random hot starting issues, copy over the start up tables on this page.
3. Airflow-General. MAF airflow vs Frequency table. Used your logged fuel trims to tweak it. All else leave alone.
4. Fuel-General-Injector Control. Normal table only. All else leave alone.
5. Fuel-Open&ClosedLoop. open loop EQ ratio table, Bank1 and bank2 O2 rich/lean vs airflow tables, set idle proportional to "disable", copy over the mode vs airflow table.
6. Fuel-Power Enrich. Copy everything that is different over to your tune
7. Fuel-Transient. Copy anything on this page different from your tune.
8. Spark-Advance. Copy both high and low octane tables and both idle spark tables. Leave the rest alone.
9. Torque Management-Engine. Copy over the Delivered torque settings and the stall protect settings.
After all this, do a write, start it up and let it learn idle for a few minutes. Turn it off, start it back up, and test it out.
Some additional background - this will by design use spark to control the idle within 50 rpm of your target and not adjust air very much at all. As a result, you should see your spark moving around between 23 and 30 degrees, but your idle speed should be pretty stable. I'm just preparing you - you won't see a flat line at 25 degrees advance.
1. Idle-RPM. Rolling idle table, and all adaptive idle tables and settings, and the stall saver tables. Pretty much everything on this page that doesn't match your tune already should be copied over.
2. Idle-Airflow. Adaptive idle tables and settings, rolling idle tables and settings. For now, don't grab the follower and cracker stuff. if you are having random hot starting issues, copy over the start up tables on this page.
3. Airflow-General. MAF airflow vs Frequency table. Used your logged fuel trims to tweak it. All else leave alone.
4. Fuel-General-Injector Control. Normal table only. All else leave alone.
5. Fuel-Open&ClosedLoop. open loop EQ ratio table, Bank1 and bank2 O2 rich/lean vs airflow tables, set idle proportional to "disable", copy over the mode vs airflow table.
6. Fuel-Power Enrich. Copy everything that is different over to your tune
7. Fuel-Transient. Copy anything on this page different from your tune.
8. Spark-Advance. Copy both high and low octane tables and both idle spark tables. Leave the rest alone.
9. Torque Management-Engine. Copy over the Delivered torque settings and the stall protect settings.
After all this, do a write, start it up and let it learn idle for a few minutes. Turn it off, start it back up, and test it out.
Some additional background - this will by design use spark to control the idle within 50 rpm of your target and not adjust air very much at all. As a result, you should see your spark moving around between 23 and 30 degrees, but your idle speed should be pretty stable. I'm just preparing you - you won't see a flat line at 25 degrees advance.
I updated the tune and went on a short drive. I didn't notice a whole lot of difference from before but looking at the log, you can see that the LTFTs are all over the place. Would this be a function of the tune or should I be looking for a leak somewhere?