LT1 cold start idle tuning
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From: st louis, mo area
LT1 cold start idle tuning I have a large ol shitpile of tuning problems with my 96 LT1. Local tuner has had it a few times but these problems can't get resolved so I acquired JET DST tuning and ecmpro logging software.
The cold start idle problem centers around an inability to idle correctly unless I give it some throttle. After about 10-15 seconds of feathering the throttle, it will idle on it's own.
I grabbed a log yesterday and today I tried to adjust the TPS. Initial monitor says the tps % 0 and tps volts .922. I adjusted the setscrew until it read 2% and turned off the car. I unplugged the tps and turned key on for 10 seconds. I then turned off the key, plugged in the tps. when I turned on the key on again the tps was still 2% and the tps volts 1.2. Wasn't it supposed to adjust to 0% when it was unplugged?
I've attached a zipped csv of the log from yesterday. I need some advice on how to get the tps volts to around .75, knock the iac counts down to 60-80 and get this thing to light off like it should. I got the cam from AI, it's the 230/236 @.050 they sell.
Thanks!
The cold start idle problem centers around an inability to idle correctly unless I give it some throttle. After about 10-15 seconds of feathering the throttle, it will idle on it's own.
I grabbed a log yesterday and today I tried to adjust the TPS. Initial monitor says the tps % 0 and tps volts .922. I adjusted the setscrew until it read 2% and turned off the car. I unplugged the tps and turned key on for 10 seconds. I then turned off the key, plugged in the tps. when I turned on the key on again the tps was still 2% and the tps volts 1.2. Wasn't it supposed to adjust to 0% when it was unplugged?
I've attached a zipped csv of the log from yesterday. I need some advice on how to get the tps volts to around .75, knock the iac counts down to 60-80 and get this thing to light off like it should. I got the cam from AI, it's the 230/236 @.050 they sell.
Thanks!
That cam should be a breeze to tune.
Are the throttle blades drilled? If not, you might need to. Start by taking off the TPS, and slotting the screw holes out, so you can adjust it. Take your curb idle screw out, and put it in from the front, and put a small nut on it to act as a lock nut. Now it will be much easier to adjust it. Set your curb idle screw to hold the blades open just slightly. Get the car running and warmed up. Check you IAC counts when warm, and adjust the throttle blade, and TPS until you have your IAC count right, and about .5 volts on your TPS.
You need to make sure your IFR and your MAF are adjusted properly. If your fuel trims are way off, that's an indicator the IFR and/or MAF table are off. If they're off the open loop fueling will be off, and make your cold idle worse.
Do you have enough timing in it? That will cause the cold idle to be worse.
Once you have the fuel and spark dialed in, you'll have to go back and readjust the curb idle and TPS. It will probably take a few times to get it dialed in.
Are the throttle blades drilled? If not, you might need to. Start by taking off the TPS, and slotting the screw holes out, so you can adjust it. Take your curb idle screw out, and put it in from the front, and put a small nut on it to act as a lock nut. Now it will be much easier to adjust it. Set your curb idle screw to hold the blades open just slightly. Get the car running and warmed up. Check you IAC counts when warm, and adjust the throttle blade, and TPS until you have your IAC count right, and about .5 volts on your TPS.
You need to make sure your IFR and your MAF are adjusted properly. If your fuel trims are way off, that's an indicator the IFR and/or MAF table are off. If they're off the open loop fueling will be off, and make your cold idle worse.
Do you have enough timing in it? That will cause the cold idle to be worse.
Once you have the fuel and spark dialed in, you'll have to go back and readjust the curb idle and TPS. It will probably take a few times to get it dialed in.
Last edited by edcmat-l1; Aug 10, 2011 at 07:23 AM. Reason: speeling lol
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The tuner has the speed density box checked so this thing is running on the ve tables. Gotta lot of work to do.
I'll take off the tb and get the tps holes widened out tomorrow or thursday. I want to make sure my tb still has the idle air directed to the idle ports in the intake. I'll probably drill the tb to let more air in.
Another question. Why do the maf values in the log show 0? the sensor wire is plugged in...
I'll take off the tb and get the tps holes widened out tomorrow or thursday. I want to make sure my tb still has the idle air directed to the idle ports in the intake. I'll probably drill the tb to let more air in.
Another question. Why do the maf values in the log show 0? the sensor wire is plugged in...
The tuner has the speed density box checked so this thing is running on the ve tables. Gotta lot of work to do.
I'll take off the tb and get the tps holes widened out tomorrow or thursday. I want to make sure my tb still has the idle air directed to the idle ports in the intake. I'll probably drill the tb to let more air in.
Another question. Why do the maf values in the log show 0? the sensor wire is plugged in...
I'll take off the tb and get the tps holes widened out tomorrow or thursday. I want to make sure my tb still has the idle air directed to the idle ports in the intake. I'll probably drill the tb to let more air in.
Another question. Why do the maf values in the log show 0? the sensor wire is plugged in...
Those engines are easy to set cold idle in SD, it just takes a little time for fueling calibration.
Do as edcmat-l1 says first.
You need to adjust fueling (VE tables). I have found those engines have a good cold idle w/ 13:1 AFR. Tune VE using LTFT's if you don't have a wideband.
There is a table for the IAC park position:
When ignition is turned off, the IAC parks to a given position (bigger value-more airflow). Next time engine is restarted, IAC will be in that open position and it'll have more airflow.
Try raising that table's values to see if it helps. The only disadvantage of that is the engine will always Rev to ~2000 RPM when started, then drop to preset idle in a few secs, annoying to some people.
The TPS volts need to be at 0.67 or less for 0%. If it is higher it will cause problems, even if scanner reads TPS at 0%
You can slot the TPS holes to rotate it, so it will read less volts for the same blade opening. You can avoid drilling the blades doing this.
Your last resource will be drilling the blade(s)
Ignition timing, proper AFR and correct airflow are the 3 more important things you need for a good cold-idle.
Change one thing at a time then test
Do as edcmat-l1 says first.
You need to adjust fueling (VE tables). I have found those engines have a good cold idle w/ 13:1 AFR. Tune VE using LTFT's if you don't have a wideband.
There is a table for the IAC park position:
When ignition is turned off, the IAC parks to a given position (bigger value-more airflow). Next time engine is restarted, IAC will be in that open position and it'll have more airflow.
Try raising that table's values to see if it helps. The only disadvantage of that is the engine will always Rev to ~2000 RPM when started, then drop to preset idle in a few secs, annoying to some people.
The TPS volts need to be at 0.67 or less for 0%. If it is higher it will cause problems, even if scanner reads TPS at 0%
You can slot the TPS holes to rotate it, so it will read less volts for the same blade opening. You can avoid drilling the blades doing this.
Your last resource will be drilling the blade(s)
Ignition timing, proper AFR and correct airflow are the 3 more important things you need for a good cold-idle.
Change one thing at a time then test
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From: st louis, mo area
removed the tb last night. Like most (maybe all) aftermarket throttle bodies, the iac air is dumped into the main plenum. I found out last night that mine is like that too. So I spent the evening fabbing up a 5/8" piece of flanged copper tubing to direct the iac air to the idle ports in the intake and jb welded it in. I watched the last few innings of the cardinals getting smacked by the brewers, then slept while it cured. I also did a little adjusting on the mounting holes of the tps. So, tonight I plan to put it back together and see if I can get the tps volts and iac counts to act right.
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another log https://docs.google.com/leaf?id=0Bw7...5NmRh&hl=en_US
BETTER!! But still have some work to do. I got the intact tract back on and made a few cold adjustments. I checked the tps volts before i hit the key and it looking great at .5. It fired right up but idled at 1500. I made a few more adjustments to the setscrew on the tb and grabbed a log. It fired up nicely and idled what i think is a bit low (~850) at first but at least i didn't have to throttle it to keep it going. then it started idling up and stabilized around 1050. I noticed the iac counts slowly lowered to 0. I dunno for sure but would that indicate a vacuum leak since the iac pintle is closed and the idle is still at 1050? Or would that indicate the setscrew is set too high, letting air in around the tb blades?
It seemed like the more i lowered the setscrew, the more it struggled on the initial start. I want to go lower on the setscrew but the low initial rpm aint cool. What's next?
BETTER!! But still have some work to do. I got the intact tract back on and made a few cold adjustments. I checked the tps volts before i hit the key and it looking great at .5. It fired right up but idled at 1500. I made a few more adjustments to the setscrew on the tb and grabbed a log. It fired up nicely and idled what i think is a bit low (~850) at first but at least i didn't have to throttle it to keep it going. then it started idling up and stabilized around 1050. I noticed the iac counts slowly lowered to 0. I dunno for sure but would that indicate a vacuum leak since the iac pintle is closed and the idle is still at 1050? Or would that indicate the setscrew is set too high, letting air in around the tb blades?
It seemed like the more i lowered the setscrew, the more it struggled on the initial start. I want to go lower on the setscrew but the low initial rpm aint cool. What's next?
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Verdad Gallardo https://docs.google.com/leaf?id=0Bw7...5NmRh&hl=en_US
BETTER!! But still have some work to do. I got the intact tract back on and made a few cold adjustments. I checked the tps volts before i hit the key and it looking great at .5. It fired right up but idled at 1500. I made a few more adjustments to the setscrew on the tb and grabbed a log. It fired up nicely and idled what i think is a bit low (~850) at first but at least i didn't have to throttle it to keep it going. then it started idling up and stabilized around 1050. I noticed the iac counts slowly lowered to 0. I dunno for sure but would that indicate a vacuum leak since the iac pintle is closed and the idle is still at 1050? Or would that indicate the setscrew is set too high, letting air in around the tb blades?
It seemed like the more i lowered the setscrew, the more it struggled on the initial start. I want to go lower on the setscrew but the low initial rpm aint cool. What's next?
BETTER!! But still have some work to do. I got the intact tract back on and made a few cold adjustments. I checked the tps volts before i hit the key and it looking great at .5. It fired right up but idled at 1500. I made a few more adjustments to the setscrew on the tb and grabbed a log. It fired up nicely and idled what i think is a bit low (~850) at first but at least i didn't have to throttle it to keep it going. then it started idling up and stabilized around 1050. I noticed the iac counts slowly lowered to 0. I dunno for sure but would that indicate a vacuum leak since the iac pintle is closed and the idle is still at 1050? Or would that indicate the setscrew is set too high, letting air in around the tb blades?
It seemed like the more i lowered the setscrew, the more it struggled on the initial start. I want to go lower on the setscrew but the low initial rpm aint cool. What's next?
IAC park position versus coolant temp........
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101 at start up, then varied 60 to 80. when the idle went up to 1100ish the iac started to dwindle down to zero. does that sound right?
Last edited by brettmc; Aug 11, 2011 at 08:52 PM. Reason: never was good at grammar
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iac park position vs coolant temp
degC Steps
-40 100
-28 90
-16 60
-4 48
8 37
20 33
32 27
44 18
56 16
68 10
80 7
92 7
104 7
116 7
the coolant temp was 46, according to the table that should have given me 18 iac counts yet iac was 101. How did that happen??
degC Steps
-40 100
-28 90
-16 60
-4 48
8 37
20 33
32 27
44 18
56 16
68 10
80 7
92 7
104 7
116 7
the coolant temp was 46, according to the table that should have given me 18 iac counts yet iac was 101. How did that happen??
Last edited by brettmc; Aug 11, 2011 at 09:16 PM.
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From: st louis, mo area
i made a couple of changes to iac park position vs coolant temp table, adding 10 counts per cell from -6 degrees C to the 50 something degree cell. I also changed the speed calibration table, putting in tire size and gear ratio. I read the pcm, then uploaded the new tune (first time i've done it...was hoping i wasn't going to make a brick). It went fine, no error codes. However, it wouldn't fire. It caught a couple of times but never really fired off, just turned over.
I then flashed the config I read earlier and tried it again. It did the same thing. I was logging at the time and the only thing I noticed was the injector pulse width was super long, in the low 20 ms range. Last night's log showed a pulse width of low single digits. I also noticed tonight's commanded afr was very low. Somewhere, somehow I'm getting a lot more fuel than last night. I'm wondering what happened.
Here's tonight's log:
https://docs.google.com/leaf?id=0Bw7...1ZGNj&hl=en_US
I then flashed the config I read earlier and tried it again. It did the same thing. I was logging at the time and the only thing I noticed was the injector pulse width was super long, in the low 20 ms range. Last night's log showed a pulse width of low single digits. I also noticed tonight's commanded afr was very low. Somewhere, somehow I'm getting a lot more fuel than last night. I'm wondering what happened.
Here's tonight's log:
https://docs.google.com/leaf?id=0Bw7...1ZGNj&hl=en_US
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I lowered the values in the prime pulse tables this morning (also added a couple degrees of timing) and it fired right up after i loaded the update. It held an idle of about 1050-1100. If the actual idle is higher than the desired idle, I decrease the tb set screw, correct?
I lowered the values in the prime pulse tables this morning (also added a couple degrees of timing) and it fired right up after i loaded the update. It held an idle of about 1050-1100. If the actual idle is higher than the desired idle, I decrease the tb set screw, correct?
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I've been working this cold start tune all weekend. I've got it lighting off pretty good but it kinda lumbers up to idle speed instead of coming up fast. The injector PWs are down in the low single digits. I played with the crank spark adv vs ect timing, taking it up to the 20s but it just won't fire that high. I had to lower it down 4 which makes sense as the spark doesn't need much lead at such a slow engine speed. However, at idle it's only getting 26-27 and I'd like to raise it to low 30s. According to the tables I'm looking at, it should be getting that. I'm puzzled as to why it's 5 down on timing.
I put the front on stands yesterday to look at the O2 sensors. There's 2. I was expecting 3, the 2 NBs and the WB. The bank 1 sensor is fat, like WB while bank 2 is skinny, like a NB. Both have the flat 4 inline connector. The bank1 connector goes into the harness, not to a WB controller like I expected. If memory serves, both connectors had 2 grays, a black and white wires. So basically I have no idea what the AEM WB gauge is connected to nor what the previous owner did to connect the gauge. I performed the WB sensor test on AEMs website and it acted nothing like that. It should read max lean in free air and go max rich when wrapped in a cloth soaked in brake cleaner. It pretty read stoich no matter what I did to it, in free air and in the brake cleaner cloth.
At any rate, I've linked the last log below. I've also linked in the spark tables I'm working with but they export as .tab file types and I have nothing that will open those.
LOG:
https://docs.google.com/leaf?id=0Bw7...zNTE2&hl=en_US
Spark correction vs map vs ect
https://docs.google.com/leaf?id=0Bw7...xZWQ2&hl=en_US
crank spark vs ect
https://docs.google.com/leaf?id=0Bw7...4NDYy&hl=en_US
main spark vs rpm vs map
https://docs.google.com/leaf?id=0Bw7...xNDhl&hl=en_US
I put the front on stands yesterday to look at the O2 sensors. There's 2. I was expecting 3, the 2 NBs and the WB. The bank 1 sensor is fat, like WB while bank 2 is skinny, like a NB. Both have the flat 4 inline connector. The bank1 connector goes into the harness, not to a WB controller like I expected. If memory serves, both connectors had 2 grays, a black and white wires. So basically I have no idea what the AEM WB gauge is connected to nor what the previous owner did to connect the gauge. I performed the WB sensor test on AEMs website and it acted nothing like that. It should read max lean in free air and go max rich when wrapped in a cloth soaked in brake cleaner. It pretty read stoich no matter what I did to it, in free air and in the brake cleaner cloth.
At any rate, I've linked the last log below. I've also linked in the spark tables I'm working with but they export as .tab file types and I have nothing that will open those.
LOG:
https://docs.google.com/leaf?id=0Bw7...zNTE2&hl=en_US
Spark correction vs map vs ect
https://docs.google.com/leaf?id=0Bw7...xZWQ2&hl=en_US
crank spark vs ect
https://docs.google.com/leaf?id=0Bw7...4NDYy&hl=en_US
main spark vs rpm vs map
https://docs.google.com/leaf?id=0Bw7...xNDhl&hl=en_US
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I pretty much wrapped this up this past weekend after working on it for seeeeveral days. The main reason I couldn't get the idle right turned out to be the iac valve. I replaced it and stuff started falling in place and acting like it should. I've got a smooth idle, well as smooth as a 230/236 cam can be and iac counts in the 30s with idle around 1000. tps is 0% at .490 volts.
Another contributor was finding out my fuel pressure was 47.5, not 43.5. After I changed the injector constant from 42 lbs to 43.9 lbs and changing the cylinder volume to reflect a 355 and not a 350. It acts a lot better now but I still have more work to do. It has a small flat spot off idle and and I'm working out some decel bugs.
Another contributor was finding out my fuel pressure was 47.5, not 43.5. After I changed the injector constant from 42 lbs to 43.9 lbs and changing the cylinder volume to reflect a 355 and not a 350. It acts a lot better now but I still have more work to do. It has a small flat spot off idle and and I'm working out some decel bugs.
