LT1 PCM gurus?
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TECH Junkie
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From: Glen Burnie, Md
LT1 PCM gurus? Are there any? Have a car that idling at 3.6 ms pulsewidth, idling stably (very big cam, 408, hyd setup) it will just shut off. Was looking into the problem with Freescan, had to reinstall my Datamaster stuff to notice that it was actually randomly (seems to be anyway) and intermittently cutting pulsewidth back tosomething like .90 for a split second (which must be the hardcoded lower limit?) Sometimes it can recover from that and you hardly notice its doing it, other times, it shuts it right off. You can see it do it (pw drop) and engines stalls, and watch pulsewidth come back up again as the engine is on its way down, but its just not going to recover this gnarly of a cam at 400 rpm falling hard because fuel was cut.
Anyone seen anything like this, know what could cause it to cut fuel that suddenly and get back just as suddenly? Its idling at 75-85kPa, nothing drastically changing there, I saw it go from fuel trim cell 16 to 17 when it did it a couple times but last time it died and I captured it trim cell stayed right at 16. If kPa doesnt change, TPS is steady .63-.65 volts and rpm is steady how can there be a fueling change?
Car is in speed density btw
Anyone seen anything like this, know what could cause it to cut fuel that suddenly and get back just as suddenly? Its idling at 75-85kPa, nothing drastically changing there, I saw it go from fuel trim cell 16 to 17 when it did it a couple times but last time it died and I captured it trim cell stayed right at 16. If kPa doesnt change, TPS is steady .63-.65 volts and rpm is steady how can there be a fueling change?
Car is in speed density btw
Are there any? Have a car that idling at 3.6 ms pulsewidth, idling stably (very big cam, 408, hyd setup) it will just shut off. Was looking into the problem with Freescan, had to reinstall my Datamaster stuff to notice that it was actually randomly (seems to be anyway) and intermittently cutting pulsewidth back tosomething like .90 for a split second (which must be the hardcoded lower limit?) Sometimes it can recover from that and you hardly notice its doing it, other times, it shuts it right off. You can see it do it (pw drop) and engines stalls, and watch pulsewidth come back up again as the engine is on its way down, but its just not going to recover this gnarly of a cam at 400 rpm falling hard because fuel was cut.
Anyone seen anything like this, know what could cause it to cut fuel that suddenly and get back just as suddenly? Its idling at 75-85kPa, nothing drastically changing there, I saw it go from fuel trim cell 16 to 17 when it did it a couple times but last time it died and I captured it trim cell stayed right at 16. If kPa doesnt change, TPS is steady .63-.65 volts and rpm is steady how can there be a fueling change?
Car is in speed density btw
Anyone seen anything like this, know what could cause it to cut fuel that suddenly and get back just as suddenly? Its idling at 75-85kPa, nothing drastically changing there, I saw it go from fuel trim cell 16 to 17 when it did it a couple times but last time it died and I captured it trim cell stayed right at 16. If kPa doesnt change, TPS is steady .63-.65 volts and rpm is steady how can there be a fueling change?
Car is in speed density btw
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TECH Junkie
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From: Glen Burnie, Md
Change the .txt to .uni and open with TTS Datamaster EE, download page here. http://www.ttspowersystems.com/DataM...downloads.html You get 20 free connections to a car, so should be no problem to read
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TECH Junkie
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From: Glen Burnie, Md
48 ld inj, nothing out of the ordinary, have the car making very good power, but this problem is an odd one. Tuned hundreds of these things over the years, never seen that though
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I had a similar thing happen to me as I was trying to lean out my idle.
I run a MAF (yeah, the old debate of VE table and MAF continues) and when I cut the VE tables by a significant amount in the RPM and KPA range for my idle, it would stall soon after it would enter closed loop. It did this with no other changes. I put the previous tune back in and it stopped stalling.
The pulseidths were real low/small. When it would start to die the IAC would open up and try to catch it from dying.
Maybe bump up your VE tables in your idle area??
I run a MAF (yeah, the old debate of VE table and MAF continues) and when I cut the VE tables by a significant amount in the RPM and KPA range for my idle, it would stall soon after it would enter closed loop. It did this with no other changes. I put the previous tune back in and it stopped stalling.
The pulseidths were real low/small. When it would start to die the IAC would open up and try to catch it from dying.
Maybe bump up your VE tables in your idle area??
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TECH Junkie
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From: Glen Burnie, Md
TECH Apprentice
Joined: May 2010
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From: Arkansas
Not familiar with edit, only tunercat for an obd1 car. It's in the constant tables. Can you hook your 02's up and see if they dip as this happens, you might also get away with raising the ve tables as stated before or raising the maf tables only at idle, but from my experiances that will cause it to run richer at idle. Also your Iac could be maxed out?
Thread Starter
TECH Junkie
iTrader: (10)
Joined: Nov 2001
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From: Glen Burnie, Md
Not familiar with edit, only tunercat for an obd1 car. It's in the constant tables. Can you hook your 02's up and see if they dip as this happens, you might also get away with raising the ve tables as stated before or raising the maf tables only at idle, but from my experiances that will cause it to run richer at idle. Also your Iac could be maxed out?
Talked to Ed Wright about it as well briefly, he was baffled why it would be doing that. Anyone have tunercats they could look at the min pulsewidth value and maybe just set the low limit higher and could try that, not finding the cause of the problem that way, but might fix the result
Teching In
Joined: Oct 2007
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From: Mount Airy, MD
Hey, Its Chris. I was at 75 and 80 that night he ran the car. Can you email me the bin and give as much info as possible. He Pm'ed me on Impalaforums and asked me to help. I'll PM my cell and we can talk off line.
Chris
Chris
