Need help with DFCO decel
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
Need help with DFCO decel trying to work some bugs out and this one is really irritating
on decel the car will cruise along holding 1400rpm or so then occassionally drop to normal and decel properly but then it goes back up to cruising, does this back and forth
when it's holding high RPM timing is around 40* and drops severely when it is decel properly
I don't know which if any of my tables have been altered but the tune will be posted below for EFI Live
Any ideas where to start? Car is a cammed automatic LS1 with 4l60e and Yank SS3600 converter. I have confirmed TPS is seeing 0%
on decel the car will cruise along holding 1400rpm or so then occassionally drop to normal and decel properly but then it goes back up to cruising, does this back and forth
when it's holding high RPM timing is around 40* and drops severely when it is decel properly
I don't know which if any of my tables have been altered but the tune will be posted below for EFI Live
Any ideas where to start? Car is a cammed automatic LS1 with 4l60e and Yank SS3600 converter. I have confirmed TPS is seeing 0%
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
the other issue I'm having is on warm startup the idle RPM jumps to 2000rpm even after readjusting RAFIG for desired idle air flow, after about 10 seconds they start to fall then shoot up again then fall until settled on normal idle
Your first problem probably has more to do with the throttle cracker table than dfco.
The second is probably more your tb.
The thing is they both could be related to your tb. I would look at sealing it up better before doing tuning. I had to epoxy around the forward edge on one side of the tb and aft edge of the other to fix the problem you're having on my car. Just a very thin coat to help seal the throttle blade to the body. It worked for me with no tuning. To much air is seeping by the larger tb. IMO
These cars were designed around a 78 mm tb. When that size is drastically increased it makes the IAC go crazy and it can't control the idle anymore.
The second is probably more your tb.
The thing is they both could be related to your tb. I would look at sealing it up better before doing tuning. I had to epoxy around the forward edge on one side of the tb and aft edge of the other to fix the problem you're having on my car. Just a very thin coat to help seal the throttle blade to the body. It worked for me with no tuning. To much air is seeping by the larger tb. IMO
These cars were designed around a 78 mm tb. When that size is drastically increased it makes the IAC go crazy and it can't control the idle anymore.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
The reason I think it is DFCO is that when it decels properly the timing is dropping to basically nothing. At highway speeds it will sometimes exhibit similar behavior even with slight throttle (around 5%?) just to a lesser extent.
I recently ported the IAC openings and it cured my cold start problem. The high idle on warm start thing was happening before but got worse, redoing desired idle airflow made it to where the decay is much much quicker but it is still present.
I recently ported the IAC openings and it cured my cold start problem. The high idle on warm start thing was happening before but got worse, redoing desired idle airflow made it to where the decay is much much quicker but it is still present.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
I will check that table.
Yes I know it is fuel cut off but doesn't it also pull spark when it cuts fuel? there is a table for set for each?
What else would cause it to pull 40* timing? I didn't see any stray cells in the timing table but will double check
Thanks
Yes I know it is fuel cut off but doesn't it also pull spark when it cuts fuel? there is a table for set for each?
What else would cause it to pull 40* timing? I didn't see any stray cells in the timing table but will double check
Thanks
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo I will check that table.
Yes I know it is fuel cut off but doesn't it also pull spark when it cuts fuel? there is a table for set for each?
What else would cause it to pull 40* timing? I didn't see any stray cells in the timing table but will double check
Thanks
Yes I know it is fuel cut off but doesn't it also pull spark when it cuts fuel? there is a table for set for each?
What else would cause it to pull 40* timing? I didn't see any stray cells in the timing table but will double check
Thanks
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
I was on a drive with friends after uploading the tune so I wasn't able to see if timing is still falling out.
I will double check but as posted above with the DFCO tables altered it does not get the heavy engine braking on decel I was talking about but I will have to see what the timing is doing.
On the other issue I really am getting about ready to junk the throttle body and get one that doesn't have all these issues controlling idle flow. As an amateur tuner trying to work around it is very frustrating. It seems I can either get it to idle properly cold or warm but not both. And on a warm restart it still wants to rev up then fall then rev back up then settle.
If I put the car in gear before it does all of it's little bullshit it will cruise control at 1400+ rpm until you come to a stop but then start doing it again. If you let it jump up and down and settle to a normal 850 idle before putting it in gear it works better.
TECH Addict
Joined: Aug 2005
Posts: 2,305
Likes: 126
From: Monroe,NY
I know when my truck goes into dfco my timing goes to zero. Before it goes into dfco timing stays the same as the timing table. Never really checked to see what makes it drop in dfco but i think at least in hptuners there is timing in the dfco tuning area.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
That's how mine acted, but it would enter and exit DFCO so quickly it was hard to keep an eye on but basically it would drop to 0* or so then ramp back to 40*. When timing was gone you could feel the car engine braking hard and when it ramped back in, RPMs would increase to what they would be for that cruise speed and the car would pull itself along or very very slowly decelerate.
I wish I knew someone with a spare 90mm TB I could toss on just to see how much if any is still pure mechanical and how much is crap idle tuning. Same setup in another car minus the Fast 90/90 and headwork took me all of 2-3 tries to get to idle perfectly (it was a m6 though) even with the a/c on.
I wish I knew someone with a spare 90mm TB I could toss on just to see how much if any is still pure mechanical and how much is crap idle tuning. Same setup in another car minus the Fast 90/90 and headwork took me all of 2-3 tries to get to idle perfectly (it was a m6 though) even with the a/c on.
TECH Addict
Joined: Aug 2005
Posts: 2,305
Likes: 126
From: Monroe,NY
See what you throttle position is reading when it goes into dfco. There are parameters to set when car will enter dfco that you can change to keep it in dfco. Speed, rpm and throttle position are some of the parameters. You have to change some of those settings.
It seems like everyone that buys those fast throttle bodies always have problems.You would think as much as they cost they would get them to work correctly.
It seems like everyone that buys those fast throttle bodies always have problems.You would think as much as they cost they would get them to work correctly.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
Thanks again.
And supposedly it is the early versions like mine that have so many issues. I am looking into replacing it now, I am fed up with trying to modify it and would rather eliminate it as a variable. I have tuned another car with the same setup as mine the variables being the Fast intake/tb and mine being an automatic rather than manual trans. The other car was so easy to get to idle it was stupid.
I seem to be wasting my time trying to tune around this thing. Hio is probably at least partially correct but I do not want epoxy which could come loose and enter my engine in the TB. I would rather buy one that works as it should so I can focus on learning how to tune correctly.
And supposedly it is the early versions like mine that have so many issues. I am looking into replacing it now, I am fed up with trying to modify it and would rather eliminate it as a variable. I have tuned another car with the same setup as mine the variables being the Fast intake/tb and mine being an automatic rather than manual trans. The other car was so easy to get to idle it was stupid.
I seem to be wasting my time trying to tune around this thing. Hio is probably at least partially correct but I do not want epoxy which could come loose and enter my engine in the TB. I would rather buy one that works as it should so I can focus on learning how to tune correctly.
It's such a thin coat your engine would chew it up and spit it out. Use a good quality epoxy and it will be fine. Mine has been done over a year with no issues. I shoulda took a pic of it but I didn't. My 102 tb is a ebay special......work fine now.
Hell we bored a oe tb years ago till it had hole in it. Epoxied it up and bored it more, made a tb blade for it. It's still alive 10-12 years later. We did that just before the fasts came out.
Hell we bored a oe tb years ago till it had hole in it. Epoxied it up and bored it more, made a tb blade for it. It's still alive 10-12 years later. We did that just before the fasts came out.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
I see what you're saying, literally just tired of messing with it.
The IAC has been ported, I had to sand where the blade seats to prevent blade hanging open, previous owner drilled a hole in the blade (which I have plugged with a bolt/lockwasher/red locktite, and now it might need epoxy around the blade too?
I would rather eliminate it as a variable entirely and sell this one cheap so if someone else wants to fix it they can.
If I can't find a good deal I might still fight it some more as I don't have $350-400 for a brand new one.
Any idea what type of epoxy is good if I go that route? I have never messed with anything other than JB Weld and I do not think it would be appropriate as it is very brittle.
The IAC has been ported, I had to sand where the blade seats to prevent blade hanging open, previous owner drilled a hole in the blade (which I have plugged with a bolt/lockwasher/red locktite, and now it might need epoxy around the blade too?
I would rather eliminate it as a variable entirely and sell this one cheap so if someone else wants to fix it they can.
If I can't find a good deal I might still fight it some more as I don't have $350-400 for a brand new one.
Any idea what type of epoxy is good if I go that route? I have never messed with anything other than JB Weld and I do not think it would be appropriate as it is very brittle.
See what you throttle position is reading when it goes into dfco. There are parameters to set when car will enter dfco that you can change to keep it in dfco. Speed, rpm and throttle position are some of the parameters. You have to change some of those settings.
It seems like everyone that buys those fast throttle bodies always have problems.You would think as much as they cost they would get them to work correctly.
It seems like everyone that buys those fast throttle bodies always have problems.You would think as much as they cost they would get them to work correctly.
I see what you're saying, literally just tired of messing with it.
The IAC has been ported, I had to sand where the blade seats to prevent blade hanging open, previous owner drilled a hole in the blade (which I have plugged with a bolt/lockwasher/red locktite, and now it might need epoxy around the blade too?
I would rather eliminate it as a variable entirely and sell this one cheap so if someone else wants to fix it they can.
If I can't find a good deal I might still fight it some more as I don't have $350-400 for a brand new one.
Any idea what type of epoxy is good if I go that route? I have never messed with anything other than JB Weld and I do not think it would be appropriate as it is very brittle.
The IAC has been ported, I had to sand where the blade seats to prevent blade hanging open, previous owner drilled a hole in the blade (which I have plugged with a bolt/lockwasher/red locktite, and now it might need epoxy around the blade too?
I would rather eliminate it as a variable entirely and sell this one cheap so if someone else wants to fix it they can.
If I can't find a good deal I might still fight it some more as I don't have $350-400 for a brand new one.
Any idea what type of epoxy is good if I go that route? I have never messed with anything other than JB Weld and I do not think it would be appropriate as it is very brittle.
I can get you the # of the stuff I used. It was a 3m universal poxy that I use mostly for gluing composite panels together. For this application I would think jb weld would work fine. Maybe even a little better as you will have to sand it some.
Thread Starter
11 Second Club
iTrader: (18)
Joined: Mar 2008
Posts: 8,358
Likes: 27
From: Northwest AR
Thank you, this is very helpful. I think that was what was happening is the MAP values were just on the threshold and it was cycling in and out of DFCO. When I put stock 5.3 truck values there it stopped entering at all.
TECH Addict
Joined: Aug 2005
Posts: 2,305
Likes: 126
From: Monroe,NY
I forgot about those other parameters. I did change my map settings so i would go into dfco. Its been awhile since i have tuned on my truck.