[L98]Idle Speed Adjustment
Thread Starter
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
[L98]Idle Speed Adjustment
I need to lower the idle in gear just a smidge. Not sure if that is controlled by the dfi or not. How do you do this? It's around high 800 to low 900 in gear where it should be 750(Also lacking that nice choppy sound).
Thanks in advance.
Thanks in advance.
Drifting
Joined: Aug 2000
Posts: 1,521
Likes: 0
From: West Islip New York
Re: [L98]Idle Speed Adjustment (JD 90 383)
It should be controlled be the IAC. There is also a idle stop screw on (in) the throttle body covered by a plug from the factory.
This info is based on stock components. There is a procedure for adjusting the idle, let me know if it applies and you need it.
This info is based on stock components. There is a procedure for adjusting the idle, let me know if it applies and you need it.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: [L98]Idle Speed Adjustment (1MoorTym)
It should be controlled be the IAC. There is also a idle stop screw on (in) the throttle body covered by a plug from the factory.
This info is based on stock components. There is a procedure for adjusting the idle, let me know if it applies and you need it.
This info is based on stock components. There is a procedure for adjusting the idle, let me know if it applies and you need it.
The adjustment procedure that uses the "idle screw" is the minimum idle air procedure. It's performed in order to get the IAC counts right.
Bottom line is you'll need to change the chip programming. I had to do this on my '90 L98.
:cheers:
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: [L98]Idle Speed Adjustment (96GS#007)
Not too familiar with the DFI unit and all it controls, but the ecm in a normal setup will control the desired RPM for idle. Unless as menioned above the blades are out of the range of the IAC. I would take to the shop that did your DFI and ask them.
Hate to say it, but you don't have a vacuum leak...that will bring the IAC out of range. If you have a scanner handy, see if the IAC are pegged at zero, if they are then it might be a leak or the blades out of adjustment...definately check the blades first :D
Hope you can track it down. :cheers:
Hate to say it, but you don't have a vacuum leak...that will bring the IAC out of range. If you have a scanner handy, see if the IAC are pegged at zero, if they are then it might be a leak or the blades out of adjustment...definately check the blades first :D
Hope you can track it down. :cheers:
Thread Starter
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
[L98]Idle Speed Adjustment
It's a new IAC. I did tinker with the little screw once. I had a problem long ago when I first got the 383 done. It'd start, then stall. LPE Said to crank the little screw a little to open the blades. I just replaced the IAC. That was some 39000 miles ago.
I'm not too sure if the DFI controls the idle now. My previous car with version 5 DFI had it's own iac. This one utilizes the gm one. Either way, I'm taking a ride to the shop who installed the DFI Wednesday. They can hook up the laptop and see what's going on. Stone cold starts need a little work also(overnight).
Thanks! :cheers:
I'm not too sure if the DFI controls the idle now. My previous car with version 5 DFI had it's own iac. This one utilizes the gm one. Either way, I'm taking a ride to the shop who installed the DFI Wednesday. They can hook up the laptop and see what's going on. Stone cold starts need a little work also(overnight).
Thanks! :cheers:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: [L98]Idle Speed Adjustment (JD 90 383)
Jay, if the DFI controls idle by bleeding air with the IAC you should be able to do the setup the same as with a GM ECM (method on my site). I see no reason why the DFI wouldn't use the same idle control method as GM.
In that case you need to extend the pintel and set base idle. Assuming the TB plates are clean and the IAC bore is still clean the DFI should then set the correct idle speed.
Anyway the scanner will show how many IAC counts the DFI is calling for; should be around 28, if like the GM setup.
Since your idle drops a copla hunderd RPM when you drop in into gear, it sounds as though the IAC is still well behaved.
In that case you need to extend the pintel and set base idle. Assuming the TB plates are clean and the IAC bore is still clean the DFI should then set the correct idle speed.
Anyway the scanner will show how many IAC counts the DFI is calling for; should be around 28, if like the GM setup.
Since your idle drops a copla hunderd RPM when you drop in into gear, it sounds as though the IAC is still well behaved.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Le Mans Master
Joined: Oct 1999
Posts: 6,366
Likes: 34
Re: [L98]Idle Speed Adjustment (65Z01)
I think the adjustment most of us on the forum do would work just the same since the DFI si a piggy back system???
BTW, do you have 2 MAP sensors on your car now?
I got a pretty nice idle out of mine doing the method mentioned here on the forum with the paper clip in the A&B terminals and unplugging the IAC controller etc...
each time I ripped it apart I found I had to reset it to get that nice idle back.
BTW, do you have 2 MAP sensors on your car now?
I got a pretty nice idle out of mine doing the method mentioned here on the forum with the paper clip in the A&B terminals and unplugging the IAC controller etc...
each time I ripped it apart I found I had to reset it to get that nice idle back.
Thread Starter
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
[L98]Idle Speed Adjustment
It's going to the Doctor's tomorrow(F***ing thing is always sick :D ) er em, the shop who did the install. Thanks Jim, we'll see how it works. It's not really that well behaved.
Bill, u got it. Two map sensors. They need to be a little more neatly placed :rolleyes: as noticed in the pic. Mark 383, a friend of corvette0096 has his mounted on the firewall near the windshield. Nicely done.
I'll keep you posted and thanks for replying.
Bill, u got it. Two map sensors. They need to be a little more neatly placed :rolleyes: as noticed in the pic. Mark 383, a friend of corvette0096 has his mounted on the firewall near the windshield. Nicely done.
I'll keep you posted and thanks for replying.
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
Re: [L98]Idle Speed Adjustment (JD 90 383)
I have mine neatly mounted on the windshield. The DFI controls the IAC and therefore idle speed. You have to also set the throttle blades properly. The procedure I use for modified engines is to set the screw so you have about 40 IAC counts at warm idle. It seems to work great. I have trouble getting mine to idle down to 500 rpm when you follow the procedure in the book because of my cam. Did you ask why you need two MAP sensors? That doesn't make and sense. I'm not familiar with the DFI you have though.
Jason
Jason
Thread Starter
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
[L98]Idle Speed Adjustment
Would someone mind sending me an e mail on how to set the blades? It did it again just now. Once it's hot, it'll jump to about 1200 in "P" idle about 1000 in gear. Cold it seems a little better weirdly.
No other gripes! :D it revs to 6000 like stink! :smash:
JD90383@aol.com
No other gripes! :D it revs to 6000 like stink! :smash:
JD90383@aol.com
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: [L98]Idle Speed Adjustment (JD 90 383)
JD
The DFI converted you from a MAF to a Speed density system right? What's ya pay for it if you don't mind me asking.
KM
The DFI converted you from a MAF to a Speed density system right? What's ya pay for it if you don't mind me asking.
KM
Drifting
Joined: Jan 2001
Posts: 1,669
Likes: 1
Re: [L98]Idle Speed Adjustment (JD 90 383)
JD, thats the neat thing about the DFI you can change it, but why go with it in sleeper mode. First thing to look at is not even DFI related, check the screw in the TB. If it is out then you have to look at your IAC, it could be causing the high idle. The best thing is not to be afraid to use your Calmap, just first thing save the ECM settings. If it makes you feel better try making changes first with just the key on and engine off, that way you get use to using the Calmap and you don't accidently change something that could cause something drastic. The key has to be in the run position though or else it will not communicate with the ECU.
Drifting
Joined: Jan 2001
Posts: 1,669
Likes: 1
Re: [L98]Idle Speed Adjustment (snaketr)
I guess I should have read the entire post. The set screw is behind the linkage. Completely back it out and then check your idle. If it will not idle you could have two problems, either the IAC is not working or it is not set right. This is where you go into the Calmap and set the IAC for your idle. Now you can also turn your IAC off and adjust the idle with the set screw for the throttle blades. DFI is a piggyback so to speak of, however you should have no engine functions running through your old ECM so a scanner will not work. By the way is this 6.0 or Gen7? Also why do you have two MAP sensors, you should only need one for the DFI.
Drifting
Joined: Jan 2001
Posts: 1,669
Likes: 1
Re: [L98]Idle Speed Adjustment (snaketr)
You said someone else was tuning it? Just a suggestion, take it to them to correct but you need to get the Calmap program so you can learn it yourself, that way you do not have to wait on someone else to tune your system.
Thread Starter
Team Owner
Joined: Apr 2000
Posts: 27,818
Likes: 8
From: CT
[L98]Idle Speed Adjustment
88-406. The system goes for about $14-1500(don't get me started on what I spent this year, I'll :U ). It's still a speed density system as far as I know.
snaketr:yes, it's frustrating not doing it myself. the poor idle thing bugs me. the fact that it's intermittent is worse. sometimes it's ok, sometimes not, more often than not. and the guy who tunes it is away(its easier to reach the president) just venting :cuss it sat for almost a month,needs a little tweak here and there which would prolly take no time,and it can't be done for another week.
I'm sincerely reaching the end of the road with this car. Once I find a job,and can have enough...I'd like to go to a c5. Keep this one, but have a normal car that doesn't just suck money constantly. Sorry if I'm ranting. I think I'm the only one with a motor of my type with soo many problems and it's never the way it's promised to be.
So be it I guess..? ? ? Thanks for the replies.
snaketr:yes, it's frustrating not doing it myself. the poor idle thing bugs me. the fact that it's intermittent is worse. sometimes it's ok, sometimes not, more often than not. and the guy who tunes it is away(its easier to reach the president) just venting :cuss it sat for almost a month,needs a little tweak here and there which would prolly take no time,and it can't be done for another week.
I'm sincerely reaching the end of the road with this car. Once I find a job,and can have enough...I'd like to go to a c5. Keep this one, but have a normal car that doesn't just suck money constantly. Sorry if I'm ranting. I think I'm the only one with a motor of my type with soo many problems and it's never the way it's promised to be.
So be it I guess..? ? ? Thanks for the replies.
Drifting
Joined: Jan 2001
Posts: 1,669
Likes: 1
Re: [L98]Idle Speed Adjustment (JD 90 383)
JD, let me help, Is this a Gen7. If you can copy the program on your ECU. Then give my buddy a call, his name is Dan Baldwin @804-598-7727. He is really good a writing programs and finding problems with others. He can either modify or write a new program and send it to you on a disk.
