The car is an 1989 L98 car with afr 190 heADS, 219 219 cam, and an accel superram mainfold. For some reason, the car idles at 750 when it is cold yet when it warms up for a few minutes it surges and stalls. Adjusting the min. air rate only allows the car to idle at 1500 rpm; any lower and it will stall. It has no vaccum leaks. It runs correctly otherwise with no check codes. Any suggestions?

------------------
1991 Firebird
350 L98 (was a 305 TBI),T-5,Edelbrock TES and cat back,Accel manifold
NOS,subframes,jegster torque arm,MSD Digital 6
AFPR,Lakewood lcas
Hurst linelock,SLP cam (206 212 .480 .486),relocated battery,cold air,Hypertech chip,centerforce df,clutch
poly bushings and mounts
AFR 190s
Harland sharp 1.5 rockers
autopower rollbar

12.33 @ 114.83 juiced uncorrected

13.510 @ 102 non juiced uncorrected

 

Let me guess, you're running the stock chip.

 

Did you reset the IAC and TPS?

------------------
87 IROC-Z
Minirammed Solid Roller 377

 

check your EGR and make sure all your vacume lines are connected properly and that your EGR passages are clean. i had the same problem on my car, hook up some discconected vacume lines and put a new EGR in, thing ran like new. plus it ran cooler as well.

 

I can respond to these, it's my car Gofaster is asking about. The EGR passages are blocked off and the chip is a Performance Resource off the shelf chip. We plan on a custom chip in the future, but this is what we have to work with at the moment. We have already messed around w/ the IAC and TPS.

------------------
89 IROC-To see mods go to: http://www.geocities.com/buckeyeroc

 

The EGR has nothing to do with the car idling, have you set the timing successfully? How smooth is the cold idle? 750 is in gear? How are the o2 and cts?

 

Like i said, you're running a stock chip. Any off the shelf chip is guaranteed to have a stock fuel map in it, or at least real close to that. Not to mention, a stock L98 idle speed is like 500 rpms. I actually think it's the latter thats killing you, a 219/219 cam w/ a big low velocity intake set-up is not gonna idle happily at 500 rpm, especially not without the chip tuned right as the low end VE is also completely different for your set-up.
add in maybe a small vacuum leak or descreened MAF and it's even worse...



------------------
Ed Maher - Moderator @ The TPI & Carb Boards
92 Z28 Convertible - Quasar blue / Tan top
305 TPI A4 2.73 - 14.8 @ 93.1
Stock except ported plenum and dual cats
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

I agree with getting another chip burned. I think even in Lingenfelter's catalog it recommends a reprogrammed chip so that it will idle at 750 rpms. You can only mess with the Min air and IAC so much before getting another chip to correct the idle.

------------------
1989 IROC-Z, ZZ3 shortblock with some bolt-ons.
13.20 @ 108.69, 2.2 60'

 

The problem is as your engine heats up the commanded idle speed goes from 750 at 111 degrees F to 550 at operating temp. Most "off the shelf chips do not change this. Your cam simply will not idle at 550 hence the engine stalls. Do the following.

Close IAC valve to set min idle speed.
Set min idle speed as low as it will run.
Play with timing and fuel pressure to get it to run best.
Fuel flow increases with the square of pressure increase (4% pressure increase = 2% fuel flow increase)
Get a chip that incorporates an idle speed of 75-125 rpm more than your min idle, an adjustment to the idle AFR from the fuel flow data you gathered from adjusting the fuel pressure and adjustment to timing curves to account for new base timing.

John

Heart of Texas Power and Performance

 

How do I close the IAC. That is what I tried to do by grounding the aldl and then unplugging the IAC. Is this correct?

 

Did you try hitting it or yelling at it?

------------------
355 c.i.
Dart 180 Heads
Lunati 224/224 cam
Harland Sharp 1.5 rockers
Performer RPM Manifold
Holley 600 cfm double pumper
Hooker Super Competition Headers
Flowmaster Exhaust
Competition Engineering Sub-frame connectors
Super T-10
GM posi 3.42 rear
Hurst Roll Control
13.9@102

 

it needs gobs and gobs of money thrown at it. wait a week and ask Rich.

------------------
daily beaten 87 formula
87 Monte SS project car