bjankuski

I have a 1986 corvette and I have a hunting idle problem. I have been fighting this problem for at least a year and I do not believe I have any mechanical problems that are contributing to the problem. The problem appears to be releted to the tune on the car. I believe the car is too lean at idle when it is warmed up and in closed loop, how do I make the idle richer when the car is in closed loop being controlled by the O2 sensor?

I have attached the sig for the corvette below:

1986 Coupe, auto, 3.45 gears, 1973 406, 11.5 to 1 compression, SLP cold air, gutted MAS, 58 MM throttle body, ported plenium, Superram intake, TPIS BASE, 23 degree Trick Flow Heads, ZZX cam, TPIS headers, TCI 3000 stall, 3" duel exhaust, Cheap and easy free mods, custom chip, daily driver
RWHP 405 @ 5400 RWTQ 436 FTLBS @ 4000

Brian Murray

no intake leaks?

if that's not it, look at the TPS and IAC and adjust them.

bjankuski

No air leaks and the TPS is adjusted correctly. The IAC is working but it is moving all over the place trying to control the uneven idle.

I have Tunercat for chip burning and EASE scan software to help record the engine date and I cannot see anything with the scans that would be causing this problem.

3.8TransAM

Does it do it in open and closed loop or just closed loop?

If its closed loop only and everything else is okay and u have verified that nothing mechanical/electrical is causing the problem than start searching under the 02 parameters/constants. U can adjust these to force it richer or leaner at idle in CL.

later
Jeremy

vernw

iTrader: (2)

One other thing for ya - are you SURE the IAC is working correctly? There is no real feedback from the IAC to the ECM to say "I have moved to setting XX". The ECM tells the stepper motor to move, but there is no guarantee it did. I had this problem and didn't realize it last summer. Way I figured it out was changing settings in the emulator (Ostrich) that should haveforced the idle to change, say the datalogged numbers change, but the engine stayed constant.

So if you see thew IAC steps changing and the motor doesn't reflect those settings, might try a different IAC. Just my two cents on this....

bjankuski

Thanks for the replies, I am using Tunercat software and I have not seen any O2 parameter/constants, do you know if Tunercat has these adjustments?

Thanks

ryan.h

iTrader: (2)

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8UpAFord

I have the same issue or had the same issue and some of the same mods as you. Is your ninth injector disabled? If so you running a 6E Bin? Do you have the throttle body coolant pass done. that migfht just be it. if so just richen up the mixture via the chip or AFPR.

Another f'ed up thing on my car when trying to figure it all out. how advanced are you running the the car? i was running 15* (Low RPMs) advance ran Like a crap at idle but sounded bad ***. I'm at 8* know in the low RPMs and its not that bad runs good too.

3.8TransAM

Email tunercat and ask for your specific app.

If they dont have a new version with them he can prolly add them if u ask.

Might be time to start weeding thru the hack and firthuring your own knowledge as well.

later
Jeremy

bjankuski

My ninth injector is disabled but I am still running the $32B calibration and the throttle body is bypassed. I will play with the timing some more I never tried as low as 8 degrees at idle. I am currently at 20 degrees at idle and there is no way to richen up the idle mixture when it is in closed loop unless I force it out of its correction range.