Open Loop Idle

[Heg87t]

Need some help understanding the open loop idle idea and the troubles I am having.

At idle my car has 128 integrator & BLM. Is this set from the open loop? Is the computer adjusting during open loop? Regular cruise at 45 mph shows block learns about 140 - 150 saying lean. Full throttle O2's about 780 - 800.

My car at idle shows O2 volts around 800 telling me it's rich. The car smells rich and idles badly, vacuum about 14 and it lopes or surges. I turned the fuel pressure down from 45 to 43 yesterday and it seemed to help but it is bad again today. I did the IAC reset and found I only needed to turn the screw about 20 degrees to get 500 rpm. It almost seemed to idle better with the IAC unplugged! IAC counts are very very high, like 150 - 170.

Some specs:
Newly rebuilt engine. Comp 212 cam
K&N filter
Dual exhaust
stock turbo & injectors
vacuum brakes

I was thinking vacuum leak so I started eliminating items like the HVAC and cruise. No change. That wouldn't explain the 800 volt idle O2's

Other strange things:
I see 0 o2 volts occasionally
MAF at wide open throttle shows only about 235

I am probably rambling but it's late & I am getting frustrated!

Any ideas?

 

[TurboDave]

The reason you're seeing 128 INT and BLM during idle is because of your open loop idle, and no, it doesn't learn in open loop, the locked INT and BLM tell you that.

There's a reason it smells rich at idle. Open loop is. A lot of people run open loop idle to mask existing problems.

What you need to do is take it out of open loop idle and let the entire range learn in. This will likely unmask any problems that may be existing in the system. You can then get the car running right, and after it's all corrected and learned in, then you can switch back to open loop idle if you like.

 

[Heg87t]

The reason you're seeing 128 INT and BLM during idle is because of your open loop idle, and no, it doesn't learn in open loop, the locked INT and BLM tell you that.

There's a reason it smells rich at idle. Open loop is. A lot of people run open loop idle to mask existing problems.

What you need to do is take it out of open loop idle and let the entire range learn in. This will likely unmask any problems that may be existing in the system. You can then get the car running right, and after it's all corrected and learned in, then you can switch back to open loop idle if you like.

Thanks for the input.

So if there is no correction at open loop the car is running on the fuel map in the chip for the idle cell right? Since I have O2's around 800 here's what I think I could have:

1) have a screwy chip specifying too much fuel at idle
2) too high a fuel pressure
3) incorrect fuel pressure gage

Would you agree? Any other factors you can think of?

I have a Thrasher 93 chip in the car now. I have another unknown chip that came with the car that I think is closed loop idle but I don't remember for sure. The car really didn't act any different with the original chip. I was hoping to see an improvement with the Thrasher. Oh, and I know i need a new TT chip but I think something else is wrong.

I agree that something is out of whack. I just need to track it down. I am going to check the coil ohm values and do the MAF tap test.

 

[TurboDave]

It has been my experience when operating in open loop idle modes, and relying only on a stock narrow band O2 sensor that readings of 800 are by no means wrong. Actually about what would be expected.


As for the IAC reset procedure you used, it's totally bunk. That's a VERY old procedure that usually caused more problems that it solved.
The correct way to set the IAC is through the use of a scan tool, using the screw to obtain idle readings of anywhere from 10-30 (while keeping the tps adjusted to within specs during the iac adjustment routine).

 

[Heg87t]

It has been my experience when operating in open loop idle modes, and relying only on a stock narrow band O2 sensor that readings of 800 are by no means wrong. Actually about what would be expected.


As for the IAC reset procedure you used, it's totally bunk. That's a VERY old procedure that usually caused more problems that it solved.
The correct way to set the IAC is through the use of a scan tool, using the screw to obtain idle readings of anywhere from 10-30 (while keeping the tps adjusted to within specs during the iac adjustment routine).

Thanks Dave. I will try adjusting the IAC to 10-30 and adjusting the TPS back to .42. That's a pretty easy thing to try.