How do i go about telling if my 87 Turbo2 is in open or closed loop mode? im getting really shitty mpg, and just wondering. Also what is open and closeed mode? whats the differance?

 

anyone ?

 

closed loop is when your car uses the O2 and other sensors to control your engine.

open loop , the car deosnt use the O2 sensor... and the ECU runs the engine off a 'defult' parameter..

 

Oh well, I'll be a post *****. Out of the loop when at idle. In the loop b/t idle and, my guess, when the tps plunger is fully extended. Only in the loop when cruising and the tps plunger is less than fully extended.

On a series four, I find the tps plunger is at its full travel just about the time the secondary plates start to open. That ain't much, but you will find that when cruising at 65 and below in fifth, the secondary plates are not open at all. My view of things anyway.

Anyone else? Then BUMP

 

The easiest way to tell if you're in closed loop is to install an air/fuel gauge. It will flip rapidly back and forth between rich and lean when you're in closed loop. Basically all a A/F gauge does is read the voltage from the O2 sensor and light up the LED in the corresponding position.

You *might* be able to see the same thing with a multimeter. An oscilloscope would definately show it to you. If you were to try this you probably want to go onto the highway and just cruise, maintaining your speed and throttle. You could do it under different circumstances, but highway is probably the easiest.

 

I'm with Snrub. I used a digital meter tapped into the 02 sensor wire for a couple of years to watch my 02 output, until I bought a wideband. Just find a good ground and tap the positive lead into the o2 wire, and place the meter on the dash.

I just went for a ride. In fifth gear, I can get up to 80 on a level road and I'm still in the loop. In forth gear, I can get up to 3300 rpm before it goes out of the loop. I forgot to look at the speed.

Its a combination of tps, afm signal and pressure sensor that decides whether your in open or closed loop. Might even throw in the neutral switch for good measure.