87Formula4bbl

Is there any easy way to tell if your car is running in open loop or not. Its an '87 350 with the cc quadrajet.

Thanks in advance,
Ben

Vader

If you have the stock ECM (1227169) in your '87, you should be able to invoke Field Service Mode once the engine is running and watch the Service Engine lamp flashes.

You can jump 'A' and 'B' terminals on the ALDL while the engine is running.

WARNING!
This must be done after the engine is running. This is called Field Service Mode and will not harm the ECM.

If the ECM is in Open-Loop mode, the SES light will flash rapidly, about 2½ times per second. If it's in Closed-Loop mode, it will flash about once per second. When in Closed Loop mode, flashing less than once per second indicates the ECM is enriching the mixture above the 128 count base line. Flashing more than once per second indicates the ECM is leaning the mixture below the 128 base line.

MrDude_1

vader, cant that harm your car if you start it with the jumper there? or is that a myth?

jfreeman74

I think that is why he said this has to be done while it is running. Vader, can you leave a WinALDL diagnostics cable plugged in at all times? Mine is using a 10K resistor from A&B. I was thinking about hardwiring it in. Can I do this without damaging the ECM?

87Formula4bbl

Thanks Vader! That was exactly what I needed. I dont have the tools to find out the complicated way. My issue is, I swapped in the 350 Goodwrench LO5 for my LG4, along with the Comp Cams 270HR cam. I also have hedman hedders, which I recently had an O2 sensor bung welded in. I was told by a few people that the hedders may not get got enough down by the collectors to heat the O2 sensor to the correct operating temp, so I wanted to see if it was even working. I didnt think of this till now, but I think my thinking was wrong. Just because its running in open loop doesnt mean that the O2 sensor is operating does it? Hehe. Ok so is there also a way to check that or will I need a voltmeter or other tool for the job? Reason I ask is because it doesnt seem to be running to its full potential. I think I've about got the timing down to where I want it. It sucked about 3/4 of a tank from Mansfield to Toledo, which is about 110 miles. So it looks like I got around 14mpg or so, and seemingly it should be higher than that, even by a little. Any help or suggestions?