I've been getting into running the codes on my '86 Z24i TBI.

http://www.autozone.com/az/cds/en_us/0900823d/80/17/ae/.../repairInfoPages.htm

Also monitoring the O2 sensor.

These are some LINKS that give some good info on what an O2 sensor does and how to tell if it is working right:


http://www.kemparts.com/TechTalk/tt07.asp


http://dodgeram.org/tech/gas/Trouble/O2_sensor.htm


http://www.gnttype.org/techarea/ecmsensors/O2sensors.html


http://en.wikipedia.org/wiki/Oxygen_sensor



Since this ECU is different that the later ones...I thought I'd start a new post.

As far as I can tell so far there might be only one mode with this ECU...diagnostic.

At this point I'm getting codes 23...24...and 42. The 23 and 42 have to do with a malfunctioning TPS. 24 is the neutral switch...but haven't gotten around to testing it yet.

Have adjusted the TPS and am now getting hard idle switching action...as evidenced by the way the engine runs as it switches right above idle....but still get a code 23.

Have also been monitoring the O2 sensor by using a digital meter to watch for cycling or going into closed loop where the mixture is leaned out more vs open loop. To do this I just put a wire on the O2 sensor lead...before the connector to avoid the shielded wire...with the negative meter lead to ground.

Found that the O2 was not going into closed loop very often...so I replaced the O2 with a Bosch generic. Now it cycles much more often...meaning better mpg I hope.

I've noticed that the O2 will go into open loop when very little throttle is applied...so that when highway cruising...any slight grade will cause an open loop condition. But the O2 will cycle in closed loop in all gears IF the throttle is feathered back some.

Not sure whether the TPS is affecting whether the ECU is utilizing the O2 cycling effectively or not.

Could be that people running larger tires are mostly running in open loop due to needing to use more throttle to maintain a certain speed?