Adjusted the TPS, now what? (RENIX)

I looked through the ReniX files post, but my problem does not deal with a high idle condition.

Recently, the idle has been choppy and unstable. I cleaned out the IAC and adjusted the TPS to output .85 volts as indicated in my '90 FSM for a manual trans car (input was 4.99 volts).

Now, it starts up a bit easier, goes immediately to 2K RPM after firing up, and immediately and smoothly drops to around 1K RPM. When cold, a few seconds after dropping to 1000 RPM, the idle will fluctuate between 600-1000 RPM until the engine warms up. At that point the idle stabilizes between 700-750 RPM.

I ran the voltage checks on the MAP and resistance checks on the CPS, CTS, MAT, and 02 heater element as well. Only problem I found here was no resistance reading on the 02 heater element. This may need to be replaced, but the FSM says that the 02 sensor is not read during warm up (open loop).

Any other thoughts as to the problem here? Perhaps a vacuum leak that gets sealed up once the engine warms?

Is there anyway to tell if the IAC is shot other than using 'exerciser tool 7558' described on 14-88 of the '90 FSM?


Thanks a lot.

Ted

PM Ecomike or 5-90 they are Renix experts. There is a circuit which uses the input from your last hot (operating temp) settings to refresh the computer when it starts again and that may be fooling the cumputer into thinking the fuel mixture should be richer thus causing a momentary high idle. But again I am not the expert on this sublect, Jon or Mike chime in here !!!

Mike,

Please check out my latest post dealing with these issues here:

http://www.naxja.org/forum/showthread.php?t=926272

I reposted because my original title, which I could not edit, would not bring attention to the new findings I've made.

EcoMike has responded twice. His comments are interesting.

Your input would be much appreciated too.

Thanks for your response,
Ted

mikeforte said:

PM Ecomike or 5-90 they are Renix experts. There is a circuit which uses the input from your last hot (operating temp) settings to refresh the computer when it starts again and that may be fooling the cumputer into thinking the fuel mixture should be richer thus causing a momentary high idle. But again I am not the expert on this sublect, Jon or Mike chime in here !!!

Click to expand...

Ted Young said:

Mike,

Please check out my latest post dealing with these issues here:

http://www.naxja.org/forum/showthread.php?t=926272

I reposted because my original title, which I could not edit, would not bring attention to the new findings I've made.

EcoMike has responded twice. His comments are interesting.

Your input would be much appreciated too.

Thanks for your response,
Ted

Click to expand...

Ted I think that the O2 sensor is your main problem. I think the test would be to unplug it and see what, if any difference, that makes. A sticking EGR valve would be my second guess. they are nearly impossible to diagnose in my experience. I have just replaced them each time I thought they were the culprit. I have tried cleaning them but that has never worked for long.
Well congradulations on your new job. Hope we can all get this resolved today so you won't have to worry about this with the worries of new employment.
Good Luck,
Mike

mikeforte said:

PM Ecomike or 5-90 they are Renix experts. There is a circuit which uses the input from your last hot (operating temp) settings to refresh the computer when it starts again and that may be fooling the cumputer into thinking the fuel mixture should be richer thus causing a momentary high idle. But again I am not the expert on this sublect, Jon or Mike chime in here !!!

Click to expand...

Just remembered the name of that curcuit I was talking about (forgive my memory I'm old) it is called the latch curcuit if I recall correctly. Search on that topic and see what you come up with.
Mike

These are the relays (square ones) located below the starter relay next to the ignition coil, right?

I think I saw something in the FSM about testing them.

Makes sense, thanks for the input. I think the 02 sensor is shot anyways, but it won't hurt to make sure it circuitry is doing its job as well.

Thanks again,
Ted

mikeforte said:

Just remembered the name of that curcuit I was talking about (forgive my memory I'm old) it is called the latch curcuit if I recall correctly. Search on that topic and see what you come up with.
Mike

Click to expand...

Ted, I think pretty much answered your questions in the other thread already. The open loop warm up the FSM references is in my opinion the O2 sensor heater warm up of the O2 sensor that they are refering to. If the heater in the O2 sensor is bad, on the Renix at least, it will affect fuel economy and engine idle speed as the O2 sensor cools during a long idle.

Just change the O2 sensor as it is defective, and verify the voltages to the O2 sensor. Then if there is still a problem investigate the EGR and EGR solenoid that activates it, and aslo look for some kind od screwy vac leak.