When checking codes on my 88', does the engine have to be running, or just the ignition on? No codes pop up when the key is on, but with the engine running the o2 code pops up ( one,2second flash). My car started having an idle of around 950-1000rpms. All emissions are removed and the o2 sensor hasn't been changed in a long time. I'll appreciate any help.

Thanks, Tony

 

Change out your O2 sensor. If that is what the code is tellin ya then you should. On the other hand, if you have no emissions it could affect the readings and the error output code.

 

does anybody have any idea at all?

 

Since you have the code checker, you've probably seen this link:

http://www.teamfc3s.org/info/article...odes/main.html

But in case you haven't, it says that you just have to turn the switch to "ON". The engine does not need to be running.

 

Change the O2 sensor!

 

thank you, and I have read that. But again, If I put the key to the "on" position, no codes pop up, but if the engine is running the o2 sensor code pops up? does the check light always flash with the engine running even if there is nothing wrong with it? My idle jumped to an unsteady 950-1000rpms just recently, tps is set right, redid every possible vaccum leak. It's totally pouring outside right now so I can't pulled the car out of the garage to run it (just put in new o2 sensor) to see if it fixed it.

 

Check out the link I provided; all your questions are answered there. On my S4, my homemade code checker lights up for a couple of seconds when I first turn the switch, then both lights go out. If yours doesn't light up when the switch is turned to "On", then maybe something isn't wired exactly right (or maybe the '88 is different from the '87).

 

I have never seen this happen before. On th '91 N/A I used to have, if it flashed a code with key on, it also flashed the same code with engine running at idle. And I never had the situation where it flashed a code at idle but not at just key on. Try this. Clear the ECU completely, by disconnecting the battery negative terminal. I know that on older models you also had to depress the brake pedal. Hook the battery cable back up and check for codes again. There won't be any at key on because you cleared them, but crank and run the car and then check again.

 

IGNORE THE ABOVE INFORMATION, IT IS WRONG.

'91 is S5. The question was specifically about S4.

The S4s, in my experience, will only display error codes when they detect an error. The ECU seems to have no memory of any sort with regards to codes, and I believe is only capable of displaying one error code at a time.

If you want a tester that will show you everything at once, including the O2 sensor test lamp, I have one for sale. https://www.rx7club.com/showthread.php?t=485934

The ECU won't look for O2 sensor output initially, but if either the RPM, manifold pressure, or TPS output reaches a certain point (I'm not sure yet which one it is), the ECU will start to look for output from the O2 sensor. If it doesn't see something it thinks is sane, it'll throw a code.

If the code goes away after a bit of driving, it's likely that the O2 sensor just hadn't heated up enough.

-=Russ=-

 

Sorry, guys! My bad. 1988 was the last of the S4's. Totally different in dumping the codes

 

I swapped out the o2 one for a new one, stopped throwing the code and does idle/run alot better than before. Thanks alot.

 

Told ya!!!...hehehe

 

Closed Loop you mean? Does anyone here actually know the conditions that need to be met in order to go into closed loop? Sometimes I wish I could convert my '86 to OBD-II.

 

The O2 sensor isn't used at idle, nor should it affect normal running in any noticeable way - the ECU ignores it most of the time, and only uses it during light throttle cruise. If it thinks the O2 sensor is bad enough to throw a code, it won't even use it there.

Strange.

-=Russ=-

 

I did tighten my booster hose and ran some new ground too , thats probably what did it

 

Yea... that's a LOT more likely to fix idle & normal running issues than changing the O2 sensor is.

-=Russ=-