Since I got my car it has always thrown code 13 o2 codes. I have just replaced the leaking injectors. I thought that the leaking injectors were fouling the o2, causing the code. This has turned out to not be the cause. I am still getting the o2 code and I just tried a known good o2. I checked the system, the wire from the o2 to the computer is good.

I also have a wild idle fluxuation, a good 300 RPM up and down. I have checked for vacuum leaks but found none, I'm not the most experienced at checking that though. I did the min. idle adjust. I checked the sensors also. The car starts up, idles fine at a higher rpm then after about ten seconds the idle RPM drops lower and it starts to fluxuate.

I tried using field service mode and watching the SES light. The car did not even try to go into closed loop mode!

I am starting to suspect there is a computer problem. I looked and the computer that is in there now is a reman.

Fuel pressure is good, the car runs strong, I've been all over and am not finding anything.

Any ideas?

As a side note, it only took two hours to change the injectors! The LT1 '94 injectors I got cheap fit very well. Thanks ZBRA! They are a much better injector then what was in there. Without the long pintle at the end they also make R&R of the fuel rails much easier.

 

If the O2 sensor is know to be good, the connection at the O2 sensor is clean and tight, the wiring has no missing insulation that maybe causing it to ground out, and the wiring is not loose at the ECM....then the ECM would be suspect. When you did troubleshoot the code 13 what did it tell you were the possible causes?

It would be nice if you had a spare ECM to swap out and try, just to troubleshoot. You might want to spend a little on a used ECM just for future troubleshooting and it may even fix the problem. The ECM's are tough and the PROM is usually what goes first.

 

So I should have a ECM and a PROM huh. I can look around, are deals out there?

I just pulled the o2 pigtail and checked the pigtail on that and on the car side. I tightened the round connector on the cars pigtail but it had no effect. I am going to pull the ECM tomorrow and check the connectors on that. Last time I looked it over, the o2 wire had continuity fine on the multi-meter.

 

Glad you got it fixed. Proper troubleshooting skills (as you have done) will just about always point to the problem. Glad it was a easy fix once all the work put into it was done.

 

Doesn't look like you fixed it.

13 is an open in the 02 signal - allmost always the wiring - the O2 is a voltage generator and in order for the ECM to see that voltage it needs a ground. That's a separate circuit from the ECM usually to the Block or Transmission - I don't have a Pin Out or Schematic for your Year, but universally it's a Tan wire and GM labels it as Circuit 413. Since the wiring from the O2 is good, you need to check this circuit. My guess is that it's open.

Having a Reman ECM isn't unusual. I'm on my 4th or 5th with 60,000 miles (on the Vette - I've had similar problems with other GM's) - most were replaced under warranty and I don't think GM got them right until OB2 became a legislated standard - and maybe because an 8 to 10 year warranty was mandated along with it.


For your idle problems, check the Engine Coolant Temp Signal. When it's cold it should match or be close to the outside air temp. Start it up and the temperature should rise to the thermostat and then drop when the thermostat opens. Climb again until the Main Fan comes on. If it's always cold/always hot/or just jumping around and there isn't any codes, that's usually an ECM problem, but you'll have to troubleshoot the wiring to and from the Sensor to be sure. Repost if you get any oddball readings.

 

Oops - see there's another post showing a new ECM fixed it. So much for my theory.

 

No prob, thanks for helping. I think you helped in a thread awhile ago to. I ended up removing and cleaning the grounds, the one above the oil filter and the one on the drivers head. The measured OK but it was still a good idea to clean them as there was a little corrosion.

 

I didn't see the post where you changed the ecm......when I had a hunting idle, I unplugged the esc. the engine smoothed out. replugged it in (is replugged a real word?) and it stayed smooth. I changed the esc as a precaution, and no problems so far. I have to find it and replug it in to see if the hunting comes back