intermittent check engine light, but no codes?

[99FiveOh]

My car is running excellent now that I replaced the O2 sensors. But now after driving for about 10-15 minutes my CE light will come on and stay on till I shut the car off. After restart it will stay off another 15 minutes or so.

I took it to my brothers shop yesterday after seeing the CE light come on and the only codes it found were on the COER test and it was for Thermactor not working on left or right banks. I have it bypassed/removed so that's normal, but in the past that's never caused a CE light to come on.

So, we have zero codes in the COEO test but CE DOES come on. What would cause this condition?

I do have my EGR blocked off, would that cause it? The EGR valve itself is still on the motor and it's plugged in with the vac line in place. I've had this same setup in my previous cars with no CE light.

 

[blksn955.o]

It could be the EGR, my CE would come on as soon as the engine got warmed up and when I first hit cruise when the EGR would normally turn on. I had my EGR tube blocked as it broke. I got a new tube and the CE went away.

Really the EGR is not something that is hurting the motor performance wise...and your actually hurting your mid load MPG by not having it working correctly. The EGR shuts off at WOT...but I am sure your no dummy to this so I am probably preaching to the choir.

Since you just replaced your O2's, did you reset the EEC by undoing the batt. to clear the KAMFR? If the O2's you had were off a bit, your computer may be having a fit with the new o2's not having a signal that matches the KAMFR (Keep Alive Memory Fuel Reference) from the old o2's.

 

[99FiveOh]

No, the fancy "Mac" diagnostic machine cleared all the codes that were in the computer. I know this because we did another self diagnostic right after clearing the codes and nothing showed up.

The only reason I don't have the EGR connected to the header is because I'm using the BBK shorties and the factory tube won't fit.

 

[Adam95GT]

No, the fancy "Mac" diagnostic machine cleared all the codes that were in the computer. I know this because we did another self diagnostic right after clearing the codes and nothing showed up.

The only reason I don't have the EGR connected to the header is because I'm using the BBK shorties and the factory tube won't fit.

The egr tube is easy to make... go get a peice of copper pipe... cut the stock one in half and steal the ends. flare the ends with a tubing flare kit and bend it in place works like a charm.

 

[blksn955.o]

KAMFR is not a code its the fuel trims stored into the EEC's memory...I dont know if a code reader/scanner will reset the KAMFR when it clears the codes.

 

[99FiveOh]

If KAMFR is not a code, the how would IT explain why my CE light is on? I thought only fault codes in the self diagnostics would trigger the CE light.

Which test would show KAMFER information?

 

[blksn955.o]

I am only brainstorming here....

KAMFR is the fuel trims gathered from the o2's and the relation to how much adjusting the fuel injectors need to make to get the A/F numbers the EEC is programed to target. As o2's age they will not hold as narrow of a range and the KAMFR will "drift" over time and become out of range as well.


My "idea" of a possible issue since your new o2's are going to send a correct "tighter" narrow band signal to the eec and it may be causing a fueling mis-match to what is stored in memory as the KAMFR. To reset the KAMFR and test this "idea" you only need to undo your batt +/- terminals and leave the door open so the dome/chime drain any residual power in the system and wait about 1min and reinstall the +/- cables to the batt.

I would say either fix the EGR or get it shut off correctly in the eec with a tune/tuner either way. There are extensions avail. if the stock tube is too short. Otherwise the copper tube method has worked for a lot of people.

 

[99FiveOh]

I will try those ideas and post up the results, thanks!