I am having problems going into closed loop. My BLM and INT values climb while at idle after going into closed loop. I have installed a heated O2 sensor and I am wondering if this is causing the problem. I have data logged and the O2 voltage is in the red. I have also noticed the O2 cross counts are 100 and higher. Any suggestions on trouble shooting this?? If I can't get my car on the road I am going to DIE!!! Any help is appreciated.

 

Is this a stock vehicle that you are trying to troubleshoot? If so I can move your post to the appropriate board.

RBob.

 

Need some clarification here. The problem is *not* going into closed loop? Or, the ECM is adding a bunch of fuel when it does go into closed loop?

Guess it's better than being in the pink-with-purple polkadots range!! What voltage levels are you seeing? If the ECM is adding fuel based on BLM/INT, the O2 voltage is probably low...

Crosscounts indicate the number of times the O2 sensor has transitioned lean->rich or rich->lean. If this number is increasing, it's generally a good thing. This means the ECM is entering closed loop and adjusting fuel according to what the O2 sensor is telling it.

You're going to have to give us a little more background info. Is this a stock engine? Which engine? Which ECM? Any modifications? When/why did you install a heated O2? Any other changes to the engine recently? Has the engine/ECM always run perfectly until now?

Hey, no pressure, right???? Are you writing this from underneath the car? Fallen and can't get up.....?

 

Well thanks for the funny remarks. I needed the good laugh.

No I am not under the car. I guess I should have included some history. I have a modified engine. It is a 355 with a ZZ9 cam, World Sportsman II heads, #24 SVO injectors, prominator running the stock ARAP program with the inj constant bumped, SLP 1-3/4" headers (that is why the heated O2). It ran alright until the injector change. The car runs alright however once in closed loop it will backfire. After scanning I noticed the BLM and INT values going up and yes the O2 voltage running low.

I searched online and read that while scanning if a vacuum leak was created the O2 numbers should go up indicating that the O2 sensor is Ok. It that the best way to check or could it be checked with a volt meter?

I am hoping just to get the car running close to stock and then do some tuning. Right now I am leary to drive the car with the backfire. I don't want to reck anything if I can help it.

 

It may be that you've bumped the injector constant too far. This would cause the engine to run lean. I would set the injector constant for a smaller injector and adjust it to give close to 128 across theboard. Then tune the MAF tables from there.

Yes, a vacuum leak after the MAF will cause the engine to run lean. A lean mix will have the O2 sensor voltage < 450 mV. Can use the scan tool to read this. If in closed loop the INT will increase (and if in learn the BLM).

RBob.

 

I have ran the inj constant at 24 and then lowered it to 22. It did run better. Should I continue to lower this until I get that 128 across the board. How low is too low to be setting the inj constant??

Here is the real puzzling thing. At idle with no throttle the BLM and INT values will trickle higher until 140 or better. When I hit the gas the numbers immediately go back to 128 and creep up again. I get this backfiring when I rev up after sitting at idle with the high 140 values.

I am kind of confused.