I am a newbie in need of some help and advice.

I just transplanted a '96 LT1 into my Porsche 944 Turbo. It seems to run well, but when I monitor the parameters with PCMComm or FreeScan, I see a problem. The driver's side BLM is around 132, but the right side BLM is 108. This is at idle and in cell 16. When I am under power or cruising, the PCM stays in cell 18 all of the time. The BLMs are more like 132/111 at that point. It worries me that so much of a correction needs to be made, and that not enough correction can be made at idle.

I currently have Bosch O2 sensors that seem to be on their way out, even though they only have about 1000 miles on them. I heard that they could be problematic, so I picked up a set of AC Delco O2s. I just don't want to install them until I figure out what the problem is. I don't want to fry the new ones over a problem that I could have fixed first.

I have brand new 30# Ford SVO injectors, new plugs and wires, all emissions equipment removed (shhh!), EGR block off plates, shorty headers, big exhaust with Borla XR-1 race muffler, and a PCM for Less tune. The engine has stock heads and cam.

Can you give me any ideas as to why my BLM's are split both at idle and under power? Why is the passenger bank of cylinders running so much richer than the driver's side? If I do the fix for the idle split (draw in more air through the IAC), will that help me under power as well? Any help that you could give me would be very appreciated.

 

i would first get a hold of some Delco O2 sensors and see if they help out your split. with that scanner.. check to see if the O2s are fluctuating properly. they should jump from 0-900 mV several times/sec and looks like a jumbled mess of numbers but that is how they work.. fast. a bad O2 will keep you in open loop anc cause you to run in cell 18 all the time but so can other things.

after you have new O2 sensors it will be a lot easier to determine whether you have a lazy sensor or just an exhaust leak.

 

Some good advice from turbo-Z.... you need to find out why it isn't going into closed loop - e.g. running constantly in Cell 18 indicates open loop.

Then, I don't think you have a problem with "split" BLM's.... mainly just a problem that only shows up on the passenger side. The 132 on the drivers side is well within normal tolerance... its only a 3% correction. Not bad for a mail order tune .

First, you need to make sure the O2 sensors are both healthy. One way to check would be to swap the left and right sensors, and see if the problem follows the sensor.... that would confirm it is a sensor problem. If you swap sensors and the problem stays on the passenger side, its not a sensor problem. Could be a wiring problem, bad ground, faulty heater circuit, or a sensor wire running too close to a plug wire.

After you get the sensors and the wiring sorted out, it should start going into closed loop. If it doesn't, check the coolant temp to make sure it is getting above 140degF. Then look at the causes of the 108 BLM, which could include leaky injector(s) on that side. It typically is not an indication of an exhaust leak... that would create a "false lean" and drive the BLM above 128.

 

I'll try the new O2s and see what happens.

There is something else that I forgot to mention though. At one point, I had switched the 2 Bosch O2s from one side to the other a few times. In every case, the passenger side read rich, so it wasn't just a bad sensor on one side. Maybe that will tell you something?

Edit - Injuneer - you wrote in while I was typing! I think you're right about the problem just being on the passenger side and not split BLMs. Since the injectors are brand new, I wouldn't guess that was the problem. I'll check the wiring and grounds and see what happens.

 

That tells us it isn't an O2 sensor problem, but it could be a wiring problem. You've just eliminated the first step in the analysis I posted above.