I have had this car for about 6 months and just recently it has this problem. The car will run relatively well in closed loop, but as soon as it switches to open loop the fun begins. The car will surge, misfire, and sometimes stall and the tach will occasionally bounce erratically. If it stalls I have to wait until it cools down again to even get it started, and in some cases if I baby it I can make it home. The odd thing is that it doesn't happen every time, but it will happen most of the time. The times it doesn't stall I just have to keep it below 2500 rpms and limp home. Instead of blowing $ at a mechanic I figured I would pull the DTC codes and ask for help. I used Data Master EE, because it was free (for at least the first 20 runs) and this is what I got. 13 (Bank 1 (left) Heated Oxygen Sensor (HO2S) Circuit (open circuit)) , 16 (Distributor ignition system (low resolution pulse) , 41 Ignition Control (IC) circuit (open circuit), 63 Bank 2 (right) Heated Oxygen Sensor (HO2S) Circuit (open circuit). I know that DTC 16 is possibly the opti spark, and the opti was replaced not but 3K miles ago (1 year ago), and I have no idea what 41 is, but I am thinking opti-spark as well. Now forgive me for my ignorance but could all my problems be with my PCM or would there be more error codes? They only reason I ask is that when I play back the file, the moment the system goes into open loop all the DTC's just pop up.

I am not saying that the car was running perfect in closed loop, but it was running much better. Another question I have is about 13 & 63. In looking at the recorded play back file the O2 mV was ranging from 100-900 in closed loop. As soon as it went to open loop the O2 mV for the Left will stay at 448 -450 mV and the Right will jump from 457 -475 mV.
I am lost cause the O2 mV readings seemed fine before the system went into open loop.

Any help with these codes would be greatly appreciated. Thanks in advance for your help.

 

I would replace the O2's and see how it runs. I didn't think the computer used them until the car warmed up. Maybe the icm is bad. I figure you will get lots of help besides my obvious observations.

 

Just to clarify.... the engine starts in open loop. When the O2 sensors warm up, along with the coolant, the PCM will switch to closed loop. It should stay there until you shut the engine off.

It appears you are saying the PCM enters closed loop, and the O2 sensors are swinging back and forth over a range of 0xx-9xx mVolts, and then all of a sudden it drops out of closed loop, into open loop, and runs poorly. The reason its dropping out of closed loop is because you appear to have an intermittent connection on the O2 sensors. When the O2 sensor circuit opens up, the PCM show ~450 mVolts on the sensors.

To repeat, its the O2 readings going to a steady ~450 mVolt that is causing it to go into open loop.... not the other way around. Going into open loop is not "causing" the O2 sensor readings.

You may have an intermittent ground, or something shorting out as the engine warms up. DTC 16 is not unusual to find as a "stored" code. It is for (and ONLY for) loss of low resolution pulse from the Optispark. It has to be a "stored" code if you engine is running (no matter how poorly), since if it was an "active" code, the PCM would shut down the fuel system and the engine would not run. Again, an intermittent ground on the engine or to the PCM could cause that code to set.

Then there is DTC 41, which is another intermittent wiring problem. Bad grounds and weak system voltage will also cause the tach to bounce. Could also be a problem with the IC Moduel overheating. Shoebox has a guide on his site on how to move the ICM away from the head to reduce the heat soak.

 

Thanks Injuneer,

I think you may be right about the wiring problem. I took out the PCM and found that there are a bunch of wires spiced together. As I traced the wires I found that that they appear to be spliced to an ACCEL ECM 6.0 behind the glove box. The wiring job looks like a hack job so I am thinking of replacing it with a new wiring harness that came with the car. The question I have now is in your opinon should I keep the ACCEL ECM or are there better tools out there to tune from the OBD 1 connector. The only reason I ask is that I don't know if it worth my time if there is no real gain from from it. In just looking at the sample programs, it is all off of DOS. Any input would be greatly appreciated.

One other question is the current set up does not have the MAF sensor hooked up. In looking at the wiring digrams for the vortech supercharger, I notice that they have one. Would this make a big difference in performance?

Thanks for your help

 

Is the engine running off the Accel DFI? Sounds like someone piggybacked it off the stock harness. You're saying the MAF sensor isn't hooked up to anything, but you didn't mention having a code for the MAF sensor.

Something doesn't add up. Without knowing why the DFI is there, and what its doing to the engine, its virtually impossible to analyze the problems.