LT-7

Ok, here goes the scenario.

A few days ago the car started running wierd after it warmed up and I guess goes into Closed loop. It misses like crazy and there is no power unless I give it alot of throttle. I searched on here and for the most part it looked like the o2 sensors were the culprit. So, I disconnect the o2 sensors and the car runs better, no missing, but running rich and fuel economy is not any better. I looked at the harnesses and one of the connectors on the right bank is melted on the o2 side of the connection. I figure this has got to be the problem.
I change that sensor out, hook them both back up and take it for a test drive....same problem.

I decide to test the voltages and grounds on both sides. Both the right and left bank engine harness plugs are getting the same readings...D= 12v, C= ground, B= 1v area, and A was .45 I believe. Either way they were both the same readings, so I deducted that the engine harness side is doing its job.

I am going to switch the left side bank sensor out with the other sensor I took off to see if it helps, but Im not too confident it will.

Is there anything else that could cause this? I am running out of ideas and the search option is not getting me any closer. I cant get datamaster to link up (lost the hard drive on the laptop and when I looked for my XP disc it was no where to be found...so it has Windows Me on it and it just wont work correctly). So I dont know of any codes that it could be throwing, I will drop by autozone tomorrow and see if i can get their scanner to link up.

This is a 97 LT1 motor, using a 95 PCM and rear o2s and a bunch of other things are deleted. Car ran great before this problem, on the program that is still in it (cant get tunercat to link up either).

Thanks for any help, maybe injuneer and the other gurus will have a clue, because I dont.

Pyro97

Don't know if this is any help but I figure I'll give some input. I have a 97 with longtubes, OBD1 conversion so a couple sensors are deleted. I had a problem with the drivers side O2 sensor for a little while after I put the motor back together. There was an oil leak on the back of the intake and oil was running down the engine, getting on the wires going to the O2 sensor and kept fouling out the sensors. What your car is doing sounds like what mine did when the sensor was bad (ran fine when unplugged) so just another piece of data.

LT-7

Thanks for your input, anyone else?

Guest47904

It sounds as though you disconnected an O2 and drove around in open loop for a long period of time to have said the fuel mileage was not any better. Is this a correct assumption?

Auto Zone will not be able to scan it as a 95PCM is OBDI. Perhaps you had the same problem they did in you were trying to scan it as OBDII.

What you will have to look at in both open loop and closed loop is what the O2's are reporting. Then in closed loop, what are the fuel trims doing.

I don't think the problem is a leaky fuel injector unless the O2 on the problem bank is also defective.

But just in case I'm wrong about a leaky fuel injector or FPR for that matter, check your oil for fuel.

See if you have a dead cylinder. Just for yuks.

LT-7

Yeah I have the obd1 software, but my laptop is all jacked up so it wont work.

I disconnected the o2 sensors to see if the problem was there when they were out of the equation. The problem went away, so I think it has something to do with when the pcm goes into closed loop mode and reads what the o2's are saying.

I know its not going to get better mileage with them disconnected, it was just a report on how mileage was.

The regulator is good, holds/increases pressure correctly when under load. Fuel pressure does drop off eventually when the car is off, but not out of the norm for my setup.

I think I am going to change the harness pigtail next and see if it works.

Thanks for the replies.... anyone else with any experience like this?

LT-7

Update.

I decided to plug the 02 sensors back in and unplug the MAF sensor. The problem is gone. It doesnt do the missing and lean condition like it did and the idle a/f is where it should be. When cruising the A/F ratios are in the 14's and under more load they descend down towards the 12's.

So, my question is, in open loop, is the MAF in the equation? The problem would only occur when the car would warm up and I assume would change over to closed loop.

LT-7

I checked the voltages, and the pink wire is getting 10 volts when not plugged in and 11 volts when it is plugged in. I think its supposed to be 12, but I dunno if that is close enough. The middle wire is not showing much voltage and the other side is coming in at around 4.5 to 5 volts.

LT-7

Bump