With the driver's side O2 sensor unplugged, passenger side plugged in, engine running, jumper wires installed, I get a reading of 4mV. Fuel trims are all over the place. Bank one reads anywhere from 0.0% in open loop to -25% in closed loop. Bank 2 reads anywhere from 0.0% in open loop to +34.4% in closed loop.

With the passenger side O2 sensor unplugged, driver's side plugged in, engine running, jumper wire installed, I got a reading of 9mV. I forgot to look at fuel trims this time.

 

If the one you put the jumpers on went to 4 mv and 9mv respectively, then it indicates the wiring is intact.

based on those results and this:
It would appear that you may actually be running too rich. It's time to look at the O2 readings and the fuel trims while everything is plugged in.

I would think based on your previous O2 readings that the fuel trims should move leaner. Confirm that if you don't mind.

Tell me if I'm wrong on any thoughts I have. Thinking out loud here so bare with me.
Then we need to figure out why it's running rich. The first assumption is the spark and compression is ok since it runs fine in open loop. Any dead cylinders should show up during that time. We think the O2s are ok since you got the same result even with a new one.

Could a fuel leak internally cause your problem? Let's suppose an injector is leaking but just slightly. In open loop it doesn't monitor the resultant rich exhaust. But in closed loop it does. So it does the only thing it can and cuts back fuel to try to bring the exhaust reading back in line. In doing that, it has to cut back all 4 on the side it sees as rich since it does not know which one of the 4 is causing the problem. Remember their is only one O2 per side. When it cuts back fuel in the other (correctly running cylinders), they go lean and don't run correctly. However, you said the problem occurs on both sides. What's the chance you have a leaking injector on both sides??????? Perhaps a more plausible reason is a leaking FPR. Check the FPR for a leaking diaphragm by applying a vacuum manually to it.

If it holds vacuum then raise up the fuel rail and jump power to the fuel pump prime connector so you can check the injectors for leaks when they should be off.

 

SG, you lost me there...

You want him to check his FPR / AFPR. i think you want him to:

--apply vacuum, and see if it holds
--measure Fuel Pressure and see how steady it holds while idling.
--measure Fuel PSI while rev engine.

--Shut car off, watch Fuel PSI to see if it stays steady, or leaks off.

--measure Fuel PSI, and put a jumper wire to the Fuel Pump, and make it run with car off, and see what pressure does. the FPR should maintain pressure, and keep rail psi steady, correct?



I agree with your TS input, but ask these questions:
--if an injector is leaking ALOT would it not drain the rail when the motor is off, and have a "hard start" condition when he tries to re-crank the car?

--this "hard start" would exist only if the injector leaked while off,

--if the injector only leaks while energized, that should be shown by monitoring the Fuel PSI during the "Key on" fuel prime cycle,
and seeing the Fuel PSI drop to a lower PSI while the motor is running.

I dunno.

Alan, shoot me a PM if you want to ride over to the house tonite, and we can work on it together.

 

Sounds good, John. I'll see you this afternoon then.

 

Update:

Today I replaced the MAP and IAT sensor and it made absolutely no difference. Do you guys think the computer tune could be the issue here? I've replaced every sensor imaginable and it's done no good.

 

So???? It's been a month

 

Sorry, ended up having to go out of town that weekend and had to give the scanner back. Do you think fuel supply would be affected in closed loop mode only? Because that's the only time the car exhibits any problems. When I force it to open loop by unplugging an O2 sensor, it runs fine.

 

Without knowing how the PCM is reacting, you don't know if it's being fooled into thinking it's lean and it's richening things up or if it is actually running rich.

Maybe it is the tune. Why don't have the exhaust gases checked in closed loop and in open loop?

 

How would I go about having the exhaust gases checked? I'm assuming an emissions inspection station, but we don't have emissions laws in SC.

 

Any good shop will use it as a diagnostic tool

 

i had the exact same problem so i went to pull the iac valve and found one of the mounting bolts broke and it was sucking air. I would double check to see if yours is tight and check for other possible air leaks

 

This sounds EXACTLY like my problem except, I have yet to go around replacing parts. I cleaned my IAC but that didnt do anything...and the car runs bad when it reaches closed loop and backfires a little and studders on accel..

Cory

 

Read post number 1

 

have you checked for air leaks on the intake manifold ??

 

You ever get this figured out?