Still running lean.

[intimdatr]

NO matter what I do this car is lean. The thing is back to stock in almost every form. Stock MAF on a B9B. I have swapped with known working parts: DIS, Cam Sensor, TPS, IAT, ECT, computers (x2j), and O2s. I have checked the MAF, Coil, and O2s all have 12 volts. I can watch the o2s switch.

Now that I put the stock MAF back on the car it wont even idle. But before if I had the MAF unplugged it would idle at 16:1 but anything above 1/8 throttle it would go super rich 11-12:1. But if i leave the MAF plugged in the car will idle 16-20:1 and while driving anything short of the WOT im seeing 15-16:1

I have checked for vacuum leakes have found NONE. I can remove every hose and cap the *******, and then hose every joint on the intake down with starter fluid, all of which do nothing.

I have perfect fuel pressure, at 38/42.

Something is forcing the car to run lean and I have no idea.

At idle the car shakes and sounds like it is almost missing now.

If I unplug the MAF and take propane and point into the intake it will idle perfectly at 14.x:1, but oddly if the MAF is plugged in the propane will pull the AFR to 14.x:1 and then creep its way back up he 15-16 range again.

Im literally at my wits end.

Could a dying coil do this? Or a crank Sensor? Only things I have yet to touch on this bloody car.

 

[sperold]

Determine if you Intake Air Temperature sensor is dying.
Because there is not much room with the ABS controller and everything else in the way, you may want to take the air box out.
Take the IAT sensor out of the box and get a portable hair dryer and pass it over the sensor and try to get the temperature way up. See if it changes your Air Fuel numbers. If it doesn't, try a paint stripping tool (looks like a hair dryer) and without damaging or burning anything, see if the ultra high temperatures change anything.
If that is too scary, take a piping hot mug of hot water and put the sensor in the steam above the cup.
Likewise, put some snow in the Styrofoam cup and put the sensor in that situation.
In other words, see if you can change the Air Fuel numbers by any of these things, and see if you can get the sensor to admit that it is out of range by turning on your CEL.
I think it is near dead and giving your computer bad information.

 

[rubydist]

Joey and I spent the past couple of weeks chasing an almost identical situation on his 3.2 mtx. He had swapped nearly all of the stuff you listed and it was still running like crap and throwing lean codes. Finally, out of frustration he swapped on a 3rd DIS module and the problem vanished. The "known good" DIS that he had previously swapped on had apparently gone bad sitting on his shelf... I did not expect the DIS to fix lean codes, but it did.

 

[SHOdded]

Good to know! The DIS is normally one of the sturdiest components on the SHO, and the IAC the troublemaker

 

[intimdatr]

Determine if you Intake Air Temperature sensor is dying.

I'll double check the sensor, but from the reading on the Tweccer it would appear that the sensor is outputting correct information.

I'll have to pull another DIS of my 89 XR7 to check the DIS as it is the only other one I have access to.

 

[intimdatr]

Went ahead and bought new Denso O2s. See what this does next weekend.