Loss of power and running rich

[Camillo08]

I posted a while back about having serious problems with my 92 Z34 Lumina (auto). I replaced quite a few parts including the ignition module and it started running nearly right. Here are my problems; its running rich to the point where you can smell it at startup and shutdown, gas mileage is nothing like it used to be. Also, whenever in overdrive the car suffers a pretty severe spark knock, there is nowhere's near the power it use to have and at 4500rpm I have a flat spot. On occasion the car will spit and sputter but it only does it when the check engine light comes on (which is only for seconds at a time). I hooked a scan tool up to it and found out after warming up for 15min or so it stops running rich but still doesnt enter closed loop mode. And on occasion the idle will oscillate between 700 and 850rpm.
The engine has less then 46000 miles on it
Brand new as of september of last summer:
-Plugs and wires
-Full timing kit
-Water Pump
-All new gaskets

Brand New as of the past 3 months:
-PCV valve
-Ignition module
-Coolant temperature sensor
-Replaced 1 out of 3 ignition coils
-Fuel filter
-Intake manifold gasket

Also the entire fuel rail and all injectors were just taken apart and cleaned thoroughly. All parts that were put on the engine have less than 6000 miles on them. I was told that the hydraulic tensioner might have failed causing the cam to jump time and is not running "retarded." That was from what use to be a GM tech. I bought a new 02 sensor for the car and will be installing it soon. Does anyone have any ideas for me?

[Superdave]

gotta be the o2 sensor...

[SappySE107]

O2, then if that isn't it, do a compression test. That should tell you if its a cam timing issue. You could also inspect the cam flats on the front bank pretty easy in relation to the timing notch on the crank damper vs the TDC locator on the timing chain cover.

[bszopi]

gotta be the o2 sensor...

x3

[Camillo08]

Thanks guys, I really appreciate it. The O2 sensor should be going in today if nothing goes wrong like our thunderstorm yesterday. I just hope its not going to be seized in there. Then if that doesnt do the trick, the timing was my next check. I'll let you know, thanks again.

-Camillo

[stoneymonk]

Thanks guys, I really appreciate it. The O2 sensor should be going in today if nothing goes wrong like our thunderstorm yesterday. I just hope its not going to be seized in there. Then if that doesnt do the trick, the timing was my next check. I'll let you know, thanks again.

-Camillo

did the o2 sensor fixed your problems?

[Camillo08]

The 02 sensor did fix my gas problems for the most part. I still have a power loss and shudder in 4th gear. Im going to try to replace the coolant temperature sensor with a better style one. If that doesnt help it Im going after the cam timing, any chance it might be the crank sensor? I know it uses a dual hall-effect.