my 96Z is still giving me fits. I got the new fuel pump in yesterday and it fired up and idled great. Took it down the road and it didn't miss, but was real low on power.
Got back to the shop and decided to check the MAF, etc. Didn't make any difference, but my codes came back and it barely wanted to run. This is what started the whole mess. Codes 335 and 336... The first is Crank Position Sensor circuit failure, the second is Crank Position Sensor 18x/24x out of range. I have already replaced the CPS when it threw the code the first time. I cleared the computer completely and the code came right back. After a few tries, the code stayed away, but the car is still stumbling on acceleration, VERY hard to start, and surging real bad at idle. Seems to be getting hot too.
I checked the grounds and they are all good and tight. I tried a different PCM and it didn't help (the tune was so rich in that pcm anyway that it didn't run well anyway).
Any ideas?

 

The crank sensor won't cause drivabiltiy problems. You could even unplug it and the engine would perform just the same. Something else is causing your poor running.

 

really? I thought the crank sensor is what told the pcm when to fire the ignition... often I see people getting no spark at all and it's the fault of the CPS

 

No.... as usual, Shoebox gave you the correct info. The OptiSpark optical sensor provides the PCM with cam position data, and that is used to set ignition timing and fire the injectors. The CKP sensor is there ONLY for misfire detection. 93-95 cars don't haave CKP sensors, and they seem to run pretty good without it .

The PCM looks for irregularities in the sensor wheel rotational speed, and compares them to the known pattern of the crank rotation. Crank speed variations outside of the known pattern will be called a misfire. You can get the "misfire" code showing up simply from a radical cam, or even extremely rough pavement.

The codes are:
P0335 - CKP sensor circuit mal;function - CKP sensor to low res pulse pattern.

The CKP pattern is not matching the Opti pattern.

P0336 - CKP circuit range/performance.

The duty cycle on the CKP signal is outside the normal range (58.8 - 77.8%

Is it possible the reluctor gear is loose on the crank? Possible the timing chain is really worn? Possible the cam sprocket is loose?

If this is the same problem I read in another thread, you actually saw a wear pattern on the end of the sensor. If that was your post, it might indicate the reluctor wheel is contacting the sensor, indicating something is loose inside.

 

Cars with direct fire ignitions will not run without a crank sensor. The LT1 is not direct fire and has the venerable opti to take care of that function.

 

my crank sensor didn't have any contact patterns, so it must have been another thread you were reading.
Anything is possible, so I won't rule out reluctor wheel issues or a loos timing chain, but it seems like an odd possibility that those would occur "suddenly." But I am shooting in the dark. Anything you guys can offer, I will check into.

 

Did you check the fuel pressure after the fuel pump install?