'96 randomly runs like crap, then fine

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Aholter90

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after a month on my new timing chain, cap, rotor, plugs and wires, my truck runs great! Right up until it doesn't.

Symptoms:
-miss at idle
-way down on power
-missing, backfiring, and overall crap running at part throttle

When this happens, I get 5 codes pop up according to the shop:
-faulty 02 sensor (right rear)
-converter efficiency right side
-faulty crank pos. Sensor
-CPS and cam correlation
-random miss

The converter efficiency I get, that one is one regularly because the cat is broken up inside. Haven't gutted it yet but I will.

Now, it runs fine, though. Only code is for the cat and I've been driving around all day.

Possible solutions?

My FIL had an Olds that behaved in a similar way because of bad grounds underneath the driver side carpet. That being the case, where would I look for ground blocks on this truck?

Alternately, what is the possible of these sensors failing intermittently?

Finally, would a bad fuel filter or pump cause this?
 

east302

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The camshaft position sensor offset (CMP retard) is set by turning the distributor and using a scanner. It should be set at 0 degrees (+/- 2) at 1000-1200 rpm. You can use either the DashCommand or Car Gauge Pro app with a Bluetooth OBD connector to read this value. That cam correlation code may be indicating that it isn't set correctly.

The crankshaft position sensor should have the relearn procedure done if the sensor is removed or replaced, that may be the code that you're getting on it, but if you can post the code numbers that would help track down the issue.

The random misfire codes are always fun. Could be an oxygen sensor flaking out, an exhaust leak, bad injectors, timing issue, ignition issue, plugs, wires, etc.

Keeping up with the fuel filter changes never hurts, but a failing fuel pump would usually manifest in poor starts. A fuel pressure test would probably be in order, that way you can verify if you have a fuel delivery issue (bad pump, leaking injector or pressure regulator).


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Aholter90

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So it's been running fine til this morning, then back to crap. This time I shut it off shortly after it started. Upon restart it ran fine, though I immediately drove it to the shop.

Only code this time is p1345, cam/crank correlation. Could this be caused by a bad crank pos. Sensor? I'm thinking that the other codes might have been caused by the truck running rough for the 45 miles or so it took me to get home.
 

Biggershaft96

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Id check your ground straps and the wires running to your crank sensor. If it's intermittent and unpredictable is probably a wiring issue.
 

C30454

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I have seen P1345 when the distributor needs to be adjusted to synch the cam/crank correlation. Start there first.


Tom
 

wheelman

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welcome to computers and fuel injection..i went through a lot with my 1996 350 R v8 vortec.had to go back to dealer cap and rotor..after market made it hard start..changed fuel pump out it was weak.a couple of sensors on the engine..i read if your crank trigger is dirty or full of mud.the engine will run bad.some vehicles if you get trouble codes.it will try and shut you down..shut your computer down..muffler could be stopped up..run the cats and get rid of the tin can mufflers..you can not beat a vehicle with no computer and fuel injection..1974 was the last year of great vehicles..the best vehicles were the ones with the ignition key in the dash..lets go back to the sixties and fifties..
 
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