'96 suddenly running really rough

[cam.man67]

My truck has been running great til today. In the past 2 months I replaced the timing chain, rotor, cap, TPS, so all that's new. Now, today, I'm experiencing a miss at idle (random), lots of sputtering and backfiring at low throttle, and a loss of piwer when accelerating. Any suggestions as to where to start looking? Somebody suggested to me the MAF/MAP sensor (I forget which this has), but I don't know for sure.

[sntrym95]

Kinda sounds like fuel pump. Check your plug wires first, make sure there's no corrosion. Then check your fuel pressure.

[1952ssr]

My '96 did the same last Friday went from running fine to crap in the stopping at a stop sign. Yours throwing a code? I've changed wires, plugs, gutted cat, tried new coil, crankshaft sensor and will replace injector spider tomorrow. Cap and rotor are less than a year old and fuel pump still sounds strong and was changed about 3 years ago. Mine is giving a P0300 code.

[cam.man67]

Go figure, when I drive it down to the shop to get the codes read, it runs like a top.

So, it's running fine now, but had past codes (all from the other day) for:
-faulty right rear o2 sensor heater
-right side converter efficiency (an on and off thing for a year or so)
-faulty crankshaft pos. Sensor
-CPS and cam correlation?
-random misfire (duh)


So I'm going to get a crank sensor, fuel filter (because it's probably time), right side o2sensors, and see what happens. May wind up gutting the cat while I'm at it.

[cam.man67]

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.

[Damien]

The cam position sensor is in the distributor. I'm not sure if it would cause the code or not, but you might want to pull the distributor and check the gear for wear. I wonder if wear on the dist. gear is throwing off the cam/crank timing. Make sure you mark the position of the dist and rotor when you pull it. The vortec engines are a pain to get the timing reset of your off.

[speedygonzales]

ICM

Don't forget thermal compound NOT dielectric grease.

[cam.man67]

Well dang if I didn't find the problem! The distributor hold-down bolt had backed itself out just slightly! It was allowing the dizzy to move about 15 degrees either direction, and I'm thinking that as I drove, the motor vibrated enough to turn it ever so slightly. So now I've got it back in place and tightened down...truck appears to be fine now. I will have to rent/borrow a code reader to get the dizzy exactly to where I need it, but I've got it within a couple degrees so that it's running fine now.

[Damien]

Glad to hear you found the problem. Stuff like this is the worst to track down.

[1952ssr]

Mine was the cap and rotor all along. Runs pretty good now just don't think it likes the cat being gutted. Trying to decide what to do about that.