Hey all, I have a 99 chevy blazer 4.3L 4x4. I hadn't been driving the blazer until the past few months. I had let a friend borrow it and when he returned it said it was acting up a bit. So I checked under the hood and found some residue/moisture around the intake manifold. So my plan was to replace the gaskets. Now the last time i had taken it to the mechanic before all this his OBD reader said bank_01 sensor_01 was reading faulty. Well we had just replaced that one. So before I tore into the Manifold gasket I had a friend take a reading with his OBD tester and I got the P0134 code ( i think thats what it was) for Cam/crankshaft pos sensor correlation problem. So When I did the manifold ( in which I completely cleaned the manifold with a parts washer as well as the central injection system, by hand) I also replaced the Cam sensor, dist. rotor and cap, installed new wires and plugs. I also replaced all the vacuum lines with new hose. While I was in there since I had to dismantle everything I found that the metal line from my exhaust manifold that pipes down to my smog pump had been eaten through by the Power steering pulley, from previous owner not having P/S pulley not mounted fully. So I also replaced that. The smog pump is not working, cause the vacuum to it and the vacuum switch before it is not connected. I dont know if this will cause the issues i will describe but I live in a state where its not required. So I get everything back together. Timing has got to be on the nose cause i'll be damned if you could get it any closer than what it is. It idles fine and starts fast with no issues. However if I maintain a city speed of around 30mph it has like a hesitation and a little of like a bucking i guess. If I go hard on the gas though it gets better. After all the work I took it back over to my friends with the OBD and its once again reading the O2 sesnor fault, but now it wasnt reading the P0134 code so I'm kinda back to square 1 as it wasnt reading that code before when i first started noticing the issue. Any ideas?

 

When you replace the cam/crank sensor you have to have a crankcase relearn done. Only high end scan tools are able to do it, such as the tech 2. Have you inspected the cap and rotor for corrosion or signs of arching? What brand of o2 sensor did you use? If it was a Bosch, then it may be bad already...