My 2000 Chevy Blazer 4.3 vortec V6 is messing with my brain. It runs like crap when started cold then evens out and is a rocket ship when warm. I've changed all sorts of sensors, fuel pump, rotor, cables, plugs, and lastly the spider injector assembly. Still does the same! I was thinking that maybe since it is related to temperature change that the thermostat could be stuck open and thus not allowing the motor to reach operational temps as it should therefore causing rough idle and stalls. I've searched the internet for answers and have found tons of people with the exact same problem but the solutions are always basic troubleshooting none sense. I'm through with the basis check wires crap. There must be someone out there with the plain and simple answer to a problem that has plagued so many Vortec 4.3 V6s. I read on the internet that GM had bad intake manifold seals and when cold fluid leaks into the cylinders and after warm the metals expand and seal it up again. Sounds logical but alot of work to just hope thats it. Please share your knowledge with me. I'm stumped. Thank you for your time.

 

Help us out, what sensors have you changed?

 

So i took the truck in to a local auto shop. Diagnostics indicate code (P1345A /crankshaft/camshaft position sensors correlation) and (P1351A Ignition control system to high voltage) Had the ignition coil, electronic ignition module and crankshaft position sensor replaced. There was humidity getting into the ignition module and causing misfires on cylinders until the engine heat would remove the humidity. See... everything has a reason. Truck is strong again and runs great. Hope this was helpful.

 

Where is the Ignition Control Module found? How expensive is it? We appreciate you posting what the solution was. That is very helpful to the forum.

 

Its the electronic part to the right of the coil pack. It has two screws holding it in place. Not to expensive.Between 40 and 50 bucks.

 

Thanks for the good info and photo. Over the Memorial Day weekend, I bought the infamous Haynes manual and 'researched' the ignition module in the 'Engine Electrical' section. Not very helpful and actually confusing.

 

Hey guys. I have the exact same problem. I just got my check engine light tested last night and it came up with the crankshaft position sensor. Any chance you can shed some light on how much it cost to replace? I normally like to make my own repairs but I heard this one is not an easy task. Thanks.

 

I believe the crankshaft position sensor is not too difficult to replace. I think it's on the timing cover on the lower part of the block right in front. However, I'm also pretty certain that once it's replaced you have to take the truck to a dealer or a very well-equipped shop with a scan tool capable of doing a re-learn procedure.

If I'm wrong I would appreciate someone posting the correct information.

 

The crankshaft position sensor is attached with one screw and the electrical connector, loacted on the front cover. Access is simple, just remove skid plate if 4wd and it is on the right side. Very easy to replace.

HOWEVER....in order for the engine computer to make use of the new sensor the crankshaft position sensor relearn must be done which requires a high-end scan tool. Not the simple ones at Autozone or etc. Likely a dealership, but call around to find a shop that KNOWS what you are asking for.

You can replace the sensor yourself but until the relearn is done, the engine computer will use the stored information from the old one.

Let us know what happens.

 

I have noticed my blazer runs a little rough when cold, but runs really well and quiet when warmed up. I am going to check my crankshaft position sensor as well, just need to find someone with a good scan tool.