Need auto mechanic help

[Strictly Street]

My car is running funny so I took it to Advance auto and had them read the computer codes.

It says I have a bad crankshaft position sensor, $30.00. But there are two possible styles so the guy says I should get under the car and look to see which one it is, ok, no problem. He says it is right by the harmonic balancer.

Now here is the problem, I can't see it.

Tried to look it up on the net. What a confusing mess of conflicting information. Useless.

Does anybody know where the sensor is?

1996 Chevy Lumina 3.1 motor.

[hue jass]

Hey Street; You're probably looking around the front of the engine. It's in back.

[ReconRat]

Front or back, it varies... Up front would be easy to see, so perhaps this is one that is in back. Up front is a bracket with sensor pointing right at the harmonic balancer. I've never even looked at one on a front wheel drive car. Just ancient rear wheel drive...

[jporter12]

Need more specific details beyond running funny!

This one could be interesting. There are 2 crank sensors on that one!!! The 7x and the 24x. The 7x is the one that the engine uses to catually run, it goes right into the ignition control module. The other goes straight into the computer, and it uses it primarily for misfire detection. Not sure which one it said, but if it's the 24x, I doubt it would make it run bad, and the 7x would usually cause it to not start, or cause it to die when hot. The 7x sensor is in the back of the engine, as in how you are sitting in the car. It's between the engine and the transmission, where it wraps around the back of the engine. It's a total pain in the rump to change, especially when they decide not to come out easily, which is most of them! The 24x is behind the harmonic balancer (crank pulley) and requires the balancer to be removed to change it. I've never changed one in the hundreds of 3.1's that I've worked on, although that's not to say that they don't fail! They DO stock it at the parts store we deal with, so maybe we've just been lucky!

Describe the symptoms better, and I can give ya some ideas, or drive the beast out here to Johnstown and I can take a look! I know the 3.1 pretty well, as GM used it in a BUNCH of vehicles, and even has current production engines that are basically the same engine (with new high tech stuf thrown in to throw us all off the trail!)

[chevysoldier]

Need more specific details beyond running funny!

This one could be interesting. There are 2 crank sensors on that one!!! The 7x and the 24x. The 7x is the one that the engine uses to catually run, it goes right into the ignition control module. The other goes straight into the computer, and it uses it primarily for misfire detection. Not sure which one it said, but if it's the 24x, I doubt it would make it run bad, and the 7x would usually cause it to not start, or cause it to die when hot. The 7x sensor is in the back of the engine, as in how you are sitting in the car. It's between the engine and the transmission, where it wraps around the back of the engine. It's a total pain in the rump to change, especially when they decide not to come out easily, which is most of them! The 24x is behind the harmonic balancer (crank pulley) and requires the balancer to be removed to change it. I've never changed one in the hundreds of 3.1's that I've worked on, although that's not to say that they don't fail! They DO stock it at the parts store we deal with, so maybe we've just been lucky!

Describe the symptoms better, and I can give ya some ideas, or drive the beast out here to Johnstown and I can take a look! I know the 3.1 pretty well, as GM used it in a BUNCH of vehicles, and even has current production engines that are basically the same engine (with new high tech stuf thrown in to throw us all off the trail!)

You have added something useful for once. haha

[jporter12]

You have added something useful for once. haha

someone deserves neg rep for that.....

[Pedro]

someone deserves neg rep for that.....

I'm on it!!!!!

[Strictly Street]

Need more specific details beyond running funny!

This one could be interesting. There are 2 crank sensors on that one!!! The 7x and the 24x. The 7x is the one that the engine uses to catually run, it goes right into the ignition control module. The other goes straight into the computer, and it uses it primarily for misfire detection. Not sure which one it said, but if it's the 24x, I doubt it would make it run bad, and the 7x would usually cause it to not start, or cause it to die when hot. The 7x sensor is in the back of the engine, as in how you are sitting in the car. It's between the engine and the transmission, where it wraps around the back of the engine. It's a total pain in the rump to change, especially when they decide not to come out easily, which is most of them! The 24x is behind the harmonic balancer (crank pulley) and requires the balancer to be removed to change it. I've never changed one in the hundreds of 3.1's that I've worked on, although that's not to say that they don't fail! They DO stock it at the parts store we deal with, so maybe we've just been lucky!

Describe the symptoms better, and I can give ya some ideas, or drive the beast out here to Johnstown and I can take a look! I know the 3.1 pretty well, as GM used it in a BUNCH of vehicles, and even has current production engines that are basically the same engine (with new high tech stuf thrown in to throw us all off the trail!)

Wow! There is a lot more to it than I thought. Two of them, figures.

Ok, car starts but when driving it will seem to stall for a second then keeps on running. On the highway it feels like it is shifting back and forth between drive and overdrive. Which lead me to believe that the ECM was going bad. (Happened on another GM that I owned, had to replace that one every year. Also had to replace the cam$haft $ensor magnet on the cam$haft it$elf on that one)

But then I noticed it doing it on surface streets and realized that the motor was acting like it was loosing ignition or fuel for a moment then recovering.

So I took it in and had the codes run on it. Code was P0336. Which the nice man at the store told me was a crankshaft position sensor. He also advised me that it was the only error code being shown.

Temp of motor, time that it has been running, outside temp does not seem to be a factor.

So the next question would seem to be, Does the code tell us which sensor of the two is bad?

[Strictly Street]

Hey Street; You're probably looking around the front of the engine. It's in back.

Part of the problem is the definition of 'front'.

The engine is mounted sideways being a front wheel drive.

So, front of motor becomes an exercise in semantics.

When sitting in the car the harmonic balancer is on the passengers side.

So the 'front ' of the motor is really on the right side of the car.

Er, maybe.

[Dweezel]

The front of the engine has the belt on it, the rear has the transmission attached to it.

[Angrish]

The front of the engine has the belt on it, the rear has the transmission attached to it.

What if it sideways!

[curby]

my honda had belts on the driver side and the tranny on the passanger side? so the driver side is the front?

[chevysoldier]

my honda had belts on the driver side and the tranny on the passanger side? so the driver side is the front?

of the engine, yes it is.

[jporter12]

P0336 is the 24x sensor. I don't think there is any way for the PCM (Not called ECM now, since it controls the trans, too, they call it powertrain control module) to determine if the main one (7x) is bad. It sounds like either a fuel delivery problem (pump, filter, injectors, etc...) or possibly a mass airflow sensor problem. I can't say for sure that it's NOT the 24x crank sensor, but I'm doubting it at this time. Keep in mind that the code does NOT mean the sensor is bad! It just means that something is not right. It could be wiring to the sensor, or the PCM itself (not as likely, the newer PCM's are MUCH improved, although I'd have to make sure that it is a newer generation PCM to be sure) or something else that make the computer think that the signal isn't right, when it very well could be.

Has the Check Engine light been on since the problem started, or is it something new to the situation?

I'd have to see live data from it on the scan tool to tell any further, I believe. And yes, that data connector does give more information than just codes!

[jporter12]

The rear I'm referencing in my earlier post, referring to the 7x crank sensor is near the firewall. It IS possible that one is bad, and not correlating to the 24x sensor properly, causing a code, since there is no code for the 7x! The 7x sensor is also succeptable to interference, as it's an A/C signal that goes to the ignition module. I have seen the harness for that thing cause headaches. It's a twisted pair type setup, and I think it has a ground running through it also.

[hue jass]

The front of the engine has the belt on it, the rear has the transmission attached to it.

:lol:rep definitely

[Strictly Street]

P0336 is the 24x sensor. I don't think there is any way for the PCM (Not called ECM now, since it controls the trans, too, they call it powertrain control module) to determine if the main one (7x) is bad. It sounds like either a fuel delivery problem (pump, filter, injectors, etc...) or possibly a mass airflow sensor problem. I can't say for sure that it's NOT the 24x crank sensor, but I'm doubting it at this time. Keep in mind that the code does NOT mean the sensor is bad! It just means that something is not right. It could be wiring to the sensor, or the PCM itself (not as likely, the newer PCM's are MUCH improved, although I'd have to make sure that it is a newer generation PCM to be sure) or something else that make the computer think that the signal isn't right, when it very well could be.

Has the Check Engine light been on since the problem started, or is it something new to the situation?

I'd have to see live data from it on the scan tool to tell any further, I believe. And yes, that data connector does give more information than just codes!

The check engine light has been on forever. Bought the car that way. Seemed to run ok so I didn't give it much thought.

The guy I bought it from said he had changed out the motor. I just figured that he left a wire off or something. Idiot lights don't tell you much except that the bulb works.

The only thing I ever noticed was that if I ran to the local store (1/2 mile if that) shut it off and then started it, the idle would go up and down for a minute or so and the car would stall if you put it in gear. If I waited till the idle smoothed out everything was fine.

Being a used POS beater I never worried about it much this summer as I was riding the whole time. It drove ok on those few rainy days when I had to go somewhere. Now though as winter is just around the corner it is starting to be a little more important.

Johnstown looks to be about a 1/2 hour from me, the car would probably make it so that is an option too.

[ReconRat]

...Ok, car starts but when driving it will seem to stall for a second then keeps on running. On the highway it feels like it is shifting back and forth between drive and overdrive...

Wut? I respect the codes found, but just to be old fashioned... make sure there isn't a vacuum leak somewhere causing this. Especially if the automatic transmission is vacuum modulated.

[jporter12]

Wut? I respect the codes found, but just to be old fashioned... make sure there isn't a vacuum leak somewhere causing this. Especially if the automatic transmission is vacuum modulated.

The transmission IS vacuum modulated on that thing, most likely. There was a changeover somewhere around there, but it is VERY possible that it is vac. I'll look it up in a min.

The big vac leak to look for is BEFORE the throttle plate. It's very possible that the crankcase vent tube is unhooked, or some other air leak between the MAF sensor and the throttle plate. I had one whip my butt one time, and I was pissed when I found out what it was. Someone else found it, making it even worse, as I don't give up easily!

[jporter12]

Looks like it IS vacuum modulated......

[Strictly Street]

Looks like it IS vacuum modulated......

Which means, what?

Am I looking for a vacuum leak?

Or is this two separate problems?

[jporter12]

Which means, what?

Am I looking for a vacuum leak?

Or is this two separate problems?

Just look for a vacuum leak, but as I said, especially between the Mass Airflow Sensor (MAF) and the throttle body. If any air is getting into there, it is not being metered through the MAF, and that throws the computer off. The transmission being vacuum modulated just means that there's another line to check, and it can also make the transmission act up if the vacuum isn't right. On that transmission, vacuum is the main thing used to regulate the pressures.

[Strictly Street]

Just look for a vacuum leak, but as I said, especially between the Mass Airflow Sensor (MAF) and the throttle body. If any air is getting into there, it is not being metered through the MAF, and that throws the computer off. The transmission being vacuum modulated just means that there's another line to check, and it can also make the transmission act up if the vacuum isn't right. On that transmission, vacuum is the main thing used to regulate the pressures.

So your thinking it is a vacuum problem. Ok that sounds cheap!

Ok, I'm looking for a leak between the air filter and the engine somewhere?

Let you know what I find out...

[jporter12]

So your thinking it is a vacuum problem. Ok that sounds cheap!

Ok, I'm looking for a leak between the air filter and the engine somewhere?

Let you know what I find out...

That's a possibility, not a definite. A good place to start checking! Anything further and I really don't want to start guessing.

[Strictly Street]

That's a possibility, not a definite. A good place to start checking! Anything further and I really don't want to start guessing.

OK, I looked all over the MAS to throttle body connection.

Couldn't find a vacuum leak. If there is one I don't know how to find it.

Everything looks tight and there aren't any wear spots on anything I could see.

I still can't see that sensor but I can see where it is that I can't see so that is prolly where it is hiding. No way I can get to it with out pulling the balancer. Don't have the tools for that job.

Starting to look like this one is beyond my abilities to fix. Sux!