It is always a good idea when replacing a part to as much as possible compare the old...

Is this the "limp" mode?

harness then of course reconnecting it. The hope is the problem is due to surface corrosion that is interfering with the sensor signaling.

Be careful. The harness and the connectors are *old*. You need to be both gentle and forceful. I hate fussing with these connectors. I had a heck of a time changing the O2 sensors cause the sensor connectors were difficult to unlatch and then pull apart.

Sincerely,

MarcW.

Assuming you have a 986, P1579 means the Crankshaft Sensor is not within it's specified range.

replaced 3.2 engine in my '02 Boxster S with a used 3.2 from the same model year and just got it running and everything seemed in order during my first test runs. Initially, I was not pushing the engine to make sure everything was connected right and all seemed in order. This weekend I tried to open it up a little bit and discovered that the engine cuts out at about 4000 RPM. It starts spitting and sputtering and will not rev to 5000. The symptoms reminded me of bad MAF's I suffered in the past. I checked the codes and it showed a P1579 or Crankshaft Position Sensor. I cleared the code and so long as I keep the RPM's under 4000 it stays clear. The engine runs perfectly up to 4K, is highly responsive and smooth. I can hold the accelerator at 4K and it runs fine, push to 4200 and the spitting starts. If I push it hard trying to achieve 5000RPM, it throws the P1579 code.

I replaced the Crankshaft Position Sensor with the one from my blown engine. That engine was running perfectly until it threw a rod through the top of the case. Same result, spitting and sputtering at 4200 RPM. I then took out the MAF sensor and cleaned and reinstalled it. FYI, that MAF is less than a year old and probably has fewer than 5000 miles on it. It is the one that was in the car when the engine blew, and as I previously stated, it was running fine. I tired running the engine with the MAF disconnected. It still would not rev to 5000 with the spitting starting around the same RPM's. I checked the codes after that run and had P0102 (MAF input) and P1579.

A bit more info, I upgraded the IMS bearing to the LN Engineering, and upgraded the flywheel to the Aasco aluminum version with a new SPEC clutch disk and pressure plate. I am at a loss. HELP!

Quote
Byron in Atlanta
replaced 3.2 engine in my '02 Boxster S with a used 3.2 from the same model year and just got it running and everything seemed in order during my first test runs. Initially, I was not pushing the engine to make sure everything was connected right and all seemed in order. This weekend I tried to open it up a little bit and discovered that the engine cuts out at about 4000 RPM. It starts spitting and sputtering and will not rev to 5000. The symptoms reminded me of bad MAF's I suffered in the past. I checked the codes and it showed a P1579 or Crankshaft Position Sensor. I cleared the code and so long as I keep the RPM's under 4000 it stays clear. The engine runs perfectly up to 4K, is highly responsive and smooth. I can hold the accelerator at 4K and it runs fine, push to 4200 and the spitting starts. If I push it hard trying to achieve 5000RPM, it throws the P1579 code.

I replaced the Crankshaft Position Sensor with the one from my blown engine. That engine was running perfectly until it threw a rod through the top of the case. Same result, spitting and sputtering at 4200 RPM. I then took out the MAF sensor and cleaned and reinstalled it. FYI, that MAF is less than a year old and probably has fewer than 5000 miles on it. It is the one that was in the car when the engine blew, and as I previously stated, it was running fine. I tired running the engine with the MAF disconnected. It still would not rev to 5000 with the spitting starting around the same RPM's. I checked the codes after that run and had P0102 (MAF input) and P1579.

A bit more info, I upgraded the IMS bearing to the LN Engineering, and upgraded the flywheel to the Aasco aluminum version with a new SPEC clutch disk and pressure plate. I am at a loss. HELP!

I assume you have secured the sensor properly, torqued it down correctly, and thus there can be no mechanical explanation for the sensor's apparent misbehavior?

Another common failure point could be the harness, that somehow this got damaged during the engine swap? Long shot I guess, but finding out what is the cause of the symptom is a matter of eliminating what it isn't... Longer shot but the behavior may be fuel supply/pressure. Whenever an engine comes out and one goes back in a car there's always the opportunity for some collateral damage to a wiring harness, connector, fuel line, etc.. It was easier back when cause there wasn't much wiring, fuel lines, etc, to fuss with but nowadays the engine compartment has as much wiring, fuel lines, vacuum lines, as it does engine it seems.

Next up for consideration is the flywheel.

The flywheel plays a critical role in the proper functioning of the crankshaft position sensor since it is the metal tabs on the inside face of the flywheel, their spacing (and IIRC one's absence), that the sensor detects as the tabs fly by.

I'm at a loss to explain how mis-spaced tabs, inconsistent gaps between the tabs, could only manifest a problem above 4200 rpms unless one or more tabs got bent/damaged somehow in the handling during installation.

This suggests then that it is not the spacing but perhaps the flywheel's balance? Or even its mounting. Did you check runout of the flywheel? Both radial and axial after bolting it up? Another possibility -- far out -- but is the standard flywheel keyed or 'timed' to the crankshaft end? It occurs to me that the flywheel may not be mounted just any old position, that the missing tab might have to located at just the right position relative to the crank's actual position so the gap doesn't fall into a time in a cylinder's stroke sequence that can confuse the DME with conflicting info.

Is the engine mounted properly in the car? All mounts in good shape, correctly fitted, etc?

I'd hate to suggest you have to drop the transmission and look over the flywheel without more substantive diagnosis (vs. just my WAGs). But if you eliminate the easier to eliminate possiblities without any improvement in the engine's behavior...

If you do drop the tranny, it might be worthwhile fitting a standard flywheel as long as your sure the standard flywheel is of course in good repair and compatible with the new clutch you have selected.

Sincerely,

MarcW.

Quote
MarcW

I assume you have secured the sensor properly, torqued it down correctly, and thus there can be no mechanical explanation for the sensor's apparent misbehavior?

Another common failure point could be the harness, that somehow this got damaged during the engine swap? Long shot I guess, but finding out what is the cause of the symptom is a matter of eliminating what it isn't... Longer shot but the behavior may be fuel supply/pressure. Whenever an engine comes out and one goes back in a car there's always the opportunity for some collateral damage to a wiring harness, connector, fuel line, etc.. It was easier back when cause there wasn't much wiring, fuel lines, etc, to fuss with but nowadays the engine compartment has as much wiring, fuel lines, vacuum lines, as it does engine it seems.

Next up for consideration is the flywheel.

The flywheel plays a critical role in the proper functioning of the crankshaft position sensor since it is the metal tabs on the inside face of the flywheel, their spacing (and IIRC one's absence), that the sensor detects as the tabs fly by.

I'm at a loss to explain how mis-spaced tabs, inconsistent gaps between the tabs, could only manifest a problem above 4200 rpms unless one or more tabs got bent/damaged somehow in the handling during installation.

This suggests then that it is not the spacing but perhaps the flywheel's balance? Or even its mounting. Did you check runout of the flywheel? Both radial and axial after bolting it up? Another possibility -- far out -- but is the standard flywheel keyed or 'timed' to the crankshaft end? It occurs to me that the flywheel may not be mounted just any old position, that the missing tab might have to located at just the right position relative to the crank's actual position so the gap doesn't fall into a time in a cylinder's stroke sequence that can confuse the DME with conflicting info.

Is the engine mounted properly in the car? All mounts in good shape, correctly fitted, etc?

I'd hate to suggest you have to drop the transmission and look over the flywheel without more substantive diagnosis (vs. just my WAGs). But if you eliminate the easier to eliminate possiblities without any improvement in the engine's behavior...

If you do drop the tranny, it might be worthwhile fitting a standard flywheel as long as your sure the standard flywheel is of course in good repair and compatible with the new clutch you have selected.

Sincerely,

MarcW.

Thanks MarcW...that is exactly what I was hoping it was not, the shutter wheel on the flywheel. Was hoping to get by without having to drop the tranny. The crankshaft does have a dowel pin that sticks out to align the flywheel so I think it is timed to the crank correctly. I am suspecting either a wrong flywheel or a bent tooth on the shutter wheel. Going to check the wiring to the CPS before I dive back in with trans removal!

It seems the vendor that I bought the Aasco flywheel from either sent me the wrong unit, or it was damaged in shipping. Either way, here is a pic of the damage it is doing to the Crankshaft Position Sensor. Looks like the shutter wheel teeth are making contact with the sensor. It is gouged pretty good. So out comes the tranny! YEA!

... having fun yet?
I know how you must feel.
Been there, done that.
But, on the bright side, you're getting really good at it
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

part to the new one to see if there are any significant differences.

Now, I admit the average DIY'r is not going to think of let alone have the measuring tools to measure the OD of the -- in this case -- flywheel CPS tabs.

But the next best thing is a trial fit with the flwwheel bolted -- but it doesn't have to be torqued all the way down -- to the crank and then a trial fit of the sensor to check there is sufficent clearance and that the tabs are equidistant from the sensor.

If one has the old flywheel then this can be trial fitted first to see what the 'factory' clearance was so one has something to go by.

Anyhow, at least you found the cause of the problem. Too bad you have to remove the transmission again but it could have been worse.

Sincerely,

MarcW.