Showing posts with label 987.1. Show all posts
Showing posts with label 987.1. Show all posts

Tuesday, June 1, 2021

Porsche Cayman S catalyst and O2 DTCs.

I have a long story about catalyst efficiency DTCs on the 2006 Cayman S.  It starts back when I bought the car in 2014.  You can see that story here.  It had 60k miles on it when I bought it.  The car had a P0421 DTC which means "Warm Up Catalyst Efficiency Below Threshold (Bank 1)".  On this car that is the passengers side.  I installed an O2 bung on the muffler on that side and moved the downstream sensor there which generally eliminated that DTC, but I would occasionally get a DTC for the front sensor of that back stuck rich.  It would set that DTC randomly but not very often.

It did get annoying to have this DTC trip though, and I wanted to upgrade to better headers so I finally did in 2019.  I put the bank 1 downstream sensor back in the proper position when I installed the headers. The DTCs were finally gone for good, or so I thought.  I went to a track weekend in April just a month after installing the headers and I had no issues.  However, I went back to then same track in October and the car tripped the P0421 and P0431 ("Warm Up Catalyst Efficiency Below Threshold (Bank 2)") after idling for extended periods during warm-up.  Normally I just start the car and drive off but at the track the car sits and gets cold between sessions and I needed to get it fully warmed up before entering the track so I would idle it for much longer than normal.  It appeared the Fabspeed headers, in combination with this cold idle warm-up, was enough to fail the warm-up efficiency test. 



I suspect that these headers with the high-flow catalysts and larger, somewhat longer primary tubed are not as good at heating the catalyst, and that catalysts are enough less efficient that the test is below the threshold at times.  One of the known ways people get around this is by adding a spacer to the downstream O2 sensors.  This simulates catalyst oxygen storage to some degree and can help the test pass.  So, I installed some short straight extensions I bought through Amazon for cheap.

After installing these, I immediately got a DTC P2198 "O2 Sensor Signal Stuck Rich Bank 2 Sensor 1".  Since the car now has 87k miles on it, I replaced both the bank 2 O2 sensors but the P2198 remained.  I noticed the bank 2 upstream O2 sensor was loose when I went to replace it.  I checked and cleaned the MAF sensor, checked for vacuum leaks, re-torqued the headers and checked for exhaust leaks, and all was good.  Finally I removed the bank 2 downstream O2 extension and the P2198 went away and my O2 and catalyst monitors tested and passed (monitors were ready and no DTCs).  

Now, with an O2 extension in bank 1 but not in bank 2, I get these OBD test results (mode $06)
when the P0431 is pending.
Test report:
------------------
TID:$01 CID:$05
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 15,458
PASS
----
TID:$01 CID:$06
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 3,639
FAIL

I can't currently find the definitions of these but given that my pending DTC is P0431 I am presuming that CID $05 is bank 1 (which passed) and $06 is bank 2 (which failed and set the DTC pending.  You can see the large difference in test result values here.  The sensor without the extension is 89% of what it needs to be to pass whereas the other bank is 377%.  All other test results in the report passed.

I bought some shorter spacers and installed one in bank 2 only. 
image.png

I cleared DTCs and drove the car again, including cold start.  The P0431 sets pending again.  Here are the OBD test results this time:
Test report:
------------------
TID:$01 CID:$05
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 13,902
PASS
----
TID:$01 CID:$06
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 803
FAIL 

Strange how it is even worse with the spacer in bank 2.   Also interesting how the medium spacer works well in bank 1 but not in bank 2.  

It seems like my bank 2 catalyst is very weak, at least for the warm-up catalyst test.  

It is strange that I installed the headers March 2019.  I did not mature any DTCs for months of daily driving.  I did not check monitor readiness and did not check for pending DTCs however.  I did a PCA track weekend at Putnam that April and had no issues (that I recall anyway).  I went back to Putnam again October 2019 and that is when the DTCs started tripping pretty often.  Sometimes just one bank, other times both.  It would happen when I warmed up the car and would sit on the grid for long periods.  Since then I have had the P0421 and P0431 keep happening.  Now it is pretty consistent on bank 2..  

I drilled my original longer spacer out to 3/8".  I cleared the DTCs and drove the car.  After about 20 minutes of driving it finally tripped the P2198 again.  I cleared the DTCs, waited a few hours and drove the car again.  This time it completed all the monitors with no DTCs.  Here is my OBD Test results from that drive.
Test report:
------------------
TID:$01 CID:$05
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 10,503
PASS
----
TID:$01 CID:$06
- Rich to Lean sensor threshold voltage(constant)
Min: 4,096
Test result value: 6,404
PASS

The test result above looks great.  It just seems very inconsistent to get for bank 2.  Bank 1 is now solid and passes every time.  Bank 2 toggles between P0431, P2198, and an occasional pass.  

I took some pictures of Bank 2 catalyst.  Here is the view from the upstream side.

and here is the downstream side.

It looks good physically.  No cracks, chunks missing, melting, or soot buildup.  

I also checked it will then infrared thermometer.  I was in the garage so not much load on the engine.  After running (mostly idle) for a few minutes, it was about 400F both upstream and downstream.  I ran the engine at about 2000rpm for a minute and rechecked.  Now both were around 480F.  Not much temperature change across the catalyst in the garage.  This was the surface temperature of the pipe, not the actual catalyst temperature.  

I finally sent the header that kept failing back to Fabspeed to get the catalyst replaced.  Fabspeed was great to work with throughout this whole ordeal.  I installed the header back and have not had the DTCs ever since.  I also checked to confirm that the catalyst monitors did complete and pass.  I moved the car to my Las Vegas home where I needed a smog check to get registration and it passed the smog check as well.  


Saturday, August 29, 2020

Cayman S Water Pump

 I did a dumb thing but it turned out OK.  When I took the Cayman out of winter storage this spring and warmed it up for the first time in a while, I smelled coolant, although none leaked to the ground.  I have seen water pump seals do this before.  On most older cars the water pump has a simple bushing that runs in coolant so a small seep that quits is not necessarily a big deal.  My F250 would do this on severe cold weather but never had a pump failure.  However, the Cayman water pump is not like that.  It has a sealed roller bearing instead, which is far better and should last for life.  However, if you get coolant seeping through the bearing, the bearing will die pretty fast.  The grease will get washed out, the bearing will run dry, and fail.  Well, that is what happened to me.  I had noticed a growling noise from the engine when I started it that morning.  My first thought was far worse than a water pump.  I feared my IMS bearing was going out.  After recalling that I did see dry evidence of coolant from the water pump I sorta convinced myself it could just be some coolant on the belt, which can make all sorts of weird noises.  Honestly I was not that convinced, I was just lazy and in a hurry to meet with some friends.  

On my way back from breakfast where I was meeting with friends I heard a pop and immediately my steering assist was gone and the charging system warning came ON.  Right away I knew I had lost the belt.  I carefully drove the rest of the way home, accelerating moderately up to speed, shutting OFF the engine, and coasting between lights.  By the time I got home the coolant temp was a bit over 200F based on the gauge.  Still safe but I would not want to get it too much hotter.  With no belt, the coolant does not circulate.  You can't go very far like that.  In the video below you can hear the pop right at the beginning.

It is not real loud and I did have the stereo going.  I quickly turned OFF the AC and opened the windows too.  

Once I was home, I removed the panel behind the seats to expose the front of the engine where the belt and water pump are.  I saw the slack belt but upon further inspection I found the water pump shaft had completely sheared off and the pulley was just laying there.


Glad to see it was just a water pump, I quickly ordered parts through the local dealers online website. 

  

Mid-engine cars have a much trickier cooling system since the engine is in the middle, and the radiators are in the front fenders ahead of the wheels.  This makes it an air pocket nightmare.  A vacuum system is needed to pull a vacuum on the cooling system and suck the coolant in.  I found this one on Amazon for $39.99.


Having the engine behind the driver and not even visible without removing bolt-in panels and carpet sounds like jobs like this would be much harder.  However, it is not too bad really.  It takes about 15 minutes to remove the carpet section and both the top engine panel, and the front engine access panel. Once you have these panels off, access is pretty good for most things.  I will say charging the water pump on this car is far easier than most front-wheel-drive cars.  

I positioned the car on a ramp on the drivers side, and jacked up the passengers side as high as my jack stand would allow.  This positioned the coolant reservoir as high as possible relative to the car. I did this to keep the radiators and heater core full of coolant making it easier to ensure all the air was out when I was done.   

I started by clamping the radiator hose and one of the heater hoses.  

I loosened the hose connected to the water pump at the bottom and stuck an Allen wrench in it to allow the coolant to drain in a more controlled fashion.  In this position, and with the clamps in place, about 2 gallons of coolant drained into the pan I had to catch it.  I then removed the water pump.  It is basically just a set of small bolts.  The nice thing is the gasket is metal and does not stick to the block so it left a clean surface.  Here is a photo with the pump removed.



  When installing the new pump, make sure the longer bolts are in the correct holes, with the alignment dowels.  Here you can see the new and old pumps, both showing the alignment dowels.

Here is a photo with the new pump installed.

Before removing the hose clamps, I drew a vacuum on the cooling system and pulled in the coolant.  

I was able to pull in almost 2 gallons right away.  Remember to open the air bleed valve in the top of the reservoir to allow the air to escape the block while doing this.  I then released the clamps, installed the belt, and ran the engine.  With the engine running I could feel more air purging through the air bleed hose that connects from the oil cooler to the reservoir.  I added about a quart more coolant at this point. I ran the engine some more until I could feel the heater hose warm up, indicating I was getting coolant flow.  I ran the engine until the thermostat opened and I could feel the radiator hose at the radiator warm up, indicating flow to the radiators. I did all of this while the car was still raised.  I took it for a good road test, hitting 7,000rpm at times to create high coolant flow and purge any remaining air.  

The whole job took me about 3 hours.  Not too bad.