jwittock

Hi all, new to this forum.



3 months ago I bought a 2002 996 targa with 175k km. I drove it for about 2000km. Than on a 30km drive home the engine started to sound more and more rough, more and more vibrations.

When the rpm got below 3000 I lost all power (engine did not die), and with full throttle it slowly picked up speed until it reached 2700 to 3000 rmp when all power returned and the car lept forward in a jerk.

Tried to make it home, but after 10km of this it finally stalled and did not want to start again.

During the last 10km of running, check engine light came on, fuel light came on, abs errors, pcm error all came and went.



Towed the car home and put a simple obd reader on the car.

I was greeted with the following codes:

• P0343: CMP sensor A bank 1 -high input
• P0303: cilinder 3 misfire
• P0302: cilinder 2 misfire
• P0301: cilinder 1 misfire
• P0300: multiple misfire detecte
• P1325
• P1341

At this point I called the Indy where I bought the car from and they said to replace the camshaft position sensor. Did not think too much of it, so I went ahead and replaced it. Cleared the codes with the simple obd reader, but the rough running remains.

At this point only code P0343 is coming back.



Putting a temperature reading on all cilinder exhausts shows that cilinders 1,2 and 3 remain cold, cilinders 4 to 6 warm up.

• I do have a fuel smell, so I assume cilinders 1-3 are getting fuel.
• Compression test on cilinders 1 - 3 gives between 126 and 128 PSI
• Took out coil of cilinder 3 and connected spare spark plug, it spraked but it was yellow.
• Used camera to inspect the cilinders, I am no expert what so ever, but my amateur opinion is that I did not see lines on the cilinder walls, and no damage to piston ( not hitting valves or anything)
• Only thing to note was that cilinder 3 had a lot of oil in it ( a puddle of 1 or 2 mm high), so I removed fuse for fuel pump and ignition, and with spark plug removed, ran the starter so it could pump out the oil. After which I put back the fuses and tried starting again, still no joy on cilinders 1-3.

I replace coils and plugs on cilinders 1 - 3. Still not firing. (I have not yet checked spark again to see if it is nice and blue, nor did I test on all 3 cilinders to ensure I have spark)



With the cmp on bank 1 disconnected, the engine behaves the same as when connected.

• Question 1: So if DME decides not to use cilinders 1-3, why do I still get spark and why do still smell fuel? I would think that if DME decides not to use a cilinder that it would not send spark signal and not trigger injectors?
• Question 2: I read that without cmp on bank1 the engine should still fire up (on all 6)?

I did some google-fu and found in the workshop manual to check signal wire from DME to sensor for short to B+.



Now I do not understand what short to B+ means, nor do I have special tool 9637. So I started measuring. Below you can find all my results, but short version is that all measurements I took for wires to and from cmp on bank 1 are the exact same as the measurements for bank 2. So I do not understand why cmp bank 1 is throwing error and cmp bank 2 is not.



Question 3: Can someone explain me between which points I need to make a measurement. And what should be disconnected before making the measurement? (note I did a lot of measurements described further in this post)



Question 4: the wiring diagrams say that the supply voltage should be 5V, but I measure 11V?



Measurements I took on the cable end that goes into the CMP on bank 1:

Let's call wire to DME gnd line A

Let's call wire to DME output/signal line B

Let's call wire to DME supply line C



A - B: 10,7V and 49k ohm

A - C: 11.2V and 70 ohm

B - C: 0.4V and 42k ohm

A to chassis: 0V and 0.2 ohm

B to chassis: 10.8V and 42k ohm

C to chassis: 11.2V and 70 ohm



Now if I disconnect pin C12 (cmp bank 1 signal) from connector to DME, than I measure no voltage between wire in plug to sensor and chassis.

Which leads me to believe that C12 is supplying voltage but 0.4V less than the DME supply wire to the sensor.



Now for the interesting bit, I have almost identical measurements for CMP on bank 2.



Question 5: Why is the computer still reporting high signal on cmp bank1 even though I get same measurements comparing CMP on both banks.



Another observation I made is that found very small oil leak at the bottom of the engine where it connects to the gearbox. Also the two connections between left and right air intake are oily. And if I open oil reservoir cap, there seems to be some negative pressure. ( I have ordered a second oil cap so I can drill a hole and add vacuum pressure meter to see if AOS might be bad) Will report measurements here once I get those parts.



Question 6: Could the above indicate a bad AOS? It was replaced already in 2017, and reading about AOS does indicate I should consider replacing every 6 or 7 years?



Question 7: IF it theory is bad AOS, how does that explain only cilinders 1-3 not working.



Question 8: What parts of the engine are dedicated to one cilinder bank? So that I can test by swapping or measuring those components to try and understand why bank 1 is not happy?



Additional info that might or might not be related:

• AOS, IMS and RMS where replaced around 2017.
• It started raining on the drive home, first time I drove it in the rain.
• Before driving home, the car was parked on a hill side. Front right wheel was highest, rear left was lowest.
• No smoke as far as I could tell.
• I was almost out of gas, so I thought it might be running out of fuel during the rough running, so I fueled up, but rough running remained.
• On the last drive before the return home drive, at points in time I thought I heard ticking (for lack of a getter word)
• When trying the start the car when towed home (and before doing any work) there was again a subtle metal ticking that went away after a few seconds of idling.
• After replacing cam shaft position sensor, coils and plugs on bank 1 (cilinders 1-3), this ticking is completely gone.

jwittock

Forgot to add that I removed and check the two variocam actuators as well. The left one (timing?) was fine, the right one (lift adjustment?) was stuck. A healthy dose of brake cleaner and a lot of testing with a 12 V battery got it loose again and working fine even when putting pressure on it. Put it back, no change whatsoever.

168Sierra

I see that you said you are getting a fuel smell, but if all three cylinders on bank 1 are not producing power, I would check the ground point for the fuel injectors on that side of the engine. IIRC the ground point is located on the end of the head near the mount for the crank position sensor plug. It is a ring connector attaché to the head with a 6mm bolt (10mm head). Hope this helps.
Mark

jumpy chunky

I’ll suggest that you should find someone with a Porsche specific scan tool.

A Durametric or PIWIS will give more info concerning cam deviation, etc.

jwittock

no ground for the fuel rail seems like a very reasonable explanation, however I am not finding any connections to ground from the rail. Unless the ground is achieved via the bolts that mount the fuel rail to the engine?
I did a quick measurement and I get 0.3 ohm from fuel rail to alternator, so I think we can assume ground for fuel rail is good? (I was hoping it would not be as this would have been easy fix)

jwittock

I hope to buy a durametric kit tomorrow so I can go and test.

If anyone has an answer to any of my above questions that would be cool. I am trying to learn as much as I can about this car as I hope to enjoy it for many years to come

Thanks for the replies! Much appreciated.
J

De Jeeper

The fuel rail is not grounded. The fuel injecors what is grounded. This harness is what was explained above.

jwittock

Oh, ok, I misunderstood. I know about the ground on passenger side, will look for the ground on driver side and test.
Thanks!

De Jeeper

Its under the aos, on the firewall side of the head. U have to look up from under the car. Even if it looks connected i would remove the bolt, clean and reinstall

jwittock

Ok, with that help I did find it. Removed the bolt and found the ground connection. It was looking dirty, so I cleaned it so it shines, bolted back on.
So now the P0343 code seems to be gone. But still cilinders 1-3 do not fire up.
Before the car would keep idling on cilinders 4-6, but now it only idles for a few seconds and then dies.

So progress as the code seems to have gone, but now I cannot do a vacuum measurement with my modified oil cap and vacuum gauge in an attempt to see if AOS is still good. I read a post somewhere that 4 to 6 inches of H2O is good, 8 or higher might indicate a bad AOS.

Speaking of AOS, I have a genuine new one. But could not get to it from the top of the engine, but now that I looked at it from under it (I do have a lift) seems like I stand a chance to remove it from under the car? (this is a 3.6 so it is slightly different compared to the 3.4).

I'm still trying to buy a duratech tomorrow so I can do a better ECU reading than my current cheapass OBDII bluetooth reader.

Thanks for the help, I'm sure with the combined knowledge and experience from the folks here I will find a way to make the engine happy once more.

J

jwittock

One other thing I thought of is the fuel pressure sensor. Since it seems fuel first goes to first to bank 2 (cyl 4-6) and then through hose to bank 1 (cyl 1-3), any chance that too low a pressure can cause not enough pressure to remain on the rail on bank 1? Or am I overthinking it from troubleshooting this for too long

Just one more

Is it possible the timing sprocket on bank one cam shaft has come loose and put bank one out of time ?

De Jeeper

Im starting to suspect a timing issue too.....we need to see some telemetry from the durametric when u get it. Cam timing is what we need.

jwittock

Ok, I'll focus on getting the durametric first. Do you guys know of any good documentation sources to teach me how to properly use it or is it pretty self-explanatory?

jwittock

I do remember hearing clicking noise (metal on metal), nothing too loud, only when I drove with the window open was it noticable. Does that point towards cam out of sync?