DrMEMS

OK Rennlisters--
I have a 2003 996.2. I've been fighting a cylinder 1 misfire for two months now have yet to resolve it. I think I've read everything posted on Rennlist and 6speed. I hope you can come up with something new.

Relevant Car History
Jan. 2015, 86 kmi: Replaced fuel pump. On the 996.2 the fuel filter is part of the fuel pump, which resides inside of the gas tank.

May 2015, 87 kmi: Replaced stock engine with professionally rebuilt X51 engine (see https://rennlist.com/forums/996-foru...mentation.html). Includes new IMS roller bearing, piston rings, main bearings, rod bearings, head gasket, seals, cylinder head bolts, water pump, LNE low-temperature thermostat, spark plugs. The ignition coils look new. The air intake manifold and exhaust manifold were upgraded to the X51 versions using used components. The mufflers were replaced with used Porsche Sport Exhaust (PSE) mufflers with the valves permanently wired into the "loud" position.

July 2015, 89 kmi: I was unable to get a standard Porsche X51 ECU flash, so I got one for the 996.2 X51 from Evolution Motorsports. I've noticed some hydrogen sulfide smell when I floor it and rev it up to 7000 rpm. I suspect that the flash results in a little too much fuel input at high revs, possible damaging the catalytic converters.

June-Dec. 2015: Several oil changes at 4000 miles with Joe Gibbs DT40 5W40 oil. Spin-on filter using the LNE adapter.

Nov. 2015, 95 kmi: Replaced stock springs, shocks, and sway bars with the ROW M030 version. These transmit the shock from large bumps to the chassis very well, so something like the cat cartridge or wiring could have been bumped loose.

Dec. 2015, 97 kmi: Replaced the M030 shocks with Koni FSD shocks. These take the big bumps much more smoothly.

Dec. 2015, 96.3 kmi: The problems starts. After the car had been driven about 10 minutes and was warmed up, while idling at a stoplight, the engine started running rough and the check-engine light came on. My code reader said P0300 (random cylinder misfires damaging to catalytic converter), P0301 (cylinder 1 misfire), and P0305 (cylinder 5 misfire). After a minute, it ran fine. I cleared the codes, drove some more that day, and only the cylinder 1 misfire returned. Cylinder 1 is the left side of the car toward the rear of the car. I replaced the cylinder 1 spark plug. It looked normal. At the same time I replaced the ignition coil, which looked normal and had a low resistance (I forgot what I read). The engine ran fine for 500 miles. I fixed it! Or did I?

Dec. 2015, 96.8 kmi: Regularly scheduled oil and filter change with DT40.

Dec. 2015, 96.9 kmi: Brief cylinder 1 misfire. Unplugged the connector to the ignition coil. It looks pristine inside. It was solidly clicked into place before and after inspection. I did notice that the overflow from the coolant tank has a hose that dumps right onto the coil. I moved it, but it wants to move back by itself.

Jan. 2016, 97.4 kmi: After many more cylinder 1 misfires, I replaced the cylinder 1 fuel injector with a new one. Afterward, the car ran fine for a few minutes, then the problem returned.
With my Durametric, I can turn off each fuel injector. Doing so makes it run really rough and almost die. The misfires that I have been feeling have not been that rough. I learned from the indy German car mechanic who installed my X51 engine that if the misfire is too bad, the ECU shuts off all fuel to that cylinder. Just turning the car off and back on restores the fuel flow.

Jan. 2016, 97.7 kmi: After revving it up, one time I got code P0430: catalytic converter efficiency bank 2 (which is cylinders 4-6 on the right side of the car).

Jan.-Feb. 2016 I have been looking for patterns with the misfires. The most common time is about two minutes after starting a cold engine, when idling at a stoplight. But is also occurs sometimes when the engine has been running for over 10 or even 30 minutes. It usually goes away within two minutes. I don't see a correlation with rainy days. I've gone through 4+ tanks of gas.

Porsche diagnosis protocol. For code P0301, Porsche says to do the following:
* Check fouled, faulty or incorrect spark plugs. Done (replaced).
* Check contact resistance. Looks OK at the connector to the coil. The next step would be to look for damage to the wire from the ECU (behind the back seats) and the coil.
* Check for loose contacts. See above. I looked that huge bundles of wires that connect to the ECU and didn't see anything amiss. The region was dry.
* Check for mixture too rich or lean. The MAF sensor could be a problem, but I doubt it because only one cylinder is misfiring.
* Fuel tank empty. It's not.
* Valve lifter chattering. I do hear a tick-tick-tick at same rate as the camshafts are spinning when the engine is idling. My indy says it's not a problem. It is not correlated to rough running.
* Camshaft control badly adjusted. All of cylinders in one bank would be misfiring, so that's not it.
* VarioCam does not switch over completely. Again, this should affect all cylinders in one bank.
* Check fuel pressure. I don't have the tool for that. All of the other cylinders are getting fuel, so this is probably not it.
* Check volume supply of fuel pump. See above. If I open up the port, I need a special replacement crush seal that I don't see at Pelican Parts or anywhere else.
* Check triggering of fuel injectors. To access the fuel injectors, I have to drop the engine down two inches and unplug one. I don't see how to run the engine and have the injector unplugged at the same time.

Your thoughts are appreciated!

5CHN3LL

I see this in the stuff above - "* Check contact resistance. Looks OK at the connector to the coil. The next step would be to look for damage to the wire from the ECU (behind the back seats) and the coil." - but I can't tell if you've done that.

Is there any chance the wire that connects to that coil pack got crushed during the engine swap? Maybe someone else can chime in on what the resistance across the two wires should be when the car is off.

Does Martin have any suggestions?

DrMEMS

Here are some clues from a freeze frame on my code reader. I don't know how to interpret most of the terms or what the values should be.
DTCFRZF = P0301
FUELSYS1 = CL
FUELSYS2 = CL
LOAD_PCT (%) = 2.0
SHRTFT1 (%) = -3.9
LONGFT1 (%) = 4.7
SHRTFT2 (%) = 2.3
LONGFT2 (%) = 3.9
RPM (/min) = 680
VSS (mph_ = 0

DrMEMS

Checking the wiring resistance to the coil and to the fuel injector is my next step. I think it will be painful, so I wanted to see if there's something easier to check first.
The engine was out for the X51 swap, and out before that when repairing damage from being rear-ended two years ago. The connector looks fine as far as I can tell.

pesuazo

I am sorry if I missed it, but...have you swapped coil 1 with any other cylinder to see if the misfire moves?...just a thought

Ahsai

The freeze frame indicates the code was tripped when engine was idling, close loop fuel control.

What are the cam deviation values on both banks? Are the valies steady at all rev when taken out for a test drive?

One suggestion I have is disconnect the two X59 big round engine connectors in the right rear engine bay and spray both sides with deoxit. Your engine(s) have been dropped a few times so it's possible those connectors got contaminated and have developed corrosion on them.

If you are sure it's cyl #1 only, a leak down test may he worth while.

DrMEMS

The first thing I did was to install a new spark plug and coil on cylinder 1. The misfire went away for two weeks, so it probably would have gone away by itself. The old plug looked fine. The old coil also looked fine and had the correct resistance.

Macster

The misfire can be due to the low/high lift feature (VarioCam Plus) of one or both intake lifters on that cylinder not working right. There is a pretty involved test which has the tech checking the O2 sensor readings under specific operating conditions to confirm this is the likely cause of the misfires.

For cars under warranty the SOP is to replace all lifters in the bank with the misfiring cylinder(s).

The lifter problem -- if that is what it is -- is a "new" engine problem. I say "new" for if my math is right the engine has around 10km or approx. 6K miles which is very low miles. The malfunctioning lifter arises from contamination -- dirt -- which affects the lifter hardware.

Hate to mention it but I note you are running a low temp T-Stat. Thus you might want to check the #1 cylinder for signs of bore scoring. However I think bore scoring a long shot for if the bore was scored enough to cause misfiring I think you'd hear something and the misfires would occur more often.

DrMEMS

I collected data with the Durametric for a 15-minute drive. To my surprise, the camshaft deviations remained constant as the car warmed up and the engine revved from 770 to 3000 rpm.
Camshaft 1 deviation: 3.91 degrees
Camshaft 2 deviation: 1.31 degrees.
IIRC, the spec is under 5 degrees.

That's a good tip. I will try it.

What would that tell me?

Ahsai

Your cam deviations are good and they are supposed to be rock solid at any rev so yhat shouldn't be surprising.

A misfire can be caused by wrong air/fuel mixture, no sparks, wrong timing, or no compression. Since you have already eliminated fuel injector, coil and plug. The rests are compression and intermittent spark failure. Compression wise it can be an intermittent lifter hang up. Leak down test can tell you if the cylinder is sealing well.

DrMEMS

Thanks, Macster.
The rebuilt engine had a 6-month warranty. I started having misfires at 6.5 months. The engine now has 12 kilomiles (kmi, not km...I'm in California near you) on it. My biggest fear is that it's something internal as you suggested could be the case. I talked to the builder and they swear that there is no way it could be something inside of the engine, but I don't buy it. They also said it's probably the spark plug or coil, even though I told them that I replaced those with new ones and the problem returned after two weeks.

If all of my electrical testing and cleaning doesn't produce a result, I need to find a shop that can run the test you described. The indy German car mechanic who installed the engine, and has taken Jake Raby's class, said that he could not think of any more tests to perform beyond what I had already done with replacing the spark plug, coil, and fuel injector, and looking at the Durametric.

I don't trust my local Porsche dealer after going there twice. Once they didn't fix the problem with the alarm going off when using the mechanical key to open the door. Another time, when they replaced the window mechanism they left the door panel loose and rattling. Both times they said that my brake fluid was really old. One of those times it was less than a week old; the other it was a year old.

DrMEMS

Thanks, Ahsai.
Can you recommend a brand of leak-down tested to buy to test it myself?

Ahsai

I use this one from OTC
http://www.amazon.com/gp/aw/d/B0030EVL60/ref=mp_s_a_1_1?qid=1454796179&sr=8-1&pi=SY200_QL40&keywords=otc+leak+down+tester&dpPl=1&dpID=51xtBQ2m0ZL&re f=plSrch

I would try the Deoxit first before anything though since it's so easy.

The test Macster described is in the diagnostic chapter of the factory service manual. Basically it's testing if the high lift and low lift are operating correctly in that bank. It still will not be able to id an individual cyl hence the remedy is replacing all 6 intake lifters in that bank.

To completely eliminate the injector, coil and plug, one would need to scope the injector and coil signal in realtime when the misfire occurs. You know that you can see the misfire counts for each cylinder in Durametric, right? It may help if you monitor those counters during cold start and the first 10min of driving to see if only cyl 1 misfires or there are other cyl misfires too. The frequency of misfires needs to exceed some threshold before the DME would trip the P030x code so no code doesn't necessarily mean no misfires on that cylinder.

ChicagoSpeed996

DrMEMS, I had a stuck intake lifter on cylinder 4. Symptoms were random misfires, but typically when I went above 3000 rpm and came down to an idle, then it would misfire. Take the car out, get it nice and warm, cruise at 4000 rpm and directly come down to an idle and stop. Wait and see if it misfires. Do it a couple times and see if you can produce it. Basically what might be happening is that the lifter gets stuck in high lift, creating a mixture imbalance for idle conditions and throws the misfire code. Give it a shot and see if you can replicate the symptoms. Also the lifter issue occurred in my car at 34,000 miles, during the winter, possibly another culprit?
Good luck!

Flat6 Innovations

I'd say the cylinder is failing. Performing a running compression test is a good way to find this.