Porsche 996 911 - bad alternator causing stalling, misfires, backfiring!

 Super weird problems to have, but a neglected 22 year old 911 with nearly 260,000km will be that way I guess.

Anyway, this morning removed the airbox, belt and alternator (this time only took 15 minutes now I've done it a few times!). Unplugged the electrical connections from the alternator, and reinstalled everything.

Car runs fine, perfect idle, not a problem. This isolates the problem to the alternator/charging circuit, and everything else is good.

Removed alternator again, and used a spare old voltage regulator (I'd put a newregulator in this alternator in 2018). Refitted everything, and same old problems arise - low revs, misfires, backfires, lots of motor rocking, eventually stalling. 

While the alternator was out, I rechecked the new Y cable (all connections appear good), checked all vacuum connections (again seem fine).

Next step? I'll probably remove the alternator and send it to an auto electrician for testing. Possible issue - alternator has some crazy internal fault that only shows up at idle? Voltage fluctuations, other things causing engine to run poorly. Hopefully a good auto elec will be able to bench test, simulate load etc. Then get alternator rebuilt, reinstall, and hope it works.

Was thinking of selling the 911 once all these issues are fixed - but I still like driving the car!

Making progress - removing the serpentine belt and the engine runs fine!

 Thought I might try a few random experiments today - removed the airbox and serpentine belt (let it dangle underneath the car) and tried starting it up.

Guess what - engine runs perfectly with the belt disconnected!

And when I replaced the belt, back to stalling immediately and idling terribly.

All the pulleys and tensioners seem fine.

So it comes down to a component driven by the belt causing the problem

1. water pump (unlikely? only replaced 2000km ago, mid 2020)
2. alternator (seems most likely to me, i did change the regulator in it in 2018)
3. power steering pump (hopefully not)
4. airconditioner compressor (unlikely, as it freewheels and disengaged/not turned on)

Tomorrow will remove the alternator electrical harness at the back, and see if the car runs OK with the serpentine belt on, but alternator disconnected. If so, then further investigate the alternator, the regulator, and all electrical connections from alternator.

Porsche 996 - continuing the saga of stalling and misfires. Replacing the fuel pump

Was psoting about these problems on FB, and Jake Raby thought it'd be worth changing out the fuel pump. Why not - pretty cheap part for $150 (non OEM) part.

Remove the battery and unbolt the battery plate to reveal the fuel pump cover.

Remove the locking ring (I used a rubber mallet and wooden stake), lift off the top plate and disconnect the two fuel lines (press in the little black tab) and remove the electrical connections.

Fuel level sender removed

Removing the old fuel pump was a little tricky - in theory, just grab it and rotate counterclockwise. Mine was stuck fast, I wrapped an old belt around it and yanked it counterclockwise to loosen it.

The new pump didn't come with any connecting pipes or connectors. I removed the swaged metal bands holding the original fuel lines in, and used new stainless fuel clips to lock them into place ont he new pump.

Reinstallation is pretty straightforward. Threw some fuel in and started the car up....

.... only a slight improvement. Car doesn't stall completely and die, revs hunt up and down, few pops from the left tailpipe.

More to come!

Porsche 911 996 still stalls after starting, continuing the diagnostic process. Replace fuel pressure regulator, check fuel pressure

So, decided to throw a few more parts at the 911, because... why not... so far they're pretty cheap.

Got a Bosch 3.8bar fuel pressure regulator for about $50, as I had a suspicion the old FPR wasn't great - the vacuum tube was a little wet.

Removed old FPR - used needlenosed plier to remove the retaining clip, and the old FPR wedged in pretty tight, so yeeted it out with some pliers. You can see a drop of dirty old fuel dripping from the vacuum port which is no good.

New replacement fuel pressur regulator. Push it into the fuel rail, and press down on it while reinserting the retaining clip.

Started up again - still terrible idle and stalling almost immediately after starting. Interestingly, getting some different codes. P1602 is because I disconnected the battery for an hour. P0341 is camshaft sensor to bank 1 - actually, I've been ignoring the code for a couple of years now.

P1514 is to do with the idle air control valve - haven't had that code before, and I've only jsut removed, cleaned and tested it and replaced it.

Anyway, next thing to do, I grabbed my fuel pressure tester and hooked it up the the fuel rail over Bank 2.

With key in, engine off and fuel pump on, we get a solid 3.3bar that doesn't fall away.

With engine running, and foot holding the throttle open a bit, we get 3.8bar as expected

So... i'm thinking the fuel pump is good, new fuel pressure regulator is good... erm - worth checking the fuel injectors? Doesn't seem like a big deal to remove them and visually inspect at least. Just drop the engine a couple of inches and remove a few wiring plugs and bolts. Maybe next weekend.

Diagnosing hard start, stalling, no idle on 1999 3.4l porsche carrera 911 996 - checking fuel system is OK

So, continuing on the saga of the 996 that barely turns over, trying to figure out if a fuel issue is causing it, as that's kinda what it sounds like to me.

Made a fused lead to jump the fuel relay pins 87-30 to manually activate the fuel pump, still hard start.

Then a thought - it looked like I had half a tank according to the fuel gauge, but the odometer read 290km or so, which is not what I can normally get on a half tank! Added 20L from a jerrycan, still same problem - no not a faulty fuel gauge then (could be empty but reading half full)

Next, to check actual fuel output.

I removed the return fuel line from the 3.4L - need a 17mm spanner. This is located under the coolant expansion tank, left side of engine.

Used some spare heater hose and a hose clamp to connect to the threaded end.

Then, used fused cable again to jump pins 30-87 on the fuel pump relay. Factory specs say there should be 850ml output in 30 seconds

Had a spare container which I'd previously marked 850ml - and guess what, exactly 850ml in 30 seconds. If there was less than this, I would test output after the fuel filter, and then again at the output of the fuel pump.

So, it appears the fuel system is OK - good pump, good filter, good fuel pressure regulator. Relay should be OK as well, since I jumped it and had the same poor idle symptoms.

Feels like I'm running out of cheap/easy things to test now!

Troubleshooting misfires and no start saga. Maintenance - oil change, clean MAF, throttle body and IACV porsche 996 911, coil pack spark plug tube change

 Oh, how much fun it is to keep old cars alive.

Few weeks back (early Feb 2021), the 911 developed a big misfire just as I was coming home - managed to limp it into the garage.

Symptoms: Flashing then solid CEL, really rough idle, audible misfire.

Pulled codes;

• P0341 - Camshaft Position Sensor 1 - Signal Implausible, Short to Ground, Short to B+
• p0300 Misfire Damaging to Catalytic Converter
• p0306 Misfire, Cylinder 6, Damaging to Catalytic Converter

Plus a bunch of old codes relating to the alarm and microswitches - irrelevant to engine. So, time for initial troubleshooting.... misfires often due to

1. ignition (spark) problem - plugs, wires, coilpacks, crank position sensor, MAF, throttle, idle control valve
2. fuel problem - pump, filter, injector
3. compression problem - valves, head, piston, bore scoring etc (this is the scary expensive problem!)

as usual... start with cheapest, easiest investigations first before going into expensive, difficult investigations. Basic maintenance first.

1) Drop oil, check filter. Found a few small bits of orange sealant/RTV in the oil filter, but no metallic particles. Wonder where this is coming from? Ususal suspect is oil sump gasket, but I've not seen this orange sealant at any prior oil change.

Mobil 1 5-50 now a recommended oil for 996s.

Removed and cleaned MAF with some CRC spray, dried and reinstalled.

Checked throttle body for any signs of oil (which can be a sign of AOS failure - was really clean before and after throttle. Gave it a clean anyway. Note this is a cable throttle early 996.1

Removed Idle Control Valve - tested with a 9V battery and found it to be pretty sticky. Cleaned it out and retested to make sure the flap opens and closes easily, then reinstalled. The gasket and bolts were a bit worn out - replacement parts ordered. Checked all connections after the MAF were secure and no obvious problems like loose hoseclamps or bolts.

Raised the rear of the car and placed bricks under the rear wheels for a bit of space, removed coilpack cover on right, and accessed coilpack on cylinder #6.

Coilpack removed had a fair bit of oil all around it and missing the end collar.

Ordered a couple of replacements (on the left)

Pulled Cylinder 6 spark plug - a dirty NGK, but no big signs of carbon buildup oil oil deposits - promising! If it was very oily, this might indicate oil getting past valves, seals or piston rings ($$$ problem). Brand new Bosch replacement FGR6KQE 4 prong plug replacement.

Used a mini endoscope to check inside the spoark plug tube - no obvious cracks in the tube, a little oil or fuel pooling at the bottom of the tube.

Top of piston - fairly caked on fuel/oil, no obvious damage to top of piston.

Pulled cylinder 6 spark plug tube - was an aftermarket replacement with O rings well worn. Made a tool with a long bolt and end waser to yank out the spark plug tube. New OEM spark plug tube and O rings from local dealer reinstalled.

Bolted everything up, checked coolant and oil levels, put the battery on a C-tek overnight.

Started everything up.... and no improvement! Hard to start, and when everything kicked over, idled very low with audible misfiring. With a few revs - just over 1000rpm, things did even out a little.

Pulled codes-  same P0341, P0300 and P0306, plus a P0305 now - for a misfire on cylinder 5!

Will recheck all wiring today - just need to make sure all the coipacks are plugged in 100%. Next step is to recheck fuel pump (though I imagine a fauly pump would cause misfires on all cylinders), check fuel filter for blockages, then.... more research required!

What am I considering right now?

- Car cranks over OK - starter is fine. I do have a spare new starter motor bought a while ago ready to replace. RPMs moves on crank - crank position sensor is OK. Replaced this part a couple years ago.

- Fuel pump issue (check working by bridging fuel pump relay), blocked fuel filter (replace, it's a cheap part), blocked injector(s) - bit harder to investigate. That said, a fuel pump problem will most likely cause multiple misfires on all cylinders rather than just 1, or 2. An individual fuel problem is most likely the injector associated with the cylinder.

- No compression - to check with compression tester. Potentially related to variocam problem (fairly common for variocam solenoids to get sticky/stuck on one cam setting), but also chains have broken. The P0341 code is a potential red flag, though related to bank 1 (cylinders 1 2 3) rather than bank 2?

Hoping it's not a compression problem, because this is where things will get expensive quickly. Ultimately I'm realistic about the potential problems a motor with 258,000km will have. Not really worth my time or money to pay for expensive engine overhauling (haven't decided what my limit will be) as the resale value of this car was always going to be modest. Never bought this car with the intention of it being a garage queen, just a cool daily driver. Worst case scenario if it's an expensive engine job is to sell this car in parts, or in whole to a wrecker. Best case scenario, I find a fuel issue and fix it myself. 

Here's hoping!

Update 28.2.2021 - Jumped the fuel pump relay with a fused wire - fuel pump runs and sounds good. Tried starting the car, bypassing the relay with the same fused wire to ensure the fuel pump is running all the time - same problem where engine barely fires up and runs poorly.

Now to check output after fuel filter, and at fuel pressure regulator.

Porsche 911 (996, 997) cabriolet - fix rear wet carpets, seats by fixing convertible cabriolet roof (top)!

  One common but often overlooked problem with earlier 911 convertibles (or cabriolets) are bad drains.

If you have a cab, just go and check it now - it'll take a minute! Feel the back carpet behind the front seats - if it's dry, great! Now, lift up the rear seat cushions (mine were only held in by velcro) and feel again. If they're dry great again!

But if either one are wet, then you've got some problems to fix. Luckily in my case it was very easy, and very cheap.

First off, tilt your front seats forwards and remove the rear speaker covers - it's only 2 torx screws.

You'll see a little black plastic reservoir, with a small hole leading to the drain that goes outside the car. On this side, the reservoir had no water in it, but this black tubing had the far end (pointing to the back of the car) not connected to anything - no bueno. This should be the outlet for all the water that's drained off the back section of the convertible top.

Removed the tube, pretty clearly split in addition to being disconnected.

Local hardware store had some plastic tubing that matched the outer diameter of the damage drain tube.

Replaced the drain tube with new one. IMPORTANTLY make sure the back end of it connects to the roof drain!! I've circled it in yellow here. 

Now, on the other side of the car there was the same problem of the tube being disconnected from the roof drain at the back, but there was also a lot of water stagnating. Clearly the lower drain was also blocked. So, I replaceed the black drain tube with the new plastic tube as pictured, then went on to unblobk the lower drain.

Simply remove the rear wheel, then remove the plastic fender inner trim which is only held on by 3 plastic bolts. I've circled the lower drain exit here.

Erm..... it looks a little blocked up. I pulled all the gunk out, and a few litres of water gushed out.

Yep, all that water was building up in the lower drain.

Now, just replace everything, and congratulations - you've fixed your drain problem!

Blocked roof drains can cause a lot of issues mainly

1. wet carpets, seats and then mould, stale smells etc
2. damage to the electronics located under the front seats (stupid place to put them, but hey europeans, amirite?