Cwedgeworth

I recently acquired a 2000 Porsche Boxster S. It has 87,000 miles on it. This morning when driving it I came to a stop and look to make a left-hand turn at a light and the car stalled. This is not uncommon seeing as I'm not the greatest driving a six speed. So I went to restart the car and it started turning over but would not actually crank. I gave it a little bit of gas and it cranked up but would die if I didn't keep giving the car gas. I was able to give it enough gas to get it going and pull it into a nearby gas station where I had a friend come pick me up with a flatbed trailer. When I got it back to his house I immediately, after reading some online forums, was thinking fuel pump or relay.
I went and got a fuel pressure tester from AutoZone and tested the pressure (via the nipple on the fuel rail on the passenger side of the engine compartment) while trying to crank it and it was sitting at about 50 PSI which led me to believe that the pump was fine. I pulled the engine codes from the OBD2 Port and they were 300 305 and 306

Random misfires and misfire in cylinders 5 and 6. This led me to believe that I should change the spark plugs and coils. I change the plugs first seeing as that was the cheapest option and the car started up (after some coaxing and throttle play) and this time did not die instantly however the idol began to surge and the CEL began to blink.

I'm currently at a complete loss as to where to go from here. And as to how stalling at a red light set all this in motion. Any help is greatly appreciated and thank you in advanced for your time.

particlewave

Inspect the coil packs for cracks. That's my guess

terbiumactivated

300 = misfire
305= misfire cylinder five
306= misfire cylinder six


Sounds like you already did the electrical, There are sensors that monitor the cam timing, you might want to check them too. This might be one of the times you want to spend money to tow it to a qualified mechanic. Repeated attempts to run it without knowing the origin of the problem might cause irreparable damage. My 986 went from a righteous sports car to a paperweight, do everything you can to prevent it from becoming a roller, I had the skill, lift and tools to replace the engine but I was not physically able. What I'm getting at is the only way it makes any economic sense to re motor a 986 is if you can do 100% of the labor, otherwise it's a huge investment in an old car, good luck.

landrovered

I agree with previous posts, it could have jumped a tooth on the timing on bank 2.

XR4Tim

Misfires on 5 and 6 will make your car run rough, but won't cause it to stall and not restart. I would suspect that the misfires are a result of the actual problem (over or under fueling perhaps), and not the root of the problem. I've seen very similar symptoms with a bad Mass Air Flow sensor.

Cwedgeworth

We tried to start the car with coil packs on cylinder five and six unplugged it and it was considerably worse than before. This was how I ruled out coil pack damage, if it got worse they must be working a bit.


My question is do you think that a bad/cracked coil or bad maf could be the culprit for why it fights me during start up and when running now surges?

I'm also going to pull codes again today now that the car runs without dying instantly to see if any new are present(I had no code reader with me when plugs where replaced last night)

XR4Tim

Two bad coils will make it difficult to start, and will cause rough running, but not what I would call "surging". A bad MAF can cause a hard start and surging. You may want to see if it surges with the MAF unplugged.

Macster

Stalling is not a common misfire symptom/side effect.

Oh, before I forget if you use fuel rail pressure test point you need to replace the cap/seal. These are not meant to be reused.

Here's a caution from the factory Turbo manual (but IIRC the same caution is in my Boxster's manual too):

Use the brass closure cap on the test connection of the fuel pressure line only once as the sealing ring cannot be replaced. To avoid possible leaks, the cap must be replaced after removal!

Anyhow stalling...

Did you check for any pending codes? If you read any post them.

What did the coils look like? At 87K miles if the coils looked bad you probably should have just replaced them. While I don't think the coils are to blame for the stalling they should be replaced on general principles if they are bad.

On a related note, how did the plugs look? Any signs of long term combustion differences between cylinders?

Before you go any further my advice would be to carefully remove the oil filter housing and pour its contents into a *clean* drain pan. Examine this oil and the filter element for any metal debris, or any debris of any significance. If you find some you're done with what you can do at home.

Anyhow, assuming the oil/filter look ok, I've come across a bad MAF that caused misfires and on just one bank too.

A shade tree mechanic's test is to disconnect the MAF at the wiring harness, clear the error codes even if there aren't any as this resets DME adaptation back to its defaults so the DME starts out with no possibly real bad adaptations from a suspected bad MAF.

Then drive the car. Drive it normally. You need to drive it longer than around the block. Ideally you would want follow a drive cycle style of drive to give the DME a chance to complete all readiness monitor tests. Some may not complete with the MAF disconnected.

Caution! Even if just misfiring reappears, the stalling reappears, then the MAF is not the cause. No need to press on. My advise then would be to get the car towed to a qualified shop for a professional's attention.

If the engine's behavior is much better, essentially without any real drama, then reconnect the MAF and clear the codes again and drive the car again. If the symptoms come back...the MAF has to be suspect #1.

BTW, at idle can you unscrew and remove the oil filler tube cap?

If you carefully remove the throttle body do you find oil on its inner surfaces? Oil at the connection where the hose from the AOS connects?

If so the AOS may be failing and this can cause the engine to run poorly and in more advances stages of failure, stall.

At 87K miles, if the AOS is original, that is very close to the miles at which my 02 Boxster's original AOS failed.

Macster

Surging, a varying ( up and down ) idle speed, is a symptom my 02 Boxster exhibited when what proved to be the AOS was going bad.

Dan951Man

I agree, if it runs try pulling the oil cap off- was it super vacuumed down? If so, a sudden failing AOS can cause these symptoms...
It would have to be pretty bad though, and at the point of causing misfires- it would be ingesting enough oil that you would see some smoke out the tailpipe upon startup after sitting for a couple hours (oil fouls plugs).

3_Angels

If you see Bank 2 misfires on your codes again, you might swap Bank 1 coil packs over to Bank 2. If the codes come back the same again, Landrovered probably should not be ignored. Aggressive trouble shooting can become expensive. Simple, safe trouble shooting first.

gfl

All good thoughts. But the stalling and refusing to run, along with mysterious misfires makes me think "Crank Position Sensor"

Grant