Stalled...Erp

[threpwood]

Hi all,

I had an incident today with my boxs, so I'm wondering if you guys can help me with your usual expert advice.

My boxster stalled for the first time during a drive today (drove about 200km today before this incident). I could push gas pedal just fine, and the rev indicator worked fine as well, but the car did not respond/accelerate, so I had to pull it over. After pulling over, the engine did not shut down immediately, but shut down (with hiccups like it was running of air or gas) after idling for about 5-10 minutes.

Some more information:
1. The gas tank indicator indicated that the car still had about half the total gas and I filled up the gas just last week, so I'm 110% sure be that I was not running out of gas.
2. No check engine light came up before, during, or after the incident.
3. I could restart the car, shifted to D (it's a Tiptro), then slowly accelerated (I tried it on the feeder road), but I could feel the car started to stall when it tried to accelerate to higher speed (like stalling when it reached around 15 mph). It felt like the engine did not have enough power to move the car.
4. When the engine shut off, I could re-started it just fine, but the engine would stall (like hiccups before it shut off) again after idling in about 5-10 minutes. It happened everytime after the incident (I tried this a few times).
5. Electrical system worked just fine.
6. I could rev the car up to 4K-5K just fine.

The boxs was towed until the dealership, but I will not heard from them until Monday since the porche mechanics are on holidays (drats). Any help is much appreciated.

[MNBoxster]

HI,

Best case - it's the MAF, worse case, it's IMS, though it could be any of a number of other things as well. Long Distance diagnosis is difficult at best. Good Luck!...

Happy Motoring!... Jim'99

[threpwood]

Thanks for the advice. I'll ask the Porsche mechanic to check the MAF first thing.

The boxster is so delicate...it has been 10 years and my ol' honda civic hasn't failed even once!

[threpwood]

Dealership called today and explained that the engine MISFIRED (apparantly they obtained the CEL code from the onboard compu). They also explained that they are puzzled because the CEL didn't come up on the dash.

They also said that they need more time to investigate and it may take 1-2 weeks

What is engine MISFIRING? and what is normally the cause?

Threpwood

[Rodger]

Misfiring occurs when the spark plug arcs and tries to ignite the compressed air/fuel mixture in each cylinder, but for some reason, can't. It could be due to oil fouling, insufficient air or fuel, spark plug erosion, etc.

My Boxster had been in the shop twice before I owned it because of similar misfire codes. Both times, they "smoke checked" the exhaust (to make sure it wasn't burning excessive oil) and then simply replaced the plugs. The problem cleared up, but about 6000 miles later it returned. Again, it went into the dealer and they simply replaced the plugs again. I've since gone nearly 15,000 miles without incident.

I suspect the previous owner didn't wring the engine out as much as I did.

You may have a failing air/oil seperator, which can dump excessive oil into the engine. Did you notice any smoke when it wouldn't accelerate?

[threpwood]

Thanks for the information. I didn't notice any smoke when it wouldn't accelerate.

Can fuel injector cleaner (such as techron etc) cause the engine to misfire?

[threpwood]

The mechanic said that there is a high probability that the 4th cylinder failed They have checked everything including spark plug, etc and didn't find any problems.

Can anybody explain why the 4th cylinder failed and if it is fixable (I mean do I need to start looking for new engine?)

Does this statement below apply for boxster (taken from wikipedia):

During use, the cylinder is subject to wear from the rubbing action of the piston rings and piston skirt. This is minimized by the thin oil film which coats the cylinder walls, but eventually the cylinder becomes worn and slightly oval in shape, usually necessitating a rebore to an oversize diameter and the fitting of new, oversize pistons. The cylinder does not wear above the highest point reached by the top compression ring of the piston, which can result in a detectable ridge.

If an engine is only operated at low rpm for its early life (e.g. in a gently driven automobile) then abruptly used in the higher rpm range (e.g. by a new owner), the slight stretching of the connecting rods at high speed can enable the top compression ring to contact the wear ridge, breaking the ring. For this reason it is important that all engines, once initially run-in, are occasionally "exercised" through their full speed range to develop a tapered wear profile rather than a sharp ridge.

[MNBoxster]

Hi,

That's a pretty drastic diagnosis. What code did they receive - P0300, P0304 or P1316? These are the only relevant codes for EOBD software which your car has, though there a misfire can be consequential of other causes as well.

Schnell describes only one way for a misfire to occur. There are many other ways this can happen such as Fuel Delivery, O² Sensor and/or MAF issues - causing the Engine to run Rich or Lean, Electrical Issues such as bad CoilPak, Wiring, etc., even water entering the engine can cause it - did you wash the car or drive in rain recently?

I'd be very surprised if their diagnosis holds up. Just because they're Porsche Mechanics doesn't make them immune to mistakes. For a Wear Ridge to develop in the cylinder, such as you describe, you'd have to have a fairly high mileage engine. The Locasil lined cylinders are not prone to this type of wear.

As I said, long distance diagnosis is difficult at best. But, your mechanic's diagnosis would be very rare and unusual. So much so, that my initial inclination is to distrust it without further information, such as the actual codes they are getting. Of course, I may be wrong and they could be right we'll have to wait and see. Good Luck!...

Happy Motoring!... Jim'99