2006 Boxster S 987.1 - intermittent engine dies momentarily then comes back immediately

[Merv the swerve]

Engine will die briefly during acceleration off a corner or stoplight, then immediately come back when I release throttle and re-apply. No error codes. Usually during warming up, in 1st or 2nd gears. Sometimes when hot.

 

I thought it was fuel pump maybe, but it seems dependent on throttle position. Leave throttle and it continues to decelerate, push throttle down and the same, release and re-apply and its back immediately and full power.

 

So then I thought electrical, maybe DME relay, maybe another relay, but where to start on that. It doesn't do it when my local Porsche expert drives (of course!)

 

It could be dangerous if someone is up my tail in traffic, and I want to track the car so dont want to lose throttle mid-corner!

[Loren]

Perhaps a pending fault since it is intermittent.

Don't forget about the crankshaft position sensor.

[Merv the swerve]

Hi Loren,

 

A pleasure to connect with you. I've read your responses on this forum many times. Thanks for your efforts for Boxster owners. Are you the same Loren as used to run monster 911's in POC 15 years ago?

 

I never thought about crank position sensor. I thought that would only affect startup, which I never have an issue with. I first got this issue 2 years ago, but it only occurred once or twice a month so I ignored it. Now it occurs multiple times a day on bad days; never on a good day. Also on bad days, the engine generally feels very slightly lumpy, which gives a clue it might happen. I think I might go ahead and replace the crank position sensor anyway - it's a cheaper experiment than replacing the fuel pump.

 

I did swap the fuel pump relay with the heated rear window relay (same relay) just to see if that might fix it, and it didn't.

 

I will report back once I've changed the sensor. Thanks again.

[Loren]

28 minutes ago, Merv the swerve said:

Hi Loren,

 

A pleasure to connect with you. I've read your responses on this forum many times. Thanks for your efforts for Boxster owners. Are you the same Loren as used to run monster 911's in POC 15 years ago?

 

 

Sorry, no. The only thing I did with POC was the annual Make a Wish ride alongs at Laguna Seca.

[Merv the swerve]

Hi Loren,

 

Unfortunately replacing the crank position sensor did not work. Problem still occurs on occasion (maybe once or twice per outing).

 

So now I'm thinking it has to be electrical. Power goes away immediately, and comes back immediately, within a second or two. I just don't see that as a fuel pressure characteristic. I haven't researched it, but somewhere there has to be a throttle pedal position transducer, feeding pedal position information to the DME. I wonder if that is intermittent or a connection is intermittent. That would explain why it suddenly goes, and then comes back as soon as I release the pedal and reapply. Maybe you might know where I can find that sensor (I'm guessing around the pedal-box, but I haven't looked)? Should also note that the engine never dies during these events, if they lasted long enough I think it would just go to idle. Also tacho does not glitch, which might suggest DME failure..

 

I did Make a Wish with POC at Laguna in 2002. Helped raise some money in the raffle, but the kids weren't so keen on my boring 944S vs. more exotic machinery!

[JFP in PA]

I wouldn't discount fuel pressure/delivery rate until you have tested it.  You can also run the car with a laptop in it using the Durametric software and have it record engine parameters to see what suddenly changes, but that will not help you with the fuel system, for that you need a test gauge as the DME does not record fuel pressure or delivery rates.

[Merv the swerve]

JFP, thanks for your suggestion. I don't have access to a Durametric cable and software, but maybe my local Porsche shop does. I do have an ICarSoft, which can record, so I might experiment with that. Also I will rig up a pressure gauge on the fuel rail and try to route it into the cockpit and try to monitor  it. Not terribly comfortable with that, but it seems that is where I'm at.

 

It only does it once or twice a week, and then only momentarily, so since it is so obscure maybe I just live with it until it gets worse or a code appears. That aside, the car is quite healthy.