I've got a '98 Boxster that is acting up. It had been running fine but lately when it gets to 180 degrees it just stalls out. Almost like a vapor lock from my first 914. I have replaced the fuel filter, Crank Position Sensor and cleaned the MAF but it is still doing the same thing. It's as if it hits a kill switch at exactly 180 degrees.
Any suggestions would be apprecited.

Any codes?

The CEL is off because I disconnected the battery while replacing the crank position sensor. I don't have a code reader unfortunately.
I have a buddy at Autozone that may try to bring his reader by the house to check it out. I'll post the results if he comes by.

I wish you were a little closer Woody. There aren't any good shops in Houston any more.

I'd just throw some Webers on it. You may want to pull the throttle body and take off the idle air control circuit. It may be plugged up with carbon. That will certainly cause issues similar to what you're seeing.

It looks like this, the black thingy.


Click to view attachment

post that on the www.986forum.com, or pelican - I have a 2001 S 986, and usually have answers to my questions fairly fast over there. i have not seen what you describe but 180 is when the thermostat kicks on , right? maybe something to do with that? - buy a code reader for $100, see if anyting pops up.

Phil

Thanks guys. I tried 986 Forum. It's like crickets over there.
I'll pull the throttle body tonight when I get home. And clean the air control circuit.

Is the fan coming on at all when this happens? Not sure what temp the fan(s) are programmed to come on for a Boxster...

A new thermostat would be a decent place to start.

Never seen a faulty thermostat cause a Boxster to stall.

Me neither. Typically it would just run hot.
But I appreciate the input.

But, I have seen a faulty thermostat cause an Accord to stall/no restart. I believe it was a fail-safe mechanism to keep from overheating or continuing to run an overheated car. The temps on the dash said everything was okay, but thermostat was definitely bad and the computer was sensing either pressure in the system or a temperature differential before and after the thermostat, and shutting the car down. Not sure if Boxsters have a similar system.

Do you know when it was changed last? It's at least a cheap place to start if you don't know it's condition.

You can get a Bluetooth OBDII scanner on Ebay cheap. Then buy an app like Torque which will allow you to scan the codes. Or rent/borrow the scanner from Autozone. Codes will at least point you in the right direction.

I did find this however:

http://forums.pelicanparts.com/boxster-cay...-when-warm.html

It might be coincidence that it happens at 180 degrees, but a failing fuel pump can act up more once it's gotten hot. However, I thought most of the time they just died.

Good Find, and I know it has nothing to do with it, but my old 84.5 Scirocco used to have a stalling issue when hot and it turned out to be clogging of the transfer pump in the tank. Worked great when cold, then crappy as soon as it got to operating temp. Obviously, it is a different system but all engines need fuel.

Still waiting to scan but I cleaned the throttle body last night. It was pretty gnarly so I'm glad I did it.
I ran the car up to 180 degrees and it stalled out. I noticed that the fuel pump relay was getting hot. I'll try to hunt one down today and replace it tonight. Also, I noticed the electric fans were not coming on. Does anybody know what temp these engage?
Thanks again.

Did you take off the IAC servo on the side of the throttle body? The fans should come on between 180 -190 but should also run all the time if you have the AC on. Do you have a fuel pressure guage?

Yeah.. I was going to suggest that. Have you been doing this test with the A/C on? If it's the fans tripping a relay or for whatever reason causing the car to stall, the A/C should automatically cause it as the fans on almost all cars come on when the A/C is on.

As Woody said, a fuel pressure gauge would help as well. You can loan one from Autozone - their kit is very professional and helped me diagnose a dying fuel pump on my Mustang.

I do have a fuel pressure gauge that a buddy let me borrow but I was told that removing the caps to gain access to the fuel system would require me replacing all of them.
The A/C was on last night but no fans. I didn't check the fuse for the fans as it was dark by the time I discovered they weren't coming on.

I did take the servo off while I was clean the throttle body. I reinstalled it afterwards. The contacts looked to be in good shape.

I've never worked on a Boxster, so I'm not sure what caps you're referring to, but there should be a schrader valve/access port of some sort on the fuel rails to test for pressure. As soon as the key is turned to 'run" the system should pressurize and stay that way. As the car is started, the pressure will fluctuate a little based on the engine's desire, but it should still hold pressure, I would imagine 35 psi +.

However, based on what you said about the fans, it sounds sounds like that's the next step then, or area to look into. Process of elimination. Check the relays/fuses first. If they are blown, replacing them might solve the problem, but it usually indicates that there is another issue to look into. Cars with modern wiring don't go blowing fuses for no reason, IMHO.

Thanks George. Just being able to bounce this stuff off of you guys and get feedback is comforting.

No problem. I feel the same way. I'm in no way an expert and certainly not a Porsche authorized mechanic, but I've learned a lot about troubleshooting over the past few years as I work on more and more types of cars. The one thing that they all have in common is that they're getting more and more complicated


Edit:
I'm adding this link for my own reference (so I don't forget where I got it), once we know what the status of the relays/fuses are.

http://forums.pelicanparts.com/boxster-cay...ot-working.html

The fuel test port has a brass cap that screws on. It is supposed to be replaced upon removal but you should be okay reusing it. As for the fans, they have resistors that are failure prone.

Woody, good call on the resistors. The Pelican article I posted also mentions the DME relay as a potential source for problems. I know, from what T.C. tells me, that those things go bad all the time on the later AC 911s. Surprised they're still using them in Boxsters!

Any update stuttgart? I love troubleshooting over the web... so much easier than climbing underneath the car

Yesterday was the wife's b-day so no progress.
I'm hoping to spend some time on it tomorrow.
I'll post updates and more questions ASAP.
Thanks again for all the input.
Chad

Ah, that was the other thing I was wondering. Nice to know your name Chad. Good luck!

Any updates?

Fixed.

George, Chad used to be part of the Tampa Brat Pack!

There's Rennsport out in Sealy and European Cars Limited near I-10 inside the loop - I've used both. Rennsport is very highly recommended by everybody (Mike Callas - he does a lot of the aircooled as well) and didn't hear any bad things about ECL.

Too bad he's not still around. Would be nice to "test drive" the car to see if I, you know, could replicate the problem

The Tampa Brat Pack. Love it.