Stalling at 180 degrees

We have a 1998 Boxster that has 170K miles on it. Once the car reaches 180 degrees it dies. It will not refire. It acts like it's starving for fuel. I can hear the fuel pump running. In search of the issue I have replaced the Crank Position Sensor and Fuel filter. Bot looked like they were original so it's not really a waste of time in my opinion. But I am still having this issue. The car runs great and then as soon as the needle hits the 180 mark it just stalls out.
Any suggestions would be appreciated.

However, this is not a failure mode I'm that familiar with. When my 02 Boxster's fuel pump decided to quit it just quit.

Which sort of leads me to suspect the fuel pump relay (or fuse) is acting up.

To eliminate the relay in my car's case my tech loaned me a fuel pump bypass relay (test relay which you can buy from the dealer parts department for IIRC under $20 but it is kind of an expensive item relatively speaking unless you repair cars for a living).

Without borrowing or buying anything you can try this: Start the engine and let it idle. As it idles check the fuel pump relay under the dash to see if it gets hot, too hot, as the engine idles. Be careful in case it gets burning hot -- unlikely but still be careful -- or there are other hot relays around.

You can remove the fuse and check it or just replace it. You could just replace the relay too --- they're not that expensive IIRC -- but it would be nice to know the relay is the cause of the stalling.

First - please confirm - do you hear the pump run?

Fuel pumps tend to run reliably and then begin to make more noise. Then they get intermittent, then they are gone. At least in Audis and BMWs. I doubt the pump is any different.

Now, in general, when you turn the key "on" (to run, nto crank), the fuel pump will activate. After it dies at 180 degrees, if you try to restart it, can you turn the key to "run" and hear the p[ump activate? If you do, will it then start? This can help you isolate the fuel pump.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

then the fuel pump, fuse, relay is probably not the problem.

Then I, like Pedro, like the MAF, though the engine stalling is not a common failure mode of the MAF. But the effort to almost certainly eliminate the MAF is relatively painless.

A temp sensor suddenly delivering a bad reading does not generally kill the engine. In at least one failure mode the DME uses a fall back temperature that should let the engine continue to run albeit it the engine might exhibit running issues. But of course until the cause is found and fixed who knows?

The OP certainly has enough ideas to sort through. Viewing the engine operating telemetry before, at, and even a time after the engine manifests this stalling symptom might turn up something. A sudden change in a temp sensor (IAT, or CLT) reading, a big change in short term fuel trims, a big change in ignition timing, possibly even the switching of the secondary air injection state any one could help diagnose the root cause.

..hear it. If it then does not start you know you have a working fuel pump and a btoken motor. Cross one off list.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

It's probably gas starvation due to one of several things:
1.- The Mass Airflow Sensor is on it's way out. Disconnect it altogether and test. Based on the MAF's signal the ECU will cut off gas.
2.- The fuel pump is overheating. If it is, replace. Problem is that it's submerged in the gas tank. Seek professional help.
3.- Engine temperature sensor is haywire and sending the ECU the wrong signal and the ECU shuts off gas.
It would be best to diagnose with a PST-II or a PIWIS, since the tech can then see any components that are or are not switching due to temp.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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It sounds like some electrical sensor or module is failing under heat.

When it dies, do you have a way to test for spark? Fuel? Its kinda hard on these cars with buried spark plugs, i know, i know.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com