911vet

Thoughts on what this might be?

I suddenly loose power for a few seconds. It happens very sporadically and mostly when I'm in 4th or 5th at about 3000-4000 rpm.

Everything is fine, then power cuts out for a few seconds. My tach doesn't change during the event.

The first time it happened was a few seconds after I misshifted into 2nd gear going 50mph. I don't think I buried my tach into the red, but it was a pretty serious "oh sh**" moment! I got it into 3rd and was accelerating when I lost power. A minute later in 4th gear it did it again. I shut the car off and when I restarted and got into 5th gear, it did it again.

Since then it's happened a few more times.

What could I have done at that misshift to cause a sporadic problem? Or do you think it's a coincidence?

I can't figure out if it's a fuel or fire problem. But I'm thinking I should replace my fuel filter and DME and fuel pump relays. Would an 02 sensor do this?

Thanks.
Shannon
87 Carrera Cabriolet
115K miles

LaughaC

My first guess is that a simple connection worked a little loose, and the gap in a circuit opens with acceleration G forces.

Might take a while to find but I wouldn't spend much $ chasing it. Did you try tightening all the ignition components?

I once had an internal distributor problem with the same symptom. After installing a new distrubutor I saw that a $0.15 wire would have been the ticket.

Daniel Dudley

Does that have a mass air flow meter [hot wire] or is it an air flow meter with a flap ? Worn spot on the potentiometer or bad connection to the meter can cause stumbles at certain rpms, esp. the rpms that are seen most frequently while cruising.

sus911

check the injector harness plugs are seated properly in the sockets just in front of the firewall.
I would say with that instant loss of power it is most likely electrical/electronic rather than fuel/pressure related.
A similar condition happenned to me, only on hard LH corners.
good luck,
Phil

911vet

Hmmm... I don't know. I've only had the car a few weeks. I'll check into it. Thanks for the suggestion.

911vet

That's good to hear. I was afraid I might have damaged something. But it seems that so far the consensus is electrical.

Peter Zimmermann

911vet: That is a classic symptom for a failing cylinder head temp sensor. Of course, other items can cause similar problems, but have your head temp sensor replaced ASAP.

911vet

That is the beauty of this forum. Because I would have never thought of a cylinder head temperature sensor.

Is there a way to determine if it's the problem before I spend the $75 to replace it? Or is it an item I should just replace as a precaution on a vehicle w/ 115K miles?

Your post leads me to believe there is some danger if I don't replace it and it's faulty. Is that right?

Thanks,

Shannon
87 Carrera Cabriolet Carmine Red
(and, btw, your book is one of the reasons I bought the car I did -- thank you!)

jester911

With the miles and age on your car it is better to go ahead and replace it. If it turns out not the be CHT view it as preventive maintenance for the future.

gerry100

Mine would be pulling at 4-5 K rpms and then cut out for a second and then come back normally. sporadic cut out at other RPMs.

DME relay seemed to solve the problem. Although I changed the CHT snesor around the same time.

If you have no record of these being replaced the DME is about $50 and 5 minutes labor, I belive the CHTS about $50 and a PITA ( how much of one depending on your experince and facilities). There is a post of the instructins somewhere,

If your DME is OK, then you'll have a spare - ,lots of us carry them as a good luck charm in the glovebox

911vet

I had planned to get a spare DME relay anyways. I think I'll take the advice here and replace it and carry the old one as my good luck charm. I'll get the CHT sensor too.

der Mond

I agree with Jester and Pete, it makes sense to put the new 2-wire CHT sensor in anyways, because if it hasn't yet failed, it probably will. My '87 already had two contacts in the CHT sensor connector socket located on the left fuel injection manifold, as though Porsche had it ready for the two-wire CHT sensor already. The OEM sensor uninstall requires a 13 mm deep socket and the install of the new one requires a 14 mm deep socket with a groove cut through one side to let you tighten it with the wires in place. Or a long pair of needle-nose pliers if you read the Pelican Parts tech article on their site. If you DIY I can mail you the 14 mm socket I cut with a Dremel tool if you like. You pay the postage and pass it on to the next guy who needs it.

der Mond

Also, I'd recommend checking the Bentley manual ground point diagram and undo, clean and refasten all the ground points you can reach, in addition to checking and spraying cleaner on all the DME system connectors you can reach in the engine compartment. And replace your DME once a year and let the guys call you OCD!

der Mond

Whoops, I mean the DME Relay. I'll shut up now.

911vet

The new CHT sensor is on its way from Pelican. Wow - if you are willing to loan me the 14mm socket, that would be great. I would gladly send it back to you or as you suggested... make it available to the next person who needs it. That's a great idea.

I'll send you a p.m. and we can make arrangements.

Hopefully my 87 is set up for the 2-wire sensor as well. I'll find out soon.

Thanks for all the help.
Shannon