Really need some help!!!
 

I just had a very worrysome thing happen while driving my '87 911.

I adjusted the valves and changed the oil last week. I noticed the car smoking "more" than usual on the 80 mile drive home. The idle was also a bit stumbly. It would drop to 600rpm, stumble around and then hike back to about 850rpm (my idle has been a bit rough for the past 6 months... this was just more rough than normal).
I figured that my first attempt at valve adjustment was not up to par and I'd have to recheck everything ASAP.
The next day, while driving in traffic, the car seemed to lose power (under mild acceleration). It lasted about 1 second and then returned to normal. Sort of a hiccup. The car didn't die, it just wouldn't respond to more gas... like it was bogged down.

Today I decided to recheck the valves on the passenger side (and the headstuds). A couple valves appeared loose, so I tightened them up. Then I went for a quick drive to see if I noticed any change in valve noise.

About 10 minutes into the drive (oil temp at 160+-... not totally warmed up), I pulled out onto a 55mph road and gave it a quick 5-60mph burst (switched gears before 5k rpm). It felt smooth and fast. I was just congratulating myself when the motor bogged down. I gave it some gas, then some more gas... nothing. It would not respond to throttle input.
Fortunately I was heading downhill, so I pushed in the clutch and started to coast. I noticed the RPMs would oscilate from 200-2000rpm, as though the computer was feeding fuel to the motor to keep it from dying. Up, down, up , down. I blipped the throttle but nothing happened.
I released the clutch and tried to give it a little gas, but it just bogged again. The motor would not respond to throttle input.
With the clutch in I coasted down the hill. Watching the tach bob up and down like someone else were tapping my throttle. I pulled into a parking lot ((high "G" right hander), and coasted to a stop with the clutch in.
I sat there shaking for a minute... then noticed the idle had retuned to normal. I gave the throttle a blip, and the motor responded. I pulled out of the lot, and headed home. The "hiccup" did not return on the 2 mile drive home.

Does this sound familiar to anyone? What could cause this.. DME relay, Head Temp sensor (I have the original 1 wire), TPS??? The car runs very well, except for this.

Please help me sort this out before Winter sets in. I'd like to drive a bit more before the long, cold, sleep.

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Dan Tolley
1987 911 Coupe
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294

Checked your temperature sensor? If it dies, the car goes to choke mode...

Relax. I don't have your answer but you will certainly get some ideas her for things to check out. Your fuel/air system is very different from mine, and my suspicion is the problem is in this area.

Nevertheless, there could not be a better time for a general maintenance and tuneup. New cap and rotor, timing, mixture, fuel and air filters, stuff like that. I like to just make sure all the basic stuff is working well before I start suspecting expensive parts.

Your valve job had nothing to do with this problem. Really poorly adjusted valves won't behave like that. Instead they would make the car buck through parking lots.

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'83 SC

Dan,

Since it isn't a Targa, we can probably rule out water in the DME box, so the DME-relay comes up the most likely suspect! What? You mean you don't carry a spare in your glove box or tool kit?

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

I would first check the usual suspcects you metioned (DME relay, CHT sensor, TPS etc.), as I don't think the problem has anything to do with your recent valve job. Keep us posted.

-Eric

Dan,

I am assuming you changed the plugs and your dist cap/rotor are in good condition. When was the last time you changed your fuel filter? I agree it is very unlikely it has anything to do with your valves.

You may want to pop the boot off the top of the injection and see if the plate is free to move and not binding or sticking.

Good luck!

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93RSA

Actually I carry a spare DME relay. It's all wrapped in the factory packaging just waiting for... well you know.

I have replaced the cap, rotor, plugs, fuel filter, air filter, oil filter and had the injectors cleaned and flow tested within the past 4000 miles (that's about 1 year).

I only get gas from Texaco or Shell (if I can help it). It feels as though there's a fuel delivery problem, and my first thought was "somethings clogged", but the lack of throttle response combined with the mechanized up/down of the RPMs leads me to believe it's "computer/sensor" oriented. It's like I'm shut out of the loop!

Why the automated hunting idle?

Thanks more...

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Dan Tolley
1987 911 Coupe
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294

same symptoms as a head temp sensor and a DME relay. both cheap fixes and very common problems, moreso than anything else on a carrera.

So should I replace both just to be sure? Should I go w/ the 2 wire head temp sensor?

Thanks even more..
Dan

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Dan Tolley
1987 911 Coupe
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294

Dan,

Yep, kill both of those demons in one afternoon!

Incidentally ... the DME relay can mimic fuel starvation with amazing skill!

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

Let me second, third and fourth the motion on the DME relay. Your car acted just the way mine did when the relay croaked on mine. I have a Targa though, so I have an excuse for it dying.

There were points that first year of ownership where I carried a measuring cup in the back seat so I could literally bail out the water. I'm not kidding. http://www.pelicanparts.com/ultimate/smile.gif

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9 RIP
The Porsche Owners Gallery

Three will get you five that it's the Head Temp Sensor! It exactly mimics my failure on an 86 Targa. The two wire job fixed it immediately. As someone said earlier--it seems to go into full choke mode when that corroded metal to metal ground connection goes south.

George 86T

Is there ANY possibility you overfilled the oil? That there is oil gumming up the works?

Probably a long shot; you've already heard from the big dogs...

Jw

Update- I replaced the Head Temp. Sender and DME relay last week. The loss of throttle response and motor cut-out appear to be cured. Thanks for the help. It's nice to know that sometimes there's a simple cure (These days $100 and 1 hour is "simple").

On a side note: The new DME relay is made in Hungary... that's close to Germany phonetically, but I was pretty surprised.

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Dan Tolley
1987 911 Coupe
http://www.cheaterswayside.com/911/gallery.asp?sort=0&userid=294

Dan ... just be glad the relay didn't come from [i]China!

Glad to hear the $100, 1-hour fix did the trick! Told YA, LOL!!!

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler