[LivingDust]

My car is a ’92 Cab with no engine mods except for a B&B exhaust. Lately I have been having a loss of power from idle to around 3000 RPM. When taking off from a stop, the only way I can get a good start is to keep the revs close to 3000, and feather the clutch in.



If I let the clutch out quickly the revs drop to around 1500, then it is painfully slow to get to 3000 or so where the change is dramatic. From 3000 up there is a steady increase in power up to redline. (I am not sure I am feeling the Variocam kick in like I used to either.)



I have been reading Dave’s info on the Variocam, and it seems the jury is still out as to what signals to the Variocam solenoid and whether the idle is the advanced (high-rpm power) mode or the retarded (low-rpm torque mode). But if it is not the Variocam, what else might I check?



And where is the Variocam electrical plug so I can disconnect it and see what happens.

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[Cloud9...68]

Scott,



Your problem sounds somewhat similar to mine (a hesitation/stumble when I try to accelerate under load). I also have the symptom you're describing when I pull away from rest; I have to give it a lot of gas to keep it from stumbling. Is your problem worse when cold, or after driving it around for awhile? Mine gets significantly worse when hot, and really became noticeable as the weather began heating up here in Austin. I've found arcing along the plug wires when watching the engine run in the dark, and my neighbor had a similar problem at the connection of the coil wire to the coil on his 911, so you may want to give that a try. I've tested about 18 things (see my first post under my thread about my hesitation problem, though I've added a few items to this list since then). This might give you a general list of things to look out.



Looking forward to meeting you on the 14th, where we can compare notes on our cars' problems. Plus I'm dying to hear your BB exhaust!



Andy

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[Bob Kovacs]

When I first got my 1993 968 in 1999, launches in first gear were VERY touchy. I had to carefully feather the throttle and clutch to prevent stalling, and I had been driving only standard transmission cars for decades. I had never driven a car that was so touchy, but I thought this was a trait of the 968.



At the same time, I had a problem with random stalling where the car would simply die and not restart for about two minutes. After a lot of head scratching and talking to various experts, I replaced the DME relay and the stalling problem has not happened since (about four years ago). I didn't notice it at the time so I'm not sure that the two symptoms are related, but eventually I realized that the car was no longer ultra-touchy about first-gear launches. In fact, the car pulls fine from a dead start in first gear now and there is no need to delicately feather the clutch and trottle.



I had done the usual stuff to eliminate the random stalling, such as a distributor cap, rotor, plug wires and cleaning every connection I could find. None of these cured the stalling. I wasn't even willing to pronounce the problem cured until a year passed without stalling. The DME relay swap was the last thing I did to fix this problem and it must have done the trick.



I wish I could say for sure that it corrected the touchy clutch/throttle but I'm just not sure. However, at some point my car went from ultra-touchy to normal and the only thing I can think of is a DME relay.



That's my story and I'm stickin' to it!



--Bob

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[LivingDust]

Thanks for your experience Bob. Do you know if there is a way to do diagnostics on the DME relay? Or is it one of those "replace it and see what happens" things?



Andy, my problem is different than yours in that the hotter my engine the better it drives! This car has always been a bit flaky during the warm-up cycle. But I haven't been too concerned with that, because here in Austin, warm-up doesn't take long. But as it is warming up, there is a lot of inconsistency.



This has had me wondering about some of my sensors, and how to test them. It has also made me wonder why everyone else wants cool air intake, when my car runs better hot.



I have not tried watching it run at night yet. Maybe I can do that tonight....

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[Cloud9...68]

Scott,



I agree with Bob that you should go ahead and replace the DME relay. It's one of those known "weak spots" in the 968 that people commonly recommend replacing, even if your car isn't exhibiting any symptoms. Unfortunately, replacing mine didn't help my symptoms. They cost about $20 from Sunset Imports. Just make sure you order the one whose part number starts with "993" rather than "944", as they have been upgraded. Good luck!



Andy

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[LivingDust]

So I just want to replace the DME Relay, not the DME, correct?

I went to the Sunset Imports web site http://www.sunsetimports.com/

And looked through the parts catalog, but I don't find the DME or DME Relay listed. Is this something I have call and ask for?



BTW I tried or local Porsche dealer. At first they quoted me a price of over $1000. Then I said, "I think you are looking at the wrong part, I wan the DME Relay." He seemed confused and had to call me back. He called me back, told me they didn't have one, and that it would be $32....

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[mitch968]

I would never get a part at a local dealer, unless I needed it immediately and they had it in stock. Paragon, Sunset and Pelicanparts are usually the best places to deal with in my experience. Here's the part you're looking for...

http://www.paragon-products.com/product_p/....615.227.00.htm

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[BruceWard]

This is what you want







$22 from Paragon http://www.paragon-products.com/product_p/....615.227.00.htm



Part number 993.615.227.00



The one in your 968 probably starts with 944..... The 993 version is newer and is the one you want.

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[Bob Kovacs]

Glad to see that others pointed out the right part for you, Dust. I recall paying $25 for mine at a Porsche dealer. I think mine is the 944 part, so I may get a new one of the 993 parts, just to have the latest version. It was no fun having the car stall on me, especially when I was showing it off to my friends and family.



I'm not aware of a diagnostic test but at $22, it's worth trying.



--Bob

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[BruceWard]

I'm not aware of a diagnostic test but at $22, it's worth trying.

If it has not broken it will. I replaced mine with the 993 part and am keeping the original as a spare.

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[LivingDust]

Thanks for the assistance. A new DME Relay is on its way to me from Paragon. I will also try and watch the engine in the dark tonight.

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[LivingDust]

I got the new DME today, and I think the acceleration is smoother. Certainly the engine performance during the warm-up cycle is better. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



Reading Dave's posts on the details of the variocam, I decided to try unplugging the power to the variocam and see how that effected my acceleration. Honestly it did not seem a lot different. <img src="/forum/images/smilies/968/unsure.gif" class="smilie" alt="" /> This makes me wonder how to go about diagnosing the variocam system. Is the Motronic system turning it on? If it is, is the solenoid doing it's job? Not sure how to tell this with amateur DIY tools.



One thing I did notice was that my A/C is making a huge difference in acceleration. I am wondering if it requiring more fanbelt power than it should. I mean I know it makes a difference, but I don't remember it make so much difference on my coupe.



Thought, the performance chips seem to make a lot of difference in the early torque figures under full load. Is it possible that is because it is turning the Variocam on sooner and perhaps more significantly? (This assumes that the variocam is variable and not just on or off.)

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[Greimann]

[quote name='LivingDust' date='Jul 12 2005, 09:55 PM']I got the new DME today, and I think the acceleration is smoother.  Certainly the engine performance during the warm-up cycle is better.  <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" /> 

[right][post="7306"]<{POST_SNAPBACK}>[/post][/right][/quote]



Odd that a relay had a perceived incremental improvement. Usually they work, or they don't.



One thought. How is your voltage when measured at the battery with a VOM? Low charging voltage will have detrimental effect on sensor signals to the computer, lower spark values and other maladies.



The AC may be a separate issue, like it is about to lockup <img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" /> Otherwise it may just be that the clutch is drawing that much more juice out of the system.

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[LivingDust]

I think I have solved my acceleration problem. I read about the adjusting the throttle cable, and checked mine. Sure enough, I was not getting full throttle.



I didn't have any slack at idle, so all I had to do was adjust the stop below the gas pedal. WOW! Now I am getting a real snarl out of the B&B Exhaust when floor it! This engine has been holding out on me.



Since the Variocam kicking in is based partly on engine load, which probably takes into account throttle position, I am thinking that the reason I did not feel it kick into Torque mode sooner is that the sensors did not think I was under full acceleration?



Anyway, it was very hard for me to go to work instead of playing hooky to go driving. <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



Thanks to everyone who responded with help!



Scott

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