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Stumble at 2K
#1

Finally got around to looking into this.



1) Did the blink test. Oddly, using unknown's procedure I was not able to get the check engine light to ever flash with the accelerator depressed. Engine off, ignition on, fully depress - no flashing light. The light does come on when you turn the key to the second position (just before turning the engine over).



2) Did the dark garage test. Both after a 30 minute drive with the engine fully warmed and again this am when cold. Other than a little CO poisoning no issues - no sparks at idle or when advancing the throttle. I heard a nice little gulp of air when throttling up since the air box mod - but that is neither here nor there.



Having the car for a few months now and having driven it about 2KI am more familiar with the problem so I will restate here.



a) Idle is fine. Starts and runs smooth and steady at about 1K RPM.

<img src="/forum/images/smilies/968/cool.gif" class="smilie" alt="" /> Runs fine during strong acceleration through all gears

c) When running at about 2000 RPM at a light, and engaging the clutch in first, it bogs a bit, looses RPM and will stall if not revved.

d) When downshifting to second when approaching a light or stop, will do the same thing at about 2000 RPM.

e) Also, and this one is concerning, when coasting at 20 - 25 MPH, trans in 2nd, and engaging clutch, engine (I think) shudders. Does this very sporadically, but if I get the conditions right (slight downhill in neighborhood going slowly in 2nd and letting the clutch out at 20-25 MPH) I'll get the shudder - both when cold and warm.



Thoughts?
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#2

bring it up and i'll take a look at it?
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#3

Hi rxter, gee, it sounded fine to me!



Actually, it reminded me of one thing that I can't specifically trace to the symptoms above, but may be worth a try. In these types of circumstances I often try a bottle of injector cleaner. For about $5-$10, depending on brand, I often get the feeling it just cleans up some of the erratic behavior of the engine, makes things feel a little smoother. It may be worth a shot. If I remember to do it, I'll just do this about every 6 months or so. They are sold under various names, injector cleaner, fuel system cleaner, I think I recall that the Lucas products were once recommended as the best, but if I recall correctly they may be the most expensive one.



But I was also thinking of the Variocam chain. The valve timing is adjusted for a bit more intake/exhaust overlap starting at 1,500 RPM. I wonder if this could be related to the symptoms, or if worn pads on the actuator could actually cause these symptoms. I don't know specifically, but since the problem is RPM specific, it reminded me of this possibility. There are various threads here and also a document .PDF file with instructions on how to check it (have to pull the cam cover). Perhaps a long shot, but maybe it will suggest to another writer if this could be a cause of the problem. And I think the recommendation is to check the tensioner pads periodically anyway.



Roland
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#4

Typically DME has to experience an out-of-parameter issue for several minutes before it'll log it as a trouble code - so you may not find anything recorded.

The 2 symptoms listed "bog" and "shudder" can be two different issues. Bogging is typically a air/fuel mix issue; either un-metered vacuum or a fuel delivery problem.

A shudder may be a driveline issue, clutch engagement perhaps. Please let us know when this conundrum is solved...
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#5

[quote name='S_Cal968' post='55779' date='Jul 3 2008, 09:38 AM']The 2 symptoms listed "bog" and "shudder" can be two different issues. Bogging is typically a air/fuel mix issue; either un-metered vacuum or a fuel delivery problem.

A shudder may be a driveline issue, clutch engagement perhaps. Please let us know when this conundrum is solved...[/quote]



Agree that they are likely unrelated. Clutch hydraulics and hardware was replaced at 82K - car has 91K now so I was assuming that the clutch was not the offending bit. Would a bad motor mount cause problems only in this isolated situation or would you expect to see vibration at other speeds/rpm as well?



Thanks Bob I might just do that - long weekend and everything <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" /> You're probably low on NewCastle anyway...



Roland the cam rubber bits were just replaced, and the chain and pads were checked off as good to go by my PPI-baseline mech in AZ.
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#6

i'm around pretty much goofing off saturday and sunday - ring me up
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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