[Kim]

Have a real problem that I need some help with.



The car, after two replacements of the valve cover gasket, is now skipping under load some of the time. seems to be missing on one cylinder periodically (ie about every half second under strong acceleration). It almost seems to be related to bumps in the road - it was fine this morning for 30 km and then I hit a bump and it was rough running under load thereafter. Not too bad just cruising along. Other than a dirty injector, broken plug wire(s), dirty MAF meter wire, what else might cause this? I am getting frustrated because the car has been in the shop more or less two months and winter is coming. The shop is very cooperative but 1) each time I bring it back without notice they already have scheduled other work so they often can't get to it immediately and 2) they haven't any 968 parts on hand to swap some out to see if it makes an improvement.



My driveway is covered in oil from all the leaks, I use my car everyday for work and it has been a real drag to be constantly trying to take cars out of the company fleet that staff with no vehicles need to use, and the car just won't work right. I have to get it fixed for good.



Any suggestions will be helpful. I don't really want to drag the convertible down to start a part-swap game but I might have to do that.

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[banditsc]

Pulling the plug wires off the plugs and bending them back is part of the valve cover gasket swap process. Perhaps one of the wires became damaged in this process?

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[flash]

i agree - i would look there first



a loose plug could do it too

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[unknown4u]

Or maybe one of the plugs is heavily oiled due the leaks. (Outside of the plug) At that time same symptomes.

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[S_Cal968]

I'd take the car back to the shop that installed the cover gasket and tell them what's happening. It sounds as if they damaged a sparkplug wire or disturbed another electrical connection. Plug wires are sometimes stubborn and it's easy to damage one during removal..

If it's a full service shop they can check the firing of each cylinder with an engine analyzer - this will pin-point the issue.

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[Kim]

New plugs changed nothing. We are now looking at the chip.

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[banditsc]

Check the wires also..

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[flash]

almost positive it's not the chip - it wouldn't create that kind of problem



if it's not the wires, i would be looking at the cap for cracks, loose contacts, etc

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[Duckman]

I'm dying to see what mystery is causing this.

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[Kim]

Well it was a plug wire. Don't know the details yet - just picked it up this morning and it runs perfectly. No oil leaks now. Wires are new and, I guess, when they were first installed they weren't pushed in enough so it was still skipping. So the master himself pushed them in better and, voila, problem solved.



Next projects are 1) trying to get the rattle in the sunroof stopped, 2) try to get the rear wing rebuilt so it doesn't rattle, and 3) replace the dash. I will keep everyone appraised of these developments. They are 2009 projects.



Thanks to all who provided advice. This has been exhausting and expensive. Pete, the chip and exhaust system are marvellous. Should have done that sooner.



Sucked a 997 turbo up the tail pipe this morning - he was parked at the time and it was easy. Dreams are great.



with any luck THIS THREAD IS CLOSED.

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[Kim]

So I am back to this again. This car really hasn't been right since I got it back but I have been looking for dumb excuses for the "skipping" such as too cold, rainy, chip didn't like Canada, etc. It has been all of things every time I have driven it and I have really only driven it a couple of times since i got it back on November 17. Remember that when I first got it back (it also leaked oil like a sieve) it skipped like crazy (no fault codes) and then the wires and plugs were replaced. After that it was better but still skipped a little bit before it warmed up. I posted a thread on here asking if cold weather could affect the Stage II RS Barn chip because I though maybe that was the problem.



Yesterday I went for a really "fun" run driving over back roads in 4th gear at about 5000 rpm. Seems to work generally OK but did still skip a little bit. Blamed it once again on "dampness" from the last time I drove it. So I picked it up today and was going to drive it for a few days since the weather was predicted to be OK. Today, however, it drives like crap. Skipping and driving like I am towing an anchor that keeps hitting the ground. I am getting a fault code 1-2-3-5 (first time for this, and the CEL keeps turning on and off repeatedly) and this suggests something "loose" in the variocam. What could this be? A wire? Obviously this was torn apart during the head gasket work. Will the car need to be torn apart again to find this? I am not sure how much more Porsche will do on this for free - I had to pay $600 bucks the last time for new wires and plugs to fix the skipping and that clearly was not the problem. I think that they want this car to go away now. This entire adventure, including the exhaust system and chip, is now past $9000 and, other than not leaking oil, I am no further ahead.



Any suggestions would be most helpful.

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[DaveN]

I don't see this suggested yet but as I live on the "Wet Coast" the first thing I thought of was moisture in the tank or in the fuel filter. Every time you take it for a romp you get a bit of H20 splash into the fuel line and eventually into the injectors?

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[Kim]

would that give a Variocam trouble code?

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[kwikt]

Check the Hall sender connections. Also check the Variocam wire connections on the valve cover. Maybe the connections aren't making good contact. You might even remove the crank speed sensor which is located behind the intake manifold and clean the tip and see if that helps.



Kevin

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[xrad]

Is the Bosch connector behind the distributor intact(little three wire connector)? Mine was cracked and caused skips due to bad contact = bad timing



I would consider replacing stock ecu chip if you have changed to aftermarket. Also, may want to swap ecu's if this has not been tried. faulty knock sensor?



Just have to start eliminating one after another.

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[Cloud9...68]

[quote name='DaveN' post='64219' date='Dec 14 2008, 05:01 PM']I don't see this suggested yet but as I live on the "Wet Coast" the first thing I thought of was moisture in the tank or in the fuel filter. Every time you take it for a romp you get a bit of H20 splash into the fuel line and eventually into the injectors?[/quote]

Good point. While this wouldn't exlain the CEL or the fault code, it at least is very simple to check. A co-worker of mine had a misfiring problem with a Corvette awhile back, and it turned out to be moisture in the fuel system. Try pouring a bottle of dessicant, which is available at any auto parts store, and is dirt cheap, into the tank, and seeing if this helps. Like I said, it's a long shot to be the cause of your problem, but it can't hurt.



I know how incredibly frustating a heitation problem can be, having struggled with one for months (mine turned out to be bad plug wires). If it helps, I kept a log of everything I tried; here it is:



[color="#FFA500"]Car hesitates/stumbles badly when flooring it, particularly after about 20 minutes of driving. Seems to be worse in hotter weather.



- Checked engine flash codes (came up perfect)

- Tested throttle position sensor, and installed a spare someone loaned me. No impact

- Replaced DME relay

- Cleaned throttle body with chemical flush

- Checked spark plugs (all perfect)

- Checked distributor cap and rotor (replaced 12/03. They are in good shape, but I cleaned up contacts anyway)

- Plug wires are just over a year old (but see below)

- Ran two tankfuls of dessicant to remove any water that may have been in gas

- Had injectors cleaned and blueprinted by Marren. Amazingly, this didn't help at all, though the car runs better than before when in its "sweet spot."

- Replaced fuel filter.

- Replaced coil with a loaner

- Added 5% toluene to tank to raise octane as a test of knock sensors.

- Replaced high performance Racer-X chip with stock chip; if anything, it made the hesitation a tiny bit worse

- Re-checked flash codes with stock chip; still indicated perfect

- Tested fuel flow volume; came out to ~900 ml in 30 sec, which is right on target per spec.

- Sprayed carburetor cleaner around intake manifold; no leak detected.

- Vacuum gauge reads 14.5-16” Hg, with an oscillation about a range of about 0.5”, with a period of just over 1 sec.

- Disconnected variocam solenoid – no change

- Watched engine run in the dark, and saw arcing and flashing along the plug wires, and around the coil. Ordered new plug wires.

- Cleaned MAF connector[/color]



I haven't looked at this list in a long time. It really underscores how many things can cause a modern engine to hesitate under load, and this is by no means a complete list. Good luck; I feel your pain...

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[flash]

1235 is indeed an intermittent variocam - i JUST had this problem - it looks like it turned out to be the connector at the little plug in thingy at the head - one of the pins was not making good contact

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[Duckman]

......little thingy at the head? Good technical description, Flash. I like it.

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[flash]

lol - i paid extra for the expanded book of automotive definitions



heck, i could have called it by its name, and likely caused confusion, but i think everybody figured out what i was talking about

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[94SilverCab]

Since this is a Porsche shouldn't you have said "kleine Ding an der Spitze" (literal translation of "liitle thingy at the head")



Whew, I feel better now...go, converse...



Jay

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