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arbita1's Avatar
 
Join Date: Aug 2004
Location: Mahopac, NY
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Jerky Acceleration

I was driving home from autocross today and something with the car just didn't seem right. I felt like when I accelerated it was jerky in certain places. It wasn't very pronounced but it was definitely there. I felt it most in 2nd gear.

The car also didn't sound "right" to me. It was almost like it had a deeper sound. I don't know if it was just me.

Lastly, I felt like it was down a bit on power.

The only thing I've done recently is added a Seine Gate shifter. So that can't be related in any way.

So where should I start?

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Matt.

83 911SC
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Old 07-11-2010, 05:03 PM
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This is where I would start, given what you've posted:

Two possibilities come to mind--ignition fault or lean fuel mix--both which could cause your symptoms which sound like a misfire. I'd check out all ignition components first to guarantee they are working properly. If that doesn't change things, next likely thing would be lean fuel mix due to too high pressures or air leak.
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L.J.
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Old 07-11-2010, 05:25 PM
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Thanks L.J.

Most of my ignition components are new. Cap, rotor, and wires were all replaced about 3 years ago. Spark plugs were just recently replaced a few months ago. I'll go through my ignition system first to see if there is anything amiss.

I did a search and saw in one of your previous posts that you can hook a timing light up to each plug wire and watch the strobe to see if there is any difference. I'll try that as well to confirm I actually have a misfire.
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Matt.

83 911SC
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Old 07-12-2010, 08:31 AM
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Matt; pull the plugs and check their color. If one is darker than the rest you can suspect an injector, maybe even swap two of them and see if the dark plug "moves" to the next cylinder. A bad/leaking injector can cause the subtle problem that you're having.

All the plugs look good? Shaking up the fuel system with aggressive driving can mess with the fuel filter, the gas supply in the tank, even the fuel distributor, so check the easy stuff first!
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Old 07-12-2010, 09:27 AM
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Status Report

I went to just do a visual inspection inside the engine compartment today...not really expecting to find anything.

Immediately I noticed something didn't look right with how No. 6 spark plug wire connector was sitting in it's hole in the valve cover. I checked it and it wasn't connected. I tried pluging it back in, but I could not get it to click. I looked at the inside of the connector and saw this...



...the tip of the spark plug!?!?

I removed the spark plug and...



...it had somehow unscrewed off.



So now a few questions:

1. How does something like this happen?

2. I can screw the tip back on. Should I reuse the spark plug or just be safe and get a new one?

3. Did I do any damage by driving around like this? Most likely killed my cat (if it wasn't clogged already). Anything else?
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Matt.

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Old 07-12-2010, 05:34 PM
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It happened to me a while back as well... I was baffled for sure, and happy I figured it out quick and didn't do anything rash-
I'm sure the spark plug is fine, on the other hand you may want to check all of your other plugs, and while you're at it just put some new ones in if you're worried it...
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Old 07-12-2010, 08:24 PM
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+1 on checking all the other plugs--just to be safe. Probably no major harm, even to the cat, given the short amount of time you drove it in that condition. Hopefully that was the problem and a very simple fix! Let us know if things are all cleared up.
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Old 07-13-2010, 07:10 AM
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Someone told me lately that you can "gas" your oil- as in fuel gets past the rings and into your oil. If you drove it for a long time like that, I'm sure its entirely possible.
(I'm not saying this may or may not harm anything, just saying)

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Old 07-13-2010, 06:13 PM
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