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Hesitation/sputtering when warm!?

 
Old 04-26-2012, 08:01 PM
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Todd951968
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Default Hesitation/sputtering when warm!?

Yesterday, while driving my daughter to school the 968 started hesitating when starting off and would not rev smoothly. It would stumble and stutter at take off from a stop and then get rough again in the upper rpm range , say over 4k.

I dublipcated the same thing this evening. It started cold just fine and ran great for about 20 minutes and then started the sputtering thing again.

Any ideas? This is the first time its done this sort of thing. It has a recent O2 sensor, plugs, and fuel filter, btw.
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Old 04-26-2012, 10:01 PM
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968 GUY
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TPS...DME relay, loose connection at MAF or fuel injector, hall sender, or maybe just some bad fuel.
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Old 04-26-2012, 11:32 PM
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ramius665
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I'm curious here... The Variocam kicks in from idle to ~1500rpm and again starting around ~5k. Maybe your variocam solenoid is going. I don't have my FSM handy right now to see what the diagnostic process is to check the variocam but I'd do some research there. But that's on top of checking the things listed above.
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Old 04-27-2012, 01:00 PM
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Lord_Galva
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Originally Posted by 968 GUY View Post
TPS...DME relay, loose connection at MAF or fuel injector, hall sender, or maybe just some bad fuel.
+1. Check all your electrical connectors starting with spark and ending with fuel. Friend of mine's Toyota did that and we discovered it was a bad "new" spark plug, ie shop put the wrong one in.
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Old 04-27-2012, 03:27 PM
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Todd951968
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Thanks. I'll start with these suggestions.
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Old 04-27-2012, 08:50 PM
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dougs968
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Maybe another thing to check would be the crank position sensor. My car developed a slight miss or stumble at about 65-75 mph in 5th gear. The plastic on my sensor was falling off in chunks where it plugs in at the upper bracket. I damaged it installing my new ground cable. Replaced with a new one and noticed that the wires' jacket where it enters the part that plugs into the bell housing seemed kind of loose to me. There was quite a bit of old black oil contamination on the end of the sensor unit.

I haven't driven it yet to confirm if it is fixed.

Doug
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Old 04-30-2012, 04:03 PM
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Well, I swapped in some old (but good) spark plugs I had laying around. The ones in the car didn't look too bad, a little sooty near the bottom of the thread body. So, after swapping them out I drove the car for almost 1 1/2 hours straight and haven't had the symptoms return. I've ordered brand new plugs and will continue to drive the car around and see if the stumbling re-appears. So far, it looks like it was the spark plugs.
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