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Join Date: Jan 2007
Location: Juneau, AK
Posts: 54
Poor running

I've let my 944 sit a couple months without really driving very often, and now it runs rough at lower rpm and is sometimes a little hard to start. It idles at 1k rpm and runs rough up to about 2500 or 3k rpm.

I think it is running rich, at least it smells a little rich at the tailpipe. I also pulled the plugs and they looked black. This leads me to think maybe the o2 sensor is at fault.

What are some other places to check if replacing the o2 sensor doesn't fix the problem? My search points at the tpm sensor, but I imagine the collective knowledge of Pelican has more thoughts up its sleeve.

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1986 944 NA
Old 11-01-2008, 12:54 PM
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I would say try running some seafoam or BG44K in the gas first to dissolve any buildup that might have accumulated by sitting around. I would particularly recommend the BG. It's some pretty strong stuff. I've used it once a while ago, and it made a noticable difference even though my car was generally running ok already. Besides, about 30,000 miles later when I replaced my fuel injectors, the intake valves were practically spotless. The engine has 140K miles and I credit a good bit of the cleanliness to be very likely from the BG. Using Shell V-Power fuel most of the time probably helped keep them clean that long.

One way to get a good idea if the O2 sensor is acting weird is to unplug it and drive around. The DME will inject fuel just according to the base fuel maps, which tend to be a little on the rich side, but are perfectly capable of running the car well as long as everything else is working reasonably well. If it improves, the O2 sensor is most likely bad. If it still sucks, or sucks in a different way, then something else is wrong, since the O2 sensor on these cars can only tweak the mixture to a relatively small degree. It can't compensate enough if there's something massively wrong. I'd start with that, as it can get quite involved from there on, and depending on what turns up.

Did it run well before it sat around? That answer could rule out a lot of things.
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1987 silver 924S made it to 225k mi! Sent to the big garage in the sky

Last edited by HondaDustR; 11-01-2008 at 02:53 PM..
Old 11-01-2008, 02:43 PM
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maybe leaking injector, use stabil before storing for months.....
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83 944....bye bye
85.5 euro spec 944, 5sp (she's gone....
74 914...hasta LA Vista baby
87 924s....don't let the door hit ya
68 912.......see ya!
Old 11-01-2008, 03:44 PM
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How would I tell if I have a leaking injector? I'm looking for diagnostic technique, as well as diagnostic suggestions.

I'll try the o2 sensor suggestion tomorrow.
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1986 944 NA
Old 11-01-2008, 04:21 PM
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disable the spark(pull coil lead to dist} unbolt 4 rail bolts and prop it up a few inches, put a towel under it and crank it, watch the spray, looking for 1 or 2 to be spraying abnormally
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83 944....bye bye
85.5 euro spec 944, 5sp (she's gone....
74 914...hasta LA Vista baby
87 924s....don't let the door hit ya
68 912.......see ya!
Old 11-01-2008, 06:52 PM
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I ran some seafoam through the gas and it smoothed right up. Hats off to the injector crowd!

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1986 944 NA
Old 11-02-2008, 10:09 AM
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idle , o2 sensor , rough , starting


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