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Car Forum / Porsche / Porshe 944 / November 2005Help: My '83 944 Misses at +3k RPM
Hi! I recently acquired an '83 944. The previous owner had it serviced regularly but drove it under 100 miles for the last several years. The engine starts right up on the first try and idles smoothly. The only problem seems to be that when you rev it above 3k the engine sputters badly. If you back it right down from this range all is well. This problem occurs even with no load. Due to the gearing of the 5 speed it is possible to avoid this range under most driving circumstances but I'm early to remedy this defect. I'm new to the Porsche / 944 line so I recently picked up a few manuals to familiarize myself with this car. I've already done some simple checks (plugs, wire, cap, etc.) and so far everything looks okay. Can someone offer some advice on what I should be looking at next? Is this a common problem on 944s? Does it sound fuel or electronics related? Any feedback would be appreciated! Cheers! try an injector cleaner and see if it helps > Hi! > [quoted text clipped - 16 lines] > > Cheers! Thanks Bill for your feedback! I already tried running some good (tetronics sp?) cleaner thru the system but it didn't seem to help. Seems somewhat odd that the problems only occurs at this specific RPM. You may have low fuel pressure or a vacuum leak. Bosch system is very sensitive to vacuum leaks. If your economy gauge is showing less than 30 at 60mph on level road you have a vacuum leak. The o rings on the injectors are a common problem. If they have not been replaced since car was built they may be a problem allowing excess air into intake. Time and heat dries them out... they crack open and do not seal properly.. Go to www.clarks-garage.com to get specifics. Ask the provious owner if he replaced the fuel pressure regulator and fuel pressure damper. If not you will need to do so. Your car should report about twenty nine miles to the gallon. Interesting... I'll have to check the injectors and fuel pressure. I had thought that if I had a vacuum leak or low pressure that there would be start-up or idle problems (which I do not have)... Thanks for the suggestion! I checked the economy gauge and was getting over 30mpg at 60mph. Does this mean that I don't have any vacuum problems? I was also able to rev it over 3k although it still was somewhat rough. It was very cold out when I did this test run. Could this have something to do with it? Maybe another clue???? Thx You probably do not have a vacuum leak if you show over 30 at 60 mph. You still need to check the fuel pressure. One other typical problem is the air flow meter either sticking or the variable resistor not making good contact. Again, check www.clarks-garage.com for details. I clean my air flow meter about once each year by removing the rubber boot and spraying gumout into the valve surfaces. You can use almost any common pressure gauge to check the fuel pressure. The foundation of any diagnosis is data. So, the more you can obtain the better your chances are of solving the problem. |
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