993 poor high rpm performance
Discussion
Hello.
I’m new here I have a 1995 993 3.6 manual gearbox. It was a bit neglected when I got it. So I did the full 60k service all new parts. However still I get poor top end almost like my timing is off or it’s slow to rev to red line. No warning lights present. I checked the distributor belt first all is well there. Tested vacuum entire system is holding good. New dme relay also replaced ignition module,coils, maf, gas filter, air filter, and cleaned isv .
Motor runs really smooth just feels like I’m down on power.
Any suggestions where to look next.
I’m new here I have a 1995 993 3.6 manual gearbox. It was a bit neglected when I got it. So I did the full 60k service all new parts. However still I get poor top end almost like my timing is off or it’s slow to rev to red line. No warning lights present. I checked the distributor belt first all is well there. Tested vacuum entire system is holding good. New dme relay also replaced ignition module,coils, maf, gas filter, air filter, and cleaned isv .
Motor runs really smooth just feels like I’m down on power.
Any suggestions where to look next.
Could it be that the car has spent a lot of time doing short trips so it’s coked up - once Virus is over you can take it on long trips really get that motor hot and use plenty of the low gears and high rpm.
There are fuel additives wynns that can help remove the carbon without taking the head off. Costs a few quid worth a try.
Similar option wynns for the injectors they might not be putting in the fuel as a fine mist rather more dripping - but you’d also see sooty exhaust/on revs from the rear.
There are fuel additives wynns that can help remove the carbon without taking the head off. Costs a few quid worth a try.
Similar option wynns for the injectors they might not be putting in the fuel as a fine mist rather more dripping - but you’d also see sooty exhaust/on revs from the rear.
Is full throttle at the pedal giving full open at the throttle body? Other checks... HT leads seated ok and both coils are operating. Air leaks at the inlet stacks/rubbers (spray carb cleaner or similar near them and see if the engine revs change). Could even be cam timing has slipped which does happen on some 993s.
The 993 use 2 methods to set cams, some have the older 964 holed sprocket and pin arrangement while others use the later clamp friction method which can slip. This would effect performance across the range. I would check the wide open throttle first then air leaks then cam slip as a last resort.
ras62 said:
The 993 use 2 methods to set cams, some have the older 964 holed sprocket and pin arrangement while others use the later clamp friction method which can slip. This would effect performance across the range. I would check the wide open throttle first then air leaks then cam slip as a last resort.
Ok thanksMy car was in a similar state. Try a bottle of Chevron Techron, and that will clear the fuel system out. If this sorts it out I’d recommend a more permanent fix would be to refurbish the injectors. An fairly easy DIY with a £25 parts kit you can get from eBay and a few basic tools and sprays.
Difference was night and day!
Difference was night and day!
Also may be worth replacing the fuel pressure regulator if it's original (as a test, remove the furthest left vacuum line from intake manifold and sniff it, if you smell fuel the FPR membrane is probably gone), throttle position sensor (very cheap) and intake temp sensor (also cheap).
Once you've replaced these take the DME out for a few seconds and replace, this will reset ECU 'learning'.
Still think your best bet is to have a look at the injectors, this is what mine were like after 25 years!
Before and after:
Once you've replaced these take the DME out for a few seconds and replace, this will reset ECU 'learning'.
Still think your best bet is to have a look at the injectors, this is what mine were like after 25 years!
Before and after:
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