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WildP1
Joined: 25 Dec 2020 Posts: 18 Location: Switzerland
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Posted: Fri Nov 12, 2021 5:52 pm Post subject: Runs rough under 2000rpm and only runs too rich |
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My 2.0 NA 1976 924 has a really rough idle and runs rough below 2000rpm. It gets better when warm but still is nowhere near perfect. The whole engine is shaking. As soon as I go over 2000 RPM it is really smooth and when driving it doesn't stutter or anything bove 2000 RPM.
Another problem is that it's running too rich. When I adjust the air fuel mixture screw to make it run leaner it just runs a lot rougher.
Before I changed the fuel pump, accumulator and fuel filters it was at like 9% CO value. The lowest I got it to before it died was 3%. The pump and filters have made it run a lot better when driving. It used to stutter randomly but now it only does it below 2000rpm.
I have also replaced the ignition coil, spark plugs, plug wires, rotor and cap, points and breakers, condenser.
Could the injectors cause a problem like this?
Many thanks in advance |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Fri Nov 12, 2021 11:39 pm Post subject: |
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Moved to General - you put this in 931, and you have an NA - get a lot more responses here!
Certainly the injectors should be checked for spray pattern, but I'm guessing you haven't checked your control pressure? _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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WildP1
Joined: 25 Dec 2020 Posts: 18 Location: Switzerland
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Posted: Tue Nov 23, 2021 7:18 am Post subject: |
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Thanks!
The spray patter didn't look too bad. I'm thinking it might just be timing related.
What is the control pressure supposed to be? I measured it once but didn't exactly know if the values were any good or not.
Thanks again. |
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BTRacing
Joined: 31 May 2014 Posts: 434 Location: Nortbrook,IL
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Posted: Tue Nov 23, 2021 3:42 pm Post subject: |
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I would start with connecting CIS gauges and monitoring fuel pressures. Most likely warm up regulator issue. It controls system pressure. _________________ www.btr-chicago.com
1977 924 Martini
1979 931 GTR Le Mans replica to be
1993 Mercedes 190E Sportline LE, one of 700 made
2020 Ford F350 Tremor daily driver/tow pig
1974 Moto Guzzi Cafe Racer
2002 Formula Fastech 382 |
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WildP1
Joined: 25 Dec 2020 Posts: 18 Location: Switzerland
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Posted: Wed Nov 24, 2021 9:18 am Post subject: |
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BTRacing wrote: | I would start with connecting CIS gauges and monitoring fuel pressures. Most likely warm up regulator issue. It controls system pressure. |
Will have a look at this, thanks! |
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scm924s
Joined: 22 Oct 2010 Posts: 261 Location: Gloucester UK
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Posted: Fri Nov 26, 2021 2:36 am Post subject: |
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There are 2 screws governing idle and mixture, the idle is controlled by a screw on the throttle body and mixture controlled by a screw on the fuel distributor, both should ideally be adjusted by using an exhaust gas analyser getting it to around 2.5%.
Always a good idea to have a fuel pressure test kit when monitoring the Kjet system. _________________ 1984 n/a Ruby Red Metallic
1988 924S Guards red- sold
1986 924S Guards Red - sold
1984 n/a Black - sold
1980 n/a Le Mans#1 - sold
1980 n/a Le Mans#2- sold
1977 Martini - sold |
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WildP1
Joined: 25 Dec 2020 Posts: 18 Location: Switzerland
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Posted: Fri Nov 26, 2021 7:01 am Post subject: |
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scm924s wrote: | There are 2 screws governing idle and mixture, the idle is controlled by a screw on the throttle body and mixture controlled by a screw on the fuel distributor, both should ideally be adjusted by using an exhaust gas analyser getting it to around 2.5%.
Always a good idea to have a fuel pressure test kit when monitoring the Kjet system. |
I had it on a gas analyser and the lowest I got it to was 3.5% and everything below would make it die. It drove the best at around 9% which is waaay too much. I suspect timing or some leak in the intake system might be the problem. |
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