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Now high idle
I know this has been discussed before but most of the results I got with the search were from people who just rebuilt the engine or purchased the car.
Mine was ok until 2 days ago. I parked it and the next day, car is very hard to start and when it does start, idle is above 2000 rpm. AFR was down to 12.4 cruising and idle. It is normally at around 13.7 at idle and between 14 and 14.5 cruising. It did slow down again after a very long time (15 minutes or so) and it did it again today. I read the deceleration valve or the auxiliary air valve? Thanks in advance guys. David
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David 1985 Black 930, K27 7006, Garretson Intercooler, Adj boost, TB: 23 - 31mm, bielstein sport shocks, ER polybronze bushings front and rear, ER monoball joints front and rear with offset camber plates, 935 X triangulated strut brace, raised spindles, racing bump steer kit 1981 Black 911sc (sold) |
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03-24-2013, 08:26 PM
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Location: S. Florida
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sounds like the rear fuel pump relay isn't working.
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03-24-2013, 08:56 PM
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rear fuel pump relay?
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David 1985 Black 930, K27 7006, Garretson Intercooler, Adj boost, TB: 23 - 31mm, bielstein sport shocks, ER polybronze bushings front and rear, ER monoball joints front and rear with offset camber plates, 935 X triangulated strut brace, raised spindles, racing bump steer kit 1981 Black 911sc (sold) |
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03-24-2013, 09:21 PM
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Quote:
The motor will run on just the front fuel pumnp but not as well. So if the rear fuel pump relay isn't working the car will still run on the front fuel pump only and also run rich with a high idle just like you described. Sounds funny but thats what mechanical CIS fuel injection design will do if the two mechanical cold start devices never warm up especially in a cold winter climate. |
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03-24-2013, 09:43 PM
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Just before I read this, I was telling my wife after reading "rear fuel pump relay": "some guys really know those cars, how can he have figured that out?"
But it all makes sense and it also matches a sound that the rear fuel pump was making first time I started the car this season. Thanks! I will check that relay tomorrow! It might be worth it to wire them individually at the same time to save the fuse. David
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David 1985 Black 930, K27 7006, Garretson Intercooler, Adj boost, TB: 23 - 31mm, bielstein sport shocks, ER polybronze bushings front and rear, ER monoball joints front and rear with offset camber plates, 935 X triangulated strut brace, raised spindles, racing bump steer kit 1981 Black 911sc (sold) Last edited by Roby466; 03-25-2013 at 06:21 AM.. |
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03-24-2013, 10:05 PM
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So I split the power source for the fuel pumps relays by leaving the first one through the fuse box and cutting the jumper wire between the two (12 gauge red wire) and running a different wire with a 25A fuse from the battery.
At the same time, I removed and checked the operation of the AAR and sprayed a bit of contact cleaner in there and lightly lubricated the port closing plate with synthetic motor oil. It seemed to work good this morning. The car stumbles a bit on startup (often needs two starts) and then gets a nice 1.5k rpm that goes back down progressively after 5 or 6 minutes. Thanks for the help JFairman! That was much appreciated! AFR is back at 13.5 au idle. David
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David 1985 Black 930, K27 7006, Garretson Intercooler, Adj boost, TB: 23 - 31mm, bielstein sport shocks, ER polybronze bushings front and rear, ER monoball joints front and rear with offset camber plates, 935 X triangulated strut brace, raised spindles, racing bump steer kit 1981 Black 911sc (sold) Last edited by Roby466; 03-26-2013 at 12:45 PM.. |
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03-26-2013, 12:41 PM
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If it stumbles a little right after a cold start it's probably a little lean on intitial cold start or anotherwords cold start control pressure is a little high and needs to be lowered a little.
Doing that a little won't change your steady cruise AFR. Try a tap or two on the cold start adjustment with a small hammer and brass drift punch while the 12 volt plug is removed from the WUR/CPR while motor idleing or before you start it. A steel drift punch is alright but will probably leave little marks. If it's an adjustable Brian Leask WIR than go a little too far tapping it in and then draw it back out with a 10mm box end or open end wrench right after a stone cold start with the 12 volt plug removed and stop when it idles smooth and doesn't miss or stumble when you blip the throttle. Then plug the 12 volt plug back in and drive it. You will have to wait for it cool off completely overnight to see if you got it just right or if a little more adjustment is needed to get it perfect. |
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03-26-2013, 01:06 PM
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Very impressive JFairman! I've been an admirer of your 930 knowledge for awhile, but this was not an easy diagnosis. You've probably solve David's concern in less than 1/2 hour. Well done.
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Scott - 1987 930: 3.45L Supertec engine w/GT3 crank, California Motor Sports upgraded 930 trans, modified suspension, Zuffenhaus 9's and 11's, black on black..."The Black (Financial) Hole" 
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03-26-2013, 02:45 PM
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I could not believe it myself! I was thinking of how many hours I would have had to pay a mechanic to diagnose all the issues I have had during my Porsche ownership life if it were not from this forum and guys like JFairman and the other ones... And they would most likely have never found the issues...
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David 1985 Black 930, K27 7006, Garretson Intercooler, Adj boost, TB: 23 - 31mm, bielstein sport shocks, ER polybronze bushings front and rear, ER monoball joints front and rear with offset camber plates, 935 X triangulated strut brace, raised spindles, racing bump steer kit 1981 Black 911sc (sold) |
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03-26-2013, 07:29 PM
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Tinkering Pays!!
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A wideband afr gauge will go a long way in helping u understand the temperament of these cars. I'd be totally lost without mine.
Sent from my MB855 using Tapatalk 2
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LIVN80S - - Red '79 Porsche 930 Steel Slant Nose Conversion [in 1987] w. 46k miles 3.3L; 964 Cams; K27HF @ 1.0 BAR, with Garrettson Intercooler; Rarly Zork; CIS Flowtech Fuel Head & BL-WUR. |
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03-26-2013, 08:19 PM
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I have the gauges to check the control presures, i should do that as soon as i have a bit of time. I don't have a BL adjustable WUR but i can modify mine to have the hex screw to pull it back out if i push too far down, thanks!
I should make it fully adjustable at the same time... David |
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03-27-2013, 07:04 PM
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1981 Porsche 911 sc (sold)
1985 Porsche 930
Porsche 930
Ford Truck
