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79-930
 
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My new fuel pressure gauge arrived Wednesday and was put to use, the WUR is fine; the tested fuel pressure was within spec. I injector flowed to examine the equality between each injector; they were all similar. I checked the flow rate between the fuel distributor and WUR, it was normal.

I did the carburetor cleaner spray with a tube through each injector with the resulting cone shape pattern. I have seen more than one person on this forum perform this same test as a baseline for an accurate troubleshooting procedure. Is this accurate considering the spray exiting the the tube is already in a somewhat atomized state?

I then checked the intake bolts torque and they were all loose, more than just a little. I tightened them to the required torque. 11 of them that is with the one under the air box manifold, left side of the engine compartment, completely inaccessible.

The big discovery was the coil impedance check. The shop manual for my car specifies, .10 - .165 ohms primary; mine measured .600. The shop manual secondary value specifies 390 - 630 ohms; my measurement was 716. Looks like it's time for a new coil. Hopefully this is the problem.
Old 07-29-2017, 05:10 PM
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The intake bolts being loose is a big one. Thats potentially a LOT of unmetered air getting in there. You really do need to get to that last bolt and get it torqued right.

What did tightening them do to the idle? And more specifically, how did it change your AFRs?

I wouldn't change the coil until you see what tightening those bolts did to your issues. One fix at a time and test in between each change.
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Old 07-29-2017, 06:16 PM
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Quote:
Originally Posted by audiadj View Post
I did the carburetor cleaner spray with a tube through each injector with the resulting cone shape pattern. I have seen more than one person on this forum perform this same test as a baseline for an accurate troubleshooting procedure. Is this accurate considering the spray exiting the the tube is already in a somewhat atomized state?
I used the carb cleaner method on my injectors and I found a bad one, so I'd say it worked for my application. One clearly didn't open under lower pressure and did not atomize at higher pressure.
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Old 07-29-2017, 07:03 PM
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Originally Posted by Jeff NJ View Post
The intake bolts being loose is a big one. Thats potentially a LOT of unmetered air getting in there. You really do need to get to that last bolt and get it torqued right.

What did tightening them do to the idle? And more specifically, how did it change your AFRs?

I wouldn't change the coil until you see what tightening those bolts did to your issues. One fix at a time and test in between each change.
Thanks for the response. To get to that bolt; I will have to remove the entire sensor plate assembly manifold. Not sure if it is worth the effort or will make any difference now that all the other bolts are properly torqued. I haven't put everything back together yet; don't know what affect this will have.

When I installed new plugs the old ones were very wet. This leads me to believe the lack of a proper hot enough spark resulted from a weak coil output. Excessive air, caused by the leaking intake, would have resulted in a lean dry spark plug condition.
Old 07-29-2017, 07:08 PM
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I know it's a pain, but loose intake bolts will give you fits. Many here have pointed that issue out on their cars.

I'm going from memory here as I'm on a plane headed to San dego, but I can get to that one in my car because the air box has been removed. Not easily, of course, but you dont need to remove the sensor plate. Maybe that's all you'll need to remove?
I'm sure someone will chime in with specific details on how to get to it, but no way I'd let that one remain loose.

Then see what difference that makes before changing the coil, which is likely going too, based on your numbers.
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Old 07-29-2017, 07:16 PM
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Originally Posted by Jeff NJ View Post
I know it's a pain, but loose intake bolts will give you fits. Many here have pointed that issue out on their cars.

I'm going from memory here as I'm on a plane headed to San dego, but I can get to that one in my car because the air box has been removed. Not easily, of course, but you dont need to remove the sensor plate. Maybe that's all you'll need to remove?
I'm sure someone will chime in with specific details on how to get to it, but no way I'd let that one remain loose.

Then see what difference that makes before changing the coil, which is likely going too, based on your numbers.
I just went out to the garage and looked at it again; it won't be that bad. I don't have or use the stock air box anymore as well. Anyway, there's three main mounting bolts, the main fuel lines, return and supply, the cold start injector feed and the two WUR fuel lines. I already have the injectors out so the solid lines could stay connected to the fuel distributor as I lift the entire assembly away. Thanks for the motivational boost, have a safe plane ride.
Old 07-29-2017, 07:34 PM
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79-930
 
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Originally Posted by Rich76_911s View Post
I used the carb cleaner method on my injectors and I found a bad one, so I'd say it worked for my application. One clearly didn't open under lower pressure and did not atomize at higher pressure.
Did you flow them on the engine when you found the one not working? Where was it flowed under "lower pressure", from the carb cleaner can?

When I first installed the new injectors a couple of weeks ago; I flowed them installed to the solid fuel lines on the car. I viewed inconsistent flow patterns between all 6. After pulling them a couple of days ago and checking them today with the carb cleaner spray method; I got all perfect patterns. I'm not really concerned, I could always re-test them again on the car.
Old 07-29-2017, 07:55 PM
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Agree with Jeff NJ - you need to get the last bolt. And try before replacing coil. Not sure it is that far out of spec really. Easy to get to later.
You asked earlier for torque values - presume you have found them. Book value 18 ft/lb. I actually used 13 ft/lb. 18 seemed a lot on plastic injector blocks. If you still have plastic injector blocks, that is another potential leak source - cracks. It would probably be unusual if one or more was not cracked after 30-40 yrs. If you can't get a torque wrench on the last nut, I would not sweat too much. Take a ring spanner and feel how tight the others are and tighten to similar. You will be close, and better than not at all. I don't think you should need to remove airplate system either.
Good luck
Alan
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Old 07-29-2017, 08:48 PM
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Originally Posted by Alan L View Post
Agree with Jeff NJ - you need to get the last bolt. And try before replacing coil. Not sure it is that far out of spec really. Easy to get to later.
You asked earlier for torque values - presume you have found them. Book value 18 ft/lb. I actually used 13 ft/lb. 18 seemed a lot on plastic injector blocks. If you still have plastic injector blocks, that is another potential leak source - cracks. It would probably be unusual if one or more was not cracked after 30-40 yrs. If you can't get a torque wrench on the last nut, I would not sweat too much. Take a ring spanner and feel how tight the others are and tighten to similar. You will be close, and better than not at all. I don't think you should need to remove airplate system either.
Good luck
Alan
I got to the last intake nut; torqued it down. Removed the 3 nuts that hold down the sensor plate box assy. This allowed me to lift the assy a few inches and gain access to reach the hidden intake nut.

Yes my shop manual states 25 nM or 18.4 ft/lb. My injector risers are black anodized cast aluminum; I torqued the intake nuts to 25 nM.

I'm waiting on a UPS order that contains new copper injector washers. Won't be doing anything more until they come in.
Old 07-30-2017, 03:01 PM
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Finally making some progress. Put everything back together, started it up without the new coil after torquing the intake nuts. There was no change; still idling poorly, popping through the exhaust. Replaced the coil with a MSD Blaster; huge improvement, stable idle no exhaust popping.

I started it up cold, low idle, adjusted the idle and let it warm up; bad mistake. The idle increased as it warmed; set the idle back to 1k. After about 10 minutes the idle dropped to around 700, probably the WUR altering the fuel pressure; raised the idle to 1k again where it stayed from that point on.

The problem I'm having now; there's a slight hesitation when getting on the throttle off of idle when fully warmed. The hesitation wasn't there when it was cold. Haven't checked the AFR; was waiting until the car was running close to correct until I did this.

Considering the addition of the Fabspeed long neck with the removal of the intermediate intake, AAR and AAV; this will definitely lean it out.

I also checked the timing after all of this; it was at the stock setting of 5 degrees ATDC at 1k idle. As I stated earlier I have no other crank pully markings besides TDC and 5 degrees ATDC. I've read on this forum site where people recommend setting idle at 0 or TDC. Does anybody else have an opinion on this 0 degree idle timing setting to get an accurate timing at 4K rpm?
Old 08-06-2017, 04:22 PM
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Knowing the warm WUR pressure would be useful. Sounds like a leaness when on throttle.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 08-06-2017, 05:15 PM
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Originally Posted by Alan L View Post
Knowing the warm WUR pressure would be useful. Sounds like a leaness when on throttle.
Alan
2.1 bar at 80 degrees Fahrenheit. Within the acceptable range according to my car manual.

What's your opinion on the 0 degrees timing at 1k idle?
Old 08-06-2017, 05:40 PM
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What WUR are you running? That sounds like a cold pressure rather than warm. Mine is supposed to be at 3.5 bar +/-
I don't know exactly about the timing - but many advance it slightly (5 deg or so) to improve throttle response. Advancing usually picks the revs up a bit. But I doubt that is the cause of the stumble issue. I would be looking at the WUR with those numbers. And when they are correct, if you still have an issue i would be checking each injector flow.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 08-06-2017, 06:26 PM
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Originally Posted by Alan L View Post
What WUR are you running? That sounds like a cold pressure rather than warm. Mine is supposed to be at 3.5 bar +/-
I don't know exactly about the timing - but many advance it slightly (5 deg or so) to improve throttle response. Advancing usually picks the revs up a bit. But I doubt that is the cause of the stumble issue. I would be looking at the WUR with those numbers. And when they are correct, if you still have an issue i would be checking each injector flow.
Alan
Yes that was WUR cold pressure. That was exactly my question; advancing the timing would put it at 0 degrees idle. Thanks.
Old 08-07-2017, 04:24 AM
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