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Poor running 87 S4 after warm up

 
Old 04-15-2019, 08:12 PM
  #31  
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with the HEI ignition system the sparks should be blue
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Old 04-15-2019, 09:11 PM
  #32  
Kevin in Atlanta
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Originally Posted by Mrmerlin View Post
with the HEI ignition system the sparks should be blue
That's what I thought. Need to see if the coils are getting battery voltage.
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Old 04-15-2019, 09:16 PM
  #33  
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I'm going to start at the battery, cleaning the feeder wires to the CE panel.
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Old 04-15-2019, 11:14 PM
  #34  
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once a 928 is not running well,
the first thing that should be done is a CE panel cleaning, service the battery, and all the ground points.
Clean the computer connections, spark plug wire inspection
this will usually restore lost voltage
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Old 04-17-2019, 01:36 PM
  #35  
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2k Ohms on PS coil ground to good engine ground. DS was 0.00

Also found this on the PS coil:
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Old 04-17-2019, 02:22 PM
  #36  
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Cleaned the ground point behind the jump post (MPIII)M and still get 2k Ohms.

According to the WSM ground goes the right ignition module and then to ground.
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Old 04-17-2019, 07:44 PM
  #37  
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Your compression numbers were low ...on PS.
Your coil ground resistance is odd...on PS.
You mentioned the plugs being glossy "mostly all around", but were the PS different?
Was your yellow spark on both sides our just PS?
Did you bench test the coils? (Primary and secondary resistances? Sorry if you already mentioned that, this thread is getting long!)
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Old 04-17-2019, 08:06 PM
  #38  
Kevin in Atlanta
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So, I replaced the coils and coil wires with late model versions. Blue spark at every wire end.

Pulling spark plug leads did not change the idle - that is odd. Swapped the MAF for a rebuilt unit from Roger,

I'm going to circle back to fuel delivery.

I've looked over the fuel lines - no kinks as far as I can see. PSI is 60 and the injectors are clicking away.
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Old 04-18-2019, 01:32 AM
  #39  
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Wow...well at least you've come across and fixed/inspected lots of other items during your journey!
Did you ever take your LH box and put it into another car to see what happened?
Yeah, fuel is where you started, and the plug conditions could point to mixture problem for sure. (Or it could have been the coils you just fixed.)
It'd be nice if you could watch the fuel psi while you drove and see what it does at your 1/8 mile marker.
I've never done it, but I know someone who used a Go-Pro camera mocked up inside the engine bay to do that......or if you have a long snake camera for your phone.
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Old 04-18-2019, 09:27 AM
  #40  
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I think I'm running low on gas - so I'm going to toss another 5 gallons in the tank.

Also, going to pull th CE panel - voltage from from the FP relay (12.26) to the fuse (11.76) needs some investigation.

Replacing all the fuses with high quality ones after the cleaning.
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