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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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 Posted: Tue Mar 30, 2010 1:08 pm |
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Any ideas how i can solve this?
91 SWB sierra 120k km.
Plugs 1,2,3 were overheating a little (and runnin lean at WOT).
Plug 4 was very fouled (carbon build up, not oil fouled).
Timing 8 degrees BTC
Cylinders 1,2,3 at 195 psi.
Cylinder 4 at 185 psi.
It doesn't blow any smoke.
Doesn't use oil.
Doesn't use any water.
My fuel economy is crappy, and my exhaust is a bit more fumey than normal.
Carby has been stripped and cleaned out etc, and assembled back to spec.
Following rebuild carby, and retune, new plugs (gapped to 0.8mm). 1,2,3 plugs looking ideal, plug 4 still looking rich.
Where should I look?
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ball
I live here!
Joined: Wed Oct 22, 2008 10:30 pm Posts: 4673 Location: Katherine
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Posted: Tue Mar 30, 2010 1:11 pm |
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jdk81 wrote: Any ideas how i can solve this?
91 SWB sierra 120k km.
Plugs 1,2,3 were overheating a little (and runnin lean at WOT).
Plug 4 was very fouled (carbon build up, not oil fouled).
Timing 8 degrees BTC
Cylinders 1,2,3 at 195 psi.
Cylinder 4 at 185 psi.
It doesn't blow any smoke.
Doesn't use oil.
Doesn't use any water.
My fuel economy is crappy, and my exhaust is a bit more fumey than normal.
Carby has been stripped and cleaned out etc, and assembled back to spec.
Following rebuild carby, and retune, new plugs (gapped to 0.8mm). 1,2,3 plugs looking ideal, plug 4 still looking rich.
Where should I look?
Compression test is a good start.
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want33s
az supporter
Joined: Fri Nov 16, 2007 10:30 pm Posts: 8134 Location: Sunshine Coast Qld
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Posted: Tue Mar 30, 2010 1:14 pm |
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Compressions look OK.. I'd be looking hard at the plugs themselves as well as leads.
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Tue Mar 30, 2010 1:31 pm |
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Forgot to add
Leads connect very well to plugs and dizzy cap.
Lead resistances are well within spec
Coil pack is within spec.
Ball the compression is within service limits
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Tue Mar 30, 2010 1:38 pm |
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It ran like a dream with new plugs for a while
Does the following logic seem like a reasonable approach?
If 4 is cooler, the plug will foul. If it fouls, it will miss, and run rich and foul more.
Is it possible plug 4 is running much colder than the other 3. Is it possible that there is some crap built up in the cooling system which might change the flow of coolant, cooling one cylinder much more than others?
Could an air lock be responsible?
I think i might flush the cooling system and see.
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ball
I live here!
Joined: Wed Oct 22, 2008 10:30 pm Posts: 4673 Location: Katherine
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Posted: Tue Mar 30, 2010 1:39 pm |
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What are your valve clearances like ?
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Tue Mar 30, 2010 1:42 pm |
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Hmm good call Ball, ill inspect them later today.
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mightymouse
Joined: Tue Dec 29, 2009 10:30 pm Posts: 146 Location: Newccastle
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Posted: Tue Mar 30, 2010 1:48 pm |
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Odds on exhaust valve rocker @ no 4 is either too tight or just a little carboned up on the stem not closing completely not enough to cause a great deal of difference in compression but just enought to create a small problem at WOT.
_________________
growing old is nature, growing up is choice.
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oozuk
Joined: Sun Aug 16, 2009 11:30 pm Posts: 1452 Location: bethania QLD
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Posted: Tue Mar 30, 2010 1:57 pm |
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Adjust the valves and run a can of "Subaru upper cylnder head cleaner"
thru the engine. This will de-carbon all the intake, valves and combustion chamber, it's good shit just don't subsatute *sorry bad spelling* for another brand get the Subaru brand
_________________
building a bling zook .......will it ever be finis
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JrZook
Joined: Tue Aug 08, 2006 11:30 pm Posts: 5517 Location: Holland Park
Vehicle: Awesome!!
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Posted: Tue Mar 30, 2010 2:36 pm |
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oozuk wrote: Adjust the valves and run a can of "Subaru upper cylnder head cleaner"
thru the engine. This will de-carbon all the intake, valves and combustion chamber, it's good shit just don't subsatute *sorry bad spelling* for another brand get the Subaru brand
x2 the only stuff to use!
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LAY80N
Joined: Tue Jul 28, 2009 11:30 pm Posts: 455 Location: Newcastle NSW
Vehicle: I drive your mum
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Posted: Tue Mar 30, 2010 3:22 pm |
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oozuk wrote: Adjust the valves and run a can of "Subaru upper cylnder head cleaner"
thru the engine. This will de-carbon all the intake, valves and combustion chamber, it's good shit just don't subsatute *sorry bad spelling* for another brand get the Subaru brand
x195823857384905 - the subaru upper engine cleaner is the ONLY stuff to get. I echo what the others have said. Check/adjust your valve clearances and give it a whole can of subaru upper engine cleaner.
Layto....
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Tue Mar 30, 2010 3:54 pm |
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Im guessing I have to buy that stuff from Subaru dealerships?
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Tue Mar 30, 2010 10:08 pm |
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That suburu upper engine cleaner is the bomb. It feels so much better now.
Valve clearances within spec. I also changed the oil + flushed coolant while I was at it.
Temp is running where it used to, and engine has about 25% more power.
Will take it for a flogging on the highway when i sober up.
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bagnkat
az supporter
Joined: Sun Aug 16, 2009 11:30 pm Posts: 346 Location: Port Stephens.
Vehicle: SJ80
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Posted: Tue Mar 30, 2010 11:01 pm |
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want33s wrote: Compressions look OK.. I'd be looking hard at the plugs themselves as well as leads.
Maybe swap plug 1 and 4 and see if the problem follows the plug, or whether the new plug in cylinder 4 fouls as well.
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jdk81
Joined: Sat Jul 18, 2009 11:30 pm Posts: 2372 Location: Ballarat, VIC
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Posted: Sun Apr 04, 2010 4:26 am |
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Fuel econ is pretty good now.
Got 300 kms (250km on the highway at WOT, and 50km in 4wd), and still had 15L left (50L fuel tank installed).
Was impressed, I was overtook 4 commondoors while going up a big hill. Sits on 110 km/h even in a head wind. Drops back to 100 km/h on hills now.
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