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| Cyliner 4 running rich at WOT https://auszookers.com/forum/viewtopic.php?f=5&t=10758 |
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| Author: | jdk81 [ Tue Mar 30, 2010 1:08 pm ] |
| Post subject: | Cyliner 4 running rich at WOT |
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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| Author: | ball [ Tue Mar 30, 2010 1:11 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | want33s [ Tue Mar 30, 2010 1:14 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
Compressions look OK.. I'd be looking hard at the plugs themselves as well as leads. |
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| Author: | jdk81 [ Tue Mar 30, 2010 1:31 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | jdk81 [ Tue Mar 30, 2010 1:38 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | ball [ Tue Mar 30, 2010 1:39 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
What are your valve clearances like ? |
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| Author: | jdk81 [ Tue Mar 30, 2010 1:42 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
Hmm good call Ball, ill inspect them later today. |
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| Author: | mightymouse [ Tue Mar 30, 2010 1:48 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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. |
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| Author: | oozuk [ Tue Mar 30, 2010 1:57 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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 |
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| Author: | JrZook [ Tue Mar 30, 2010 2:36 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | LAY80N [ Tue Mar 30, 2010 3:22 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | jdk81 [ Tue Mar 30, 2010 3:54 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
Im guessing I have to buy that stuff from Subaru dealerships? |
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| Author: | jdk81 [ Tue Mar 30, 2010 10:08 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | bagnkat [ Tue Mar 30, 2010 11:01 pm ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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| Author: | jdk81 [ Sun Apr 04, 2010 4:26 am ] |
| Post subject: | Re: Cyliner 4 running rich at WOT |
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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