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Low Compression - Cylinder 4

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Old 05 April 2017, 11:07 PM   #1
Malcolm Bull
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Default Low Compression - Cylinder 4

hi, I'm after some thoughts and advice about my 2006 Hawkeye WRX 2.5

At 100,000miles it developed a misfire, MIL light (P0304) and high oil consumption. Cyl 4 spark plug was oily. So off it went to Zi Motorsport, Wrexham for a rebuild.

I wasn't fully happy with it when it came back (slight wobble at idle) and a further couple of MIL incidents (P0304) - but no obvious cause. Same code after I swapped the coil and plugs between 2 and 4. But no codes for the past few months.

They were a bit vague about what was wrong. Rings and bearings replaced and valves lapped in as part of the rebuild.

Now, 5000 miles after coming back, I have a full misfire on no.4 (P0304), oil consumption is not excessive, no. 4 plug smelt of fuel when removed. A cold compression test shows 100psi on 3 cylinders, but no.4 is down at about 20psi

Zi don't appeared interested and are suggesting perhaps an ignition or injector issue has caused the problem. I would thought that would have be obvious when they opened it up i.e signs of lean running/detonation or bore washing.

So now I'm stuck looking at another rebuild (possibly just one of the heads) assuming its a valve rather than a piston problem. I don't feel inclined to use Zi again, although I can't prove they did anything wrong with the rebuild.

Any thoughts of a good place to take it somewhere in the sussex/surrey/kent area?

Any idea of the likely cause - valve, spring, tappets....
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Old 06 April 2017, 10:18 AM   #2
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Slowboy racing at brands hatch. Been using them for a long time.
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Old 06 April 2017, 10:27 AM   #3
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Sorry to say but you should have not accepted it back if it wasn't right and been straight back onto them.

do you know what components went into the build?
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Old 06 April 2017, 11:49 AM   #4
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Thanks for the slow boy recommendation, I hadn't come across that name previously.

yes, I regret not doing more when I got I back and when the light reappeared. But it did seem generally OK and nothing these past months. Things are further complicated by the distance involved to Wrexham.
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Old 06 April 2017, 12:16 PM   #5
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Did you pay via credit card ?
You may have some recourse that way.
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Old 06 April 2017, 03:17 PM   #6
Malcolm Bull
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Paid by bank transfer :-(
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Old 06 April 2017, 04:10 PM   #7
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Second slowboy. Just had my secondary air pump taken off and mapped out. Going back in may for a remap
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Old 06 April 2017, 04:27 PM   #8
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Secondary air, Yes my valves failed so I had them replaced, then the motor failed, but got it rebuilt with new bearings. Removing it all and switching of the diagnostics would seem to have been a better bet
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Old 06 April 2017, 05:29 PM   #9
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Andy Williams - Williams motor sport built my 2.35 and is Based near Queensferry North Wales
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Old 06 April 2017, 08:31 PM   #10
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Use best; Finch motorsport Northampton
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Old 07 April 2017, 08:45 PM   #11
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☝️☝️☝️☝️☝️ what he said☝️☝️☝️☝️☝️
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Old 07 April 2017, 11:23 PM   #12
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Something cant be right, I have a 2007 wrx 2.5 and my compression test ive just done was 158,158,148,146 and its on 120k those are really low numbers.
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Old 14 April 2017, 11:34 PM   #13
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Yep, my 2007 wrx hawk 2.5 mid 140-mid150 on all with 105k on it, warm engine when tested
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Old 19 June 2017, 11:34 PM   #14
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Any other recommendations in the Kent/Sussex/Surrey/Hampshire area? Slow Boy has gone quiet on me after saying he could take the car in a few weeks ago
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Old 20 June 2017, 06:00 PM   #15
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East Kent Subaru. Richard Nicholls is spot on. He won't mess you around!
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