Would unplugging o2 Sensor rather than Crank sensor Skew Comp test results?
Mar 21, 2018, 11:19 AM
#1
Would unplugging o2 Sensor rather than Crank sensor Skew Comp test results?
I was stupid and unplugged the o2 sensor (the triangle one in the spark plug area) thinking it was the crank sensor when I was performing the comp test
Evo 8, 2005, 71k miles.
Car was hot, stock block, GSC valvetrain with Kelford 272s. Borrowed a tester from Oreillys Part store, got 115 across the board with WOT on the gas and clutch, 5-7 crank overs.
Seems strange that the car is running so well with 'low' comp, or that the fuel being shot in would skew it. Car made 380whp/320 trq (stock turbo, 20 psi) 5 years ago at English, and then the same number a few months ago, at English again, same month roughly.
Would ignition and fuel cause a different compression number since the crank sensor was still plugged in?
Im thinking to just send it, or use another gauge + unplugging right sensor lol
Evo 8, 2005, 71k miles.
Car was hot, stock block, GSC valvetrain with Kelford 272s. Borrowed a tester from Oreillys Part store, got 115 across the board with WOT on the gas and clutch, 5-7 crank overs.
Seems strange that the car is running so well with 'low' comp, or that the fuel being shot in would skew it. Car made 380whp/320 trq (stock turbo, 20 psi) 5 years ago at English, and then the same number a few months ago, at English again, same month roughly.
Would ignition and fuel cause a different compression number since the crank sensor was still plugged in?
Im thinking to just send it, or use another gauge + unplugging right sensor lol
Mar 21, 2018, 07:25 PM
#2
Evolved Member
The main reason for unplugging the crank sensor is to keep gasoline from spewing from the cylinders.
Edit: Not the main reason, the reason.
Edit: Not the main reason, the reason.
Last edited by barneyb; Mar 21, 2018 at 07:33 PM.
Mar 21, 2018, 09:39 PM
#3
Account Disabled
The best way is to pull the fuse for the ECU.
Yes fuel in the cylinders will make the numbers a bit higher.
It's also a fire hazard.
115 PSI is a bit low?
Do it again ?
Yes fuel in the cylinders will make the numbers a bit higher.
It's also a fire hazard.
115 PSI is a bit low?
Do it again ?
Mar 22, 2018, 07:35 AM
#4
EvoM Guru
iTrader: (1)
Try another gauge, also make sure the Schrader valve in the line is working properly. I had one that was a little difficult to move, and it made the gauge read low because it wasn't opening all the way.. 115 is on the low side. Should be at least 140..
Mar 22, 2018, 08:49 AM
#5
I watched the compression drop 20 psi with 2 cycles and thought to myself: how did that happen? $30 down the drain.
Mar 22, 2018, 01:36 PM
#7
Account Disabled
Lots of broken engines out there?
Compression tests are pretty much waste of time.
Looking at the sparkplugs usually tells you everything you need to know.
Photos?
Compression tests are pretty much waste of time.
Looking at the sparkplugs usually tells you everything you need to know.
Photos?
Last edited by RightSaid fred; Mar 22, 2018 at 01:43 PM.
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Mar 22, 2018, 10:56 PM
#9
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2006EvoIXer (Mar 23, 2018)
May 8, 2018, 09:59 AM
#15
I took this pic after I did my plugs, did these like 3 weeks ago or so right before my dyno tune
Sorry for such a huge pic
The car made 497whp 380 trq at 31 psi on a dyno jet 92 octane with a FP red SS
We backed it off cause the CEL was flashing, running about 24 pounds right now probably around 460~