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Discussion Starter · #1 ·
so the car was running great, drove to work and when I went to go home upon starting my car it give a check engine light ? pulled to code and was p0300 that was the only code ?

this motor had the top end completely rebuilt not 6 months ago, new wires and plugs , new cap and rotor , I check the firing with a timing light looking for miss's and found none ?

the car was running really good , so unsure of what went wrong ? could this a fuel issue ? being as the coil and can sensor are built into the distributor no way to check unless some of you know how as I have looked and found nothing ?

also when I check the compression the back bank is around 180 and the front is around 120 ? theses heads had a valve job less then 6 months new everything ?

new gaskets new everything !

can anyone point me to what i am missing ??

thanks

Steve
 

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Discussion Starter · #4 ·
I did the work , I am a really good mechanic and it was fine everything by the book , thinking that perhaps the head gasket did seat right ? the heads just had a complete valve job done, the motor only has 132,00
as the back is good I really doubt there is any issue with the piston or rings on this bank. just bad head gasket.

pain in the ass to tear it apart again but hey if that's what it take fine @LOL

the question is will that fix the the P0300 code ?

thanks for any help
 

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2001 Spyder GT
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How did you measure those pressures? Book answer is hot engine, all plugs out, WOT. The spec is 119 psi normal, 83 psi min, and 14psi differential max.

Your 120 psi is about right for a single crank on a newish engine. 180 psi is little low for multiple cranks and letting the pressure build. Not sure what's going on here without knowing how you ran the test.


the question is will that fix the the P0300 code ?
I don't think your compression is causing the P0300. Excessively low compression can cause a P0300, but your compression doesn't look low and the car would idle poorly with low compression. Since you recently did a top end rebuild, my money is on your timing belt being off by a tooth. It happens very easily during reassembly. The engine will sound and perform normal, but you'll get a P0300. Could be other things too, but the timing marks is a logical place to start even though you used a timing gun.
 

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Discussion Starter · #6 ·
well put a brand new one in when I had the heads done, the reason for all this work was to replace the original timing belt to begin with, done and was very carful about doing it , I triple check the marks ! lol
also think it would have shown up a while back not 5 months later ? car ran great no problems at all, drove to work and then when I went to start to come home it thru this code, new wires , plugs , 02 sensors
no vacum leaks.

Bu I can recheck to see if jumped ?
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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Almost anything can cause a P0300. But 120 vs 180 is too big a psi difference and indicates a problem with your rings or valves. Are those pressures dry or wet?
If compression is running really low on one cylinder, it is going to affect that whole bank. The O2 sensor is going to try to correct the mixture on that side and it will screw the mixure up on the other two cylinders. ...J.D.
 

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Just fyi I did a compression and leak down test back in July had
Cylinder 1 - 200psi 10%
Cylinder 2 - 206psi 10%
Cylinder 3 - 199psi 10%
Cylinder 4 - 205psi 10%
Cylinder 5 - 200psi 8%
Cylinder 6 - 201psi 12%

The percentage is of leak and that was through the rings. Mind you I have 189k miles on my motor never been rebuilt. You’re 120 on the front bank is really low I would be concerned about that prob should do a leak down test and see why it’s low on compression.
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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I could see where this low compression could trigger a P0300 code. The low cylinder is going to run rich. The O2 sensor is going to try to lean that out. So the other two cylinders on that bank are going to go lean. It might cause a lean misfire situation. You could do a wet /dry compression test to see if it is rings or valves. There is also the rare possibility you have a cracked piston or ring. You are going to have to go inside either way. ...J.D.
 
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