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Discussion Starter · #1 ·
Well, I did a compression check on my 1991 Sentra SE yesterday. My car has 180K miles on it. My results were the following:

205, 205, 195, 200.

The FSM states standard is 192, minimum is 164, and difference between cylinders is less than 14.

It appears I have some carbon buildup as my compression numbers are TOO high. I did a carbon soak about 30K ago. The high compression is probably why I get some pinging even on 92 octane gas and timing at 15 degrees.

Any suggestions for removing that carbon w/o taking the motor apart?
 

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wont go any faster?
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johnand said:
Well, I did a compression check on my 1991 Sentra SE yesterday. My car has 180K miles on it. My results were the following:

205, 205, 195, 200.

The FSM states standard is 192, minimum is 164, and difference between cylinders is less than 14.

It appears I have some carbon buildup as my compression numbers are TOO high. I did a carbon soak about 30K ago. The high compression is probably why I get some pinging even on 92 octane gas and timing at 15 degrees.

Any suggestions for removing that carbon w/o taking the motor apart?
actualy that i kno of the only way to get carbon off is to take the head off. also why not try to retard your timing just a little bit to get rid of the pinging
 

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Try a diff plug

You should try a different plug a hotter one to be exact. Don't spend too much money on fancy ones because you are not going to want to keep them too long. All you would want to do is change them add the fuel additive for carbon build up and drive moderalty hard for a little while. Might be a couple tanks of gas or so but as soon as your pinging goes away you can change back to your normal plugs and that should help. It did on my car '92 sentra and my mom's '95 mustang.
 

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Slashie
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man... I wish my compression was close to that. I've got 150s all the way across.
 

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Discussion Starter · #5 ·
the_new_kid said:
You should try a different plug a hotter one to be exact. Don't spend too much money on fancy ones because you are not going to want to keep them too long. All you would want to do is change them add the fuel additive for carbon build up and drive moderalty hard for a little while. Might be a couple tanks of gas or so but as soon as your pinging goes away you can change back to your normal plugs and that should help. It did on my car '92 sentra and my mom's '95 mustang.
Thanks for the reply. I am using the cold NGK BKR6E plugs, for a very long time. I drive the car pretty hard most of the time, and the car sees 90% highway driving. I may try the BKR4E's for a while.
 

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Wise Cracker
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Whoa whoa whoa.... Are you suggesting a hotter plug when he already has problems with detonation? If you DO ping AT ALL do NOT put the hotter plugs in and run it hard without putting the timing back to stock. I also would not switch to 4's I would go back to 5's which is what is recommended from the factory.
 

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in^3,N20,RPM,PSI
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you'll get that carbon on the top of the pistons regardless. I can take a picture to show you how thick that stuff gets on the pistons.

there was a thread somewhere about letting carb cleaner soak on the piston overnight... something like that. might be worth a shot. that stuff is thick and is pretty hard too...
 

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Discussion Starter · #8 ·
wes said:
Whoa whoa whoa.... Are you suggesting a hotter plug when he already has problems with detonation? If you DO ping AT ALL do NOT put the hotter plugs in and run it hard without putting the timing back to stock. I also would not switch to 4's I would go back to 5's which is what is recommended from the factory.
Wes, Yes I know that a hotter plug will increase the chance of detonation, so I will back off the timing to compensate.
 

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Discussion Starter · #9 ·
James said:
you'll get that carbon on the top of the pistons regardless. I can take a picture to show you how thick that stuff gets on the pistons.

there was a thread somewhere about letting carb cleaner soak on the piston overnight... something like that. might be worth a shot. that stuff is thick and is pretty hard too...
James, a pic of the carbon would be great, just to see what I am really dealing with.
 

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Discussion Starter · #13 ·
Thanks James. That is nasty. How many miles on those piston's?

PS: Cute dog, what breed?

Oh, you want to see nasty?!? Wait until I post the pictures of my motor with the valve cover off :rolleyes:
 

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carb cleaner

spark plugs off, 1/2cam of carb cleaner on each cylinder, whait 2 hours, run the engine (w/ eletrical plugs off) to purge the liquid by the exhaust, start engine and be happy
 

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in^3,N20,RPM,PSI
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johnand said:
Thanks James. That is nasty. How many miles on those piston's?

PS: Cute dog, what breed?

Oh, you want to see nasty?!? Wait until I post the pictures of my motor with the valve cover off :rolleyes:
110k miles on those pistons. I used injector cleaner (chevron) sometimes but I don't think it helped at all.

Oh, the dog is a chow, 7 months old! :)
 

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Destroyer of worlds.
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fanl said:
carb cleaner

spark plugs off, 1/2cam of carb cleaner on each cylinder, whait 2 hours, run the engine (w/ eletrical plugs off) to purge the liquid by the exhaust, start engine and be happy
what about giving ants little itty bitty tooth brushes and sending them in there? lol. i'm afraid of stuff falling into my engine if i leave the plugs out...i've already had a little chunk of plastic go in...next time who knows what.
 
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