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Discussion Starter #1
I have a 96 Altima with 90K on it. Recently idling started going bad with a drop in mileage and exhaust ejecting lots of smoke. The car keeps jumping around 500 - 700RPM when at a halt. Soon the check system light came on and went off again in half an hour. I got the AutoZOne people have a look at the error codes and they said it was one of the Knock Sensors and another one was for Cylinder 4 misfire.
I took the car to one of the mechanics and he tested the cables and spark plug. All of them seemed fine with no carbon desposit. Then he checked the compression level in cylinder 4 which came about 90 to 100 which he said was low according to the standards. Now he is asking me about 2 grand for the complete engine service. So is that wat it really takes to get the needed compression level back.. what problems i am looking at if i dont get it repaired.. and what is actually causing the compression drop.. Please suggest?
 

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Biru O' Kudasai
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The engine should have a cylinder leakdown test performed to isolate the cause of the low cylinder pressure. From the symptoms it sounds like a possible problem with one of the exhaust valves in no. 4. I would pull all of the spark plugs and check them over if they look worn or the least bit bad then replace them with a new set of NGK spark plugs part no. BKR6E-11 and run about $2/ea. and then drive it to another shop where they will give a good diagnostic instead of you need to rebuild the engine when it may be something less drastic.

Troy
 

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Discussion Starter #3
Compression is low in all Cylinders ..leak at Intake

Thanks for your guidance Troy. This time i went to a different mechanic and he checked the compression in all the cylinders and found all the Clyinders had a compression level of about 100. Also the spark plugs are new and of the specifications u mentioned. So its definitely not the spark plugs. He checked the distributor points and contacts and found them working perfectly fine. He checked for engine firing sound after deplugging the connector wire for each engine cylinder in a sequence. The firing changed for all the cylinders except for the fourth one. The firing remained almost same.
After some more testing he heard a whistling sound near the intake and finally told me that the intake manifold needs to be changed and will cost me somewhere around 500 bucks. Please suggest?

KA24Tech said:
The engine should have a cylinder leakdown test performed to isolate the cause of the low cylinder pressure. From the symptoms it sounds like a possible problem with one of the exhaust valves in no. 4. I would pull all of the spark plugs and check them over if they look worn or the least bit bad then replace them with a new set of NGK spark plugs part no. BKR6E-11 and run about $2/ea. and then drive it to another shop where they will give a good diagnostic instead of you need to rebuild the engine when it may be something less drastic.

Troy
 
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