Rough idle

Tiny
CARLOS1382
  • MEMBER
  • 1999 CHRYSLER CONCORDE
  • 162,000 MILES
1999chrysler concorde 3.2 v6 started to idle rough I changed spark plugs air filter and three ignition coils and its still the same so took it to a shop they said compression in #5was at 70 and and it was suppose to b at 100 then I took it to the dealer where I got it and they say its reading fine so my question is what is the compression suppose to b at and how low can it go before it is considered a bad cylinder also between 40-50mph car shakes horribly
Tuesday, June 14th, 2011 AT 8:53 PM

8 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
If the dealer says the compression is good on all cylinders something else is causing it could be one of the following below:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

1.Defective spark plugs
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression
4.False air leakage.
5.Faulty fuel injectors.
6.Insufficient fuel pressure.
7.Contaminated fuel.
8.EGR valve that is leaking.
9.Oxygen sensors.
10.Throttle position sensor.
11.Manifold absolute pressure sensor
12.Mass Airflow Sensor
13.Idle air control valve
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Tuesday, June 14th, 2011 AT 9:05 PM
Tiny
CARLOS1382
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Would u know what the standard compression is supposed to b at
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Tuesday, June 14th, 2011 AT 9:23 PM
Tiny
RASMATAZ
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Should be around 140-160psi and no more than 10psi differences from each cylinder
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Tuesday, June 14th, 2011 AT 9:45 PM
Tiny
CARLOS1382
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  • 5 POSTS
So if cylinder five is at 117 should I b worried
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Tuesday, June 14th, 2011 AT 9:52 PM
Tiny
RASMATAZ
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Give me all your compression readings and also you can do a cylinder leakage test to confirm where the excessivbe leak at-
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Tuesday, June 14th, 2011 AT 10:34 PM
Tiny
CARLOS1382
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  • 5 POSTS
Ok I can get that info
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Tuesday, June 14th, 2011 AT 11:24 PM
Tiny
CARLOS1382
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  • 5 POSTS
#1 120#2 117#3 120#4 118#5 117#6 120
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Wednesday, June 15th, 2011 AT 9:32 PM
Tiny
RASMATAZ
  • MECHANIC
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Is these dry or wet tests-Do a cylinder leakage test-sounds like timing chain or belt problem
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Thursday, June 16th, 2011 AT 12:29 PM

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