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 Symptoms of bad compression

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nebstewart07
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PostSubject: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 3:51 am

What are the symptoms of bad compression?
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AA
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 7:49 am

Low/inconsistent PSI readings when performing a compression check.

_________________
'98 SC Riviera • 281k miles • 298 HP/370 TQ • 0-60: 5.79s • ET: 13.97 @ 99.28 • 4087 lb • 20.1 avg MPG • Nelson Ledges Lap: 1:30
3.4" pulley • AL104 plugs • 180º t-stat • FWI w/K&N • 1.9:1 rockers • OR pushrods • LS6 valve springs • SLP headers • ZZP fuel rails
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'05 GTO • 85k miles • 0-60: 4.8s • 16.9 avg MPG • Nelson Ledges Lap: 1:26
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 10:06 am

AA wrote:
Low/inconsistent PSI readings when performing a compression check.

Haha!

Low compression in one or more cylinders kinda feels like running around with one or more dead spark plugs.Not the end of the world but will f**k up yer day if ya like to run on all six or eight or ten or twelve or whatever.
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nebstewart07
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 2:38 pm

So here are my issues:

When driving around flat surface very little to no issue.

When driving up a hill or incline she will hesitate, or kind of stutter right at about 2500 or 1500 rpm

I have no hard shifts anytime. Car has hard time starting unless pressing the gas when starting it the first time. If I shut it down and try starting it up again she starts better.
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 2:59 pm

My personal suggestion based on how the symptoms sound would actually be the maf sensor. Our lesabre has twice now in it's life developed a bad maf and it will be fine until driving on a grade. At first it just acts like it's choking/starving for air a bit and over time it develops into the point where it will literally act as though you're driving with mixed up plugs and then died. Swapping out the maf and it runs good as new. Took my dad and I to fix that after the dealership spent $1800 being useless... Same issue again on our 88 reatta and sane results from replacing maf. Just my suggestion

Although will say, never required fuel feed to start car although maybe to hold idle on cold start occasionally.

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AA
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 3:22 pm

Ignition wires and/or plugs, imo.

_________________
'98 SC Riviera • 281k miles • 298 HP/370 TQ • 0-60: 5.79s • ET: 13.97 @ 99.28 • 4087 lb • 20.1 avg MPG • Nelson Ledges Lap: 1:30
3.4" pulley • AL104 plugs • 180º t-stat • FWI w/K&N • 1.9:1 rockers • OR pushrods • LS6 valve springs • SLP headers • ZZP fuel rails
KYB GR2 struts • MaxAir shocks • Addco sway bars • UMI bushings • GM STB • Enkei 18" EV5s w/ Dunlop DZ101s • F-body calipers
EBC bluestuff/Hawk HP plus • SS lines • Brembo slotted discs • DHP tuned • Aeroforce • Hidden Hitch

^^^ SOLD ^^^ frown

'05 GTO • 85k miles • 0-60: 4.8s • 16.9 avg MPG • Nelson Ledges Lap: 1:26
Because fun


'70 Olds Ninety-Eight Holiday Coupe • 116k miles • 455 Rocket V8
Because cool


'95 Celica • 152k miles • 0-60: yes
Because free
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96riv
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 4:05 pm

Fuel delivery is my guess, either a pump or regulator.
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nebstewart07
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 8:56 pm

New fuel pump, new fuel injectors and new fuel filter
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stan
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyThu Feb 13, 2014 10:00 pm

Engines lose compression over time when you click certain miles.Turbo is the answer....u don't feel it that much.....hahaha
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LARRY70GS
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyFri Feb 14, 2014 7:46 am

nebstewart07 wrote:
What are the symptoms of bad compression?


How would it manifest itself?  Probably a misfire, but that could be caused by lots of other things.  When you have a symptom, you don't go right to the most unlikely cause, you check the more likely causes first, which would also be the simpler things.  You can lose compression from a bad valve seal, or bad ring seal, both very unlikely.  Very simple to check cylinder pressure with a screw in gauge, which you can rent.  You can also do a leak down test, but that is a bit more complicated.  Compression can actually increase a bit over the life of an engine due to combustion chamber and piston deposit build up.

_________________
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deekster_caddy
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyFri Feb 14, 2014 9:49 am

The hard start could be the CTS. They can get globbed with coatings of dex-cool if the car had it's antifreeze not changed for too long. Have you ever done the LIM gaskets? If so, do you recall if the 'free' coolant ports on the heads were plugged with mud?

I'm with everybody else though, the MAF sounds suspect. Do you have the factory airbox or a cone?
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nebstewart07
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyFri Feb 14, 2014 4:46 pm

I talked to my dad and before he shipped the car he put a new mass air flow sensor on.
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llamalor2112
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptyFri Feb 14, 2014 5:20 pm

Potential it could be bad though as well. First maf replacement on our Lesabre was a reman delco unit done at the dealership and the frickin thing did not work at all.
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bmcd9179
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PostSubject: Re: Symptoms of bad compression   Symptoms of bad compression EmptySun Feb 16, 2014 5:36 pm

stan wrote:
Engines lose compression over time when you click certain miles.Turbo is the answer....u don't feel it that much.....hahaha

hahahahahahaha exactly!!
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