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1995 acheiva tapping/knocking noise
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jeffholderness
New User
Oct 14, 2007, 12:11 PM
Post #1 of 4
(1564 views)
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1995 acheiva tapping/knocking noise
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Hi all,
I would appreciate any pointers on where to go next with this. I’ve listed the problems I’ve been having with my car, and would like to try fixing them myself if possible, but am fine with taking it in to a shop for diagnostics if you recommend it. Any suggestions would be greatly appreciated. I have tried to include all relevant history on the car that I know of. Anything I'm missing I would be happy to check on and add.
Also, does anyone know of an inexpensive OBD program/kit for a 1995 olds achieva that would also work with the current OBD2 interface? It's apparently wierd year for OBD, and oldsmobile used different interfaces on different models. Perhaps something I can hook up to a laptop? I’d prefer to not spend a lot of money on something that will only work on this car.
Thanks in advance.
The car:
1995 Oldsmobile Acheiva
Mileage: 120k, bought used at 90k in 2004 with no maintenance record
Engine knocks/taps at idle (I’ve been told it sounds like the timing belt needs replacing, however the achieva uses a chain so I'm not sure), Increases intensity and speed as RPMs increase
Decreased (60% of cold) noise when hot (15 min running)
Burns oil. Needs 1qt/1k miles. Not seeing it in exhaust.
Oil pressure gauge at 40psi during idle (1k) and increases to 60psi when RPMs at 3k
Pressure gauge on the dash jumps by 5 psi while applying gas at idle (ie immediate change from 40 to 45 psi and back down again after I let off the gas)
Replaced transmission at 95k, however, I just checked it and looks rather dirty
When in neutral, revving the engine, the RPMs sputter at 3.5k (I didn’t press my luck after the drop in RPM, so I don’t know if I can push through it)
Tune-up about 20k ago:
The problem doesn’t appear to be associated with any of the tune-up parts.
Checked PCV valve (open and sucking air while engine running, but closed when off)
Changed spark plugs (they looked OK, NGK iridium plugs with 20k miles on them)
Plug cables look fine.
Air filter looks fine
Added seafoam to the fuel (91 octane, doesn’t help) and crankcase.
Also delivered 5 oz of 50/50 seafoam/gas via the PCV.
This seemed to have helped it briefly (10 minutes) (however, that may very well have been optimism)
Thanks again for any advice. I'll be sure to let you know what the problem is as soon as I find out.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 15, 2007, 4:37 AM
Post #2 of 4
(1555 views)
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Re: 1995 acheiva tapping/knocking noise
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Whooa baby! You rev this engine to 3,500 RPM with no load and didn't want to try for more?? An engine with no load on it can easily get damaged by over revving. See that RED line? That's for when all is good and it's in gear with load on it.
Second trans going bad? Hmmm? Sounds like this vehicle gets abused. This engine needs a compression test to determine the mechanical condition of it. Repairs won't help for long without correcting operator judgement,
T
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jeffholderness
New User
Oct 15, 2007, 7:01 AM
Post #3 of 4
(1554 views)
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Re: 1995 acheiva tapping/knocking noise
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I didn't realize it was worse to rev the engine when it wasn't in gear. Good to know. Thanks. As far as the tranny, the first one was in bad shape when I bought it. I don't think I abuse it, and wouldn't normally rev the engine like that I was just trying to figure out if the oil pressure was being regulated.
As you can see I'm rather new at this. Maybe I should just forget about it and take it in before I do more damage than good.
Thanks for your help.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 15, 2007, 8:45 AM
Post #4 of 4
(1551 views)
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Re: 1995 acheiva tapping/knocking noise
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Just to follow up and so you know, the deal with RPMs is funky. It goes beyond automotives. Things need the resistance to stay stable. An odd example would be understood by many is the feeling you get when running down hill. You lose control of your legs but if you are strong enough you could run that speed up a hill. Most critters of the world can run faster level or uphill than downhill with no resistance - it's true!
As far as oil pressure: If an engine can't stay in at least the low end of the range at idle (say 650 RPM) then there is a problem. By perhaps 1,200 it's about as high as it's going to get. It is regulated not to go too high by a spring and by-pass which almost never fails to making too much oil pressure. That problem is almost unheard of.
You are hearing mechanical noises it seems and that with it not running well at RPM does suggest mechanical problems that could be so expensive you want to know before you go too far with the bucks when another option might be better.
Good luck with it,
T
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