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1994 Pontiac Grand Am noise and oil pressure flux

Tiny
OLDRAIL
  • MEMBER
  • 1994 PONTIAC GRAND AM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 12,000 MILES
Recently bought car for grandson, engine had been taken apart not rerpaired. Tinming chain tensionener had come apart and dropped valves. Person I bought it from had removed timing chain, ohc and head and had the head sent out for rebuild, planed, and a few new valves etc. I purchased and put back together per repair manual. When I start car engine has clatter, like lifter? That does quiet when power steering is used and then resumes and now oil pressure fluxuates 50 to 65lbs. And engine hesitates at times.
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Monday, October 13th, 2008 AT 10:07 AM

7 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
55-65 lbs warm oil pressure is not bad for an engine with 120K. How much have you driven the car since you put it back together? Do you get a check engine light? Did you put in new lifters and cam or reuse existing? Please advise.
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Monday, October 13th, 2008 AT 12:27 PM
Tiny
OLDRAIL
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  • 4 POSTS
Agree pressure seems good, but the bounce is often and rapid and when it bounces the engine rpm drops and jumps up but does not do it every time I start it. Last two times I started it has not fluctuated. I have not driven much since putting it back together, maybe five miles, afraid the tensioner will fail again, but have started several times and let it warm up. The check engine light does not come on.

I did nothing to the cam assm. Other than reinstall it, I did not ask him if he moved the lifters around but the assm. Itself was not taken apart.

Just borrowed stethescope and tried to locate noise, not all but most seems to come from the timing chain area and quiets considerably when I use the power steering.
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Monday, October 13th, 2008 AT 1:52 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
What happened to the original chain tensioner that it broke, or was it just rotten luck? Did the chain have to be replaced? Now that you have run the motor, has the new tensioner taken up the slack? You would have to pull the valve cover to find out.
If you are sure everything is OK with the cam chain, I would run it around the block a few time and see how it runs. If the check engine light is on you could pull the trouble code(s) and see what they are. This could be a valuable clue.
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Monday, October 13th, 2008 AT 2:31 PM
Tiny
OLDRAIL
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Apparently rotten luck, now told this is second time, they did replace the timing chain and cam gear so I reused them when I put it back together. I also replaced the water pump as it was very rough.

Thought tensioner would pick up slack right away, is there a run in on it? How can I tell if tensioner has picked up slack if I remove the valve cover? I was careful of timing marks and the engine started right up, has good throttle response, smooth accelleration and seems to have good power when I hold the brakes. Just noisey and oil pressure jumps although did not when I started yesterday, will drive a few miles today.

As info I'm old 50's-60's mech. Just retired and haven't done a lot since so like coming from dark ages and have never worked on a 4 cyl. Maybe they are naturally noisey?
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+1
Tuesday, October 14th, 2008 AT 11:37 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,395 POSTS
50's and 60's huh? That's when the only thing you had to worry about was gas and points. The first motor I ever tore apart was a '56 ford 272. I remember wondering what that "lumpy rod" (cam) was for. I've been pulling wrenches ever since. Retired now.
A quick way to check timing chain slop. (The old 350 chevy trick.) Grab the crankshaft pulley and turn it back and forth. You will be able to feel it when it hits the can. Little or no free play? The tensioner is good.
I put a headgasket in one of these motors, years ago, and remember the wear block on that chain tensioner was broken. The guy a the parts counter told me it was from turning the engine "backwards" and putting the strain of the cam on the tensioner which it can't take. Makes sense to me.
Oil pressure- You could screw a gauge in place of OP sender and check actual pressure.
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Tuesday, October 14th, 2008 AT 12:29 PM
Tiny
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Sorry took so long had to remove wheel and come up from below to turn crank, seems tight, very little play. Put back together and ran for several miles ran good but noisey oil pressure stayed right on 60lbs. No surging.

Seems all noise is in the cam shaft, clatter terrible while driving and idling but when put slight turn of steering wheel quiets right down. Had wife turn wheel little, and doesn't have to be much just enough to require torque on the cam to power steering pump or if I push on the belt with a bar and as you listen to the cam and timing chain area quiets right down to hum. Suppose requires cam and lifter rebuild was hoping would be something simple like pour a little auto transmission oil in the crankcase to quiet the lifters!
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Thursday, October 16th, 2008 AT 4:53 PM
Tiny
JAMES W.
  • MECHANIC
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I wouldn't recommend using ATM in the oil. ATF is a high detergent and is great for removing varnish on lifters and piston rings but, you don't have that problem. I would try an oil pollimer enhancer of some type. There is a zillion of them out there to choose from. If your lifters are slow in pumping up, this should help
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Thursday, October 16th, 2008 AT 6:33 PM

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