1995 Monte engine knock

Tiny
CZR1760
  • MEMBER
  • 1995 CHEVROLET MONTE CARLO
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 120,000 MILES
I recently bought a 1995 Monte Carlo with 3100 V6 with 120,000 mile. Before buying the car I looked it over and drove it with no problems. Drove the car home with no problems. I did some work to the car and drove it with no problems. Drove it to work the other day and still no porblems. When I went to leave for the day, as soon as I started the car, I had a problem. The car seemed to be running rough, had acceleration problems and a noticeable "hollow popping" noise coming from the engine and the service engine light came and stayed on. The car acted as though it wanted to die at idle, but did not stall. The previous buyer had just purchased the car and didn't know it's history. He seemed like an honest person and told me the few things he had done to the car. I'm thinking I'm the sucker. So far the car has had the following work done. Previous owner had new serp belt, radiator, hoses and battery installed. I changed oil, installed new tensioner pulley, new knock sensor. Fuel pressure is showing 41 lbs. Checked all wires (good), plugs (one was loose, but looked good), tightened coil pack. Haven't driven the car anymore because of the now definite "knock", which seems to be coming from the top of the motor (driver's side maybe, but definitley top). The car starts everytime and seems to idle better now than before, revs ok, but has nasty "knock". I cannot check flash codes because the ALDL plug has only "A" & "M" positions. Please help. I am out of ideas, time and money and think I'm stuck with a piece of crap that I won't even be able to sell. Thanks.
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Monday, March 21st, 2011 AT 12:32 PM

11 Replies

Tiny
FIXITMR
  • MEMBER
Knock, tap, tick can you locate sound with an ear directional aid like tube or stethescope? Do you know what rod and crank knocks sound like?
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Monday, March 21st, 2011 AT 1:02 PM
Tiny
CZR1760
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I will try to isolate where the noise is coming from. I have not isloted exacley where yet, but it does sound like top driver's side. I couldn't say what sounds are what, since I'm no mechanic. If I were to wager a guess, I would say it sounds like a rod knock. The noise has gone from a tinny hollow popping to sharp snapping knock sound. The noise somewhat goes away when reving, but sounds bad when throttles back down to idle (snapping knock). I really don't know what happened, the car was running great and now it sounds like it's going to blow up. I'm wondering if the problem was always there and the last owner just lied and somehow covered it up. The oil looked really bad when I changed it?
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Monday, March 21st, 2011 AT 1:14 PM
Tiny
CZR1760
  • MEMBER
Hope everything worked out for you and your family issues. Thank you again for the help. Am I able to make a donation once my question has been asked? Just wanted to know, since you're trying to help.
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Monday, March 21st, 2011 AT 1:16 PM
Tiny
FIXITMR
  • MEMBER
I'm still wrestling thru the issues but I couldn't concentrate on both at the time. About the oil. It sounds like there may have been an attempt to cover up the issue of the knock. If you still had the old oil you could check it out to see what it consists of. What oil did you put in?
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Monday, March 21st, 2011 AT 4:24 PM
Tiny
CZR1760
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Valvoline 10W-30. I don't have the oil anymore that I took out of the car, it's been recycled. It appeared to be "thicker" (as if very old) and it also looked dark with some grey color in parts of it.
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Wednesday, March 23rd, 2011 AT 12:23 PM
Tiny
FIXITMR
  • MEMBER
I have a tempo with a really bad lifter and if it sets for a day or more will really tap scary/loudly for a few minutes. I have added a thickener to 20/50 oil and this makes it go away after a few minutes for the rest of the day. In my case I would have to pull head to get to lifter. You only have to pull intake if it's a lifter in your case. Might be something with rocker arm you might want to remove valve cover and check?
I think in order to donate you will have to start a new question as a thanks for the help/suggestions.
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Wednesday, March 23rd, 2011 AT 2:13 PM
Tiny
CZR1760
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I'll try and pull the intake off sometime this week and I'll let you know what I find out. Thanks.
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Wednesday, March 23rd, 2011 AT 2:24 PM
Tiny
CZR1760
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I was wondering if there is anything else I should be looking at (EGR, oil pump, etc.)? I am not a mechanic so I don't know what specific noises are what, but I've tried to descibe this noise as best I can. I have no problem pulling off the intake, but I'm unsure what I'm looking for once I do, other than something obviously wrong (pieces broken, etc). I really don't want to think that I was taken for a sucker and don't want to spend much more money trying to figure this thing out. The big problem I have, is that I could never try to sell it off and be decieptful to someone else. Thank you for your help.
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Thursday, March 24th, 2011 AT 4:48 PM
Tiny
FIXITMR
  • MEMBER
I would check under valve covers for any damaged parts first.
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Friday, March 25th, 2011 AT 4:25 AM
Tiny
CZR1760
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That's my plan this weekend. I tried to let it run for a little bit to rule out "piston slap". After running for aprox 10 mins. The noise was still there, with a vengance. I'll let you know what I find out once I pull the intake. I've been doing research and found that these engines have alot of trouble with LIM gaskets leaking, so who knows what I'll find once I start tearing into this thing.
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Friday, March 25th, 2011 AT 12:12 PM
Tiny
CZR1760
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I pulled off the front valve cover and found that I had a push rod out. A broken ear on the push rod guide was to blame. I went to my local pull a part and snagged a new one, no problem. I also swapped out the cam position sensor and a new ignition module to help with trouble codes. Car seems to be running great. Thanks for all your help.
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Monday, March 28th, 2011 AT 12:39 PM

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