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Chattering Noise on 2.2 - Piston Slap?

The problem

Isaac Conver wrote: my 1993 Sundance (2.2L FI) seems to be developing a noise that can only be described as a chattering noise on startup. I used to hear something strange every so often when I had the hood up, and now it seems to be at least almost everytime the engine is started (heard when hood up) when fairly cold, increases with throttling, and seems to be somewhat louder than before as well. I have listened quite intently with my head practically against the engine block, and it really seems to come from inside the engine block somewhere near the timing belt....

John Mastriano wrote: This sound like a classic piston pin slap. It is very common with the 2.2L and 2.5L engines and it gets louder with age . If this is the case, it is really nothing to immediately worry about. I have seen engines go well over 100K miles with this problem with no lasting detrimental effects. I would however take it in to a repair shop just to verify the problem.

Paul wrote: Could you also be hearing symptoms of a timing belt tensioner pulley bearing failing?? That would be pretty easy and cheap to repair/replace yourself. If it's piston slap, just get earplugs and run it.

John wrote: I had a 86 Aries with "piston slap". When my ear was close to the oil pan you could hear it loud and clear. The noise wasn't too loud otherwise. I thought my bearings/lower engine was just going to seize up on me at some point. I just changed the oil, kept driving, put on over 130,000 miles while I owned it, junked it at 230,000 miles because of an accident. I only found out that this symptom is common with the engine from this website.

Bob wrote: I had the supposed classic piston slap noise, and I changed the grade and type of oil and brand of filter, and the noise that I had every winter for the past 3 years went away completely. I used to run Castrol 10W-40 since new in my '92 Daytona 2.5L non-turbo, with Fram filters. Now I use Mobil One synthetic 5W-30 with Purolator filters. I can't say whether it was the synthetic, the grade change or the filter, but the noise is gone! It was a rapping sound, like lifter noise, but louder and lower in the block. It would haunt me for 2-3 miles with the engine cold in cold weather (below 20F), going away when warm. It did this starting around 120k miles. Now I have 148k and it runs perfectly.

Dave / webmaster wrote: Agree wtih Bob, except I simply switched from 10W30 to 5W30. That solved the problem immediately. Our Neon also seems to run quieter on 5W30. Chrysler, incidentally, recommends 5W30 oil, but few dealerships will put it in. That's one reason why I don't use a dealership to change the oil (shamefully, I don't do it myself, either! - but I go to a local guy who I trust. When I used synthetic, I bought it for him since he gets oil from a parts shop).

The oil weight was not the issue in this particular case.


Paul clarified: Piston slap will be of a much lower frequency than will that from a bearing that's going south which is running at engine speed. I still bet it's the timing belt adjustment pulley bearing. In the meantime, it might be "walking" the belt off the cam pulley, so pulling the top belt cover might be in order...fairly soon.

Ian Howard added: I have a 1989 Dodge Omni (TBI Non-Carb 2.2l) and it is making a smimilar noise. And has been getting louder. My mother in law says it may be piston slap or a going piston. This is what I noticed. It makes a "clack" noise every time the engine rotates, It's sounds as if it were a little diesel engine. I can't figure it out. It isn't as audible if the RPM is above 2000. It's been a good car (give it some credit, it's 11 years old with 225,000km [not sure in miles...]) Is this piston slap or something different?

Paul responded: The noise you describe is very different than that which Isaac seems to describe. I'd agree with your mother in law.


What is piston slap? (courtesy Steve M)

I believe that "Piston slap" is when the skirt of the piston is draging, slaping, on the side of the cylinder wall. In an ideal situation the piston never touches the sides but is held away by the rings but because of increased clearances with age the piston wobbles in the cylinder. When the engine is cold it's worse. Aluminum has twice the expansion rate of iron and closes the gap when operation temp is reached.

But we don't live in an ideal world. On the 2.2/2.5 pistion rod there is a small hole that directs oil toward the cylinder wall to provide lubrication and a barrier against pistion drag. If hole is not pointed in the right direction you wind up with one pistion (No. 4) not geting the proper lub and it will cause excessive wear and then the slap which won't go away with heavier oil. I'd asume that if one of these holes became pluged (they're not directly pressurized by the pump) such wear could happen in any cylinder.

Had the case of a rebuilt engine with the rods put on backwards and it cost a complete rebuild. Noise was too low in the engine for a valve noise and had just had the head redone and too high pichted to be a rod or main. Still check the bottom end rods and mains and pulled the valve cover before commiting to pulling the pistions out and that's when I found the scuffed cylinder.

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