piston slap
 

I have a ’97 Accord EX 4-door. Bought it new. It now has slightly over 90k miles. Oil (Pennzoil 5W-30) and filter (Fram 3593A) have been changed by me every 1-1.5k miles (no flames, please). All other engine maintenance by the book or sooner. Engine has not been abused although I do put my foot in it and lay the ears back on it from time to time. About 6-8 months ago, a knocking sound in the engine came to my attention and has gotten progressively louder. It occurs in a range of 1.5k to 2.5k rpm under very light engine load. With the A/T in neutral and the engine holding at 2k rpm, the noise is not audible but, if the throttle is opened just a bit more, the knocking can be heard. During a “normal” rate of acceleration from a dead stop, the sound is very, very faint or not audible at all. It does not do it when cold.

Today, took it to my closest Honda dealer for his opinion. This dealer has worked on both my car and my wife’s ’96 Civic LX in the past - both had the extended emissions warranty and were given a complete tune-up including an oil and filter change free of charge. The work was done to my satisfaction; this dealer has a good reputation.

Upon arrival, told the Service Dept. “greeter” that I wanted to see someone with 4-cylinder engine experience. He left and returned with the Asst. Service Manager. Told him about the sound then opened the hood and let him hear it firsthand. He immediately nodded and said that it was “piston slap”. OK. “What is piston slap?”, I asked. “It’s the sound of a piston hitting a valve”, he said. “Are you sure?”, I asked. “Or, it could be the sound of the piston hitting the head”, he said. Oh, OK. “Not to worry”, he said, “they all do it; this model engine is notorious for it”. With that, I looked for the closest exit, thanked the man for his time and left.

So…. Just what IS piston slap. Do my symptoms the meet the requirements. If so, is it fixable without removing the engine. Or, what’s REALLY wrong with the engine?

RE: piston slap
 

smart... I would have left too... here's an article on piston slap http://www.pistonslap.com/whatisit.htm anyway, if you have piston slap then chances are you're burning oil and fouling plugs too, plus most likely a loss in compression.... When was the last time a valve adjustment was done? Does the car do anything besides make that noise at certain times? Can you re-create the noise in neutral at a stand still?

RE: piston slap
 

Your car is an interferance type engine, meaning if your timing belt breaks then the piston is probably going to slap the valve, so you get either a bent valve, a hole in the piston head, or both.... Piston hitting the valve my rear....

RE: piston slap
 

thanks for the interesting article.

plugs look good; they're as clean now as they've always been with no indication of oil being burned. no apparent oil loss between changes. engine recently had a complete freebie tune-up (new plugs, wires, dist. cap & rotor, checked/reset ignition timing, oil & filter) thanks to Honda.

don't know about compression but car feels as good as it ever did. winds out readily to the red line in all gears (except 4th) never tried to find top-end. VTEC operating OK.

valve adjustment has never been checked. new timing belt package (timing belt, balancer belt, seals, water pump, etc.) to be installed tomorrow. specifically asked that valve clearances be checked. was told it's part of the timing belt package. a 5-hour job, i'm told - in by noon, out by 5.

the noise can be produced in neutral. hold rpm at 2k = no sound. increase speed very slightly = noise but only as long as the engine is loaded - no load = no noise. when driving, very light load = noise just before 1-2 shift (15mph) and 2-3 shift (20mph); can't hear it at 3-4 shift (30mph). noise very, very faint or not at all under "normal" driving conditions.

have my fingers crossed that the timing belt work with valve adjustment might solve the problem. wondered if one or more of the wasted motion assemblies for the middle intake rocker might be worn thereby allowing the big rocker to "flop" around a bit. we'll see tomorrow.

RE: piston slap
 

I can't believe a Honda service manager told you it was the sound of a piston hitting a valve. What a crock of s***. I'd look for a different Honda certified shop.
Let us know if the t-belt job fixes the noise.
You never know, you might not even be experiencing "piston slap." It could be something else. Start using a different filter other than Fram. I have heard bad things about fram on here.I use purolator.Many say the Filtech filters you buy at the Honda dealer are some of the best money can buy. Try putting in some Marvel Mystery oil on your next oil change as well. the noise may even go away completely.

RE: piston slap
 

MMO is good for lifte noise mainly..... that could be the sound that you are hearing ..... or valve adjustment. Piston slap, pffffff!!! If that were the case, the engine wouldn't perform correctly! You should tell the Service Manager that he needs a new assistant or should at least send this one back to school.

RE: piston slap
 

got the car back today after installation of the timing-belt package. the knock's gone. by knock, i don't mean a clicking due to excessive valve clearance; it was a knock similar to a bad rod bearing.

tried to get it to happen all the way home from the honda dealer but couldn't. at home, opened the hood and tried again but couldn't get it. can only speculate as to the cause. thanks to all for your intrest and input.

RE: piston slap
 

I have a 2000 Accord LX 2.3L vtec which has the same knocking sound. Although mine is a little more pronounced when the engine is cold its a definite 'knock' between 1k - 2k rpm during light throttle, loudest with no load, or on engine down rev. The engine has 74k miles on it, never abused and maintenance carried out religiously. I have fished around for this problem for a few months now. Did a valve adjustment, though they all turned out to be within spec. It's def. not an exhaust vibration and it is a 'knock' not a click form injectors or valves. It is internal in the engine and does kinda sound like piston slap (side wall slap) or loose wrist pins but the car burns no oil and is above specs on compression. Seems like its a common complaint for this car as I look around. Honda says its normal but it bothers the crap out of me. I'll look into an early timing belt and water pump change but I have a hunch that wont fix it. I have been wrong before though.

RE: piston slap
 

F22B1s are notorious for piston slap. It's from piston skirts (the area below the wrist pin) being made smaller and smaller in surface area to reduce weight and friction. What happens when it's cold is the ring tension is not enough to hold the pistons perfectly straight and when it rolls from TDC to just after, the piston moves and taps the cylinder wall. There's no wiping or anything going on and it's aluminum to aluminum that's harder so there's no wall wear(a lil on the piston), it's just annoying and goes away when the engine warms up and the softer aluminum in the piston expands to fit the hole better. All 4cyl reverse rotation hondas valve clearances tightenover time though. A properly adjusted F22B1 will make quite the racket when cold. If yours doesn't, your valves could be hanging open when warm and they'll burn eventually. I adjust my ex. valves a bit loose just so I don't have to adjust them so often. The lil bit of noise they make is easily drowned out by my stock radio [8D]

Hey - did it sound like this: http://www.youtube.com/watch?v=HnY5_DKgaAw ? Read the post there too if you don't mind... The noise I'm talking about is hard to pick out on the video because of all the valve lifter noise... It actually sounds worse than that (if that makes sense...)

I've been searching high and low and this noise is being made only when the engine is hot (good and warmed up).

I bought the car with 94,000 miles on it and now have 114,000 -- its been making the noise since I got it (in fact, I first heard it on the way home and thought there was something SERIOUSLY wrong with engine and almost took it back! (in fact, I did take it back to have them take a listen.. and they said it was nothing...) God only knows it didn't do it on the test drive because it wasn't fully warmed up!

makes the noise under light load -- if i'm accelerating normally it doesn't make it, but if I accelerate very slowly between a certain rpm range, i hear it...

ALso, just like you said... in neutral, if i hold the accelerator steady at like 2000 rpms, the noise isnt really there... but if i blurp the gas even only slightly, i hear it!

I've heard of the timing belt tensioner and other stuff that is possible... And my timing belt is now 10,000 miles overdue... I was afraid to change it because i was thinking the noise was a rod bearing or something!!! But after reading your post, i think i might make an appointment to get it changed and the valves adjusted!

one thing that concerns me is that the noise gets quieter when the #3 spark plug wire is removed... (on numbers 1, 2 and 4 I don't think i hear a change... But even still I guess it could be something with one of the valves and a piston?

thank you so much for the reply and I'm so sorry to bother you... (I am just so excited that someone else had something similar!)