91 KA24DE Confusing knock, need help

[Sygerwulf]

Alright, nearly a year ago my 240 started to knock. At first I was told it was a rod bearing, then a few days later that it was the timing chain. I checked the chain and it had some slack so I de gunked my tensioners and removed my upper guides. The chain tightened up significantly, but the sound remained. Since there was markings on my valve cover I just assumed it was slack in the chain since several people had told me thats what it was. The car had 176,000 miles on it then

Now it has 200,000 on it and the knock is still there. I read in a post to remove the spark plug wires of each cylinder and see if the sound stops to identify if it's a rod bearing or possibly piston slap. I did this and it stopped when I removed the #2 cylinder plug wire. The problem is that by all accounts from what I've read on here and by what I've been told my car should have thrown a rod 20k miles ago. The sound isn't that noticeable, you can barely hear it when going down the road and you can't even hear it if you have the radio on at all. There's also no noticable performance hit. It knocks about 4-5 times at start up and then stops and doesn't sound again till it gets to around 3k rpm and it only knocks on acceleration and stops when you hold it at a steady speed (ie 3-4k rpm). Also I just recently did an engine flush and put in some higher grade oil and the noise has reduced. All of this seems to be against it being a rod bearing, just the fact that it's driven 30k miles and hasn't blown yet. I need to know if there is any chance that this could be something else doing this.

If there isn't I need to know if this could be done just by dropping the oil pan, and hard it would be.

[NISTECH]

It is definitly a problem with the components traveling up and down in cyl 2. No question. Now it could be one of 3 things. Rod bearing, wrist pin slop, or piston slap. to determine if it is piston slap or rod knock you need to use a set of engine ears [ looks like a stethescope with a metal rod on it] listen for the noise at the bottom of the block and near the top of the block by cyl 2. [not on the head] if its louder at the top it is probably piston slap. If its at the bottom its rod bearings. To determine if its wrist pin which by the way is a more rapid knock noise. You need to pinch of the pcv fresh air line going to the valve cover. You will want to hold it for more then 30 secs. If the noise goes away it is wrist pin slop. What pinching the PCV line does is allow pressure to build in the crank case which will hold the piston on its wrist pin upward.

[Sygerwulf]

Is it normal for it to quiet down after an engine flush with any of those? And would piston slap be a direct cause of the loose wrist pin or is it something completely different?

I don't know alot about bottom end internals so I'm kinda daft about this lol

And is it normal for it to last this long without giving out?
Modified by Sygerwulf at 9:26 AM 9/17/2005

[NISTECH]

Is it normal for it to quiet down after an engine flush with any of those?

sometimes yes

And would piston slap be a direct cause of the loose wrist pin or is it something completely different?

No piston slap is when the cyl is bigger then the piston and the piston slams into the wall of the cyl when it reaches the top of its travel. Wrist pin slop is when the piston is loose on the pin and it hits at the top of the travel and the rod is on its way back down then the cyl fires and slams the piston down on the wrist pin hence the double speed of the noise.

And is it normal for it to last this long without giving out?

Easily being the noise will quite down and cant be heard with other noise in the car it hasent gotten that bad yet.

[Chezedik]

I would think it may be worth checking clearance on the lifter shims on Cyl 2. If you have never done it, they could be out of spec for any number of reasons. This should not cause any sort of issues as far as the motor self-destructing, but will cause a slight loss in power. Basically, get a set of shim stock feelers, and feel it out with the cam lobe in the position to open the cylinder, use a feeler that is just big enough to go between the two with a little resistance. I believe the spec is .012" when warm. Any KA I have ever seen has a 'lifter' knock between 3 and 4 after, say 50K mi., it would naturally get worse with mileage. The deal is since there are no actual lifters, they cannot self adjust. The shims should be checked periodically, at least anytime you have the valve cover off. I never mean to try to supercede Nistech, because he knows his Shiznitel, but that is my $.02

[NISTECH]

There is one flaw in that. when he pulled the #2 plug wire the noise went away. If it was valve train noise ,it wouldnt go away when pulling plug wires.

[Sygerwulf]

couple things I forgot to mention...

In the oil changes since it started I haven't noticed any changes, ie metal shavings in the oil. Also sometimes I can rev it just right or shift at just the right time and it doesn't do it at all.

And noise isn't a "double knock" sound, it's a constant single knock sound, kinda like someone knocking on a small door quickly lol

[NISTECH]

Get the stethescope and listen to the engine as I mentioned before. I am betting its rod bearing.

[Sygerwulf]

I'm gonna check tomorrow to see where it's coming from, but let's go ahead and assume that it is rod bearings.

I've looked and I've found the standard replacement bearings and then oversized bearings. What's the difference here and how do I know which ones I'm gonna need?

[Chezedik]

well Nis, I have got to say it yet again, good call.

[NISTECH]

I'm gonna check tomorrow to see where it's coming from, but let's go ahead and assume that it is rod bearings.

I've looked and I've found the standard replacement bearings and then oversized bearings. What's the difference here and how do I know which ones I'm gonna need?

Well heres the deal. You need to measure and figure out which bearing you will need. You need to measure the crank shaft journal for the #2 connecting rod. we will call that measurement DP, then you need to measure the inner bore of the connecting rod well call that "c" now you need to subtract Dp from C to come up with your clearance should be somewhere in the .010to .035mm[.0004 to .0014"] the max is .09mm[.0035"] so if you exceed that number you need to add the excessive amount to the recommended bearing grade stamped on the front of the crank shaft. There are 2 numbers on the front of the crank counter wieght. that look like this "1 0 2 1 " then one just below it " 1 0 0 1 0" The first 4 numbers are your crank rod bearing grades in order. If you had a 0 in there then you need to add your number to determine if you need a 1 or 2 grade bearing. If you already have a 2 in there then you need to have the crank machined and add an undersize bearing.

Ok thoroughly confused?? so am I..lol

Now how about the easy way. Pull the number 2 connecting rod cap off and measure the thickness of the bearing in there. through a piece of plastic gauge in between the cap and the bearing and reinstall the cap and bearing on the crank[with the plasti gauge in there], tighten it to torque spec. DO NOT rotate the crank. Then pull it back off and measure the thikness of the plasti gauge. Add that to your existing bearing thickness. This will give you your total clearance. Then subtract .0009 " from that number to come up with the bearing thickness you need.

[Sygerwulf]

Thanks a lot. What should I use to messure the thickness?

Also I dunno if this matters but I was driving it today and I noticed that when I downshift to slow down it doesn't make the sound, no matter what rpm I downshift into. Shouldn't it be knocking when I downshift and go above 3k rpm?

[NISTECH]

This

[InsanityInc]

It's a vernier caliper (a digital one at that, oooh pretty), assuming you've never seen one before, sygerwulf.

[NISTECH]

I like digital, it avoids the thinking factor..lol My micrometer is the same way. and it has the inch/mm button on it so I dont even have to convert..lol

[Sygerwulf]

lol I've seen one before, but not a digital one. How much does a digital one run? And where would you get one? all the little parts stores out here don't have ****

[NISTECH]

That picture I grabbed off ebay. That particular one was like 10 bucks at the point I looked at it.

[Sygerwulf]

I'm most likely gonna buy BDs14se's ka and just swap it in.

Is there anything specific I need to take into account swapping an s14 ka into my s13?

[NISTECH]

Nope just swap your intake and exhuast manifolds to it and you wont have to do anything special.

[Sygerwulf]

Awsome. I'm just afraid I'm gonna get the bearing off and my cam is gonna be scared beyond hope, and I don't have time to take it out and take it to a machine shop.

Thanks for all the help NISTECH!

[NISTECH]

Your cam??? We were talking about the crank. But none the less I get what your saying. I had the exact same problem with my camaro. When 1 and 3 rod bearings seized it tore up my crank shaft journals beyond recognition.

[Sygerwulf]

lol yeah the crank sorry I was alittle blasted when I posted that.

I wish I could get ahold of Ben so I could find out how far he is from pulling his engine. I'm hoping since it isn't that bad yet that it'll last long enough

[freebird21207]

there is a piece of metal near the timing chain. mine broke off and was hitting the inside of the chain area, as the chain moved. check that. I took off the metal piece and the knocking stopped.