1993 k24E engine knock and high idle

[jpmb]

Could anybody help me figure out why my 1993 nissan 4wd pickup knocks at high rpm about the time you shift to the next gear. Could it be the timing chain? or a rod?

The truck also idles high once it gets warm. when it is cold it idles fine. It could be related to the knock? also the distributor is maxed out clockwise to get accurate timing.

[PEZi]

not too sure on the idle... it could be numerous things...

but are you sure its knock as opposed to a rattling noise? i'd assume its the timing chain tensioner if its more of what most would describe as valve rattle

[seang]

You need to learn your "engine noises terminologies", it would better express what you are saying.

[Bgjohnson]

I had a VERY bad timing chain/guides when I first got my truck. It would rattle terribly between shifts and about 2-3k rpm. And of course idle.

Miles on the truck?

[jpmb]

the Noise is hard to describe not quite a deep knock but not a rattle either. The truck has 180000 miles on it. looks like the timing chain may have been replaced before; I see silicone around the gaskets. Can I tell if the timing chain is bad by taking off the valve cover gasket? I am thinking about replacing the timing chain but I don't really want to put $150 or so into it and have to replace the engine soon anyway.

[PEZi]

the chain can get stretched over time... hard to tell by simply looking at it unless its really bad tho... tensioner is your best bet... not too expensive if you do it yourself

[seang]

I'm not aware of any life span for the timing chain on either SOHC or DOHC KA24's. It was made to last the life of the engine. The tensioner is very sensitive to contamination and this is likely what causes the excessive rattling on start up.

Early (90-95) single cam KA's did have chain guide problems because they were backed with plastic. They wear through over time and the situation gets critical. The single cammers found in 96-97 HB pickup trucks have metal backed guides.

When my truck (SOHC 1997 HB 4x4) rattles on start up, I shut it down immediately, and re-start it. This takes care of the problem, and I have been doing this since I bought the truck 25,000 miles ago. I believe the starter to be original, and it is holding up to the repeated use quite nicely. I have been taking measures to clean the inside of my engine, and this has alleviated the issue to 1 re-start, or even zero re-starts. At the worst it required me to re-start it 3, or even 4 times before the tensioner kicked in. That was when I said f*** that, and started using Marvel Mystery Oil in my crankcase a few hundred miles before oil changes, changing the oil more frequently (2100 miles for now), and sometimes changing the filter after 1000 miles. I have manually cleaned the inside of my valve cover using a cleaning brush and gasoline. What came out looked like flat black paint. I rinsed it, and dried it in a 200 degree oven until the breather baffles were clear of water, and re-installed it. This has helped some. I would also like to manually clean the inside of the oil pan, but my truck is a 4x4 and it's a good deal of labor to do that. IDK how that damned engine got so filthy, but I think my dear old Dad may have neglected to change the oil enough during his 6 month tenure of ownership. My intensive treatments have certainly been helping, that's a fact.

About that chain stretch thing, IDK what to make of that unless someone has actually measured an old one against a new one. Like I said, the chain was intended to last the life of the engine and has no factory recommended service interval. Any excessive rattling is likely caused by a sticky tensioner. The plastic guides are what sucked the most.

I did see BigVinnie recommend in an earlier thread that it is still wise to replace the timing set, and lots of people do just that.

[jpmb]

I took off the valve cover to inspect timing chain and guides. Everything looks good the chain has tension on it. the Chain guides appear to be plastic but still in good shape. Could the tensioner be loosening at high rpm's? It definately rattles at start up in the morning.

[PEZi]

the rattle at start up is just common for basically all nissan 4cyl trucks... mine does it too if its pretty cold out... but only does so for a second or two... i make mine stop my giving it throttle immediately then letting off to drop the idle... it works for me... it is possible that you just need to re-adjust your valves for the higher rpm problem... but i can't say for sure

[cosmomick]

Hey Brother, I can honestly feel for what your going through. I too have a 1993 Nissan puke/up 2.4 L, 12V, in line and have acquired what sounds like the same problem you have expressed. I have worked on my own cars all of my adult life and the "knock", that I could swear is a rod knock, has had several mechanics split down the middle about whether it is indeed a rod knock or a hydraulic chain tensioner slap. One would think that the two sounds would be discernible and a cinch to differentiate by the most casual of an observer just by listening. Be that as a may and aggravating as it is the jury is out on my truck I can't get a definitive answer except to replace the tensioner. Regardless of who hears what in your case and in mine it would seem that the most prudent and logical “Chain” of events, no pun... would be to replace the tensioner if its time has come for it is the least expensive arguably and inferentially sounds as if it requires replacement at 180K. In and around 80K from what I have read.. Individual mileage may vary...This all might make sense to me and it is just my opinion given My circumstance and my perception of yours. I have this opinion because my situation appears similar to yours But keep in mind sill unique. Moreover; there may be less opinions and more collaboration if myself and everyone else had what's in your back pocket riding on the line. I will be curious to see how you proceed and what you discover. I'll continue to follow this thread and if I have an epiphany or revelation relative to “our” problem I will share it with you. Sincerely the best of luck & God bless. Michael C.

[yankabilly72]

i have the same problem, my truck is an 93 also. i will be looking in to this and i'll post any info i find out . i'll also be looking for a good bottom end in case its a rod knock not just a chain rattle. does you guys make some noise when the motor frees up on the freeway?

[seang]

does you guys make some noise when the motor frees up on the freeway?

Just the normal valve clatter. My truck has no carpets or sound deadening material, so it's more pronounced. Usually the valves clatter while the engine is at speed (2900-5000 rpm) while at the same time under very light load. At full throttle, or lift throttle deceleration, the valves don't clatter as much. Some noise is normal.

[yankabilly72]

mine is more than norm. it almost sounds like a knock . the motor has 204,000 on it. i'll rebuild if i have to but i don't want to . i have a line on a k24de out of a frontier but i don't know when i'll get it so i'm going to change timing chain tensioner if it don't stop it i'll do a bottem end rebuild

[seang]

^^I have heard that the plastic from timing chain guides (on models so equipped) can clog up the oil galleys in the crank, and can starve the main bearings of oil causing them to fail.

Here's a Nico write up on repairing ticking/stuck lifters. Thakfully, mine aren't that loud anyway, just a little clattery.http://www.nicoclub.com/articles.php?id=215864

[yankabilly72]

i changed the head gasket i also changed the timing chain guides to the metal type so i don't think its that

[jpmb]

I installed all new timing gear set and the noise still persists. time for a new engine.

[seang]

Is it pinging (detonation or preignition)? Is the timing set right? Your truck doesn't have a knock sensor, therefore it wouldn't pull timing if it was knocking, so you would hear it if it was loud enough. I didn't see anyone mention it in the above posts, but it is less expensive than a new motor.

Did you read the plugs? If a cylinder is leaner than the others, it might be going lean and detonating. The plugs can tell you this.

Wouldn't it suck if the new motor had even worse problems? I know you are sick of this goose chase, but there are alot of old parts on our trucks, and you can probably expect continuous issues; I know I do.

[jpmb]

the Timing is set right. Alsp previously I played with the timing to see if I could get it to stop and it did not work. What happened is the timing cover didn't seal right around the water vein to the head so the Oil and water mixed (briefly) and the noise in the engine got alot louder. I repaired the problem and changed the oil and coolant and the noise has not gone away.

[seang]

What about the lifters? Could the oil have foamed when it mixed with the water, and got air into one of the lifters?

[jpmb]

That is a possibility what can I do to clean them out? Change the oil again?

[seang]

I posted this same link a few posts up, it is a Nico tech article on how to clean and replace the ka24e lifters. There is a crucial bleeding procedure that gets the air out of them: http://www.nicoclub.com/articles.php?id=215864

If you revved the engine while you were under the hood, could you tell where the sound was coming from, like under the valve cover?

[jpmb]

the link doesn't work. I can definately hear the loud noise from under the valve cover top end from the recent event of water and oil mixing this noise is different than the original problem noise posted. It still has the other high rpm noise that it had before that sounds different than the lifters/valves I am guessing a wrist pin?

[seang]

That sucks that the link doesn't work, I don't know what happened. That is a good article.

I don't know what a bad wristpin sounds like, I'm not sure on that one.