hello, i am thinking of getting a 93 nissan maxima with the 190 hp v6 with dohc 24 valves. the guy is letting me drive it for 3 days and if the noise occurs bring it back. he had 3 different people look at it and the noise would not occur. but i drove it a few hours today and it came up. it is coming from under a valve cover . if i rev it up a few times, it will start to quiet down and then stop i can rev it to 6000 and it won't come back. it seems to happen after driven for a while and then at idle or a little after startup when hot. but i can't believe it just goes away like that. i think it is a bad rocker or something getting stuck under the valve cover. the dealer said he will fix it free of charge if makes the noise in front of the mechanics that he took it to. it would have been fixed if it made the noise yesterday and today in front of them but it didn't. it has good gold oil and no metal shavings. anybody have any clue as to what this could be. i really like the car as it is fully loaded and has leather. thanks
off topic: 93 nissan maxima engine noise
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I was gonna say lifter tick but its a dohc, so that cant be it. Id bet its just something loose in the valvetrain, possibly a rocker arm?
that was fast, yeah it has got to be a rocker. it trips me out and everybody else because it doesn't do it all the time and when it needs to it doesn't. i was going to drive it to and from work tomorrow. if it starts doing the sound, i am going to take it to a shop and have them check it out and hopefully it will do it. that way they can write out an estimate and statement saying the diagnosis and i may be able to get the dealer to pay to fix it.
ohc engines have lifters, although they call them diff things like cam followers, buckets, lash adjusters etc.. you could have a lifter bleeding down. without hearing the noise it is all hear say.it is pretty loud, i can hear it in the car with the ac on high. rev it a few times and it is totally gone and quiet again. one more problem it has is the check engine light. it will flash a few short times then stay on for a 10 seconds or so and then flash some more, i am guessing that is a code that is decoded by how many times it flashes. i think it may be related to when i shut the car off sometimes i smell raw fuel. but i cannot find any leaks under the hood or the car. anybody know what that may be. thanks
I'd be pretty shy to follow through with that whole deal. It reminds me of the days when dealerships would swap the engine oil with 90W gear oil and "let ya drive it for 3 days" so you could make sure that all was well. If you know the guy pretty well then forget what I said. If not, just be wary.
Dbeck002
New Member
Sorry to break the news to yall but OHC engines dont have rocker arms lol...
By the way the tapping could just be too much clearance between the cam and tappet, this makes a slapping noise when the lobe begins to push in on the valve.
It probably goes away when you rev it because your flooding the valve cover with lots of oil pressure which cushions the lash. This is what im guessing.
As for the raw fuel, that could be a problem. I cant think of what that that could be.
By the way the tapping could just be too much clearance between the cam and tappet, this makes a slapping noise when the lobe begins to push in on the valve.
It probably goes away when you rev it because your flooding the valve cover with lots of oil pressure which cushions the lash. This is what im guessing.
As for the raw fuel, that could be a problem. I cant think of what that that could be.
It's been a long time since I was a Nissan parts manager, but I think that thing has the variable timing setup on it. If it does, they are notorious for the VTC sprockets (think V-Tec) going tits up and costing about $500 in parts alone. The noise can come and go. I'd stay away.
well i know it doesn't have gear oil but i talked to the guy today and he said to get some estimates. i had my mechanic friend check it out when the noise was occuring and he is pretty sure it's a spring or a rocker. it does not have lifters on this motor though but it has rockers. there are plenty of ohc motors with rockers. they ride on the cam. and as to the oil pressure issue, there is none. the you don't have to rev it to make it co away but you can, it won't go right away it takes a little bit after revved. when we were checking out the location of the noise, it just slowly got quieter and quieter until it stopped. i really don't think it is an oil issue but i don't know. if he says he is going to pay for it then i believe him. he said i can choose a mechanic. the parts place quoted me 26 but 7 for shipping for one rocker arm. that isn't bad. but i won't be paying. we will see though.i need a nice 4 door with good gas mileage and cold ac like this one. i am still making up my mind on this one, although i can't find a good car to go with. i will let you know more after i get some quotes. thanks for all of your replies. they have been helpful.
Dbeck002
New Member
go to seanhylandmotorsports.com to find replacement rockers for 4.6's. as far as the ohc engines with variable ratio rocker arms, i'll have to wait until someone has a valvetronic head tore down at work as me describing it doesn't do it justice. some other engines i know for a fact(been real deep into) that are ohc and have rockers are mitsu 3.0(diamante, 3000gt), ford 2.3(svo, t/c), bmw all newer v8's and v12's.Dbeck002 said:Show me a picture of one please.
here is a cartoon illustration of variable ratio rocker arms in an ohc engine, currently used in BMW's V8's, V12's, and the new generation I6. note the rocker arms under the cam pushing down on the valve spring(similar to 4.6 ford)
View attachment 508457
View attachment 508457
yeah i decided to go with most of you and not get the car. i am taking it back tomorrow. i don't wanna blow it up. if anybody has any good 4 door cars with ac and gas mileage then hit me up. i am looking to trade my 95 v6 that is in my sig. you have to be in texas though.
I had a nissan 4 cylinder (94 sentra) that made a ticking noise constantly. Dont remember if it had rockers or not, but there was no adjustment on the valve train that I could see. Made loud noises if revved in neutral. Would not make the same noise under load.
Mother in Law has the car (donated) and it makes nasty noises but it is still running and running with good gas mileage.
As far as finding a car, check out autotrader.com to find a car and edmunds.com to find out how much it should cost you.
Mother in Law has the car (donated) and it makes nasty noises but it is still running and running with good gas mileage.
As far as finding a car, check out autotrader.com to find a car and edmunds.com to find out how much it should cost you.
if you go back into the history of the very first internal combustion engines, they were ohc design that did not use rockers but rather used solid tappets much like the pic of the yota engine above. the lifters shown in that pic can be hydraulic or solid, solid having periodic adjustments required. the 4 cyl sentra just mentioned prolly was due for an adjustment which is why it was noisey, shims can be placed between the cam and lifter to adjust lash. the rocker arms in the other pic i posted actually have a hydraulic lifter on the opposite side of the rocker, these can also be solid and require frequent lash adjustments. in this day and age of fuel injected cars more manufacturers are going to a hydraulic setup for 2 reasons, one to minimize routine maintenance and 2 is to keep the knock sensors from receiving false input. the engine i posted the pic of went from a dohc to the sohc with the rocker arms as to facilitate the varaible valve lift. the variable lift with the accompanying variable cam timing and infinitely adjustable intake runners can actually run without a throttle body, crazy stuff.pconway said:
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