Hey everyone, Im new here, but I have been recommended to come here for help so I hope I do a good job explaining the issue!

 

I have a 98 240sx with a 2002 Camaro LS1 + cam + dual valve springs and many other suspension and handling goodies.

Problem is, the car, when cranked up, sounds like there is severe scraping/knocking (no codes thrown) that is matched with the rpm even at idle.  This just started today and i have had what i believe is a very small coolant leak that I have yet to diagnose...I have checked:

- o2 sensors

- MAF

- Fuel Filter

- Air Filter

And noone of these are the issue to my, what i think as lean/possible detonation, problem.  Ideas are: bad oil pump,  My brother had suggested a possible vacuum leak, even possibly a worn out tensioner bearing.

I know that there are some things that I have left out that I dont even realize are significant, so ask away!

Thanks guys for any help you can offer. 

those ecu's expect to see like 60psi of fuel pressure, check that.

im not really sure why a bad oil pump or tensioner would cause detonation. I say pull the plugs and check them, if they show signs of det, start looking for a vacuum leak and check the fuel pressure.

The bad oil pump was suggested from the guy who built the car.

I second the checking of the plugs and vacuum.

Whats the process for checking for a vacuum leak?

Bad oil pump could cause the lifters/engine to start goin which would make quite a lot of noise, ive heard what it sounds like on an old LS1 and they are kinda similar in sound.

Fuel pressure gauge is avail at a local parts store right?

So after some checking, here is the update: (sorry about the stupid questions earlier)

Plugs look good so far;
oil is covering the rocker arms and springs so oil pump seems to be still good;
havent gotten a read on the fuel pressure yet;
all the vacuum lines i can see look intact, yet im not quite ready to start the car again to check using a spray or something bc afraid of possible damage from running the motor;

Is it possible one of my front bearings is going out and trying to seize up the engine?

Thanks guys and ill keep the dumb questions to myself for now on

Stupid question. Is it an accessory?

http://www.youtube.com/watch?v=X6yiJL1ztdk

wfs

That is the car running. Please listen to the crazy sound. I really think its a vacuum leak.

wow. I am....that sounds like an angry 4 cyl now as opposed to the normal snarl...

Fuel Pressure at 70 psi.

Im beginning to think my leak is in my brake booster b/c my brake fluid is unusually low and this seems like it could be a likely culprit given the age of the car.

Ideas?

Posted By ramblin240 on 12-14-2009 08:21 PM

I have a 98 240sx with a 2002 Camaro LS1  

There's your problem. Just kidding (but not really). 

I don't know LS engines, but does it have hydraulic lifters? Is the aftermarket cam made for hydraulic lifters? I know the package may have said 02 Camaro LS1 w/ hydraulic lifters, but if it was mispackaged and the cam is ground for a solid lifter you may have a problem if the base circle was expecting there to be some clearance there.

You are more concerned with the knocking noise right? I wouldn't concentrate on stuff like fuel pressure and vacuum leaks. You should be concentrating on the source of the knocking noise. It's a mechanical knock that isn't affected by vacuum leaks and fuel pressure. Try checking the oil pressure.

Like Mark said, is it an accessory? Is the power steering pump or a/c compressor jacked up? You'd hate to rip everything apart just to see that it was a bad a/c clutch bearing. It probably wouldn't hurt to quickly remove the fan belts and start it up for a couple seconds.

Good luck.

There's your problem. Just kidding (but not really).

Must have missed the punch line in there...but not really

I'm a bit perplexed on how fuel pressure doesn't effect knock.

It probably wouldn't hurt to quickly remove the fan belts and start it up for a couple seconds.

Thats exactly what I was goin to do next. Someone else has recommended that I do that as well. Just have to make sure I dont kill the battery haha!

However, it does seem odd that it couldnt be a vacuum leak, it is idling higher than normal right now and I would be lead to believe that a vacuum leak would cause knock b/c of a lean afr it causes with the ecu knowing.

Anyways, Ill let yall know! THanks.

coevolve: he is searching for a mechanical knock, not detonation/pre-ignition knock. There really isn't enough cylinder pressure there to cause knock at a fast idle. All an engine will do with low fuel pressure is run crappy and eventually die. A high compression engine may knock, but it sounds like ramblin240 has a near stock engine.

It could be a vacuum leak and then you can also have your knock problem. I assure you that the knocking noise isn't going away after you fix the vacuum leak.

That makes a lot of sense. Thanks Eric.

In retrospect, my perplexed comment appears sarcastic; not intended.

Andrew, are you sure it is knocking at idle?  (we are both knew to the diagnostic as such)

Eric, did you hear knock in that video he posted?

This is just a random idea, but could it be something like worn out lifters bc of my cam? I have had the car about 2.5 years in this config so maybe they are worn out being that they came with the stock engine when i got it.

btw I checked the springs/rocker arms and they all look good as new with plenty of oil covering them so thats at least nice to know...

keep on keepin on

have you checked oil pressure? The folks on HorsePower TV had an LS or LQ motor that they built and had a oiling problem because of a o-ring on the oil pump pickup was damaged when they but the motor back together after a rebuild. Did you have to change oil pans for this swap?

You might be able to find the episode of Horsepower TV on the PowerBlockTV.com website.

I hope this helps.

Tony D
New Edge Performance

It could very well be failed hydraulic lifters. Not necessarily because of your cams, but just because hydraulic lifters sometimes fail. Like I said, I don't know LSes, but is it a common thing for an LS hydraulic lifters to fail? Are they even hydraulic? I think I asked like 3x so far.

Stock are hydraulic and apparently upgraded springs can cause them to prematurely fail?  (this was just a quick, just-got-to-work google search)

Apparently the ls7 lifters are a direct swap

Time to check the oil pressure then. Even if the oil pressure is good though a hydraulic lifter can fail. The Mitsu 4G63 is a good example. When you hear the tap, it's a good chance there's a bad lifter.

I want to check the oil pressure, and have a gauge, but apparently the fitting on the block to check the pressure is not a pipe fitting so I have to get something special to do it. Pulling the lifters tomorrow or tonight.