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Thanks, Duncan. The mechanic said that the crank looked fine. I am no expert, so cannot comment. He says he threw out the old bearings as many of them had some copper showing on them, but the front main one was more worn out. I dont know if it actually had spun out of position completely, because if that happened, the crank would have bent a bit. possibly. So I am not sure. He also said that the oil pump looked fine, but he replaced it anyway with the N1 pump. Again, I didnt see the old one as he said he threw it away. I have a Link ECU, which does have the capability to read an oil pressure sensor's readings. I just don't know the exact wire to connect the sender to - 5v source, earth, etc.. I will do some research on it. Hopefully, the mechanic can look behind the cam cover and identify if there is any indication. Could a timing of 18 degress BTDC at 1100 rpm cause that tiny bit of thumping noise to it? I know sometimes, retarded timing can cause an engine to run slightly rougher. Interestingly, he was at a loss about why the engine failure happened. It was not a catastrophic failure at all. In fact, the car ran great till I stopped driving it. The only thing was that noise, which is not there anymore. I had a pair of Garfrett 2860-9s on this car, and the front one sseemed to have failed, and then after I replaced the turbos with new ones, this engine thing happened. So it is hard to say what caused what. The oil quality was bad.....I mena baadd. It was all black. He had to wash and clean the whole bottom end. He rehoned the cylinders, put new rings in, with the same pistons and rods and crank. He actually did a great job putting it together. I just dont know what could have been put together wrong. I doubt there is any way to check if everything is working as it should, unless you put the engine back in, start it up and run it for a while. Otherwise, it is not possible for mere mortals to bench test an engine. I am keeping fingers crossed that he will find the problem (if any) and it is a minor thing. Or better still, it is simply the timing kit settling in. Once I know more, I will post the update. And when I go to his shop next, I will do my best to record the sound or make a video of it and post it here. Keep it coming...thanks.

Hi everyone. Update: Found out thru oil analysis that there were some metal shavings in the oil. Front main bearing spun and the rest were all ok. At any rate, new oil pump (N1), new timing kit, new ACL 1 thousandth oversize main and rod bearing, new rings, new gaskets, and everything is put together. Car started just fine but there is slight thumping sound up top near the timing cover area. The oil pressure is lower than it was before. Prior to the whole thing, I was using 15W40 Shell Rotella oil. Currently, it is running 5W30 conventional oil for the first 100 miles until I do a new oil change. Pressure is reading around 4-5 kg/cm2 upon cold start and then settles to around 1-1.5 kg.cm2 when warm. I know that is really low, but then I have no way of knowing the actual pressure because I don't have an aftermarket oil gauge. I do have an aftermarket pressure sender teed in, but don't know how to connect it to a gauge. The mechanic who rebuilt the engine is at a loss as to why that slight thumping noise is there up top. It is not very audible at cold start but then it is there after it has warmed up. Revving the engine, it sort of disappears but it could be due to the noise. Also, he set the base timing to 18 degrees BTDC at around 1000 rpm. I have spent close to $5000 on this and still not sure what this new slight thumping sound is. Doesn't sound like metal on metal, and it is not a whine. Engine seems to run smooth with a slight physical vibration. All cylinders are at around 150 psi cold compression, as per the mechanic. If anyone has some ideas, please throw them my way. I will share them my mechanic. Thank you.

Thanks to everyone for your responses. I have since removed the timing cover and found that the noise is particularly very loud when I put the stethoscope directly on the CAS (Cam angle sensor) itself or the metal bracket behind the CAS. It is also louder on the exhaust cam cover, and not so much on the intake cam cover. Also, the bottom end does not seem to have the noise when I put the stethoscope on the part of the engine block behind the idler and tensioner Fearful of what Duncan said, I took some oil samples out and have sent them to a lab for analysis. Let's see what they say. Will know in 2 weeks or so. Two samples - one the current oil, which I just put in less than a month ago, and one from a month ago, from the time when the turbo had failed I recorded the sound clip in my original post @Duncan, what "underlying oil problem" would cause the front turbo failure? Why does the sound fade away with increased temperature or revs? I don't have an aftermarket oil cooler in my R33 GTR, unless you are referring to the round thing with the lines/fins on it near the oil filter? If so, perhaps one can flush it and run some brake clean through it? What water cooler are you referring to, @Duncan? Also, is it advisable to flush both turbos with brake clean fluid as well? How do you flush out the rest of the engine of any debris IF there is any? I may also replace the oil pump and piston rings, along with changing the timing belt, idler, tensioner and coolant pump Thank you all. I will update this as we go along.

A few questions: 1. Should I be able to hear this at idle as well? 2. If I do not hear it at idle at all, and if I put a stethoscope to the bottom end somewhere, should it be more audible at the bottom than it is at the timing cover? 3. Does rod knock or spun bearing sound go away or diminish with the engine warm? That is what seems to be happening here. Once the car is warmed up, the noise is quite faint. 4. Also, at after 3500 rpm, you cannot hear it. And you can barely detect it even with a stethoscope. Possible that the frequency due to higher revolutions is so high that you are not able to distinguish it from other engine noises? 5. The oil filter filament when I changed the oil after I started hearing this noise showed no metal shards or shavings. Usually, you split the filter open, lay the louvered filament out flat and look for any copper shavings. I did not see anything. 6. What causes front turbo failure on an RB26? Is this a known phenomenon due to oil-related issues or oil pump issues? Thanks.

Thank you, Duncan. I thought as much too, but there was no metal in the oil filter. In addition, after 3200 rpm or so, the noise disappears. It doesnt get louder as the revs go up beyond a certain rpm. On idle, you do not hear anything at all. I hope I am right and you are wrong, but I do not know for sure. Do you think there is a chance it may be something less sinister?

Hi. I'm worried about this noise from my 95 R33 GTR. It all started after a recent tune on the car. Had a front turbo failure (didn't break off, just became noisy). The car had Garrett 2860-9s. Only the front one went. Is that strange? What causes only the front to fail? When I removed the turbos, they moved freely but the front one had a clear internal grinding noise when I spun it by hand. I decided to put new turbos in and went for a brand new pair of 2860-s with upgraded internals. After the turbos were installed, I came home and noticed this noise. I checked the oil and it was pitch black. Drained it out. Didn't find any copper or metal shavings in the oil filter. Didn't check the oil itself in the drain bucket. It's gone now anyway. Put in new Shell Rotella 15W40 oil in it and new filter. The noise is still there. It is slightly lower when it really warms up, but it is still there. Oil pressure with stock gauge stays around 2 bar at idle and then goes up to 4 bar when revving. Cold start it is between 5 and 6 bar on the stock gauge. You can hear it as I rev the engine up and then it disappears somewhat after 3000 rpm. I put a stethoscope on the car and it is the loudest on and around the front timing cover and near the front turbo. Please help. I live in a small town in Montana, USA and there aren't many resources available to diagnose this, let alone fix it. SAU has been a resource for me since I got my first Skyline in 2006. I have read thru some posts about timing belt noise, etc., but I am not sure if it relates to timing belt or idler/tensioner or CAS. Thank you for reading. 20221216_170622.mp4

I have a 1995 R33 GTR, which is fairly stock, except the usual exhaust and intake pod filters. Here is my issue and this has me stumped. A year ago, I had started a thread here about seeing something called a VACS (Variable Airflow Control System) come pre-installed on my car when I bought her. The VACS is conneced to the ECU with 5 wires - two go the AFMs , one goes to ground, and the other two are soldered into the ECU circuitry, away from the pinouts. I knew that thing was useless, so people on here suggested I take it out. I disconnected that VACS from the ECU (just unplugged it), and the car starts to run crazy rich - 10.3-10.6 afr on idle. Then I tried to use a stock R32 GTR ECU, with the O2 sensor ground connected so that it runs on the R33 GTR loom (as suggested by Nistune), and the car starts off, but idles extremely lean - around 17.3-17.8 afr. I am confused as to why it would be. Asking for help from anyone who might have some ideas about the causes. The AFMs are stock and so are the injectors, at least from what I can tell. What throws me off is the inconsistency between the R32 and R33 ECUs, where one is causing extreme leanness, and the other is causing extreme richness. Shouldnt there be a semblance of similarity in the two, as they both run RB26DETT off of the same sensors, and shouldn't have opposing effect. There are also these images that I want to share, of my R33 GTR ECU's internals, for anyone who might be able to tell me if the ECU is stock (in terms of the R580 chip) or it seems to have been modified with a chip or anything else. The first image shows the ECU itself with the chip, and the second one shows the wiring that goes from that stupid VACS into the ECU. I disconnected the VACS from the plug you see on top left corner of the second image and that is when the car runs extremely rich. With an R32 GTR ECU, the car runs extremely lean. Any help will be greatly appreciated. Thanks, all.

I am reviving the thread, as I recently changed my engine after frying cylinder 5 (zero compression). Now that the new-ish engine is in, I decided to disconnect this VACS.The VACS has 5 wires - two go to each of the pics for the two AFMs (MAFs), one goes to 12V power, and the other two go further back into the ECU and are soldered into god knows what. Since I could not just cut the wires out, I unplugged these wires from the VACS box itself and the car started running stupid rich - 10.2-10.6 afr, even under idle. Now this has got me stumped. If the stupid box is not connected anymore to the ECU, why would the car be running so rich on the R33 ECU? I have stock AFMs and stock injectors, so there is no reason it would be so. Does anyone have any ideas about it? As a test, I decided to swap out the ECU and used an R32 GTR ECU to run the car and with that, it runs crazy lean - 17.5-18 afr. Now I am stuck between a rock and a hard place - R33 GTR ECU runs it stupid rich and the R32 GTR ECU is running it crazy lean. Please help me here if someone can, with any ideas. The four wires coming out of the ECU and going into the VACS are still soldered into the ECU but they are no longer connected to anything on the other side, they shouldn't be causing any issues - basic electronics, right?

The mechanic who did the compression test says that it is unlikely anything within the bottom-end, although I have my doubts. It could be the rings or ring land, but I am not an expert to comment. There is no oil-coolant mixing in the radiator or the oil pan. The car doesnt smoke black, blue or white. The AFRs on my wideband are kinda spot on when itdling, but are erratic and go up and down quite a bit, and running leaner under WOT. The plug for cylinder 5 was covered in oil/petrol mix, totally black and oily. He thinks it is the head/valve/springs, etc.. The car still pulls strong even with this issue, and boosted fine. Just that I can see the rear turbo doesnt spool as well as the front, possibly due to loss of exhaust pressure from cylinder 5 coming in, which makes me think that perhaps the exhaust valve is burnt or messed up? He says that there is no need to do a leakdown test as we cant really ensure the cylinder 5 chamber would be completely sealed.

Just checked compression. 70 psi in cylinder 5. I drove the car to a shop and it drove fine, even with this low compression. Injector was firing, and so were the coils. Seems either the bottom end is fried or the top end is messed up - could be a partially stuck valve/lifter/ faulty spring, or do you guys think it is the bottom-end? This is devastating. I dont know what to do....

Were you offering this to me or to STATUS? Secondly, on the issue itself, if the cylinder was toast, wouldnt I smell fuel on the plug no.5? All I see on the plug itself is that it coated with black oily stuff and its not like it is covered in oil...just a complete oily blackness. If the cylinder was toast, would the car still rev high? The AFRs are erratic, but lean out under boost/WOT. I dont have a compression tester, but assuming the compression is zero, what symptom(s) would the car have? There is only a slight drop in performance under load. It does spit black soot out of the exhaust upon cold start, mixed with water. But there is no blue or black smoke coming out.

Hello all, I have a 1995 R33 GTR and I recently completed an LS2 coil swap on the car. It ran great until recently, when I started noticing a slight shudder and rougher idle. Thought it was a MAF issue so I cleaned them up, and resoldered them. I also decided to clean up the plugs and to my surprise, found that plug no. 5 was completely black, and oily. Now I dont know if this is a sign of a blown cylinder or low compression, but I decided to swap out coil no. 5 and changed the coil wire, but no change. I am at my wit's end, trying to figure out what is wrong with that cylinder and would really appreciate if someone could shed some light on what to do here. I live in a remote town in Canada, and do not have access to most things people do in larger towns, so have to depend on myself to carry out any tests or check things. This has gotten worse over the last 2-3 days, as I drove the car on a 200 mile trip, which was great until I got back home and it started to show signs of running stupid rich while cruising and lean when boosting. I have checked the coils, the wires and the plugs are all good. When I disconnect the coil wires no. 5, there is a very very minor change in the revs if at all. I can hear the coil ticking and the spark is there. If the injector wasnt firing, would it foul up the plug with black oily stuff? How do I check without the car running if the spark is strong enough? Could it be faulty injector or a weak spark? Is it also possible that cylinder 5 has lost compression? Please help me Thank you.

If it is just blow-by coming back from the BOVs, and oil is returning with it, why is it escaping though the rear MAF only, and out the rear filter, and getting sucked in by the turbo since the whole point of recirc is to keep the metered air within the intake system? I dont know if what I am saying makes sense....the BOVs recirculate air, it comes back into the MAF-turbo pipes (through the Y-pipe that connects to both turbos), and ideally, should at stage be sucked back in by the turbos. Instead, it is escaping out of the rear MAF...

There is no smoke at all from the exhaust. I will post a pic when I get home today

In addition to this, I do not see any oil at all in the catch can....maybe a tiny droplet, but that's all. And while the car is running OR I am revving the engine, I do not detect any suction from the catch can into the hose I am running to the rear turbo-MAF intake pipe. If this means the turbo is not spinning, it wont be sucking in any air from that hose, could this also be causing the recirc from the BOV to come out of the rear MAF? When I let go of the accelerator, I can see air/oil blow out of the rear MAF filter. This has me perplexed.