Help Needed To Troubleshoot Rb26 Problem

[Darrel]

Hi everyone. Just a bit of an introduction, My name is Darrel and I’m quite mechanically inclined but new to the GTR scene, just got my car, BCNR33 V Spec about 3 weeks ago and the very same night I got it the engine took a dump on me.

What happened was I was cruising around in 60 and 70 kmh zones with a friend and went onto the highway and did a couple of hard pulls (if you can even call it hard, rolling start from 2nd into 3rd gears only and only got up to 140 kmh for 2 seconds unkowingly). Went back onto 70 kmh zone and cruised around for a bit before pulling into a gas station, turned off the engine and the turbo timer started counting down from 1 minute, everything was fine at this point. We decided to go across the road to get some supper and when the engine shut off I started it again, that was when the problem started.

Started hearing a loud knocking noise which increases with RPM (depressing clutch does not affect it) from the engine and idling was rough, even stalled as I was backing up out of the parking lot. After a few minutes stopped at the traffic lights the idling and noise got so bad I just pulled off the road. I did not get a video of the sound but my first thoughts were I’d spun a bearing & suffering from rod knock (I’m inclined to say that rod knock this severe doesn’t happen instantly but I could be wrong). So let the car sit for half an hour and checked the oil, it was low, on the L of the dipstick, still suspecting rod knock. Added a liter of oil and started the engine again, struggled to start, same noise, same rough idle, misfiring, stalling & quite a lot of blue smoke from the tail pipe. Gave up and parked the car, towed the car home the next day and have since started taking the engine apart slowly to pinpoint the problem so I can get a rough estimate of the damage cost. After listening more closely, sounds like the knocking is coming from the top of the engine instead of the bottom.What I’ve done and found so far:

1. Checked coolant and engine oil, they have not mixed.

2. Shined a light into all cylinders, did not look like anything (compressor wheel) had been sucked in & chewed up, checked plugs, all fine except for being stained from running rich.

3. Did dry cylinder compression test, all tested 130+ psi from cylinders 6 to 3, cylinders 2 & 1 got 20+ psi (at this point I’m inclined to say bent valves from the noise it makes but could also be blown head gasket but oil and coolant have not mixed). Did wet cylinder compression test on cylinders 1 & 2 went up to 35 psi (could it be blown piston rings which explains blue smoke and misfiring?).

4. opened cam gear covers to check if timing had jumped, found that on IN: 1 tooth retarded & EX: 1 tooth advanced (in addition it has HKS cam gears & EX has been retarded 2 degrees by previous owner). This could cause rough idle & stalling but could it be enough to cause a piston/valve collision?

Next course of action is to redo timing & see if it improves. Engine has HKS cam pulleys, Power Enterprise timing belt, & from what I can tell, the engine internals are stock, has a Trust intercooler, brass button clutch (don’t know what make/model yet but it is slipping slightly), turbos look stock, boost increased to 14 psi running on 98 octane BP petrol.

It is apparent other things/mods have been done to it by previous owners but they have been removed prior to being imported to Australia last year. I have no experience at all with RB26’s so I really need help here and I really hope everyone in here can lend a helping had to a newcomer to GTR’s & any insight, opinions & experience are welcome & will be much appreciated. Really really hope you guys can help, thank you in advance & have a nice day, cheers!

[Ben C34]

Its a gtr.

It spun a bearing.

Low oil in a gtr is a bad thing.

The cam timing isn't a problem.

[KiwiRS4T]

If you have 20psi on two cylinders at the least the head will have to come off - probably bite the bullet and pull the motor now. BTW post up your location if you ever want someone to have a look at your car or recommend a shop or service.

[Darrel]

Hi Ben & Bob,

Cheers for the reply, I'm located in Melbourne, Victoria, sorry about that, will update my profile. Spun bearing & rod knock was my first hunch although I've never experienced it first had does severe rod knock come on so severely & abruptly and loss of compression? Sorry, just trying to figure it out.

I plan to take off the head but as it is my tools are very limited, not being able to get under the car is a huge disadvantage Do you think bent valve? Thanks again, guys, really appreciated & do keep the ideas coming!

Regards,

Darrel.

[Darrel]

Just an update in case you gentlemen (and women) are interested. 

I found the problem, loss of compression was due to pistons 1, 2  & the squish pad melting & the debris scored the cylinder walls and ruined the rings.

 

Noidea how it could have leaned out only in 1 & 2, apparently cylinder 6 is usually the one that leans out, shame, they were HKS forgies too.

Engine has since traveled to Malaysia, been rebuilt with 87mm 9.0:1 cr CP forgies, ACL racing big end & main bearings, HKS metal HG, used head with brass valve guides, injectors serviced and flow tested and power FC going on to be Dyno tuned. 

Thanks for the help and input, guys, cheers!

[KiwiRS4T]

Wow! Thanks for the update.

[Darrel]

No worries mate! Feels like a GT-R again! Oh yeah, stock turbos upgraded with steel wheel and A/R .60 cold side too ?

[Dose Pipe Sutututu]

Sounds like injectors may have played up initially 

[Darrel]

Yes, thought so too, 2 injectors at once is a real coincidence, maybe dirt got past the filter somehow. I was also thinking the stock ECU had been chipped and tuned badly but it appears to be stock. I'll have to monitor this to make sure it doesn't happen again.

Oh yeah, after the rebuild it wouldn't boost past 7 psi, felt like it was being held back by something, this was with no boost controller.

After driving around like that for 500 k's I installed a manual boost controller to see if I could bring the boost past 5 psi. It did, when pulling in 1st gear it would reach 19 psi, then in 2nd it would cut out at around 11, in 3rd it would barely go past 7 psi again before cutting out. Then it started misfiring intermittently and eventually I permanently had a boxer engine instead of a straight 6. I figured spark blow out but couldn't be plugs cos new BKR7-E11 plugs were put in during the rebuild so must be coilpacks or ignitor or the crumbling coilpack connectors.

So put in splitfires, new coilpack connectors and new style ignitor, gapped plugs to 0.8mm, still boxer engine! Checked injector resistance, coilpack signals and everything, eventually found that cylinder 3 wasn't firing.

Swapped coilpacks around, still no.3, swapped plugs around, bingo, dead plug...good as new now, doh ???

But something must have caused the new plug to fail, I'm thinking the higher boost damaged the aging coilpack and consequently killed the plug, what do you guys think?

[GTSBoy]

High boost doesn't kill coils.  It just exposes a soft coil's lack of ability to supply enough energy.  Plugs don't die from dying coils.  They may foul, but they don't die.  The plug doesn't care if you're not feeding it enough energy to make a spark jump the gap.

[Darrel]

Makes sense, what do you reckon killed the plug? Overheating? Contamination? Fouling? Plugs looked normal across the board, can't figure it out ?

[Dylannn]

Could be coincidental that the plug died?

[Darrel]

That could very well be it ?

[GTSBoy]

Yeah, I wouldn't be looking for anything more sinister unless the new #3 plug fails.

[Darrel]

Will keep an eye on it, cheers!