GTR Sounds like it's missing?????

[awurth]

Took a mate for a spin in the GTR yesterday and after a run down the local 1/4 (two white lines 400m apart) I did a u'y to go back home and wound it out to the speed cut, as soon as I hit it i backed off and continued home. as i dropped my mate off i noticed it was running like a pot was down. I thought "Hmmm not good" anyway no smoke coming out the back so not so bad, I gave it a bit (still being cautious) from an intersection and it seems to rev out clean. got home noticed the motor was shaking like a pot was down and thought "plugs" straight away, I checked the exhaust for an unburnt fuel smell and it didn't smell good and made my eye's water. Checked the the plugs and all good, Pulled the 12v feeds to the coils off 1 at a time and I noticed that pot 3 doesn't make a difference to the idle on or off. swapped plugs around and still pot three. So I got another plug in the coil and earthed it onto the motor and there is spark, about an inch long if you slwly pull it away. I pulled the injector electrical connection off and the idle does change so it must be all OK, so it has me a bit stumped. I re-set the computer, pull the positive off the battery and leave the internal light on 5 mins later the car still ran the same. a bit stumped, any ideas folks? could it be the speed cut out has messed something up? it stopped shaking after I had messed with it, but it still sounds different on idle.

[Morgs]

Sorry im kinda confused, isn't it quite simply coil number 3?

[Sydneykid]

Sounds like fuel is OK and ignition is OK, so it is compression. Get a leak down test done.

[awurth]

Ok, I bought a compression tester today and checked the compression. Going from the front cylinder to the back one here are the results.

1. 10.75 bar (150psi)

2. 11 bar (160psi)

3. 10.75 bar

4. 11 bar

5. 11 bar

6. 10.75 bar

Any other thought folks? I assume a leak down test checks how the cylinder holds the pressure and how quickly the pressure drops, didn't do that test. should i do that? I assume if a valve is burnt it's going to have a vastly different result to the other cylinders

[DAN00H]

sounds like a cracked head / head gasket starting to fail... did you do the comp test when the engine was hot???

[awurth]

yeah drove the car around and got it to operating temp then did the test immediately afterwards and got those results.

I bought brand new NGK plugs today, just v grooved standard plugs. With the apexi plugs when you started it it would cough, splutter, shake alot and struggle to hold idle, (like the timing was all out). put the new plugs in and it started fine doesn't shake but still sounded funny (sounds like it is lumpy).

A mechanic here with a 32 GTR reckons that I might have an adjustable exhaust cam gear. my timing is set to 15 degrees advanced and the pickup is nearly fully advanced compared to his 32 where it is sitting close to the middle. pick up is on cylinder 1 and light set to 0 and I have it on the 4th white line (line=timing 1=0 2=5 3=10 4=15). There is no obvious detenation under load as you would expect if the timing was that far out. I wonder if something could have come out of wack n the cam gear, if there is one on it?

[DAN00H]

you can check to see if it has a cam gear if you mark all the positions and replace exactil the same. At idle you should be able to balance a 50 cent on it's edge on the plug cover...

[awurth]

on the Back of my GTR there is a "tuning sports RICAP" sticker. Anybody heard of this company? and what they do? When I was putting my alarm system in I noticed that the sticker had been removed off the ECU and that there was some altered wiring in the ECU wiring loom. Fact that the speed cut is still present makes me think it is nothing. I will have a look a exhaust cam gear later tonight.

I just started it and noticed the fuel pump takes a while to pressurise the fuel line. then when you start it then car struggles to start and idles badly for a sec or two. Could this be a fuel pressure problem?? Mind you my car never did this before I posted this thread.

[awurth]

Ok folks, beleive the problem has been found. took it to the mechanics today and he seems to have figured it out. he checked a few of the things I had and he noticed that the inlet manifold gaskets seem new. he pulled out a bit of carby cleaner spray and the inlet around no. 3 cylinder seems to have a small leak in it. spray a bit of the stuff around that area and the idle picks up, it's one of three things, the seals around the throttle shafts, the gasket onto the head or the gasket onto the plenum. using some co-contact cleaner i beleive it is the gasket onto the head, we will see! the boost spiking and dropping on the speed cut must have been enough to blow something out. who would have guessed!

[awurth]

Ok beleive it might be the seals around the throttle shafts, anyone ever had to replace these? it seems anything to do with the exhaust or intake manifolds it would be easier to pull the motor out and do the work, DOH! any idea's as to taking the inlet manifold off? I mean with enough messing around I will get it off but anyone got little tricks I should know that will make the job easier?

[awurth]

Ok, it was the gasket between the head and that inlet manifold that sits between the throttle bodies and the head. a big leak right on No.3. Anyways I cleaned everything up throttle bodies where full of carbon. putting it all back on the car idled at around 1500rpm. I screwed the idle screw in and it dropped it to 1300rpm. I adjusted the screws on the throttle body but now it sits just over 1100rpm. I was looking at the throttle bodies when I had cleaned them and there are very, very small gaps around them when they are closed. using spray it can't find any leaks. I have reset the computer as well. any ideas????

[ylwgtr2]

the bypass air controll valve,its under the inlet manifold.It has an idle adjustment on it...you should be adjusting from there!What you might have to do is take it off and have a look on the side of the valve there is a hole that has been glued up from factory.This is the parts where they fit the spring in to hold the valve closed then they fit a screw in there and glued the door closed.....i have found that this spring looses its tension over the years so the go is to get all the glue out,give the screw a few more rotations(its not screwed all the way in from the factory,so there is a bit of life left in it)then re araldite the screw hole closed....simple

[awurth]

Ok, I pulled the Bypass air control valve off and noticed how the spring looses it's tension, So a bit of fitting and turning and I had fixed that all up, but! The solenoid still doesn't operate. I noticed before I did all this work that if you disconected the supply to it the engine would struggle to idle. now it doesn't make a difference. but the solenoid operates with a 12v supply and the wiring gives a supply of 10.9v. I'm thinking that it could be throttle bodies. before I cleaned them they had stacks of carbon in them. when I had cleaned them they close properly but there are very, very small gaps around them when they are closed. i'm thinking that there is just enough air getting past to let it idle up. maybe time and a bit of carbon build up will fix it. I pumped heaps of spray into the engine bay trying to find a leak and i can't find jack.

[rb25]

just getting back to the inlet manifold gasket: i have seen these get 'sucked' in twice on rb26's around cylinder 5 & 6. might be a common problem.

-rb25

[awurth]

bit more info, when you start the car it idle's around 1100rpm, drive it for a bit then let it idle and it will sit around 1400rpm, turn it off for five mins start it and then it sits on 1100rpm, drive it back to 1400rpm?????

[awurth]

Well it seems I'm doing allot of posting on my own thread but i'm still having drama's. I pulled the throttle bodies off again last night to check the gaps around the butterfly's. I took it to a mechanic today and asked him what he thought about the gaps (I had it touching top and bottom and gaps where more around the side). After a bit of fiddling he got the gap even around the whole butterfly, he then set them so you could just see around the whole thing. Does anyone know if you should be able to see any gaps or whether it should fully closed, when I cleaned them firstly I sprayed cleaner on the butterfly and if you didn't open it the cleaner wouldn't leak away.

Fully closed makes sense to me considering you have separate idle control. I rang up Nissan and apparently each throttle body is a complete assembly and your looking at over $2000!!!!!!

[awurth]

well the GTR has been at the mechanics due to me having no time to play with it, and after a couple of days of changing my clutch and rear cranks shaft seal (seal not faulty just changed it), finding out my front universals are stuffed and that my tappet cover leaks they have seemed to have found the problem. The air regulator when closed still allows air to pass through when it shouldn't, it should be half shut at 20 Degrees Celius and fully shut at 60 degrees and should time out and shut after 7 mins. It seems with the caked up throttle bodies letting no air past this bit of air flowing by didn't bother the idle. Now with the throttle bodies letting some air by again plus this bit of air coming through the air regulator makes the revs pick up. The AAC valve is fine after we had fixed it up earlier.

Anyone had problems with the air regulator on a GTR before, are they the same as the unit on a RB25? And whats the cost from Nissan? I'm prepared to buy genuine for the sake of it!