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R34 Gtr Strange Problem

Don Dada

By Don Dada,
in Engines & Forced Induction

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Don Dada Mentor

Don Dada

Posted
Posted

I'm getting a rough idle problem with a 34 gtr and I have tried basically everything without sucess.

First off the car has a r33 head&blk using back the 34 harness with some unknown cams, which I believe are 34 as well as it uses back the 34 type cas

When idling if I pull the connector for the coil pks I can hear a noticeable difference in the beat of the engine on all except no. 2, so i'm assuming the problem is with 2.

Checked for spark...good. Switched around pks and plugs same thing. Checked for inj pulse....good. Changed with a next set of inj and same thing.

Changed afms same thing, changed resistor pk same thing, changed cas same thing. Checked timing and dots on gears line up with backing plate while crank pulley is on the first orange mark 0* so I assuse everything is good there.

Compression test 150-160 with the highest being no. 2

Dont think its an electrical problem the spark from no.2 seems healthy and test light looks the same for all inj when checking for pulse.

Is r34 gtr cams compatable with the r33 gtr head?

What you guys think?

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XKLABA Grand Master

XKLABA

Posted
Posted

the only difference between 32/33 and 34 cams is timing and the CAS key, otherwise identical and heads are the same right through

try spraying brake cleaner around the intake runner on number 2 and see if the idle changes, try compression test with throttle closed as well as open

have you tried changing the CAS,

but generally if you have fuel-compression-spark then you should not have a problem, so interesting, hope you find it

keep us posted

GTRNUR Grand Master

GTRNUR

Posted
Posted

Your on track with your troubleshooting, but have moved down the wrong path a little.

A vacuum leak around number 2 would cause it to burp and pop at idle a little, but not flame out completely. A faulty cas also would not drop the same cylinder consistently. It would be doing it on all the cylinders or not run at all.

Does it rev cleanly and crisply, or does cylinder number 2 never appear to fire.... Or is it only drop ignition on Cylinder 2 at idle?

What is the idle speed?

Is there a noticable drop in RPM when cylinder 1 is unplugged, and did you PROPERLY balance your throttles when connecting your throttle linkages.

Does it do this cold as well as when hot?

Last of all... is it losing coolant, and is the number 2 spark plug clean or wet when its removed? If its wet see if it will evaporate instantly to dry if you blow on it (indicating fuel), or not (indicating coolant/water).

GTRNUR Grand Master

GTRNUR

Posted
Posted

I'll get some carb spray and check for leaks. If is was a matter of valve clearance, would be be isolated to no.2 as is now?

Yes

Its possible that variation in clearences or impropper shimming of the bucket could hold valves in one cylinder open, but that would also be evident in a compression test. It would test lower than the others, not higher, so I would be inclined to think not.

Don Dada Mentor

Don Dada

Posted
  • Author
Posted

Idle is 900-1000rpm and it does not rev out clean at all hot or cold. The plugs appear to be consistent across all but does come out a little wet, doesnt seem bad

When you unplug no.1 you definitely notice it as it wants to cut off, and basically no change when you unplug no.2

The car was bought recently and did notice the temps climbing, but havent driven it long enough to notice any coolant loss. Also tried bleeding from the 10mm bolt on the balance tube but that was clogged so just left it at that until I sorted out this problem.I havent noticed any coolant and oil mixing though

I'll have to take another look at those plugs though and check to see if that little wetness is infact water or if its fuel across all

GTRNUR Grand Master

GTRNUR

Posted
Posted

Sounds like a pretty solid fault. You need to confirm fuel or water on that plug.

You can eliminate fuel by disconnecting the injector for that cylinder and starting the motor for a moment with no plug to dry the cylinder. The install a clean and dry plug, re-start and idle for 30 seconds or so. The stop again, remove and inspect the plug.

How did you check the ignition for the cylinder was working ok?

Don Dada Mentor

Don Dada

Posted
  • Author
Posted

Yea...Will diagnose with a new set of plugs.

As far as checking ign, I took out the coil attached a plug and checked spark which looked healthy, and was same when compared to other cylinders using the same method.

Also swapped around pks and plugs....splitfires btw

DVS JEZ Grand Master

DVS JEZ

Posted
Posted

Spray wd40 along the plenum gasket. U will find ur problem.

Had to replace the inlet gasket on a 32 GTR the other week for this exact reason. My smoke tester proved my theory.

Had a constant miss in cylinder 2. Disconnect coil no difference. Disconnect injector slight difference. Spray wd40 or similar and idle cones good. Replaced with Nitto gaskets. Runs perfectly now.

4e3966ce.jpg

Don Dada Mentor

Don Dada

Posted
  • Author
Posted

Hmmm....Interesting. Will definately try that, just that it seems like the fuel pump has now shit itself....Actually not even sure.

Added some fresh fuel to the car as it was parked up a couple mths and after that it barley starts and idles. Pulled the return to the tank and no fuel, so we went inside the tank and found a walbro pump, took it out and hooked it up front plumbed to the rail in a container of gas and it works.....pressure in the return, but the car barley starts. Tried an oem gtr pump up front and same problem.

So the plot thickens. Done troubleshooting for today, and until I get a fresh set of plugs.

XKLABA Grand Master

XKLABA

Posted
Posted

Spray wd40 along the plenum gasket. U will find ur problem.

Had to replace the inlet gasket on a 32 GTR the other week for this exact reason. My smoke tester proved my theory.

Had a constant miss in cylinder 2. Disconnect coil no difference. Disconnect injector slight difference. Spray wd40 or similar and idle cones good. Replaced with Nitto gaskets. Runs perfectly now.

4e3966ce.jpg

This is exactly what happened to my 32, and is why I suggested the brake cleaner as it doesn't leave any residue and will change the idle if there is a leak

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