Gt-r Engine Problem

[DSF]

  Adriano said:

About the only thing that will make the car make boost in neutral like that is a skipped timing belt, retarding the cam and ignition timing.

Okay, got the mechanic to change the timing belt and this did not solve the problem. He said that it did not skip a tooth and all marks line up (found out that it has Toda branded adjustable intake and exhaust cam pulleys). He then disconnected the exhaust at the Cat converter and when revving it out of gear it did not make quite so much boost. We took it for a drive with it disconnected but the same problem was still there. The mechanic said that it feels if there is a blockage somewhere in the intake. While driving the car it was coming on to full boost at 3000rpm but is struggling to get there.

Things that have been checked so far;

turbo's spin freely,

cat converter is not blocked,

compression tested with all cylinders passing,

spark plugs are fine (the car does not missfire),

This problem is proving difficult to find, I am hoping someone out there might have some more suggestions on what could be causing all of this.

[WHT11]

DSF

i would try a set of AFM and ecu if you can swap them with somone, so you know there good AFM problems usally limit car to 2000rpm or below. Also a backfire can damage the hot wire in the AFM.

Is it overfuling whith no load (in neautral), do have black smoke out the exhaust? what rpm can you get when free reving? are you still getting boost in neautral when the engine is cold?

cheers

[DSF]

  WHT11 said:

DSF

i would try a set of AFM and ecu if you can swap them with somone, so you know there good AFM problems usally limit car to 2000rpm or below. Also a backfire can damage the hot wire in the AFM.

Is it overfuling whith no load (in neautral), do have black smoke out the exhaust? what rpm can you get when free reving? are you still getting boost in neautral when the engine is cold?

cheers

Yes it is overfuelling with no load, with plenty of black sooty smoke.

At this stage while in neutral I am not confident in revving past the 4500rpm as it is hitting mas boost before that (though I have taken it past 6000rpm once).

All symptoms are the same whether the engine is cold or warmed up.

I have two spare AFMs (working conditions uncertain) but changing them over has not improved the engine problem so far.

Cheers.

[DSF]

Well the mechanic reckons that it is a possible sticky/faulty BOV. No the problem is intermittent as we were able to drive it normally for a little while, and now when driving anywhere between 4000-5500rpm it will dump all boost. Only change was the mechanic blowing pressure from the intake of the intercooler up to the plenum chamber.

Would a possible faulty OV be the cause of all of this? I am hoping this is it and all will be fixed.

[neo32]

i will check all sensors sounds like its in lime mode like when u unplug a afm etc so be checking voltages from sensors

[DSF]

  neo32 said:

i will check all sensors sounds like its in lime mode like when u unplug a afm etc so be checking voltages from sensors

But I thought that the ECU will not let you rev past 2000rpm when in limp mode? At the moment the car is running fine except when you get anywhere between 4000-5500rpm, where it cuts all boost/timing/fuel/whatever I am not sure but once it is below 4000rpm it runs fine.

I have been searching other posts, I found one where the symptoms are similar and the possible fault is either BOV's or the boost solenoid.

Cheers

[Dinstg8r]

Hey I reckon your problem would be a blocked vac line.

I say this because I have the same car, same prob exaxtly

(blew hose than had more probs later) checked everything.

Found a dead vac line on the very bottom of the intake plenum,

closest to the firewall.

Dont know the best way to unblock this one as it was inside the plenum(not the line itself)

So I just gave a quick blow in the line with an air compressor, and its been fine since.

Hope this helps

Jason

[Tomei_33]

i cant explain the overboosting but my car hesitated to go past 2500 rpm and stalled on idle, soldered up the afms and its fine now, try finding a working set of afms to test it, no point using dodgy afms to test if ur afms work or not

[neo32]

sory mate didint read the page 2 posts

  DSF said:

But I thought that the ECU will not let you rev past 2000rpm when in limp mode? At the moment the car is running fine except when you get anywhere between 4000-5500rpm, where it cuts all boost/timing/fuel/whatever I am not sure but once it is below 4000rpm it runs fine.

I have been searching other posts, I found one where the symptoms are similar and the possible fault is either BOV's or the boost solenoid.

Cheers

[Travis Trayhern]

check ya pipes arnt cracked those old gtr rubber pipes split and its hard to see where also it sounds like afm

[Chunners]

It might not be the AFMs themselves but a problem in the plug or wiring. I had similar problem when i first got my car and swapped my ARF with known working ones, but the problem was still there so i ruled them out. It turned out to be a problem in the wiring causing one ARF to intermittently drop in voltage, thus causing the stalling/rough running. I rewired both my AFM and have never had a problem since.