Can anyone out there shed any light on this topic?

 

I had a new timing belt fitted (with all the usual extras) about 3 months ago.

 

The car ran very well for a few weeks but started to get a bit lumpy at higher revs and boost. By 4-5 weeks after the timing belt, it had got to the stage where I was getting backfires and serious detting at high boost. I went in to GPS and after a bit of checking (and a full ECU diagnostic) it turned out that the timing has running at 30 degrees, rather than 15!

 

Original Garage, claim to have set it at 15, but I was sceptical, until I noticed that the now perfect running of the car started to deteriorate once more. Car was booked in for some suspension and gearbox work, so I had them check the timing problem out.

 

I have just been told that the only solution is to bypass the bleed valves which are currently upping the boost level.

 

So what is the variable in this equation? Why did the car run well for a few weeks after the timing was reset and then get graduallt worse?

 

All sensible suggestions welcome!

Nigel,

 

Sounds like we have a similar problem - mine was at around 30 degrees too! Mine also seemed to get gradually worse - can't think why that would be...there is a known problem with wear on a locating pin on the crankshaft on early Z's apparently.

 

Since setting your timing back have you found performance to have degraded i.e. peak power and torque down?

 

I've borrowed an ECU just so I can rule my existing ECU out. Will test at the w/e.

 

 

Cheers!

 

RobH

Sounds like slipping timing belts. Remember the CAS is driven off the N/S exhaust cam, so if that jumps a few teeth on the belt, your CAS will also be out in relation to TDC.

 

HTH

 

CheerZ,

 

Andy

Found on other Turbo'd Nissans i've had, if the TPS switch is not set correctly or worn internally, it slowly but surely advances the timing further on, so worth checking that out at the same time, just in case.

smithy :cool:

Hmm....

 

I replaced my TPS around about the time this started to be a problem. I had some erratic idle probs so I replaced and reset the TPS - settings still look fine according to the AVC-R reading though...

 

RobH

Hi Rob, i know the AVC-R is a nice piece of kit, though i wouldn't rely on it to let you know the TPS is set correctly to begin with.

Having watched a nissan mechanic do it a couple of times he used a feeler gauge, voltmeter jobbie and played with the revs a little, showed on his sun machine how the moving of the TPS altered various settings. In most Nissan manuals it shows how this is done.

smithy :cool:

Umm...what do you use the feeler gauge for?

 

I'll have a bash with the multimeter tonight.

 

Cheers!

Andy - I'd like to think that slipping timing belts is the one thing I can rely on it not being, as the timing belt was replaced by a reputable mechanic with quite a bit of 300zx experience (he even used to own one). I had this problem both before and after the new belt.

 

Someone mentioned a fault in the cam might be the cause, but I don't know what this fault might be (?).

 

Don't know about the TPS switch - what the hell is that!?

tps = throttle position switch

SENSOR even...........sorry. :rolleyes:

Agh!

Throttle position sensor - I got one of those built into my ankle too!

 

:D

Right the feeler gauge bit, this uses no tech terms whatso ever :D :D

On the side of the throttle body is a point where i believe you can alter the idle ? it is like a nut with a metal plate that springs down on top and you can lift it back, with me so far :D

with the engine running, hooked up a sun tuning machine or similar, a feeler gauge is placed between this nut and plate i mentioned and a multimeter attached to the wire on TPS, by moving the switch/sensor a little up/down, forward/back you get different readings, move it until the reading is as per the book and tighten the sensor/switch little nuts up and remove feeler gauge. Watched him do it on 3 silvia's and 1 Zed that were either having problems with moving timing or fitting a new switch.

cheers

smithy

I'm sure the techies out there will give a more accurate description :D