Hi guys, posted this on RSOC but thought I would put up here to see if anyone can help?

My saph, 2wd standard has been running spot on for the year I have owned it however after being laid up since November I have just taxed her again and have carried out the usual checks, oil, plugs etc.

Anyway when I am driving at low speed it is perfect, however if I floor the accelerator suddenly it begins to build boost and then jerks and cuts the turbo (violently), however if I gradually put my foot down the boost builds and the turbo spools no problem?

Just wondered if anyone had any ideas as was thinking it could be a split hose but which one would cause this?

cheers

 

Possible phase or crank sensor fault, I'd be checking both of these, also what plugs are you using and what gap?

 

currently running NGKPFR7B plugs gapped at 0.7mm,

How would I check the phase, just replace it?

 

Personally i'd replace due to the cost of it, and peace of mind, but if you know it's been done recently then maybe not....
Anyway, if you take off the distributor cap, rotor arm and the dust cover thing (if there is one), you should be able to see the sensor and the wires, often these corrode or degrade over time and cause a missfire. "Usually" if I may go out on a limb here, most missfres on these engines are caused by either bad crank or phase sensor, but can also be a mutitude of other things, pkus thiese are easy and good places to start your diagnosis.

 

sounds same what happened to a old evo of mine mate.i no its not a cosworth but it was my actuator what was overboosting and the boost cut in sensor or what ever you call it was stopping it from over boosting.cuts in violently so hard u could get put through the windscreen lol.hope you get it sorted

 

Agreed that sounds like overboosting to me, any fiddling been done to the actuator over winter?

 

Really violent, I thought my teeth were gonna come out)

 

No nothing has been done over winter, although I would think that the guy who owned it before me was a bit of jack the lad and I have a feeling he would of turned the boost up.

As it's standard and I don't have a gauge what would be the best means of testing the boost pressure, is there a measurement on the actuator arm for standard?

 

Check amal valve and boost pipes round turbo.best to get boost gauge or risk it going pop

 

without a boost gauge there's no way of 100% knowing the boost you're running, you can pick up a boost gauge for 30 quid though and it's a 5 minute job to connect one up just so you can check it if you don't want one fitting in the car. really does sound like overboost though, mine did it when i bought it as the know it all previous owner had wound the boost up to 35 psi on a standard t3 and off the shelf chip

 

Have you done the fuel filter ?, the bacteria that thrive in tanks and filters love these rest periods, ideally done every year.
tabetha

 

A dirty fuel filter will cause these symptoms how?!

 

Quickly where would i connect up a boost gauge on a standard saph and run pipe into interior for a temporary purpose only, don't want a permanent gauge.

And do I take the reading on normal driving, reason I ask is in the workshop manual it says drive at 3500rpm and than apply brakes while still driving.

 

On the inlet manifold mate.think anywer past the throttle body should be ok.i hav my hose going to a little connector joined in the manifold it self

 

on full throttle more fuel is required, if the filter is partly blocked then it will starve the engine but may show no signs of problems if the throttle is used progressively untill high in the rev range

fuel filters are all ways over looked on cosworths

 

i agree this was causin mine to miss fire on boost, changed the filter and its been fine ever since

 

i agree a blocked or partially blocked filter will cause a missfire in the higher revs or under heavy load but there is a world of difference between a missfire and overboost! sure change the filter if it hasn't been done at last service but the symptoms seems way too harsh to just be a missfire to me.

 

Check the hoses as said, you want to be looking at the one which comes from the compressor housing to the Amal and the one from here to the actuator, if one of them has fell or or split you will run more boost, there is no point just upping the boost by itself, it's also very dangerous to do so, at 7000 RPM or 13PSI of boost on the standard software fuel injection is cut totally (Hard cut) which sounds like what you are experiencing.

Also the said fuel filter should be changed as this IS a servicable item regardless of the car.

You can connect a boost gauge to the plenum, but it's best not to tee into the MAP sensor or the fuel pressure regulator vaccum pipe.

Martin