Renault Scenic 1.6 K4M 2001 - Loss of powerArchived Message
Posted by John Kennard on February 23, 2007, 1:54 pm
Hi everyone, have got this one perplexing me at the moment. Vehicle came in yesterday gutless with same symptoms as 3 months ago when we replaced the ign coils. So i tried another set of coils & no differance. I have code read with 3 scan tools and no codes. I have checked to ensure the correct plugs fitted. I have now checked the gases which when the vehicle is first started runs perfectly until you rev several times and then the O2 rises to 5.5% C.O. rises to 7% and the vehicle runs rough and gutless. Turning off & on again restores everything back to normal until revved. I thought of a seal getting sucked in causing air leak so went around every seal with my butane gas probe and no change in engine note but improves if directed straight into manifold. I have since removed all the manifolds and air bleed pipes and breather on top of engine and replaced all seals, I have isolated the carbon canister pipe, neither does this engine have a EGR system to come into the equation.
When the engine starts running rough the cat starts o/heating (excess fuel) but the idle device in the air box starts whistling only when running rough convincing me it is an air leak. I have since removed the MAP sensor and attached a Mitivac to 15" and started the engine with an independent vac gauge attached to manifold. when I raise the MAP sensor to 19" the vac gauge in manifold also rises to 19" and engine runs smoothly for a few moments, all of a sudden the engine runs rough if I drop the vac on the MAP back to 14" the engine improves the idle otherwise it would stall.
I have ruled out air leaks and as such don't have a donor vehicle handy, neither does our local dealer stock the £81.00 MAP sensor. Before ordering the part would a faulty MAP cause such a rise in O2 and Vac drop from 19" to 15" fluctuating, only occurs after a few revs applied? Hoping your experiace can help. John Kennard.