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Check the brake booster. It is connected to the inlet manifold as it uses the vacuum coming from the inlet manifold. A leaking diaphragm might cause to much air entering the inlet manifold. Start the engine and let it idle - check that it doesn\'t idle to low, if so adjust first - step hard on the brake pedal as during an emergency stop. If the engines stalls it is the brake booster.
Fuel/air ratio is correcting rich for an overly lean condition. Possible Causes: Fuel System---Exessive fuel presser, Leaking fuel injector(s), Leaking pressure regulator, Low fuel pressure or Contaminated injector(s). Induction System--Air leaks after the MAF, Vacuum leaks, Restricted air inlet, PVC system, Fuel purge system or Improperly seated dip stick. EGR--Leaking gasket, Stuck open EGR valve or Leaking diaphragm. Base Engine--Oil overfill, Cam timing, Cylinder compression, Exhaust leaksbefore or near the HO2Ss. CHECK AIR FILTER, AIR FILTER HOUSING FOR BLOCKAGE. VERIFY INTEGRITY OF THE PCV SYSTEM. CHECK FOR VACUUM LEAKS. HOPE THIS HELPS YOU ??
hi. it sounds like a prolem on the vacuum pipes going to the inlet manifold. a split in one of these vacuum pipes would result in too much air going into the engine, resulting in the exact symptoms you are describing.
check each pipe for any signs of damage or collapsing or holes. make sure that they fit tightly at the ends and at any junction points.
also remove the pipe going into the brake servo unit and blow into it. you should feel some resistance, and when the pressure is released, you should feel the air blowing back a little. if you can keep blowing into this pipe with no resistance the diaphragm in the servo unit has a hole in it which will also let air into the manifold.
I would check the medium sized rubber hose that goes to the brake booster from the inlet manifold as it can swell internally and prevent vacuum getting to the power booster. Replace if necessary. I would also check all those pesky little rubber vacuum hoses that are used for pollution control. They tend to go hard and split where they connect to the metal piping if they are over 10 years old, allowing air / vacuum leaks into the inlet manifold. It could also mean that the rubber diaphragm inside the brake booster has developed a leak and causing loss of power assistance.
In relation to the brake booster, try looking at the vacuum hose that runs from the inlet manifold to the brake booster. It could have become hard and brittle and split causing a bad air/vacuum leak.
Sometimes in older vehicles the rubber diaphragm inside the brake booster can perish and split allowing excessive air through the booster into the inlet manifold
The EGR (exhaust gas recirculation) valve What is it? This is a device that reduces engine emissions
of nitric oxides by allowing a measured amount of exhaust gas to re-enter the
intake manifold and mix with the air prior to entering the cylinders.The EGR can be vacuum or electrically driven
or a combination of both. Where is it located?The EGR is most often associated with the intake manifold.The EGR will be sited at a point of contact
with both the exhaust and intake manifolds.If the exhaust manifold is remote, for example on the other side of the
engine to the intake manifold, there will often be an exhaust feed pipe leading
from the exhaust manifold to the EGR
sited on the intake manifold. How does it work?Generally intake manifold vacuum acting on a diaphragm draws up on a
valve to open a connection between an entry port from the exhaust gases and an
exit port to the intake manifold.An
open EGR port makes starting difficult so the valve operation is often impeded by
an electrical over-ride until the engine has warmed up, as signaled to the ECU
by the coolant temperature sender.In
some cases, a differential pressure
feedback exhaust (DPFE) sensor fed by pipes from the exhaust feed to the
EGR informs the ECU when and by how much the EGR should be open. Symptoms of faulty EGR The EGR has
two possible fault modes either it is a) open when it should be closed or b)
closed when it should be open. (some EGR faults are in fact more likely to be DPFE related)
Poor idling:‘hunts’ at idle
and generally rough engine performance.This is due to the air ingress through the split diaphragm or the
EGR valve being left open, either event compromises the intake manifold
vacuum and in turn this interferes with the ECU’s ability to deliver accurate
fuel to air ratio for a given engine speed.
Misfire and ‘pinking’:if the EGR is jammed closed or the
exhaust feed pipe is blocked (e.g. gummed up with baked carbon) the engine
ignition runs lean and very hot, so hot in fact that the fuel air mix can
spontaneously ignite causing a misfire.The misfire if pronounced can, in turn, be detected by the engine
knock sensors and this gives the appropriate on board diagnostic error
codes along with the check engine light.Due to the diesel engines creating more soot in the exhaust a blocked
EGR is a much more common complaint in diesels than petrol cars.
Surging:A sticking EGR valve can lead to an
effect of rhythmic surging a bit like the MAF fault, especially in turbo
charged engines.Normally on a
warmed up engine the vacuum from the inlet manifold opens the EGR.If the EGR fails to open promptly the
turbo can be subject to a slight boost.Extra fuel/air mix is pushed into the inlet manifold as a result,
increasing pressure (decreasing the vacuum).Without vacuum in the inlet manifold the
EGR closes again but if sticky does so only slowly.This may allow inlet gases to flow
through the EGR into the exhaust manifold for a split second.There is a time lag in the sequence of
these events leading the engine to surge in cyclical manner.
How to check?With the engine running it may be possible to force the EGR valve open
by pressing on the diaphragm with one’s fingers.Failing that pulling off the vacuum line to
the EGR, blocking the pipe on the inlet manifold and applying vacuum to the EGR
to monitor function will determine if the diaphragm is split.Removal of the EGR assembly and examination
of the ports and valve mechanism will reveal any carbon build up. How to fix? If the diaphragm is split then the
EGR needs to be replaced.Most EGR problems are linked to carbon
soot build up and this can be cleaned using a cloth, brush and carburetor choke
cleaner spray.If the exhaust feeder
pipe is blocked this can be cleaned using a piece of frayed hand brake cable as
an internal brush. This makeshift brush can be further enhanced by mounting it
in a drillto sweep dirt from the interior of lengths of pipe.Some cars (Hondas are a good example) have an
elaborate passage way system to provide exhaust gas to each inlet pipe runner.The only way to clean these out is by
removing the blanking plugs (no easy task) and then using the makeshift rotary wire
brush and carburetor choke spray.New
blanking plugs have to be reinstated to make good the passage ways assembly.
Section 03-04A: Fuel Charging and Controls—2.0L
1995 Contour/Mystique Workshop Manual
DESCRIPTION AND OPERATION
Fuel Pressure Regulator
The fuel pressure regulator (9C968):
Is mounted to the fuel injection supply manifold (9F792) downstream of the fuel injectors (9F593) .
Regulates the fuel pressure supplied to the fuel injectors .
Is a diaphragm-operated relief valve in which one side of the diaphragm senses fuel pressure and the other side is subjected to intake manifold vacuum. Nominal fuel pressure is established by a spring preload applied to the diaphragm.
Balances one side of the diaphragm with manifold pressure to maintain a constant fuel pressure drop across the fuel injectors .
Bypasses and returns excess fuel to the fuel tank (9002) .
Fuel Pressure Regulator
Engine Vacuum Reference Tube (Part of 9C968)
Ball Seat (Part of 9C968)
Spring (Part of 9C968)
Upper Housing (Part of 9C968)
Diaphragm (Part of 9C968)
Lower Housing (Part of 9C968)
Fuel Outlet (Return) Tube (Part of 9C968)
Fuel Inlet (Supply) Tube (Part of 9C968)
O-Ring Grooves (Part of 9C968)
Mounting Plate (Part of 9C968)
Fuel Filter Screen (Part of 9C968)
Spring Seat (Part of 9C968)
Valve Assembly (Part of 9C968)