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Saxo Common Problems & Fixes
by BobC 9th July 2009

Overview

Your Saxo requires three things to start and to run:
1) Correct fuel and air mixture
2) A spark
3) Compression
The ECU, with the help of sensors, choreographs these to perfection. However, when things go wrong it can make fault finding difficult. A systematic process of elimination needs to be followed to first pinpoint the problem as being: 1) fuel mixture related or, 2) Spark related or 3) compression related and then to diagnose and correct the problem rather than a symptom.

For example, a flat battery can be “fixed” by charging or replacing it. However, if the underlying cause was that the alternator was not charging the battery then the fault will come back.

Mixture
When all the fuel is combined with all the free oxygen within the combustion chamber the mixture is chemically balanced and this Air to Fuel Ratio (AFR) is called the stoichiometric mixture. Lambda (λ) is an alternative way to represent AFR. Any mixture less than 14.7 parts air to 1 part fuel is considered to be a rich mixture as it has too little air, any more than 14.7 to 1 is a lean mixture.

Fuel supply is under the direct control of the ECU and not the accelerator. The ECU adjusts the fuel injection time based on feedback from various sensors. The fuel is pumped from the tank through a filter to the injector rail to the injectors. The injectors are electrically operated, using magnetism, by the ECU. If they physically stick closed then insufficient fuel will be delivered but if they stick open closed then too much fuel will be delivered.

The accelerator throttle physically controls the air flow from the air box and air filter into the inlet manifold. The inlet manifold vacuum changes under load and it tries to suck in the air it needs via the throttle body. The inlet manifold must have an air tight seal to the throttle body in order for the throttle to control air flow and thus the engine speed.

The ECU makes adjustments to the fuel injection time based upon engine load, air and coolant temperature. For example, during cold starts the mixture is enriched in a similar way as applying a choke to a carburettor.

During idling, the ECU sets the idle speed to cater for high-drain applications (air conditioning, electrical components) by increasing the idle speed by allowing air to bypass the throttle regardless of the throttle’s position. The idle control valve (ICV), aka idle air control valve or stepper motor, allows air into the inlet manifold to speedup the idle and to help with smooth deceleration.

Fuel supply suspects: Fuel, fuel pump, fuel filter, fuel pressure regulator, fuel pipes, injector rail and fuel injectors.
Fuel supply electrical suspects: MAP Sensor, air intake temperature sensor, coolant temperature sensor, fuel injectors, fuel injection relay, fuel pump, idle control valve (ICV).

Spark
The spark signals are generated by the ECU. The low tension side of the coil or coil pack induces a high voltage in the high tension side of the coil for cylinders 1 and 4 then 2 and 3 as one of these cylinders will always be in compression whilst the other is in exhaust. The crankshaft sensor (aka TDC sensor or engine speed sensor) tells the ECU when Top Dead Centre is approaching; some coil pack signals can tell the ECU which cylinder is in compression and thus which fuel injector to trigger. The high voltage flows down the coil pack or HT lead and into the spark. The spark plug is earthed against the engine and the spark “jumps” the spark plug gap to ignite the fuel mixture.

Electrical suspects: Crankshaft sensor (aka TDC sensor or engine speed sensor), coil, coil pack, HT leads, spark plugs.

Compression
During the compression stage both the inlet and exhaust valves are closed whilst the piston compresses the fuel air mixture ready for ignition by the spark plug. The valves close, and open, at the right time under the control of the timing belt (aka cam belt). The valve springs keep tension on the closed valves to ensure that they are tightly seated against the cylinder head. The piston’s rings compress the fuel mixture in the cylinder against the closed valves ready for combustion.

Mechanical suspects: Timing belt (aka cam belt), valves, valve springs, valve seats, valve clearances, piston rings, cylinder wear.

Saxo Common Faults, Common Problems and Fixes.
4 - most common engine faults:
 Erratic idling due to the idle control valve (ICV)
 Erratic idling due to the upstream oxygen sensor falsely reporting a lean mixture; also causes high CO readings during MOT and leads to catalytic converter failure
 Clogged fuel filter
 Head gasket failure caused by overheating caused by a faulty thermostat or low coolant levels
3- most common suspension and transmission faults:
 Driveshaft constant velocity (cv) joint failure caused by split gaiters allowing grease to leak and water and dirt to get in destroying the cv joints. Other symptoms: clicking whilst steering, clunking at full lock
 Power Assisted Steering (PAS) pump failure due to leaks caused by fluid pipes rubbing after front of car is lowered
 Noises due to worn bushes and mounts. Such as engine mounts, gearbox mounts, anti-roll bar bushes and droplinks, lower suspension arm bushes and ball joints, track rod end ball joints mainly due to wear and tear; but can be accelerated by incorrect lowering.
2- most common electrical faults:
 Blown fuses
 Battery and charging
1- the single most frequent cause of Saxo faults is YOU.
 “I pressure washed the engine bay and now it doesn’t start” (but it is clean)!
 “I took it apart and now I cannot remember how it goes back together”
 “Whilst doing that, I broke this…”


Saxo Faults, Problems & Fixes

Honest John's list of recalls
1997: faulty driver's seat catch on 3-door model.
1/2/2000 (Sept/Oct 1999 build only): brake servo valve may fail, leading to loss of servo assistance. Inspect and possibly replace brake servo valve.
28/2/2001: Build 1/1/2001 - 31/1/2001: Possibility that brake relay lever may be faulty. Recall to replace relay lever.
11/5/2001: 2000 Build 5-door models only: Lower fixing bolt of adjustable upper anchorage of LH front seat belt may not be to specification. Recall to replace bolts.
16/5/2001: Build date: January 2001, VIN VF7S*****57426214 to VF7S*****57436943: Front disc brake calliper bolts may not be to correct spec and may fail. Recall to replace calliper bolts.
8/8/2001: 484 1.6 VTRs built 1/1/2001 - 28/2/2002 recalled because defect in rear brake caliper may cause parking brake efficiency to be reduced. Check and replace caliper if necessary.

 Will not start
 Engine does not crank
▪ Battery flat: charge battery, check alternator + wiring
▪ Starter motor / starter motor solenoid & wiring
 Engine cranks over but does not fire
▪ Fuel cut-off switch, “inertia switch” tripped: reset it
▪ Petrol low: doh!
Fuel injection relay
▪ Fuel pump
▪ Fuel filter clogged: especially if ran on empty
▪ Immobiliser: key symbol lit on dashboard
▪ Spark plugs
▪ Coil, HT leads, coil pack
Fuel injectors
▪ Air filter
Crankshaft sensor (aka TDC sensor, engine speed sensor)
▪ Cylinder head gasket
▪ ECU power supply from fuel injection relay wire broken; Engine loom at rear of engine bay: See: http://www.saxperience.com/forum/sho...ng+back+engine Nasty fault, possibly caused by light front end damage, 7 pages, two people suffering but resolved
 Difficulty starting when cold
▪ Spark plugs
▪ Coil, HT leads, coil pack
Fuel injectors
▪ Air filter
Intake air temperature sensor
▪ Fuel filter: especially if ran on empty
Idle control valve (aka idle air control valve, stepper motor)
Coolant temperature sensor
Crankshaft sensor (aka TDC sensor, engine speed sensor)
▪ Cylinder head gasket
 Difficulty starting when hot
▪ Spark plugs
▪ Coil, HT leads, coil pack
Fuel injectors
Intake air temperature sensor
Coolant temperature sensor
Crankshaft sensor (aka TDC sensor, engine speed sensor)
▪ Cylinder head gasket
 Poor idling: revving – low to high
Idle control valve (aka idle air control valve, stepper motor)
Lambda / oxygen sensor
Manifold Absolute Pressure (MAP) sensor
Coolant temperature sensor
▪ Leak in inlet manifold area
 Poor idling: revving high to low; tendency to stall
▪ Fuel mixture too rich: oxygen sensor, air or coolant temperature sensor, fuel injector
▪ Fuel mixture too little air
 Poor running warm / hot
▪ Spark plugs
▪ Coil, HT leads, coil pack
Fuel injectors
▪ Air filter
▪ Intake air temperature sensor
▪ Fuel filter: especially if ran on empty
Idle control valve (aka idle air control valve, stepper motor)
Manifold Absolute Pressure (MAP) sensor
Coolant temperature sensor
Crankshaft sensor (aka TDC sensor, engine speed sensor)
▪ Cylinder head gasket
Lambda / oxygen sensor
▪ Inlet manifold air leak
 Overheating
▪ Coolant levels low
▪ Coolant leak – external or internal
▪ Thermostat stuck closed
▪ Faulty cooling fan switch (if fitted)
▪ Faulty cooling fan
▪ Cylinder head gasket - Coolant leak = internal engine leak; exhaust gases in coolant
▪ Radiator internally corroded / blocked
▪ Oil & Coolant warning light flicker: low engine oil or low oil pressure
▪ Coolant warning light on continuously but levels ok– Coolant temperature sensor / switch; reset ECU
 Electrical
▪ Airbag light on: check wiring to orange plugs under seats
▪ No charge light / battery charge light: alternator wiring or alternator
▪ Fuel gauge needle goes to FULL 3 times then returns to EMPTY and stays there. See here for possible fix: http://www.saxperience.com/forum/sho...67#post4481167
▪ Speedometer & Rev Counter both not working – reset ECU; unplug battery for a few hours
▪ Indicator relay constantly clicking: bulbs, indicator / flasher relay, indicator stalk
ALL not working:
▪ Power Assisted Steering (PAS) &
▪ Heater blower &
▪ Rear window demister / heated rear window
▪ See fix in thread: PAS, heater fan , rear demister Repair.
▪ Dashboard dials not working: speedo, petrol gauge, rev counter, oil temp (VTS only), reset ECU / disconnect battery for a few hours. See: Dashboard dials not working
▪ Problems with headlights, tail lights and dashboard lighting up when you brake. One or both of your brake/tail light bulbs is installed incorrectly. The "380" Bulb - P21/5W Stop and Tail light bulb has 2 filaments; one for the tail light and the other for the brake light. It has offset bayonet lugs and MUST be installed the right way round or the headlights, side lights and dash will light up when you brake.

 Power Steering pump not working
▪ Check fluid levels
▪ Lightly hammer to release (may get a few more months before it needs to be replaced)
 Manual Transmission
▪ Gear lever feels loose, lots of play: gear linkage rods need to be changed 4) SELECTION LINK Citroen part: 2452 E1 = £15.24 inc VAT
5) GEARSHIFT LINK Citroen part: 2452 83 = £13.94 inc VAT; or 2) Citroen part 2449 65 "CONTROL RETURN" (which is £36.85 Jun 2010) in picture below needs to be changed

▪ Difficult to select gears: gear linkage rods, clutch cable adjustment, transmission fluid levels, clutch
▪ Car revving but not pulling whilst driving;
▪ Clutch slipping due to wear or oil contamination
▪ Juddering when clutch is depressed or released;
▪ Clutch worn or damaged or contaminated with oil
▪ Release bearing / thrust bearing worn
▪ Clutch friction plate springs
▪ Clunking noise
▪ Release bearing / thrust bearing worn
▪ Clutch friction plate springs
 Noises, Shakes, Rattles & Rolls
▪ Shakes & Vibrations
▪ Engine mounts
▪ Gearbox mounts
▪ Tapping
▪ Check and adjust valve clearances
▪ Knock: Premature ignition possibly due to low fuel pressure: fuel obstruction, fuel pump or filter
▪ Knock sensor (pinking sensor) not working
▪ Clunks & Knocks
▪ Engine mounts
▪ Gearbox mounts
▪ Suspension springs
▪ Suspension struts
▪ Driveshafts
▪ Anti roll-bar / droplinks bushes
▪ Lower ball joint worn
▪ Lower suspension arm bushes worn
▪ Grinding
▪ Clutch friction plate
▪ Driveshaft / constant velocity (cv) joints dry/worn: check for gaiter splits and escaping grease
▪ Wheel bearings
▪ Squeaks
▪ Suspension bushes
▪ Driveshafts / cv joints
▪ Squeals, squealing
▪ Brakes pads or shoes
▪ Alternator belt: tension too tight or too loose
▪ Alternator belt bearing
▪ Water pump bearing
▪ Power steering pump bearing
▪ Wheel bearing
▪ Release bearing (aka thrust bearing)
▪ Rattles from rear
▪ Tailgate rattles: adjust striker plate
▪ Tailgate spoiler
▪ Spare wheel cage
▪ Sloshing noise in cabin
▪ Air in coolant; bleed air; could be cylinder head gasket leaking exhaust into coolant
▪ Engine noise on radio
▪ Ignition coil suppressor fault
 Leaks
▪ Oil
▪ Internal engine leak = blue smoke from exhaust
▪ Cylinder head gasket
▪ Oil in coolant
▪ External leak = oil under car
▪ Rocker cover
▪ Oil filter
▪ Sump plug
▪ Driveshaft seals
▪ Coolant
▪ Internal engine leak = white smoke - like steam from exhaust; excessive water from exhaust
▪ Water in oil - Yellowish brown mayonnaise looking stuff on inside of oil filler cap
▪ Coolant under excess pressure is escaping from coolant / radiator filler cap
▪ External engine leak
▪ Coolant under car
▪ Coolant hose split
▪ Radiator leak
▪ Petrol
▪ Fuel under car
▪ Fuel hose
▪ Fuel injection pressure valve leaking
▪ Water inside car, often passenger side
▪ Rain / water getting in through:
▪ Window / sunroof
▪ Engine bay
▪ Aerial
▪ Wheel arch
▪ Leaking coolant heater matrix or hoses
 MOT Emissions Failure

Read here

*** Please PM me if you have a symptom, fault or problem that has been resolved by something not on this. Please forward the forum URL and I'll update this thread to include it.
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Last edited by BobC; 18th June 2010 at 20:42. Reason: Added brake light bulb inserted incorrectly.
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