Focus ST170 cold start puzzler
Discussion
All advice gratefully received on this one.
Here's my symptoms:
56k mile 2003 ST170
From cold, if I just turn the key, the ignition will fire, but the engine won't catch. After 5 or so minutes of trying repeatedly, eventually the engine will catch and lurch/splutter into life. I have to hold on the throttle at higher revs to keep it alive. Once it's running I come off throttle but then (still stationary) after about 60- 90 seconds when the idle speed drops, it will suddenly run out of puff and stutter, almost stalling and misfiring before eventually recovering.
If the car is in motion during that 60 - 90 second window, I lose power and the car stutters almost on the point of stalling before recovering.
Once warm and running the problem disappears e.g. if I stop after a journey then come back, the car will restart perfectly first time which makes me conclude it's absolutely something to do with temperature - either components not warm enough or something not responding correctly at the appropriate temperature or some sensor not providing the right temperature data.
The car has brand new OEM battery, sparks and HT leads. Took it to local Ford dealer who replaced fuel filter, but the problem is still occurring and they seemed a bit clueless as to what might be the next plan of attack.
Fuel pump? Some temperature related sensor in engine management?
Here's my symptoms:
56k mile 2003 ST170
From cold, if I just turn the key, the ignition will fire, but the engine won't catch. After 5 or so minutes of trying repeatedly, eventually the engine will catch and lurch/splutter into life. I have to hold on the throttle at higher revs to keep it alive. Once it's running I come off throttle but then (still stationary) after about 60- 90 seconds when the idle speed drops, it will suddenly run out of puff and stutter, almost stalling and misfiring before eventually recovering.
If the car is in motion during that 60 - 90 second window, I lose power and the car stutters almost on the point of stalling before recovering.
Once warm and running the problem disappears e.g. if I stop after a journey then come back, the car will restart perfectly first time which makes me conclude it's absolutely something to do with temperature - either components not warm enough or something not responding correctly at the appropriate temperature or some sensor not providing the right temperature data.
The car has brand new OEM battery, sparks and HT leads. Took it to local Ford dealer who replaced fuel filter, but the problem is still occurring and they seemed a bit clueless as to what might be the next plan of attack.
Fuel pump? Some temperature related sensor in engine management?
First port of call would be a failed coolant temp sensor that's telling the ecu the engine is hot when it's actually still cold. Normally they have a resistance of about 3000 ohms cold and 300 hot or thereabouts. Test it with an ohmmeter both cold and then in a pan of hot water. If the resistance is always low then that's your problem.
Engine stuttering, seems logical that some component in the system isn't providing enough fuel at the right time so Fuel Filter made layman sense to me as a first point of call, and couldn't hurt to replace (due at next service anyway).
In practice it's probably made the problem slightly less severe, but the idling/temperature issue remains, hence some other component must be root cause.
In practice it's probably made the problem slightly less severe, but the idling/temperature issue remains, hence some other component must be root cause.
brotherharry said:
Engine stuttering, seems logical that some component in the system isn't providing enough fuel at the right time so Fuel Filter made layman sense to me as a first point of call,
No, really it absolutely doesn't. The amount of fuel flow per second required to start a car is miniscule. There is almost no load and minimal revs at startup and therefore very little fuel demand. Sure it requires a richer mixture to start from cold than hot but this pales into insignificance when compared to the amount of fuel flow required to run the engine at high rpm, high load i.e maximum power. If the fuel filter can supply the flow needed at high load, high rpm with the engine hot which is 1000 times more than that needed to start the car then it can't be the bloody problem when the car won't start from cold. Capiche?The problem is blindingly obviously one of air/fuel mixture strength to initiate combustion when cold and NOT one of absolute fuel flow limitation. So it can't be fuel filter, fuel pump or anything else that lets the car work ok when hot.
Pumaracing said:
No, really it absolutely doesn't. The amount of fuel flow per second required to start a car is miniscule. There is almost no load and minimal revs at startup and therefore very little fuel demand. Sure it requires a richer mixture to start from cold than hot but this pales into insignificance when compared to the amount of fuel flow required to run the engine at high rpm, high load i.e maximum power. If the fuel filter can supply the flow needed at high load, high rpm with the engine hot which is 1000 times more than that needed to start the car then it can't be the bloody problem when the car won't start from cold. Capiche?
The problem is blindingly obviously one of air/fuel mixture strength to initiate combustion when cold and NOT one of absolute fuel flow limitation. So it can't be fuel filter, fuel pump or anything else that lets the car work ok when hot.
Cheers for the education. That makes more sense.The problem is blindingly obviously one of air/fuel mixture strength to initiate combustion when cold and NOT one of absolute fuel flow limitation. So it can't be fuel filter, fuel pump or anything else that lets the car work ok when hot.
stevesingo said:
Are you using the correct oil and when was it last changed.
Oil changed during 10 year service in May last year.The ST engine uses graded tappets, not hydraulics.
The ST engine opens the idle valve right up and retards the spark at cold start to send a load of burning mixture down the exhaust manifold to light the cat off. As they have cable throttle I can only imagine that the idle valve is jammed and not opening when expected so the engine is running over rich? If you open the throttle further on cranking I guess it shoves in more fuel?
The ST engine opens the idle valve right up and retards the spark at cold start to send a load of burning mixture down the exhaust manifold to light the cat off. As they have cable throttle I can only imagine that the idle valve is jammed and not opening when expected so the engine is running over rich? If you open the throttle further on cranking I guess it shoves in more fuel?
Bobley said:
The ST engine uses graded tappets, not hydraulics.
The ST engine opens the idle valve right up and retards the spark at cold start to send a load of burning mixture down the exhaust manifold to light the cat off. As they have cable throttle I can only imagine that the idle valve is jammed and not opening when expected so the engine is running over rich? If you open the throttle further on cranking I guess it shoves in more fuel?
I've further discovered that sometimes, holding the throttle 1/3d ish open when I turn the ignition seems to help it catch, although there's still a touch and go moment after 90 seconds. If I miss that first catch, a little pumping of throttle or holding at different positions sometimes seems to make a difference (although I'm hesitant about doing too much of this in case it gets flooded).The ST engine opens the idle valve right up and retards the spark at cold start to send a load of burning mixture down the exhaust manifold to light the cat off. As they have cable throttle I can only imagine that the idle valve is jammed and not opening when expected so the engine is running over rich? If you open the throttle further on cranking I guess it shoves in more fuel?
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