Poor starting, idle, running . . . .
Discussion
Hi again!
Having had two successful runs out following a change of MAP sensor (see "Houston, we may ...." thread for full details) I was obviously getting a little too confident in the car's ability to behave itself!
Third run began with great difficulty actually starting the car (has always fired and idled perfectly well before - this time was fundamentally different). It would fire and then die straight away, and then after 5-6 more goes and a dab of throttle, just sound like it was idling on about 3 cylinders, struggle, then die.
Persistance allowed me to actually get going, but the idle hunts (if this is the correct term!?), bouncing from 5-600 revs to about 900 and sounds like it may stall at any moment - which sometimes it does. Initial driving was difficult without stalling at junctions etc (need to rev to keep going).
Once warmed up on out on the open road, runs better but feels like it is missing badly - poor acceleration, vibrating gearstick, lumpy and erratic running etc (symptoms a bit too similar to the ones I thought I had just solved!). Once home again idle still low and lumpy.
So - to cover the basics I have ordered new ingition bits (distributor cap, rotor arm, leads and plugs), but to be honest I am not at all confident this will help much.
I am thinking Idle Control Valve? But not sure this would explain the poor running once warmed up and at speed? There could be two separate problems of course. Also wondering if change of MAP sensor could have screwed anything up once the ECU started making adjustments? Air leak possible - but I think this causes high idle rather than low? Could throttle pot affect idle? Other ideas?
All help (very) gratefully received. Supposed to be 'cruising' up to the Silverstone Classic in just over a week and would really like to avoid another 'SCH-esque' weekend of problems and head scratching!!
Having had two successful runs out following a change of MAP sensor (see "Houston, we may ...." thread for full details) I was obviously getting a little too confident in the car's ability to behave itself!
Third run began with great difficulty actually starting the car (has always fired and idled perfectly well before - this time was fundamentally different). It would fire and then die straight away, and then after 5-6 more goes and a dab of throttle, just sound like it was idling on about 3 cylinders, struggle, then die.
Persistance allowed me to actually get going, but the idle hunts (if this is the correct term!?), bouncing from 5-600 revs to about 900 and sounds like it may stall at any moment - which sometimes it does. Initial driving was difficult without stalling at junctions etc (need to rev to keep going).
Once warmed up on out on the open road, runs better but feels like it is missing badly - poor acceleration, vibrating gearstick, lumpy and erratic running etc (symptoms a bit too similar to the ones I thought I had just solved!). Once home again idle still low and lumpy.
So - to cover the basics I have ordered new ingition bits (distributor cap, rotor arm, leads and plugs), but to be honest I am not at all confident this will help much.
I am thinking Idle Control Valve? But not sure this would explain the poor running once warmed up and at speed? There could be two separate problems of course. Also wondering if change of MAP sensor could have screwed anything up once the ECU started making adjustments? Air leak possible - but I think this causes high idle rather than low? Could throttle pot affect idle? Other ideas?
All help (very) gratefully received. Supposed to be 'cruising' up to the Silverstone Classic in just over a week and would really like to avoid another 'SCH-esque' weekend of problems and head scratching!!
I would change the service bits you have ordered before going any further.
That said, I know its like holding back water trying not to get stuck in to get the car running perfect. What about the electrical connector plugs under the bonnet? I removed mine because when I checked it one of the sensor cables just pulled out easily. IIRC it was on the drivers side up near the rocker cover and had lots of cables from various sensors going through it.
I am of course working on limited knowledge and someone will reply soon with a more practical answer. Someone will have met and solved this previously.
That said, I know its like holding back water trying not to get stuck in to get the car running perfect. What about the electrical connector plugs under the bonnet? I removed mine because when I checked it one of the sensor cables just pulled out easily. IIRC it was on the drivers side up near the rocker cover and had lots of cables from various sensors going through it.
I am of course working on limited knowledge and someone will reply soon with a more practical answer. Someone will have met and solved this previously.
Viper1day said:
I am thinking Idle Control Valve? But not sure this would explain the poor running once warmed up and at speed?
I doubt it, but it's easy to take it off and clean it.Viper1day said:
Could throttle pot affect idle?
Have you tried running with the TP unplugged. It should eliminate the TP from your investigations at the very least.Hi again Adam
Oddly enough, one of our group at SCH (that was Mike with the green S4 parked just opposite you) had changed his MAP sensor a while ago but couldn't get the car to run properly, so he took it to a specialist car tuner (who has been tuning cars in Edinburgh for at least 40 years!) who used a breakout box to diagnose that the ECU hadn't properly recognised the new MAP sensor - he reset the ECU and apparently the car is now running perfectly.
Mike had already tried disconnecting the ECU and reconnecting it (to reset it) but that had no effect - it needed this specific reset operation.
LastS4's advice on that electrical connector on the RH rocker cover (under the coil) is also worth investigating - all of the engine sensors go through that one connector, so a corrupt signal from a bad connection could be screwing things up.
Oddly enough, one of our group at SCH (that was Mike with the green S4 parked just opposite you) had changed his MAP sensor a while ago but couldn't get the car to run properly, so he took it to a specialist car tuner (who has been tuning cars in Edinburgh for at least 40 years!) who used a breakout box to diagnose that the ECU hadn't properly recognised the new MAP sensor - he reset the ECU and apparently the car is now running perfectly.
Mike had already tried disconnecting the ECU and reconnecting it (to reset it) but that had no effect - it needed this specific reset operation.
LastS4's advice on that electrical connector on the RH rocker cover (under the coil) is also worth investigating - all of the engine sensors go through that one connector, so a corrupt signal from a bad connection could be screwing things up.
Always worth checking this too...
http://www.fordscorpio.co.uk/faultfinds.htm
in my experience (S3) I found the connections in the loom under the dash were corroded and the supply to the engine run sensor and fuel pump relay were causing the misfire and similar symptoms to what you are describing (except at idle which was fine on mine). replacing the connections (and removing about a foot of cable to get nice clean copper) cured mine...
Good luck
K
http://www.fordscorpio.co.uk/faultfinds.htm
in my experience (S3) I found the connections in the loom under the dash were corroded and the supply to the engine run sensor and fuel pump relay were causing the misfire and similar symptoms to what you are describing (except at idle which was fine on mine). replacing the connections (and removing about a foot of cable to get nice clean copper) cured mine...
Good luck
K
Thanks for the ideas guys. I will have a play at the weekend - hopefully clean/swap the idle control valve and do the plugs, leads etc. I will also re-check all the connections and see what happens.
TVR-git, If the ecu does need some sort of 'complete re-set', who would be able to do it do you think? Edinburgh is very nice but a bit far from here!!!
TVR-git, If the ecu does need some sort of 'complete re-set', who would be able to do it do you think? Edinburgh is very nice but a bit far from here!!!
Gassing Station | S Series | Top of Page | What's New | My Stuff