Missing under light throttle
Discussion
She starts and idles perfectly. If you rev it,it revs great. But under load on a light throttle (not very often granted 
) whatever the gear or speed it misses.
I've done a couple of searches and most of them talk about the potentiometer.
If you give it more than say 20% throttle, again in any gear or speed, it's fine, goes like a good un. Wadya recn? anyone had similar?
Pain in the arse coming through the village, sounds like an old machene gun..........a particularly loud one!!
Unless I speed up a bit, then let it slow down, then speed up a bit....etc
) whatever the gear or speed it misses. I've done a couple of searches and most of them talk about the potentiometer.
If you give it more than say 20% throttle, again in any gear or speed, it's fine, goes like a good un. Wadya recn? anyone had similar?
Pain in the arse coming through the village, sounds like an old machene gun..........a particularly loud one!!
Unless I speed up a bit, then let it slow down, then speed up a bit....etc
Actually sounds like a dirty injector.I've had this problem for some time. Sometimes worse than others; sometimes not at all. It's definitely improved over time, but as I've replaced a number of things I can't say if any of them have ben directly related to the improvement. Just for the record this is the list:
1. Rerouted cooling pipes to header - the one from the swan's neck needs to go to the top of the bottle. I was getting air locks and the temperature sender was giving duff info to the ECU.
2. Replaced temperature sender to ECU
3. Replaced throttle pot
4. Replaced coil
5. Replaced spark plug leads
I'm beginning to think there may be a problem with the distributor advance retard. Perhaps the weights are sticking or the vacuum system is faulty. I might try stripping it out and cleaning it to see if it makes any improvement.
I also need to check the throttle pot wiring - see thread elsewhere as mine appears to be different from that shown in the Bible.
As it's only a minor niggle, given the time, I'd rather drive it than spend time fixing it.
1. Rerouted cooling pipes to header - the one from the swan's neck needs to go to the top of the bottle. I was getting air locks and the temperature sender was giving duff info to the ECU.
2. Replaced temperature sender to ECU
3. Replaced throttle pot
4. Replaced coil
5. Replaced spark plug leads
I'm beginning to think there may be a problem with the distributor advance retard. Perhaps the weights are sticking or the vacuum system is faulty. I might try stripping it out and cleaning it to see if it makes any improvement.
I also need to check the throttle pot wiring - see thread elsewhere as mine appears to be different from that shown in the Bible.
As it's only a minor niggle, given the time, I'd rather drive it than spend time fixing it.
I would try putting in a new set of plugs and see if the problem goes away. Check what heat range you are using at the moment, you may need to adjust this to suit your driving style. Use 5's for track day constant high revs, 6's for fast road, and 7s for driving leisurely. I think that is the right way round.
Let us know what the outcome is.
- Jim
Let us know what the outcome is.
- Jim
Wyn popped around with Ugly just now on their way to Coombe.
His throttle pot was reading about 120 mV which is too low in my book. Right first thing to check is butterfly valve gap. However there is no adjusting screw for this! is this correct? should there be no gap at idle on a hotwire setup? Anyway I set the pot to 325mV let's just hope he makes it to Castle Coombe
His throttle pot was reading about 120 mV which is too low in my book. Right first thing to check is butterfly valve gap. However there is no adjusting screw for this! is this correct? should there be no gap at idle on a hotwire setup? Anyway I set the pot to 325mV let's just hope he makes it to Castle Coombe
petros said:
Just so you know,in the last year I've had the following done to my 450. Engine Blueprinted by Power, new cam, heads ported. New, plugs, leads, shrouds, coil,ecu, stepper motor, throttle pot, airflow meter,distributer and ignition amp...... And mine still does the same at low revs
my guess is it's none of those things then
petros said:
Just so you know,in the last year I've had the following done to my 450. Engine Blueprinted by Power, new cam, heads ported. New, plugs, leads, shrouds, coil,ecu, stepper motor, throttle pot, airflow meter,distributer and ignition amp...... And mine still does the same at low revs
It's not at low revs it's at a light throttle opening. If you take it up to 4500rpm in third then ease of the throttle, it starts to miss. It seems to be directly related to throttle position.
If i'm in fourth at 1200rpm and I take the throttle past "the missing zone" it will pull cleanly and strongly
If I'm stood still, in neutral, and I take the revs up with "that" much throttle it will miss.
pwd95 said:
petros said:
Just so you know,in the last year I've had the following done to my 450. Engine Blueprinted by Power, new cam, heads ported. New, plugs, leads, shrouds, coil,ecu, stepper motor, throttle pot, airflow meter,distributer and ignition amp...... And mine still does the same at low revs
It's not at low revs it's at a light throttle opening. If you take it up to 4500rpm in third then ease of the throttle, it starts to miss. It seems to be directly related to throttle position.
If i'm in fourth at 1200rpm and I take the throttle past "the missing zone" it will pull cleanly and strongly
If I'm stood still, in neutral, and I take the revs up with "that" much throttle it will miss.
can you rig a voltmeter into the cabin so you can tell accurately if it is at just one set position on the throttle pot track .. if it is just change the pot?
petros said:
Sorry mate, yes, mine to is at light throttle , ie, slowing down from 80 into a 30 limit and you can feel the car hesitating, accelerating up to the 6250 rev limit is no problem at all, just trying to keep her at a steady 30 or 40 causes the hic cups.
have you tried tightening the chassis bolt under the dash on the nearside transmission tunnel? it's where the ecu earths through and if it's become loose with chassis flexing it causes all sorts of untraceable misfiring issues .. might be worth a tighten. you have to slice the carpet to get to it, but you can't see it afterwards.
trackcar said:
can you rig a voltmeter into the cabin so you can tell accurately if it is at just one set position on the throttle pot track .. if it is just change the pot?
On my to do list for tomorrow (Sunday), rig voltmeter up to TP and gradually open throttle to see if the voltage drops off at any point.
dickymint said:
Wyn popped around with Ugly just now on their way to Coombe.
His throttle pot was reading about 120 mV which is too low in my book. Right first thing to check is butterfly valve gap. However there is no adjusting screw for this! is this correct? should there be no gap at idle on a hotwire setup? Anyway I set the pot to 325mV let's just hope he makes it to Castle Coombe
His throttle pot was reading about 120 mV which is too low in my book. Right first thing to check is butterfly valve gap. However there is no adjusting screw for this! is this correct? should there be no gap at idle on a hotwire setup? Anyway I set the pot to 325mV let's just hope he makes it to Castle Coombe
Bumped to find out should there be a gap or not?
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