More Idle Problems
Discussion
Well no idle issues on the forum for a while then they come along like buses! This is a strange one, for three days now at the same point in my 25-minute journey home - the same set of traffic lights - the 400SX won't idle properly. I can keep it going by opening the throttle fair amount, it seems to be missing a bit but there's no black smoke. Also power is down significantly.
This condition remains for around between a minute and three mins, and after I've cleared the junctions and gone half a mile it clears up and it's idling fine again, all the way home.
I suspect the engine temp sensor or possibly the ignition amp but also hope it isn't the ECU or anything like that. I thought it might be fuel-related but I had a new tankful of petrol on Weds and it still happened.
This condition remains for around between a minute and three mins, and after I've cleared the junctions and gone half a mile it clears up and it's idling fine again, all the way home.
I suspect the engine temp sensor or possibly the ignition amp but also hope it isn't the ECU or anything like that. I thought it might be fuel-related but I had a new tankful of petrol on Weds and it still happened.
It's not common knowledge, but i have it on good authoity that there's a secret government electronics establishment located beneath that junction and the microwave enery emmitted by their dronsic bontarticle discharge soundwave frequency capacitor plays havoc with ECUs of a certain age. I'd go a different way if I were you.
adam quantrill said:
This is a strange one, for three days now at the same point in my 25-minute journey home - the same set of traffic lights - the 400SX won't idle properly.
I think you are referring to the 'Cambridgeshire Triangle' where mysterious things have been known to happen. I was driving through those lights once when my engine cut out and there was total silence, yet the car still seemed to be accelerating. It's either that or your car needs a tune up! :-)Tony. TCB.
adam quantrill said:
This is a strange one, for three days now at the same point in my 25-minute journey home - the same set of traffic lights - the 400SX won't idle properly. I can keep it going by opening the throttle fair amount, it seems to be missing a bit but there's no black smoke. Also power is down significantly.
This condition remains for around between a minute and three mins, and after I've cleared the junctions and gone half a mile it clears up and it's idling fine again, all the way home.
I suspect the engine temp sensor or possibly the ignition amp but also hope it isn't the ECU or anything like that. I thought it might be fuel-related but I had a new tankful of petrol on Weds and it still happened.
Hi AdamThis condition remains for around between a minute and three mins, and after I've cleared the junctions and gone half a mile it clears up and it's idling fine again, all the way home.
I suspect the engine temp sensor or possibly the ignition amp but also hope it isn't the ECU or anything like that. I thought it might be fuel-related but I had a new tankful of petrol on Weds and it still happened.
Would that be the lights at the M11 Junction at the bottom of Madingly Hill!
Adam
Hello Adam. What's happening, is this:
Circumstantially, your journey hitherto the junction starting from work and starting from cold, is running on a fairly rich mixture created by the cold start system initially and perpetuated by the ECU cold enrichment circuit as determined by the coolant temp sensor.
Most of this time the engine has been running cold/cool and some of the extra fuel that has been variously injected has condensed out on the inside of the cold/cool plenum chamber and places thereabouts.
When you reach your dreaded set of traffic lights the engine is probably up to temperature and would be expecting a leaned out mixture as determined by the sensors.
However, the fuel is still hanging about, but because there is a sudden drop in intake depression induced by some mild overrun and engine idling when at standstill, the condensed fuel evaporates and becomes a player with regards to the idle mixture.
This is very much the same way that similarly condensed fuel evaporates from the same places when our engines are on a fast overrun with a very high intake vacuum, causing the signature crackling exhaust so desired after by boy racers and TVR owners! ;-)
See here: http://www.vintagemodelairplane.com/pages/Rover_Te...
In your circumstances, however, the excess of fuel is beyond the knowledge of the ECU so it cannot compensate for it.
For a brief period, therefore, you have an unacceptably rich mixture and the engine misfire and even stalls.
All this is not enough for black smoke, but certainly enough to temporarily affect power output as reported. Hot engines dislike rich mixtures. Booting the throttle will relieve the symptoms as you have found. Try booting it some more - but before you reach the traffic lights?
Once you get going again the excess fuel is probably all used up as you accelerate through the gears and the ECU is once more in control the next time you go to an idle condition, with a fully hot engine and no excess fuel in the intake system.
So you can put away your worry beans secure in the knowledge that all your components are tickety boo, and that your problems and my description of its cause are at the forefront of using the old grey matter to good effect.
On the other hand, however, you are entitled to ask - Why Me and Why Now?
Well the answer to that question could be that your engine is slightly off-tune and needs to be serviced and fettled. Just guessing about the last part - of course, but all that preceeds it is just science and circumstance! Such are the vagaries of our Rover Efi System.
Circumstantially, your journey hitherto the junction starting from work and starting from cold, is running on a fairly rich mixture created by the cold start system initially and perpetuated by the ECU cold enrichment circuit as determined by the coolant temp sensor.
Most of this time the engine has been running cold/cool and some of the extra fuel that has been variously injected has condensed out on the inside of the cold/cool plenum chamber and places thereabouts.
When you reach your dreaded set of traffic lights the engine is probably up to temperature and would be expecting a leaned out mixture as determined by the sensors.
However, the fuel is still hanging about, but because there is a sudden drop in intake depression induced by some mild overrun and engine idling when at standstill, the condensed fuel evaporates and becomes a player with regards to the idle mixture.
This is very much the same way that similarly condensed fuel evaporates from the same places when our engines are on a fast overrun with a very high intake vacuum, causing the signature crackling exhaust so desired after by boy racers and TVR owners! ;-)
See here: http://www.vintagemodelairplane.com/pages/Rover_Te...
In your circumstances, however, the excess of fuel is beyond the knowledge of the ECU so it cannot compensate for it.
For a brief period, therefore, you have an unacceptably rich mixture and the engine misfire and even stalls.
All this is not enough for black smoke, but certainly enough to temporarily affect power output as reported. Hot engines dislike rich mixtures. Booting the throttle will relieve the symptoms as you have found. Try booting it some more - but before you reach the traffic lights?
Once you get going again the excess fuel is probably all used up as you accelerate through the gears and the ECU is once more in control the next time you go to an idle condition, with a fully hot engine and no excess fuel in the intake system.
So you can put away your worry beans secure in the knowledge that all your components are tickety boo, and that your problems and my description of its cause are at the forefront of using the old grey matter to good effect.
On the other hand, however, you are entitled to ask - Why Me and Why Now?
Well the answer to that question could be that your engine is slightly off-tune and needs to be serviced and fettled. Just guessing about the last part - of course, but all that preceeds it is just science and circumstance! Such are the vagaries of our Rover Efi System.
Edited by honestjohntoo on Friday 1st March 11:31
Looks like they are everywhere..
..Well adam i guess the best thing is to avoid them traffic lights if possible...Or get into the junction box and rig up a remote switching device so that when you are approaching them they are always green and that way you wont need to stop and stall..Simples..
..Well adam i guess the best thing is to avoid them traffic lights if possible...Or get into the junction box and rig up a remote switching device so that when you are approaching them they are always green and that way you wont need to stop and stall..Simples..Yeah well - today it also happened on the way _to_ work. Also at a set of lights, just after coming off the motorway.
On the way back home (it happened again) I started playing with it a bit - some more symptoms - it doesn't cut out idling completely, but it sits at an incredulously low speed of around 100-200 rpm!
I reckon I'll start with a tune-up first - check the timing etc.
On the way back home (it happened again) I started playing with it a bit - some more symptoms - it doesn't cut out idling completely, but it sits at an incredulously low speed of around 100-200 rpm!
I reckon I'll start with a tune-up first - check the timing etc.
Yeah this is a flapper so no stepper motor issues.
Well "something was happening in my garage this weekend" so I checked the ignition was basically working first and all the plug leads are between 8k and 14 k ohms so that's all good, some needed the ends cleaning a little.
So I rant eh car under idle and the good news is that it will get into this condition on it's own - no need to drive to work and back! So this one should be easy to diagnose - well, not as hard anyway.
So - things checked so far:
a) Ignition timing - this was well out, at around 25deg BTDC, the correct setting for the 400SX is 17BTDC with vacuum off. The mechanical advance works, and the vacuum advance works too. So I set up the timing but no improvement to the idle problem.
b) Tried reseating the ECU plug - no improvement.
c) Measured Engine Temp Sensor - at 300 ohms it was slightly high but not far off, anyway shorted the plug but no improvement.
So my current thought is on the ECU - it's out already and I'll reflow the PCB's - needs doing anyway (also I want to make note of the "special" components inside that DPR had put in there).
Well "something was happening in my garage this weekend" so I checked the ignition was basically working first and all the plug leads are between 8k and 14 k ohms so that's all good, some needed the ends cleaning a little.
So I rant eh car under idle and the good news is that it will get into this condition on it's own - no need to drive to work and back! So this one should be easy to diagnose - well, not as hard anyway.
So - things checked so far:
a) Ignition timing - this was well out, at around 25deg BTDC, the correct setting for the 400SX is 17BTDC with vacuum off. The mechanical advance works, and the vacuum advance works too. So I set up the timing but no improvement to the idle problem.
b) Tried reseating the ECU plug - no improvement.
c) Measured Engine Temp Sensor - at 300 ohms it was slightly high but not far off, anyway shorted the plug but no improvement.
So my current thought is on the ECU - it's out already and I'll reflow the PCB's - needs doing anyway (also I want to make note of the "special" components inside that DPR had put in there).
adam quantrill said:
Yeah this is a flapper so no stepper motor issues.
Well "something was happening in my garage this weekend" so I checked the ignition was basically working first and all the plug leads are between 8k and 14 k ohms so that's all good, some needed the ends cleaning a little.
So I rant eh car under idle and the good news is that it will get into this condition on it's own - no need to drive to work and back! So this one should be easy to diagnose - well, not as hard anyway.
So - things checked so far:
a) Ignition timing - this was well out, at around 25deg BTDC, the correct setting for the 400SX is 17BTDC with vacuum off. The mechanical advance works, and the vacuum advance works too. So I set up the timing but no improvement to the idle problem.
b) Tried reseating the ECU plug - no improvement.
c) Measured Engine Temp Sensor - at 300 ohms it was slightly high but not far off, anyway shorted the plug but no improvement.
So my current thought is on the ECU - it's out already and I'll reflow the PCB's - needs doing anyway (also I want to make note of the "special" components inside that DPR had put in there).
17BTDC, WOW!!! that's a lot, i take it the SX is a very different set up to normal 400! is that at idle? Well "something was happening in my garage this weekend" so I checked the ignition was basically working first and all the plug leads are between 8k and 14 k ohms so that's all good, some needed the ends cleaning a little.
So I rant eh car under idle and the good news is that it will get into this condition on it's own - no need to drive to work and back! So this one should be easy to diagnose - well, not as hard anyway.
So - things checked so far:
a) Ignition timing - this was well out, at around 25deg BTDC, the correct setting for the 400SX is 17BTDC with vacuum off. The mechanical advance works, and the vacuum advance works too. So I set up the timing but no improvement to the idle problem.
b) Tried reseating the ECU plug - no improvement.
c) Measured Engine Temp Sensor - at 300 ohms it was slightly high but not far off, anyway shorted the plug but no improvement.
So my current thought is on the ECU - it's out already and I'll reflow the PCB's - needs doing anyway (also I want to make note of the "special" components inside that DPR had put in there).
Yes 17 degrees at idle with the vacuum diconnected, rising to 28 with full mechanical advance.
The spark itself is very healthy and isn't missing.
I opened up the ECU and apart from the adjuster pot there's a small piggyback circuit board made of veroboard in thre with a couple of op-amps on it, I'll post up some pics tomorrow.
Yes I'll clean out the adjuster on the flapper - could have crud in there. and check the idle CO too and the injector opening times tomorrow. Might substitute a spare ECU when it gets into this mode to see if it idles OK, though I'll be careful with it as the fuelling won't be right for the top end.
The spark itself is very healthy and isn't missing.
I opened up the ECU and apart from the adjuster pot there's a small piggyback circuit board made of veroboard in thre with a couple of op-amps on it, I'll post up some pics tomorrow.
Yes I'll clean out the adjuster on the flapper - could have crud in there. and check the idle CO too and the injector opening times tomorrow. Might substitute a spare ECU when it gets into this mode to see if it idles OK, though I'll be careful with it as the fuelling won't be right for the top end.
adam quantrill said:
I wonder if the timing marks or pointer is accurate? I think a quick test drive to decide that is needed!
Adam..I did read that there was a service bulletin posted up as regards to RV8's..Not sure of the date..Apparently the timing marks were found to be very in-accurate and were sometimes as much as 20 degrees out!..Very frustrating if you are taking the timing marks as gospel..ZigaGassing Station | Wedges | Top of Page | What's New | My Stuff