Poor idle / running rough after hard driving
Discussion
After a few fixes the car has been running great and with the new wideband I've been a able to really dial in the fuel map.
However I've been getting an intermittent problem; after driving for a while, the idle sometimes get very irratic (hunts between about 350 and 700 rpm, and will occasionally stall). The car also starts to run rough at low rpm, but ok at higher revs.
This only seems to happen after driving the car hard. If I just drive at cruising speeds its fine. so appears that something is breaking down at high loads ( hopefully not the engine!)
Adjusting the plenum screw helps maintain the idle enough to get the car home. Stepper motor is not the problem though as it's disconnected. Also noticed that the rev counter starts jumping about a bit, although logged data from the ecu is pretty smooth.
It seems like the most likely cause is an ignition fault, HT leads, plugs or coil pack (BTW I'm running the Gems coilpacks located behind the plenum).
Just checked the plugs and they are all fine, just wondering what else to check before I pull off the plenum to check the leads and coilpacks and wiring.
Throttle pot maybe?
.
However I've been getting an intermittent problem; after driving for a while, the idle sometimes get very irratic (hunts between about 350 and 700 rpm, and will occasionally stall). The car also starts to run rough at low rpm, but ok at higher revs.
This only seems to happen after driving the car hard. If I just drive at cruising speeds its fine. so appears that something is breaking down at high loads ( hopefully not the engine!)
Adjusting the plenum screw helps maintain the idle enough to get the car home. Stepper motor is not the problem though as it's disconnected. Also noticed that the rev counter starts jumping about a bit, although logged data from the ecu is pretty smooth.
It seems like the most likely cause is an ignition fault, HT leads, plugs or coil pack (BTW I'm running the Gems coilpacks located behind the plenum).
Just checked the plugs and they are all fine, just wondering what else to check before I pull off the plenum to check the leads and coilpacks and wiring.
Throttle pot maybe?
.
Edited by angus337 on Monday 3rd July 00:22
Edited by angus337 on Monday 3rd July 00:24
Edited by angus337 on Monday 3rd July 00:33
I recently had a similar issue (although not as severe) which I traced to an electrical drain relating to the alarm system, a few months ago my central locking started playing up which forced me to test the central locking relay (which was fine) and the related wiring where I found a big drain. This lead me to test the system with and without the door switches connected, I found the drain could be eliminated by disconnecting both door switches even though the switches themselves tested fine.
This drain must have been present for years getting progressively worse, eventually it got so bad the central locking would lock the car but not unlock it reliably. With the door switches disconnected the car locked and unlocked perfectly and from this point on my door solenoids snapped in and out like never before, the sound they made locking and unlocking the car was noticeably stronger than I'd ever heard in the seven years I've owned the car! With this big electrical drain now eliminated what really surprised me was how much better the car ran, my car uses the Canems system so it already ran very well indeed, but now with the door switches disconnected there was an even greater improvement. The ECU seemed to control the idle valve better and my injectors clearly liked the extra current, Idle quality was improved as was low speed drivability.
In my opinion the Italian Meta security system used by TVR wasn't the best choice, and the way they wired it was poor. It's well documented TVR wired the immobiliser incorrectly which is the source of most of the 'No Start' issues you read on these pages, I'd bypassed mine many years ago due to starting issues which solved that problem but clearly there were other long standing parasitic drain issues with the system. I'm not saying this is your problem but it takes minutes to disconnect your door switches, you'll lose your automatic interior light when you open the doors but you can still operate it from the switch on the light itself. The locking/unlocking function will remain unaffected so there's really no issue with running the car with the door switches disconnected and you can reconnect them in minutes if there's no improvement, if your problem goes away you will likely have the same drain in the security system as I did.
Also check your alternator output when the car is properly hot and all earths, especially the ones to the engine block/cylinder head. What happens when your rad fans chime in, does the engine speed fall? As your rev counter is jumping about also suspect HT leads, the dreadful failure prone plug extenders, your ignition coil and the ignition amp, all can start to breakdown with heat.
Like most of these things there could be many different causes so you're unlikely to find one magic bullet answer on a forum, the way to fix it is to go through the entire ignition, charging and electrical systems being systematic in your approach.
Good luck with it, Dave.
This drain must have been present for years getting progressively worse, eventually it got so bad the central locking would lock the car but not unlock it reliably. With the door switches disconnected the car locked and unlocked perfectly and from this point on my door solenoids snapped in and out like never before, the sound they made locking and unlocking the car was noticeably stronger than I'd ever heard in the seven years I've owned the car! With this big electrical drain now eliminated what really surprised me was how much better the car ran, my car uses the Canems system so it already ran very well indeed, but now with the door switches disconnected there was an even greater improvement. The ECU seemed to control the idle valve better and my injectors clearly liked the extra current, Idle quality was improved as was low speed drivability.
In my opinion the Italian Meta security system used by TVR wasn't the best choice, and the way they wired it was poor. It's well documented TVR wired the immobiliser incorrectly which is the source of most of the 'No Start' issues you read on these pages, I'd bypassed mine many years ago due to starting issues which solved that problem but clearly there were other long standing parasitic drain issues with the system. I'm not saying this is your problem but it takes minutes to disconnect your door switches, you'll lose your automatic interior light when you open the doors but you can still operate it from the switch on the light itself. The locking/unlocking function will remain unaffected so there's really no issue with running the car with the door switches disconnected and you can reconnect them in minutes if there's no improvement, if your problem goes away you will likely have the same drain in the security system as I did.
Also check your alternator output when the car is properly hot and all earths, especially the ones to the engine block/cylinder head. What happens when your rad fans chime in, does the engine speed fall? As your rev counter is jumping about also suspect HT leads, the dreadful failure prone plug extenders, your ignition coil and the ignition amp, all can start to breakdown with heat.
Like most of these things there could be many different causes so you're unlikely to find one magic bullet answer on a forum, the way to fix it is to go through the entire ignition, charging and electrical systems being systematic in your approach.
Good luck with it, Dave.
I recently had my ECU changed to Emerald by himself from Chesterfield.
He not only maps it on the rolling road, but takes it out on the road to check its road manners, and fine tunes the cold start.
Only thing he didn't get quite right first time was the hot idle, and then only the idle when it had been run for a while and had got a lot of heat soak.
No idea how he was meant to fine tune that, so i am certainly not complaining.
Anyway, my symptoms were exactly as you describe - hunting at very low revs and then stalling without the introduction of right boot.
One phone call and he came over to my house with his laptop, and we spent an enjoyable half hour just tweaking small sections of the fuel maps with the engine running nice and hot. Problem solved.
ETA - he used 16 gallons of fuel mapping my car - thorough is an understatement!
He not only maps it on the rolling road, but takes it out on the road to check its road manners, and fine tunes the cold start.
Only thing he didn't get quite right first time was the hot idle, and then only the idle when it had been run for a while and had got a lot of heat soak.
No idea how he was meant to fine tune that, so i am certainly not complaining.
Anyway, my symptoms were exactly as you describe - hunting at very low revs and then stalling without the introduction of right boot.
One phone call and he came over to my house with his laptop, and we spent an enjoyable half hour just tweaking small sections of the fuel maps with the engine running nice and hot. Problem solved.
ETA - he used 16 gallons of fuel mapping my car - thorough is an understatement!
Thanks for the input Dave,
Looking at the logs, the voltage seems pretty constant at about 13.5 while driving, It does however dip when the revs drop below about 450rpm due to the idle issue, but picks up again as soon as the rpm recovers. The minimum I’ve seen is 11.5 volts @ 300 rpm. I assumed this was a symptom of the Low RPM causing the low voltage, rather than the other way around. I also get a slight stumble when the Fans come on, but haven’t really noticed a drop in RPM while they are running.
The issue does not appear to be directly temperature related as it runs perfectly fine at idle in the garage, from cold to fully hot. I’ve done some extended tests and several restarts from hot, to get the warm-up enrichment and MAT correction curve set correctly.
The HT leads are the Moroso ones from real steel. I’m not running plug extenders, but the leads look in good condition at the plug ends and the heat socks seem to be doing a good job. The leads were DIY cut to length so it’s possible I didn’t do a great job crimping them up, and may me they are struggling at high loads.
Anyway I think I’ll just take the Plenum off tonight to check the leads, coilpacks and wiring, might just change the leads to rule them out.
Think I’m starting to regret installing the Gems coil packs, as all though its makes for a neat installation, access is a PITA.
Looking at the logs, the voltage seems pretty constant at about 13.5 while driving, It does however dip when the revs drop below about 450rpm due to the idle issue, but picks up again as soon as the rpm recovers. The minimum I’ve seen is 11.5 volts @ 300 rpm. I assumed this was a symptom of the Low RPM causing the low voltage, rather than the other way around. I also get a slight stumble when the Fans come on, but haven’t really noticed a drop in RPM while they are running.
The issue does not appear to be directly temperature related as it runs perfectly fine at idle in the garage, from cold to fully hot. I’ve done some extended tests and several restarts from hot, to get the warm-up enrichment and MAT correction curve set correctly.
The HT leads are the Moroso ones from real steel. I’m not running plug extenders, but the leads look in good condition at the plug ends and the heat socks seem to be doing a good job. The leads were DIY cut to length so it’s possible I didn’t do a great job crimping them up, and may me they are struggling at high loads.
Anyway I think I’ll just take the Plenum off tonight to check the leads, coilpacks and wiring, might just change the leads to rule them out.
Think I’m starting to regret installing the Gems coil packs, as all though its makes for a neat installation, access is a PITA.
Hi Nick, if you're on coil packs clearly you're not running the 14CUX anymore, out of interest what system are you on?
What are your AFR's doing when the issue occurs?
I had a similar issue as you at idle when the engine was properly heat soaked in stop start traffic which I solved using air temp correction. By logging air temps I was able to see the condition coincided with a spike in air temp which only occurred on the hottest day and only when stuck in stop start traffic.
An interesting point is Lucas clearly felt their 14CUX system as fitted to Range Rovers & Discos needed a fuel temp sensor and correction for fuel temp. I'd say during development they must have come across issues that forced this addition although my guess is it related to hot starts and hot idle issues due to fuel vaporisation in the rail.
I also found running 28 degrees of ignition advance significantly reduced the heat produced by my already decatted exhaust manifolds, anything you can do to reduce under-bonnet heat will help with hot idle quality and don't forget your alternator's performance can fall by as much as 10% from cold to hot, in fact the resistance in all your under-bonnet wiring will go up dramatically when the engine becomes heat soaked.
However, I have to say by far the biggest improvement came when I disconnected my door switches and eliminated the drain at the alarm unit, battery voltage didn't really change but clearly my ECU, idle valve and injectors liked the extra current
What are your AFR's doing when the issue occurs?
I had a similar issue as you at idle when the engine was properly heat soaked in stop start traffic which I solved using air temp correction. By logging air temps I was able to see the condition coincided with a spike in air temp which only occurred on the hottest day and only when stuck in stop start traffic.
An interesting point is Lucas clearly felt their 14CUX system as fitted to Range Rovers & Discos needed a fuel temp sensor and correction for fuel temp. I'd say during development they must have come across issues that forced this addition although my guess is it related to hot starts and hot idle issues due to fuel vaporisation in the rail.
I also found running 28 degrees of ignition advance significantly reduced the heat produced by my already decatted exhaust manifolds, anything you can do to reduce under-bonnet heat will help with hot idle quality and don't forget your alternator's performance can fall by as much as 10% from cold to hot, in fact the resistance in all your under-bonnet wiring will go up dramatically when the engine becomes heat soaked.
However, I have to say by far the biggest improvement came when I disconnected my door switches and eliminated the drain at the alarm unit, battery voltage didn't really change but clearly my ECU, idle valve and injectors liked the extra current
Edited by ChimpOnGas on Monday 3rd July 11:02
Running megasquirt.
From what i rember from the logs, AFRs are pretty stable, if anything I would say slightly richer than my normal 13.5 at idle. Ill check again tonight.
One other symptom I forgot about is the car is hard to restart, turns over but won't fire, and feels like it's flooded. .
My car did also suffer badly from heat soak, due to the location of the MAT sensor, I've added quite a bit if air temp correction to the standard ideal gas curve and normally hot starts are fine.
From what i rember from the logs, AFRs are pretty stable, if anything I would say slightly richer than my normal 13.5 at idle. Ill check again tonight.
One other symptom I forgot about is the car is hard to restart, turns over but won't fire, and feels like it's flooded. .
My car did also suffer badly from heat soak, due to the location of the MAT sensor, I've added quite a bit if air temp correction to the standard ideal gas curve and normally hot starts are fine.
Mine is a turbo, so suffers particularly from hot fuel.
I suspect your issue may also be hot fuel, as I saw in the posts above, in which case making the bottom of the fuel map a little richer may resolve it.
If you think it might be of any use to you to have a look at my Emerald fuel map, then please just say and i will download it.
ETA - I noticed from my AFR gauge that mine was showing an AFR of between 16 and 22 when I was having the hot start issue.
I suspect your issue may also be hot fuel, as I saw in the posts above, in which case making the bottom of the fuel map a little richer may resolve it.
If you think it might be of any use to you to have a look at my Emerald fuel map, then please just say and i will download it.
ETA - I noticed from my AFR gauge that mine was showing an AFR of between 16 and 22 when I was having the hot start issue.
Edited by QBee on Monday 3rd July 12:22
Its an old skool trick, but when it happens again depress the throttle about a quarter of it's travel and crank to see if the engine starts better with more air.
If it does it's rich
I'm sure you'll have some temp related cranking correction settings in MS but it sounds like it may be going rich or lean at idle when heat soaked too, that puts you back to air temp or coolant temp correction but you do need to establish the ignition side isn't the issue first.
Did all this start after you deleted your idle valve, or did you delete it in an attempt to resolve another issue?
It's certainly true less involvement from your idle valve the better but it's there for a reason so I wouldn't necessarily delete it entirely, my Canems system uses a Bosch rotary idle valve running closed loop which works extremely well, however it became very clear to me it's a very voltage/current sensitive device which is one reason why my car runs so much better since I eliminated the parasitic drain at the alarm unit.
Good luck with it and let us know how you get on.
Dave.
If it does it's rich
I'm sure you'll have some temp related cranking correction settings in MS but it sounds like it may be going rich or lean at idle when heat soaked too, that puts you back to air temp or coolant temp correction but you do need to establish the ignition side isn't the issue first.
Did all this start after you deleted your idle valve, or did you delete it in an attempt to resolve another issue?
It's certainly true less involvement from your idle valve the better but it's there for a reason so I wouldn't necessarily delete it entirely, my Canems system uses a Bosch rotary idle valve running closed loop which works extremely well, however it became very clear to me it's a very voltage/current sensitive device which is one reason why my car runs so much better since I eliminated the parasitic drain at the alarm unit.
Good luck with it and let us know how you get on.
Dave.
On qbee's car it was a weak mix on very hot restarts .. I overcame that by extending the afterstart fuel table to 999turns (the max I can go to on the emerald) and adding extra fuel on hot starts only (the rest of the afterstart fuelling was ok so left alone).
The extra fuelling added was just enoug to prop up the afrs and keep the idle quality until fuel had purged through the fuel rail, and intake temps had stabilised due to cooler air coming through the intake system. (though on a turbo this is always going to be hot air unless you run a chargcooler system. An intercooler only cools if air is passing through it, or you spray it with water /CO2 extinguisher!)
Hope that helps.
The extra fuelling added was just enoug to prop up the afrs and keep the idle quality until fuel had purged through the fuel rail, and intake temps had stabilised due to cooler air coming through the intake system. (though on a turbo this is always going to be hot air unless you run a chargcooler system. An intercooler only cools if air is passing through it, or you spray it with water /CO2 extinguisher!)
Hope that helps.
Edited by spitfire4v8 on Monday 3rd July 12:55
Update:
Tried a few things over the last week.
Tested coil pack resistances – all ok 1ohm primary /13k ohms secondary
Throttle pot and coolant temp sensor-both fine
Inspected and cleaned plenum (was pretty clean to start with)
Swapped HT leads (moroso to Magnecors)
Checked TDC
Reset base idle
Reconnected stepper (now seems to be working fine)
Checked timing
A few tweaks to the map
Tested the car at idle from cold to fully warm and everything is initially fine. Once its fully warmed up, probably after about 3 or 4 cycles of the fans switching on and off, the engine started to run rough again and the revs started dropping, not as bad as before, as the mapping tweaks have tamed the wild oscillation to a point.
I checked the timing advance again and while it was doing this and it drops from the normal 14-15 to about 8 or 9. The strobe frequency was also inconsistent which seems to indicate a spark problem on cylinder 1. Put the timing light pickup on cylinders 3 and 5 and they seemed to be ok.
At this point if I increase the base idle by 1/2 a turn of the plenum screw it runs fine and the advance comes back to normal. The AFR doesn't really change that much. Maybe increases by about 0.2 when the fans come on.
So pretty sure its and ignition fault, but at bit of a loss as to why increasing the idle seems to resolve the problem. Is it possible that something could be restricting airflow at high temperatures and causing the problem, (possible a vacuum leak, that seals when hot?)
I was also going check the fuel pressure, but the gauge I ordered hasn’t arrived yet.
The bigger worry is that there is more serious issue, cam, rockers, lifters etc.
Tried a few things over the last week.
Tested coil pack resistances – all ok 1ohm primary /13k ohms secondary
Throttle pot and coolant temp sensor-both fine
Inspected and cleaned plenum (was pretty clean to start with)
Swapped HT leads (moroso to Magnecors)
Checked TDC
Reset base idle
Reconnected stepper (now seems to be working fine)
Checked timing
A few tweaks to the map
Tested the car at idle from cold to fully warm and everything is initially fine. Once its fully warmed up, probably after about 3 or 4 cycles of the fans switching on and off, the engine started to run rough again and the revs started dropping, not as bad as before, as the mapping tweaks have tamed the wild oscillation to a point.
I checked the timing advance again and while it was doing this and it drops from the normal 14-15 to about 8 or 9. The strobe frequency was also inconsistent which seems to indicate a spark problem on cylinder 1. Put the timing light pickup on cylinders 3 and 5 and they seemed to be ok.
At this point if I increase the base idle by 1/2 a turn of the plenum screw it runs fine and the advance comes back to normal. The AFR doesn't really change that much. Maybe increases by about 0.2 when the fans come on.
So pretty sure its and ignition fault, but at bit of a loss as to why increasing the idle seems to resolve the problem. Is it possible that something could be restricting airflow at high temperatures and causing the problem, (possible a vacuum leak, that seals when hot?)
I was also going check the fuel pressure, but the gauge I ordered hasn’t arrived yet.
The bigger worry is that there is more serious issue, cam, rockers, lifters etc.
Been away for the last couple of weekends haven’t been out in the car for a while.
In the meantime, I’ve installed one of Clive’s Decatt Y-pieces, a new coilpack, refurbished alternator and Iridium plugs. I also re-routed the grounds from the wideband controller and ECU coil drivers to the engine block.
So yesterday was the first drive for a while and everything seemed perfect, started-up and idled perfectly right up to temperature. The car seemed to be driving and sounding better than ever with Clive’s Y piece installed. However just is I was heading home the Throttle cable snapped! so had to wait for the AA.
Anyway while I was waiting I looked though the logs and although not as bad as before, it still appears that the idle is deteriorating after about 45 minutes or so of driving. At the start of the run the idle was ~1000 RPM and by the time I pulled over it had dropped to about 750 RPM average and hunting between about 500 and 850 rpm.
Getting frustrated with this now, but thinking the next things to check would be:
• Fuel pressure regulator (already replaced fuel pump and filter)
• Injector settings (dead time, Voltage correction etc)
• Wiring (could heat soak be affecting the wiring either in the footwell or at the coilpack plug next to the plenum)
In the meantime, I’ve installed one of Clive’s Decatt Y-pieces, a new coilpack, refurbished alternator and Iridium plugs. I also re-routed the grounds from the wideband controller and ECU coil drivers to the engine block.
So yesterday was the first drive for a while and everything seemed perfect, started-up and idled perfectly right up to temperature. The car seemed to be driving and sounding better than ever with Clive’s Y piece installed. However just is I was heading home the Throttle cable snapped! so had to wait for the AA.
Anyway while I was waiting I looked though the logs and although not as bad as before, it still appears that the idle is deteriorating after about 45 minutes or so of driving. At the start of the run the idle was ~1000 RPM and by the time I pulled over it had dropped to about 750 RPM average and hunting between about 500 and 850 rpm.
Getting frustrated with this now, but thinking the next things to check would be:
• Fuel pressure regulator (already replaced fuel pump and filter)
• Injector settings (dead time, Voltage correction etc)
• Wiring (could heat soak be affecting the wiring either in the footwell or at the coilpack plug next to the plenum)
Thanks Andy, just had a look and it looks fine. However I may replace anyway or add an additional one.
Checking the logs again I've noticed that although the battery voltage is generally higher with the new alternator, it does vary quite a lot even at cruising speeds. Checked the cables and found this under the heat shrink on the short cable from the starter to the 100 amp fuse. The one from the alternator wasn't much better.
Will replace these tomorrow which looks like a much easier job than replacing the throttle cable!
Checking the logs again I've noticed that although the battery voltage is generally higher with the new alternator, it does vary quite a lot even at cruising speeds. Checked the cables and found this under the heat shrink on the short cable from the starter to the 100 amp fuse. The one from the alternator wasn't much better.
Will replace these tomorrow which looks like a much easier job than replacing the throttle cable!
Based on the condition of the cables at the 100amp fuse, decided it was a good idea to replace the cables all the way from the alternator back to the battery.
Got the 3 cables made up at a local auto electrical suppliers, for a bargain £28. Surprisingly straight forward to install. Only problem I'm having is that I can't get the old battery to starter cable out, seems to be secured above the bell housing somewhere so may have to just cut out as much as I can for now.
Got the 3 cables made up at a local auto electrical suppliers, for a bargain £28. Surprisingly straight forward to install. Only problem I'm having is that I can't get the old battery to starter cable out, seems to be secured above the bell housing somewhere so may have to just cut out as much as I can for now.
So with the the new battery cables and throttle cable installed the car was idling and driving better than ever. No hunting at all on idle and really smooth power delivery. Battery voltage is stable throughout the rev range and AFR much steadier.
Went out for a about 2 hours Sunday morning including a stop for lunch and about 20 minutes stuck in traffic and everything was perfect, so I thoughed I'd finally cracked the rough idling issue.
Took the car out again later and noticed after stopping for fuel the AFR had dropped slightly, after few more miles I stopped at a T junction and the revs immediately dropped to zero and stalled! The car would restart ok but wouldn't maintain idle.
After adjusting the idle screw I was able to get it idling normally. Also tried clamping the stepper motor hose to check base idle and the revs didn't change, So I think the stepper had stuck closed? The car ran fine like this all the way home.
Once back home I restarted the car and it went very lean and struggled to idle. Closed the idle screw back to normal and It idled perfectly again. So appears that the stepper had reset and was working correctly again.
I think I've solved the rough idle issue cuased the variable battery voltage, but still have a intermittent issue with the stepper motor sticking closed? I've tested two different stepper motors and both work fine in the car so think there may be an issue with the wiring to the stepper. If one of the cupircuits fails could the stepper be driven closed?
I'll try running with stepper disconnected again, to rule out anything else. In the meantime I can investigate the wiring.
Went out for a about 2 hours Sunday morning including a stop for lunch and about 20 minutes stuck in traffic and everything was perfect, so I thoughed I'd finally cracked the rough idling issue.
Took the car out again later and noticed after stopping for fuel the AFR had dropped slightly, after few more miles I stopped at a T junction and the revs immediately dropped to zero and stalled! The car would restart ok but wouldn't maintain idle.
After adjusting the idle screw I was able to get it idling normally. Also tried clamping the stepper motor hose to check base idle and the revs didn't change, So I think the stepper had stuck closed? The car ran fine like this all the way home.
Once back home I restarted the car and it went very lean and struggled to idle. Closed the idle screw back to normal and It idled perfectly again. So appears that the stepper had reset and was working correctly again.
I think I've solved the rough idle issue cuased the variable battery voltage, but still have a intermittent issue with the stepper motor sticking closed? I've tested two different stepper motors and both work fine in the car so think there may be an issue with the wiring to the stepper. If one of the cupircuits fails could the stepper be driven closed?
I'll try running with stepper disconnected again, to rule out anything else. In the meantime I can investigate the wiring.
Edited by angus337 on Tuesday 15th August 00:53
Edited by angus337 on Tuesday 15th August 00:59
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