Revs dropping/stalling after starting - small throttle input
Discussion
Hi all
I've got a small new problem that's only started in the last month or so. Car starts fine, idle is a little lumpy for a few seconds but nothing out the ordinary I don't think. However when I touch the throttle, literally giving it the smallest of inputs, the revs drop down almost to 0, sometimes if I hold that throttle position for a second it will stall.
If I push past this throttle position the revs build what seems like normally. If I give it some revs then it will sort itself out, i.e. after driving it away from my house, after a few minutes of normal driving, the problem goes away.
Any ideas what this could be at all? When I changed all my ignition components a while back, this problem wasn't there at all, it's only started recently, not after changing any components or anything.
It's not the biggest issue as it does go away but it's annoying so would like to fix it.
Cheers
I've got a small new problem that's only started in the last month or so. Car starts fine, idle is a little lumpy for a few seconds but nothing out the ordinary I don't think. However when I touch the throttle, literally giving it the smallest of inputs, the revs drop down almost to 0, sometimes if I hold that throttle position for a second it will stall.
If I push past this throttle position the revs build what seems like normally. If I give it some revs then it will sort itself out, i.e. after driving it away from my house, after a few minutes of normal driving, the problem goes away.
Any ideas what this could be at all? When I changed all my ignition components a while back, this problem wasn't there at all, it's only started recently, not after changing any components or anything.
It's not the biggest issue as it does go away but it's annoying so would like to fix it.
Cheers
blitzracing said:
Sounds like its running lean when cold or possibly an air leak. From memory you have RoverGauge? Check the temperature readings as a first point of call.
I'd say it's way more likely the engine is in a rich condition not a lean one, I say this because this is a common issue with Chimaeras and the OP states.....Technoholic said:
Hi all, I've got a small new problem that's only started in the last month or so. Car starts fine, idle is a little lumpy for a few seconds but nothing out the ordinary I don't think. However when I touch the throttle, literally giving it the smallest of inputs, the revs drop down almost to 0, sometimes if I hold that throttle position for a second it will stall.
Although the OP does not specifically sate the condition is during cold start, the above does very much sound like he is talking about a cold start. I say this because he states the problem only started in the last month or so, during which time ambient temps have dropped, he then goes on to describe the classic Chimaera cold start condition of stalling when you first touch the throttle. The OP also goes on to state.....
Technoholic said:
If I push past this throttle position the revs build what seems like normally. If I give it some revs then it will sort itself out, i.e. after driving it away from my house, after a few minutes of normal driving, the problem goes away.
All the above indicates at small throttle openings the engine is flooding under the cold start enrichment, as the OP opens the throttle butterfly further more air is introduced reducing the flooding condition. Technoholic said:
Any ideas what this could be at all? When I changed all my ignition components a while back, this problem wasn't there at all, it's only started recently, not after changing any components or anything.
Technoholic, did you by any chance change your ignition components during the warmer months?You need to think about what's changed in the last month or so when the problem started, as already stated the answer is almost certainly the fall in ambient temps. The 14CUX system applies a very aggressive cold start strategy below a certain coolant temp threshold, a little over two months ago your coolant temp would have been above this threshold so enrichment during a cold start would have been far lower.
The TVR Chimaera does suffer poor earths, a weak spark and an abnormally high misfire rate, the Rover V8 cylinder heads also offer poor airflow and the ancient tech Lucas disc type injectors offer very poor atomisation. Now consider the huge amount of fuel the 14CUX is throwing in on cold start during these colder months, the cylinder head ports are cold so fuel will condense and puddle only to then be inducted into the combustion chamber as large globs which will be almost imposible to burn completely, without the very fattest healthiest spark this will only ever end in a flooded condition.
Consider that 1 litre of combusted petrol under optimum conditions will produce almost 1 litre of water, but under super rich conditions the production of water increases significantly as combustion is very inefficient, have a look at whats coming out of your Chimaera's tailpipe during cold start and I'd put money on you seeing a nasty black liquid slurry for the first minute or so.
This is not the fuel as such but the high levels of water being produced which washes the soot particles from the inside of your exhaust and exits your tail pipe as a nasty black slurry, if an injector becomes stuck open you will see the exact same slurry. This slurry is further evidence of a very rich mixture and or incomplete combustion, and by far the most likely cause of incomplete combustion is a weak spark which sadly is a standard TVR Chimaera trait.
Just because you replaced all your ignition components a while back doesn't mean you've got a good enough spark to deal with the huge quantities of fuel the 14CUX ECU has recently started throwing into the engine on cold start since we started seeing colder ambient temps. My advice would be not to make assumptions that your ignition system is as healthy as you think it is, you do not say what spark plugs you're using or if you are still running the dreadful failure prone spark plug extenders, or even what exactly you replaced during your ignition service?
However the following will definitely help:
1. Ditch the plug extenders if you still have them and find a better solution to protect your HT lead plug ends from being burnt on the exhaust manifolds, there are may better options available to you
2. If you're still running the highly inappropriate B7 ECS spark plugs throw them in the bin, fit a set of NGK BPR6EIX Iridium plugs as these definitely improve cold starts
3. Switch your vacuum advance from ported vacuum that idles the engine at 10 degrees to full manifold vacuum, this will give you 18 degrees at idle which will also make a massive improvement to cold starts and the way the engine behaves during the warm up phase
After that it's about making sure your engine is properly earthed (do not underestimate this one) and the general condition of your HT leads, distributor cap, rotor arm ect.
One final top tip is to use some dielectric grease on your HT lead plug ends, the use dielectric grease (silicone grease) is often overlooked but is actually one of the biggest steps forward in eliminating misfires in recent years. Dielectric grease (silicone grease) when smeared sparingly inside the spark plug boot is incredibly effective at sealing our moisture which is the key reason for misfires on internal combustion engines.
This is especially true during the colder damper months we are experiencing now, the moisture is actually drawn up the boot from the atmosphere when the engine cools, it then sits there causing corrosion and more specifically waiting to cause misfires when you restart the cold engine.
People do seem to get confused about the function dielectric grease, to be clear it should never ever be used on the plug terminal itself as this will actually cause problems not cure them. Dielectric grease should only be applied sparingly to the inside of your silicone or rubber spark plug boot to create a watertight seal between it and the spark plug porcelain insulator.
Here's how it should be used:
https://www.youtube.com/watch?v=-542IYGBbpg
I hope all this helps and do let us know how you get on?
One last point I'd make is when I was still on the old Lucas 14CUX system I suffered the exact same issue under cold start conditions you describe, suspecting over fueling and as an experiment I heated the coolant temp sensor in a mug of hot water to fool the ECU into thinking the engine was warm. When I started the stone cold engine like this it burst into life and ran way better with no black slurry from the tail pipe, I could also drive away immediately without a stall...
Sounds a lot like my 1st car and it turned out to be the AFM. Assuming most things were/are ok, something has changed. I have an old thread on here about it and one place even wanted to remap my car! Dan Taylor changed parts one at a time for known good ones and it was the pattern part AfM.
The problem with diagnosing a complex system using assumption.... is that the system is way too complex to make assumptions with.
We can all provide our individual experiences that seem to match the OP's symptoms, but the correct process the OP should follow is one of logical and systematic investigation.
The correct process also avoids the 'Parts Darts' method of fixing things, like this you may get lucky and eventually find a faulty air flow meter...... but what of all the other new parts that were needlessly fitted before the faulty air flow meter was discovered?
Saying all that I would definitely encourage the OP to start his search at the ignition system
We can all provide our individual experiences that seem to match the OP's symptoms, but the correct process the OP should follow is one of logical and systematic investigation.
The correct process also avoids the 'Parts Darts' method of fixing things, like this you may get lucky and eventually find a faulty air flow meter...... but what of all the other new parts that were needlessly fitted before the faulty air flow meter was discovered?
Saying all that I would definitely encourage the OP to start his search at the ignition system
ChimpOnGas said:
The correct process also avoids the 'Parts Darts' method of fixing things, like this you may get lucky and eventually find a faulty air flow meter...... but what of all the other new parts that were needlessly fitted before the faulty air flow meter was discovered?
Saying all that I would definitely encourage the OP to start his search at the ignition system
The op suggested he has changed a lot of the ignition. It may not be changed to what you would choose but it’s been changed once and was working fine. Now something has changed and I had the same. The car made good power, but wasn’t right when it once had been. No spare parts were wasted on my car. To diagnose, it was a case of swapping parts for known good ones. Saying all that I would definitely encourage the OP to start his search at the ignition system
Also, op, can you hear the stepper resetting itself? My faulty AfM stopped that happening.
Hi guys
Sorry I’ve been quiet I’ve been stuck in whole day meetings and haven’t had much chance in the evenings to reply.
What COG described above is exactly the description of what is happening to mine, and to sort of support that, if I do get it to stall, restarting is impossible for a while until the cylinders clear out a bit I guess. It definitely has started when the weather has been cold, so I’m thinking of trying the trick of warming the sensor to see how that affects things. Is that just a problem to be lived with in cold weather (without upgrading ignition to emerald or the like?)
Sorry I’ve been quiet I’ve been stuck in whole day meetings and haven’t had much chance in the evenings to reply.
What COG described above is exactly the description of what is happening to mine, and to sort of support that, if I do get it to stall, restarting is impossible for a while until the cylinders clear out a bit I guess. It definitely has started when the weather has been cold, so I’m thinking of trying the trick of warming the sensor to see how that affects things. Is that just a problem to be lived with in cold weather (without upgrading ignition to emerald or the like?)
ChimpOnGas said:
The problem with diagnosing a complex system using assumption.... is that the system is way too complex to make assumptions with.
We can all provide our individual experiences that seem to match the OP's symptoms, but the correct process the OP should follow is one of logical and systematic investigation.
The correct process also avoids the 'Parts Darts' method of fixing things, like this you may get lucky and eventually find a faulty air flow meter...... but what of all the other new parts that were needlessly fitted before the faulty air flow meter was discovered?
Saying all that I would definitely encourage the OP to start his search at the ignition system
Same here - would start with ignition system - after changing out the old plug extenders, a few weeks later started having what I thought was fueling issues on start up - after wasting a lot time looking at fueling discovered the new plug caps were lifting off the plugs so that the full wack was not getting into the plug. OK when hot but with the extra fuel on less than hot would cause the engine to die. We can all provide our individual experiences that seem to match the OP's symptoms, but the correct process the OP should follow is one of logical and systematic investigation.
The correct process also avoids the 'Parts Darts' method of fixing things, like this you may get lucky and eventually find a faulty air flow meter...... but what of all the other new parts that were needlessly fitted before the faulty air flow meter was discovered?
Saying all that I would definitely encourage the OP to start his search at the ignition system
My last Chimaera did this. In 2015, if I stalled it within the 1st minute, it would NOT restart. I had to pull one of the relays and crank it with no fuel pressure to clear the cylinders out.
After I had the injectors professionally cleaned, it wasn't an issue. The car had 82k miles on it when I had them done and they weren't that bad (all fair to good) prior to cleaning. It may be a bit drastic but if they've never been done, it will be of benefit.
After I had the injectors professionally cleaned, it wasn't an issue. The car had 82k miles on it when I had them done and they weren't that bad (all fair to good) prior to cleaning. It may be a bit drastic but if they've never been done, it will be of benefit.
To the O.P.
i would not worry at all about your "problem".
A famous TVR saying TADTS.
My 4.0ltr Chim does exactly the same, mainly during the winter, lower temps and all that.
I still use the car on dry/sunny winter days.
I did sorn it in the past, but just starting the engine now and again is nowhere near as good as taking the car out for a good blast.
Thing is, at this time of the year, i have learnt to start the car, no throttle, leaving it running for a few minutes, and then drive it out
of the garage. This way the car behaves perfect.
Just as you describe, if i start the car and immeadiatly touch the throttle to drive out the garage, it will usually stall, with all the
added problems of restarting. Any other time of the year, start it up and drive straight away no problems.
i would not worry at all about your "problem".
A famous TVR saying TADTS.
My 4.0ltr Chim does exactly the same, mainly during the winter, lower temps and all that.
I still use the car on dry/sunny winter days.
I did sorn it in the past, but just starting the engine now and again is nowhere near as good as taking the car out for a good blast.
Thing is, at this time of the year, i have learnt to start the car, no throttle, leaving it running for a few minutes, and then drive it out
of the garage. This way the car behaves perfect.
Just as you describe, if i start the car and immeadiatly touch the throttle to drive out the garage, it will usually stall, with all the
added problems of restarting. Any other time of the year, start it up and drive straight away no problems.
Its generally thought the engines do run too rich on start up when cold, but on cars with catalysts you will hear the engine note change as the mixture leans off once the lambda probes get hot and the mixture then corrects. This takes around 20 to 30 seconds after a stone cold engine is started. Realistically the engine should never run so rich as to die when you touch the throttle, even if over fueled by the Range Rover cold start mapping, so there is an underlying issue somewhere. Over rich idle mixtures are frequently down to the AFM giving an over voltage, or lean mixtures tend to be air leaks around the plenum. What are the long term trim values showing in RoverGauge?
ChimpOnGas said:
The following will definitely help:
1. Ditch the plug extenders if you still have them and find a better solution to protect your HT lead plug ends from being burnt on the exhaust manifolds, there are may better options available to you
2. If you're still running the highly inappropriate B7 ECS spark plugs throw them in the bin, fit a set of NGK BPR6EIX Iridium plugs as these definitely improve cold starts
3. Switch your vacuum advance from ported vacuum that idles the engine at 10 degrees to full manifold vacuum, this will give you 18 degrees at idle which will also make a massive improvement to cold starts and the way the engine behaves during the warm up phase
If you do flood it, flat floor the accelerator pedal and crank the engine.1. Ditch the plug extenders if you still have them and find a better solution to protect your HT lead plug ends from being burnt on the exhaust manifolds, there are may better options available to you
2. If you're still running the highly inappropriate B7 ECS spark plugs throw them in the bin, fit a set of NGK BPR6EIX Iridium plugs as these definitely improve cold starts
3. Switch your vacuum advance from ported vacuum that idles the engine at 10 degrees to full manifold vacuum, this will give you 18 degrees at idle which will also make a massive improvement to cold starts and the way the engine behaves during the warm up phase
With the throttle butterfly wide open the engine will be receiving maximum air which will eventually clear out the combustion chambers, the flooded engine should start like this but will likely run like a bag of nails for the next 30 seconds as the remaining fuel burns off.
Hi OP, I was away when I posted my suggestion about AFM. This was the thread I was referring to - https://www.pistonheads.com/gassing/topic.asp?h=0&...
Reading my symptoms, the car didn't like cold weather to much but did pull well (full fat 400).
Listen to the Stepper motor reseting itself when the ignition switches off. It is a very light rachet type noise for a second or two. If the Stepper doesn't reset correctly, I think it can affect things when running.
In any event, swapping the AFM did the trick on my car.
If you get stuck, I think I still have a bag of known good parts (Leads, AFM, Extenders, Ignition AMP, disti cap, etc) from when I up-graded my current car. A couple of people have borrowed them but can't remember the last time I saw them! If you need anything, let me know and I will have a dig around in the garage.
Reading my symptoms, the car didn't like cold weather to much but did pull well (full fat 400).
Listen to the Stepper motor reseting itself when the ignition switches off. It is a very light rachet type noise for a second or two. If the Stepper doesn't reset correctly, I think it can affect things when running.
In any event, swapping the AFM did the trick on my car.
If you get stuck, I think I still have a bag of known good parts (Leads, AFM, Extenders, Ignition AMP, disti cap, etc) from when I up-graded my current car. A couple of people have borrowed them but can't remember the last time I saw them! If you need anything, let me know and I will have a dig around in the garage.
Thanks very much. Are you saying that the symptoms were the same but the AFM cured the problem?
I.e., im pretty sure now this is due to the rich running under cold conditions, I tested it yesterday, I started it and left it running for about 2-3 minutes, then it was fine. I was going to just leave it as it's not a big deal, but if the AFM would cure this then I'd consider changing it
I.e., im pretty sure now this is due to the rich running under cold conditions, I tested it yesterday, I started it and left it running for about 2-3 minutes, then it was fine. I was going to just leave it as it's not a big deal, but if the AFM would cure this then I'd consider changing it
Technoholic said:
Thanks very much. Are you saying that the symptoms were the same but the AFM cured the problem?
I.e., im pretty sure now this is due to the rich running under cold conditions, I tested it yesterday, I started it and left it running for about 2-3 minutes, then it was fine. I was going to just leave it as it's not a big deal, but if the AFM would cure this then I'd consider changing it
I am not sure how the AFM works, but the stepper not reseting was definitely linked to the AFM. I.e., im pretty sure now this is due to the rich running under cold conditions, I tested it yesterday, I started it and left it running for about 2-3 minutes, then it was fine. I was going to just leave it as it's not a big deal, but if the AFM would cure this then I'd consider changing it
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