Various running problems - what to try next?

[Dr Mike Oxgreen]

My car is showing a number of engine running problems at the moment, two of which I've raised threads about before, but I'm beginning to think they're all inter-related so I thought I'd raise a new thread to bring all the symptoms together.

Issues I've got:

1) "Dead throttle syndrome". Engine abruptly and randomly loses all power for a second or two and doesn't respond to the throttle, then abruptly resumes pulling normally.

2) Misfiring after the car has been stationary. This seems to be heat related - on a warm day, if I stop for 10 to 20 seconds and then pull away, the engine is misfiring until I get back up to speed, then it returns to normal.

3) Stalling after stopping and switching engine off, e.g. refuelling. I sometimes have to keep the throttle open with my foot to stop it stalling, and it is misfiring. Again, this seems to be heat related because the problem disappears once I get on the move again. It's as if something is getting heat-soaked while the car is stopped.

4) Terrible running when starting from cold, as if running on only 6 or 7. The engine runs normally for about 10-15 seconds, then starts misfiring very badly, and then abruptly starts running okay after maybe a minute or two.

Here's what I've tried so far:

• New HT leads. This instantly cured the "dead throttle syndrome", although exactly why I'm not sure. The problem disappeared for about 6 weeks, but unfortunately it is now back with a vengeance, sometimes happening every few hundred yards. Again, this seems to be heat related, because if I stop and lift the bonnet it'll go away temporarily.

• New coolant temperature sensor. This seemed to cure the rough running on start-up, but it has come back recently.

• New ignition amp module. I did this just yesterday, and it has also instantly cured the rough running on cold start-up.

• New coil on order, but not yet fitted. However, the car had a new Bosch coil about 3 years ago when I broke down in France, so it really shouldn't be this - but I can't rule it out.

Since changing the amp module, I haven't had a recurrence of "dead throttle syndrome" yet, but I have had it stalling after stopping to refuel (problem 3). There also seems to be a hesitancy between 2000-3000 rpm which suddenly disappears above about 3500-4000 rpm and the engine pulls keenly. Does this point to a fuelling issue?

Everything I've tried so far has had a definite positive effect, but in some cases only temporary and in other cases leaving other aspects of the problems still there. It's as if several parts of the ignition system were a bit tired, and replacing them has helped, but there's still something else wrong.

So what should I try next, assuming the new coil doesn't cure things (which I suspect it won't)? I'm wondering about lambda sensor(s), but they're not cheap. I've read that I should be able to see their voltage flip-flopping, but how quickly? Will my cheapo digital multimeter be able to show it?

Any suggestions gratefully received!

Edited by Dr Mike Oxgreen on Monday 7th September 13:28

[Dr Mike Oxgreen]

Follow-up question:

If I do test the lambdas with my multimeter, should I do this from a cold start, and if so what would I expect to see as the engine warms up?

I've read somewhere that the ECU doesn't use the lambda readings until the coolant temperature is up to 70 - is that correct? If so, should I only bother checking them when the engine is warm?

How should I check the lambda voltage - at idle, or with the throttle partly open?

Many thanks for any help you can offer!

[Dr Mike Oxgreen]

Thanks guys!

Yes, I'm pretty sure that I've seen the RPM gauge remain steady while the engine is in "dead throttle syndrome". Does the RPM gauge count the pulses coming out of the amp module?

The coil is next to try - I've just received a text telling me that it's been delivered, and I have a day off on Friday so will try fitting it then. If that doesn't work then at least I have a spare coil (and a spare amp module, and a spare set of HT leads!). I'll add the rotor arm to the list of parts to replace, and on the basis of blitz's comment I'll relegate the lambdas to the bottom of the list (which is a good thing - £100 each???). Plug extenders will have to go on the list as well.

At least this all means that I will have done a fairly complete refresh of the ignition system components, which is no bad thing.


Edited to add: That looks like a useful tool, blitz - I think I'll have one of those if the coil doesn't fix things, because I could easily waste a lot more money on other stuff.

Edited again: I might decide to have one anyway, cos it's a tool with lights on!

Edited by Dr Mike Oxgreen on Tuesday 8th September 12:07

[Dr Mike Oxgreen]

I changed the coil today, but it doesn't seem to have made a difference. I also noticed that the vacuum assembly on the side of the distributor was very loose, so I tightened its screws up.

Unfortunately the traffic around Woking has been too congested to test it properly, but it still seems that when I stop or get stuck in a slow-moving queue the car is then lumpy and hesitant in the mid-range for the next half a mile or so, and on the rare occasions when I can keep moving at a moderate speed for a while it seems to smooth out and pull normally. I wasn't really able to tell how well it was pulling at the top end - too much traffic. I'll try again in the morning.

I've now replaced the two ignition components that I know can be sensitive to under-bonnet heat: the coil, and the ignition amp. Are there any other things under the bonnet that might react to heat and cause lumpy running? I do have a rotor arm and distributor cap on order; hopefully those might arrive on Monday when I have another day off.

I suppose there is another potential explanation: what if it's running rich and fouling its plugs when idling? Then perhaps after a short while of running at normal speeds it burns the fouling off?

I might pull the plugs out tomorrow and have a look. Traditionally you expect plugs to have a nice tan brown colour; does that hold true for the RV8 as well? What if I were to let the engine idle for a few minutes and then look at the plugs? Would you expect them to be clean, or does the RV8 habitually foul its plugs a bit at idle?

At least I haven't had "dead throttle syndrome", or the rough running after a cold start, or the tendency to stall. It's now only showing the lumpy, hesitant running in the mid-range. If I can just cure that it'll be great!

Edited by Dr Mike Oxgreen on Friday 11th September 17:02

[Dr Mike Oxgreen]

Supplementary numpty question:

When I fitted the new coil, before bolting it onto the mounting bracket I connected it up and tried a test-firing of the engine. It cranked, but didn't even try to start. So I connected the old coil back temporarily - again, it didn't even try to start.

Only once I'd reconnected the new coil and bolted it to the bracket did the engine start - albeit slightly reluctantly, probably because it was slightly flooded.

So does the coil earth itself through the bracket, or something like that?

[Dr Mike Oxgreen]

FlipFlopGriff said:

What do the plugs look like?
What are your leads, extenders, dizzy cap and rotor arm like?
FFG

Don't know yet - will remove and inspect the plugs today when the engine is cold.

Leads were replaced about 8 weeks ago. At that time, "dead throttle syndrome" was happening almost every time I drove the car, though usually only in isolated incidents. After the new leads, it stopped for at least a month - but the problem returned with a vengeance whilst on holiday a few weeks ago.

I have a new cap and rotor arm on order - should arrive shortly.

The extenders looked okay when I had them off while replacing the HT leads - but you're right, I shouldn't discount them as a possibility, particularly in light of venus' experience with them.

Would I get away with doing a test drive without the extenders, and without socks - or would the heat quickly damage the leads?

Edited by Dr Mike Oxgreen on Saturday 12th September 03:31

[Dr Mike Oxgreen]

I've found some woven heat shield material and some heat-reflective material, so I could even make my own home-made heat socks if I can be arsed! Or I could simply wrap some tinfoil around them and go for a drive.

I'll make sure they're not touching the manifold.

[Dr Mike Oxgreen]

Aha! That would explain why it wouldn't start with the coil dangling freely. Every day's a school day!

So, here's what the plugs look like. To my eyes they look rather sooty, and they all look much the same although number 3 is maybe slightly greyer and the porcelain is not quite as sooty - but there's not much in it. Bear in mind, though, that the last drive I did was a frustrating test-drive in Friday afternoon traffic, so a fair amount of idling in queues.




And here's a close-up of number 4, which is fairly typical. The electrodes and the porcelain are sooty but dry:




The gaps all look quite big - well over a millimetre. What should they be?

[Dr Mike Oxgreen]

Well, that was a very interesting test-drive!

I put the plugs back in exactly as they were, deliberately without cleaning them. But I left off all 8 plug extenders and simply wrapped a bit of tinfoil around a couple of the leads that were particularly close to the exhaust.

I drove a good 20 miles, including a mixture of urban main roads and some slightly faster roads.

The engine is now pulling keenly, with none of the hesitation I have been seeing. I even stopped and idled in a pub car park for a couple of minutes, then accelerated away briskly - and again there was no lumpiness or hesitation, it just pulled hard.

So, I might be converted to the anti-extender school of thought.

Once it has cooled down I might pull one or two of the plugs and see if they've cleaned themselves up after a slightly more spirited drive. If not, is it worth cleaning them?

[Dr Mike Oxgreen]

Any comments on the sootiness of my plugs? Are they "normal for Norfolk" when it comes to a TVR RV8, or normal for a stuck-in-traffic run, or is my engine over-fuelling?

I must admit I've never bothered to remove the plugs before so I don't really know what is normal for this engine. Access is a bit tight, isn't it? I was glad of the universal joint adaptor in my socket set. It also took me a while to realise that life would be easier on the nearside if I removed the intake elbow first.

Actually, I've just realised I did do one other thing as I was putting things back together: I squirted some contact cleaner into the connector of the air mass sensor. That might have made a difference; who knows? And I might splurge a bit of dielectric grease in there as well.

[Dr Mike Oxgreen]

So are the standard extenders resistive? If so, I should replace the plugs with resistive ones if I'm going to ditch the extenders, should I?

Thanks for the kind offer, QBee, but I think I've decided to ditch the extenders altogether. I've ordered a set of socks, and will consider changing plugs as well. Yours look very clean compared to mine!

Edited to add: Now ordered a set of BPR6EIX as well. Heck, it's only money!

Edited by Dr Mike Oxgreen on Sunday 13th September 08:18

[Dr Mike Oxgreen]

ChimpOnGas said:

• New good quality distributor cap - new Lucas brand seem fine
• New (new old stock) genuine Lucas rotor arm or the red one from the Distributor Doctor - avoid new Lucas brand!
• New genuine Bosch branded coil - avoid Intermotor and other cheap rubbish brands
• New ignition amp - new Lucas brand seem fine

Tick, tick, tick, tick. Well, not sure whether the rotor arm I've got on order is new or old stock - it's whatever TVR Parts are selling. That and the cap haven't arrived yet but will be going on.

ChimpOnGas said:

• Replace your leads with the best you can buy

I've gone with OE Lucas leads, because the consensus on most threads I've read is that fancy leads are no better, and may even be worse. Certainly the new leads cured "dead throttle syndrome" for at least a month before something else caused it to return.

ChimpOnGas said:

• Ditch the God awful plug extenders and double wrap starting with MSD Pro-Heat Guard and followed by DEI Titanium Protect-A-Boots over the top

Agreed. I've just done another test drive to confirm that it wasn't a fluke - the engine really is running better without them. I'll wrap the ends of the leads with some woven heat shield material, then with some heat-reflective material, and finally with a set of boot protectors. Should be arriving shortly.

ChimpOnGas said:

• Use an advance adjusting strobe to accurately set your dynamic (not static) timing
• Set your throttle pot and base idle as per the Land Rover workshop manual

I'll let Str8Six take care of that sort of stuff. I know they did calibrate the throttle pot a few years back.

ChimpOnGas said:

• Fit a set of the best extended electrode NGK plugs you can afford

Set of NGK BPR6EIX on order. Should arrive in next couple of days. I'm planning to attach a label to one of the HT leads saying "Iridium plugs - do not replace".

Edited by Dr Mike Oxgreen on Monday 14th September 16:51

[Dr Mike Oxgreen]

Just pulled the number 4 plug again, after two short test drives with the engine no longer missing. It's still not exactly clean, but both the electrodes and the porcelain are definitely cleaner, perhaps even with a hint of brown on the porcelain:

[Dr Mike Oxgreen]

ChimpOnGas said:

Why are you even still wasting your time with those dreadful and clearly shot B7ECS?

Because the new plugs haven't arrived yet!

I was interested to know whether Blitz was right when he said that the fouling is due to the misfire, so I thought I'd take a look, and the fact that they've cleaned up a bit lends weight to what he said. I'd like to fix the problem, but I'd also like to learn by studying the symptoms.

Rest assured, there's a set of BPR6EIX on its way to me, and they will be fitted as soon as free-time allows.

Edited by Dr Mike Oxgreen on Monday 14th September 19:12

[Dr Mike Oxgreen]

By the way, it has occurred to me that motoring is probably the only area of life in which it's a good thing for your porcelain to be coated in brown deposits.

[Dr Mike Oxgreen]

ChimpOnGas said:

Step 1: Lob those feked old B7ECS in the bin and never fit them again

That would be a slightly silly thing to do before the new plugs have actually arrived. I think the engine will run even worse with no plugs in at all!

And by the way, my existing plugs aren't shot - they're merely fouled. They would clean up perfectly if I could be arsed, and there's a decent chance they wouldn't foul up again now that I've solved the misfire.

ChimpOnGas said:

Step 2: Fit your lovely new NGK BPR6EIX iridium plugs

That will be a tremendously difficult challenge while the said plugs are somewhere in a courier's delivery network!

ChimpOnGas said:

Step 3: Buy an AEM wide band kit for £150 and start looking at true factual data

What, spend yet another £150 when I appear to have already solved the problem by removing the extenders? Nah.

What I might do is invest further money on other parts that might be at risk of failing on an 80,000 mile car, such as a pair of lambdas and maybe an air mass sensor. Not cheap parts, but at least they'll probably buy me improved reliability for another 5-10 years - and I'll have more spares.

[Dr Mike Oxgreen]

blitzracing said:

Im going to have to have a little laugh if £60 worth of new plugs soot up or misfire then and a set of knackered plugs is not the root of all evil. Problem is here we have not got any facts- just lots of guesswork and throwing parts at it. We dont know what the HT voltages are doing, we dont know if the ECU is in limp home mode, we dont know what the fuel trim values are doing or AFM output, so you throw money at the issue until you get lucky. Im sure a new set of plugs will help things but could mask the issue if its not the plugs at fault in the first place.

The way I'm looking at this is that most of the ignition components are probably due for a routine replacement anyway, and by swapping them out I'm (a) giving myself the experience and know-how to be able to do it at the roadside should I ever need to, and (b) giving myself a useful kitbag of spares to keep in the boot. I also have a new rotor arm and distributor cap on the way to complete the ignition refresh.

I'm pretty sure the ECU isn't in any kind of limp mode, judging from the way it gallops away from a standing start now that the misfire is gone.

As for the plugs, well they're quite badly fouled - although the evidence of the number 4 plug cleaning itself up a bit during just a short period of driving without the misfire seems to support your assertion that the fouling is caused by the misfire. If I were to go on a long motorway journey, or better still find some quiet roads* to give the engine a real workout, I reckon those plugs might well clean themselves up completely. I disagree with ChimpOnGas when he says that my plugs are shot; I don't think there's much wrong with them apart from some temporary fouling (although they are near the end of their service lives, as evidenced by the gaps).

By deleting the plug extenders I appear to have fixed the misfire; it will be interesting to see whether the new plugs give any additional benefit. I can't really drive the car for any appreciable distance at the moment because the ends of the HT leads have little or no protection from the exhaust manifolds. But once my 'socks' have arrived I can give it a more thorough test.

Up to a point, I don't mind throwing some money at the TVR and fitting new parts to see what happens - it's all a learning process for me. All in I've probably only spent about £200 so far, and that's not too bad.

* alas, quiet roads don't really exist in Surrey

[Dr Mike Oxgreen]

New plugs and socks now fitted!

Quick test drive this evening. Lots of tedious idling in traffic queues, which is quite a good test. Always pulled away smoothly and keenly.

Is the idle a tiny smidgen smoother? Maybe, but not sure. It's very marginal, and I'm rather glad it hasn't completely lost its slightly bobbly idle - it gives the engine an impatient quality which I like.

It's impossible to tell whether the different plug type has improved things, partly because I've replaced old plugs that were shortly due for replacement with minty fresh ones - so one would expect the engine to be a little smoother, and it possibly is.

One thing I'm sure of: removing the plug extenders has cured the misfire. All the old plugs had cleaned themselves up quite a lot - both electrodes and the porcelain were much greyer, although the black soot persisted around the lip of the plug.

I still have a rotor arm and distributor cap which have now arrived, but they'll have to wait until I can be arsed - maybe at the weekend.

Many thanks for everyone's advice - it's all very much appreciated.

I'm very much inclined to agree with Chimp's view that it's worth periodically replacing all the ignition components - perhaps every 30k or 5 years. It has only cost about £200 for the leads, amp, coil, rotor arm, cap and plugs - which really isn't much in the scheme of owning a car like this.

[Dr Mike Oxgreen]

ChimpOnGas said:

just be careful as what I found was the socks aren't always enough on their own to fully protect the HT leads.

Yes, I've got some woven heat shield material; I'm planning to cut it into strips and wrap it around the ends of the leads inside the socks as extra protection. Another job for the weekend.


Edited to add: I suppose for the sake of completeness I should refill the electrical system with OE Lucas smoke. I haven't actually seen any escaping, but you never know...

Edited by Dr Mike Oxgreen on Friday 18th September 09:04

[Dr Mike Oxgreen]

Well, on Friday I drove it to work and it was running brilliantly - possibly better than it has ever run. Drove it at lunchtime and ditto.

But then when I started it to drive home I could immediately tell it was misfiring as soon as the engine was running, and it drove like an absolute pig - stuttering and misfiring really badly. It did improve very slowly, and by the time I'd got home it was almost back to how it had been earlier in the day.

What on earth could have caused it to change so dramatically when it was just sitting in the office car park for a few hours? Well, I do remember being in a meeting that afternoon and we could hardly hear ourselves over the rain drumming on the roof, so I'm suspecting water ingress. It's possible that I may have failed to get the rubber sheaths of the HT leads properly slid down over the body of the plugs - I found that the socks made it harder to feel what you're doing when fitting the leads to the plugs, and I'm wondering whether I may have slid the sock down over one or more of the plugs without sliding the rubber sheath as well.

The engine was too hot to check at the time, and I was busy with other things yesterday, so today I will check, clean the bodies of the plugs and refit the HT leads more carefully. I think that is the most likely explanation. I may have a tube of dielectric grease somewhere, so I'll consider putting a smear around the porcelain body of the the plugs.

Edited by Dr Mike Oxgreen on Sunday 20th September 07:54