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The source of the Resources
For all things Rover V8, the TVR Griffith and Chimaera and TVR T-Cars
Stepper motor
The stepper motor, or idle control valve, is a throwback to a pre-digital age. It is a mechanical device which alters the flow of air to the plenum chamber at idle to limit the engine’s desire to stall. It resets itself when the ignition is switched on and is the source of the clicking noise from under the bonnet before the starter is engaged. It requires regular cleaning, the frequency of which can depend on the type of driving you do. Lots of town work can lead to rapid carbon build-up whereas the open road can not only clear your head but the stepper as well.  Many people clean theirs annually. Some criticise this as opting for perfection and others recommend it for the same reason. See The Resource for an example of one being removed and cleaned.
Fuel pump
If the fuel pump, arrowed in yellow, below left, isn’t working then your engine won’t be either. No fuel means the engine won’t run at all. However, on occasion the fuel pump may be intermittent.
If the misfire only occurs at high revs then there is a chance that the pump can’t satisfy the demands of the engine. This is unusual and can only be tested with the proper equipment, which normally means a visit to a garage. One option which can work: swap the two fuel pump relays, marked with the red diagonal line, picture below right.

Wrong ECU
If the problem present from the time you bought the car then this is a possibility. Many owners ‘upgrade’ the chip, some thinking that the cheapest option is the best way to go. But this can cause all sorts of weird behaviour.
Your first port of call should be the chap you bought it from but if he professes to know nothing of any changes then you are on your own. Changing the chip can be an expensive option and many specialist garages will let you try a standard ECU to see if it cures the problem. However, see Connections below before opting for this. That said, if you intended to upgrade the chip in any case then you might feel now is as good a time as any.
Misfire
The stepper is located on the rear offside of the plenum chamber.
FUEL
Most RV8 engines run on unleaded but you should check before committing yourself to considerable expense.
Fuel varies and the ECU should be able to cope with these variations. That is one of its functions. However, sometimes they struggle and for reasons which confuse petrol engineers. So many people find a fuel that suits and then stick to it. It can be a problem discovering if the fuel is any different as it requires a couple of tanks full before any change to become apparent. Note that using fuel of a higher octane rating than the engine needs is unlikely to be of benefit and will be a bit of a waste of money. But if the head, for instance, has been worked on or skimmed then the compression ration might well have been raised, giving problem with heat and pre-ignition.
One option, favoured by many who have more powerful engines, is the super-fuels, such as Optimate. These contain a number of additives over and above those found in the ‘normal’ fuel. Many people say that they noticed a significant improvement by the second tank-full. It has been suggested that the fuel has to be used for some significant mileage before its full benefits are realised but once reached there is no noticeable deterioration if alternative fills of ‘normal’ fuel and super-fuels are used.
One a personal note, my 4.0 Chimaera runs much better on Optimate, having more power lower down the rev range, running slightly cooler and giving better mileage. The last would more than pay for the extra cost if I could only resist using the extra power. However, despite being a bit of a messiah for Optimate, it is apparent that it does not benefit every car and the newer the engine, the less benefits are apparent.

ECU
The ECU circuit board can fracture and the connections can become faulty. The former is quite easy to spot. Remove the circuit board – GO TO HERE – and examine both sides under a microscope, taking care not to touch any of the electronic components, especially the contacts and the integrated circuits (chips). If there are any cracks then it is probable that the ECU is duff and has to be replaced. A faulty or dry contact is much more difficult to spot. The only sure-fired way is to resolder all the joints, something of a monumental task even for those experienced in such things, and those not so blessed are advised not to even think about doing it.

Plugs, HT leads and coil
Before you do anything else, switch off your engine and check that all the HT leads, including the one to the coil, are nicely embedded in. Rotate them slightly to ensure a good contact.
If your car has just been serviced then a faulty plug is always an option that should be considered. It is unusual but in 40 years of doing my own servicing I’ve had three duff ones. One kept overheating, presumably a fault in manufacture, another had a crack in the ceramic allowing dirt to get in and short out and the third had a defective central contact. The last two faults were probably due to poor handling by delivery drivers.
With eight cylinders the tried and tested method of changing just one plug at a time is probably not the best option. However, if you have just bought the car, the rearmost plugs can be difficult to remove and the previous owner might well have run out of energy.
As the head is made of alloy, it is easy to cross-thread on replacing the plug. See The Resource for a way to limit the chance of this. If this has happened then one of the two main function of the spark plug, that of dissipating heat, can be compromised. If it has been cross-threaded then you have the option of having the thread replaced, which can also give heat dissipation problems, or another head.
The OEM plug leads have no wire in them, just a central core with carbon attached. This can deteriorate with age, vibration and handling and such plug leads should be seen as having a limited lifespan. Some say every two years, which seems to me to be preaching perfection, whilst others double this period. The choice, as they say, is yours. HT leads are all but impossible to check as they might just falter under a specific load. Consider upgrading the leads. A coil’s function is very difficult to check dependably. It is always handy to have a spare one so buying a replacement and it providing no improvement is not a complete disaster.

Connections
If you have just had work done on your car under the bonnet, or you have done so, then it is always possible that a connection has been dislodged. Whilst you might think this would be inexcusable for a pro, they work under time pressures and they might not be familiar with your specific engine type. So if the problem arose right after such work was carried out then examine the engine for anything flapping or a nice shiny contact with nothing attached.
It is advisable to take a number of photographs of your engine for reference as soon as you buy the car. Whilst this might get you an unwanted reputation if discovered doing so, it does provide a fail-safe way of checking if anything has changed or is missing. Any modern digital camera with a flash is more than adequate for the job.

Sensors
The ECU depends on its sensors in the same way you depend on your senses. If one becomes faulty then the ECU cannot function correctly. The number and location of the sensors varies with various engines.
Checking requires specialist equipment and is really down to a garage or someone skilled in motor vehicle electronics.

Poor contacts
As a car ages contacts can corrode and a resistance can build up or, indeed, in extreme cases, stop all current.
On the top of the ECU case there is a multi-pin connector. I know of three cases, including my own problem with misfiring, where simply pulling the multi-pin apart and then replacing it effected a total cure. I put a small amount of contact cream on the terminals although I have no idea whether this has any positive affect or not.
In some cars, most notably TVR Chims and Griffs, the connector can be dislodged when replacing the battery or the fuses.

Steve Kelly had some misfiring problems with his RV8 engine which took a fair while and a lot of persistence to sort. Here is his story. If you want to know his solution, got to the end of the article or click HERE.

He explained the initial problem on Pistonheads as:

 

Now that I'm getting more confident I'm venturing into the top of the rev range now and then. However, at around 5,000rpm it's like I'm hitting the rev limiter.

I've seen it pull right round to the 6k mark before so I'm quite sure it's not the rev counter being inaccurate.

I cleaned the cap and rotor today and checked all the leads are secured. I read that swapping the relays around can cure this? I also read that the fuel pump could be to blame but that it is rare for this to be the issue?

I also know it does it at any load - not just under load, it will do it just by reving on the spot

 

RV8R’s contributor Mark Thompson, Bitzracing on PH, suggested replacing the coil. First reports flattered.

 

Bitzracing, thank you for your suggestion, the new coil fixed it!

Also another niggle that turned up towards the end of last year disappeared - the rev counter needle started to bob around very slightly at about 2,000rpm - 3,000rpm and that has now stopped. Nice because I was sure it didn't always do that! Thought my rose tinted spectacles might have been playing mind games with me!

 

But then:

 

Damn! Its still there! Why did I think it was cured? Well, on the day I fitted the new coil I gave it one blast in 1st gear and it revved cleanly to 6k. I had driven 5 miles on the M1 to let it warm up then on the way back I gave the loud pedal a good prod so maybe it's temp related? Today I had been running around a fair bit before I noticed it's still there - the engine/underbonnet would have been well warm by then.

I don’t like caning it so hadn't noticed ‘til this afternoon that in fact it still isn't cured! Oh well back to the drawing board, oh but at least the coil cured the rev counter!

 

Hope springs eternal:

 

Think I might have something now.

I'd just gone over the connectors to the ignition module and AFM and suddenly the car wouldn't start.

However, quick look back under the hood and when I'd reconnected the ignition module plug the yellow wire had simply fallen off! Right where the wire is crimped into the connector.

It must have been hanging on by a thread for ages now.

Annoyingly there wasn't a very elegant way of repairing this without soldering it and far too much of the wiring would need to come out to remove that part of the wiring harness. So I had to split the plug open, shove the unbroken connector back on the module and attach the broken wire via a crocodile clip and it started again.

So lets hope when I buy a new plug (Ford) and attach it all properly the misfire has gone. Certainly it wouldn't have transmitted the proper current with only a strand or two of wire so it can only help.

 

And rather depressingly:

 

Okay new module fitted - misfire still there. My last fill up is being caned with all this high rpm nonsense!

Rotor arm tomorrow. Silly really should have been one of the first things to do.

Also checked leads thoroughly and all okay.

 

But we all know about the rotor arm:

 

For sure. I'm taking it to TVR Centre on Thurs.

I just did the rotor arm - no change but then I cam home and tried the ECU plug. All I did was remove and plug in again and so off I went slowly out of the village. Pulled onto the main rd in 1st and up she went all the way to 6k - great, frigging the ECU plug seemed to do it but wait, I'll try again (remember I thought the coil had cured it?) NOPE back to the 5k rev limit.

I'm starting to think its fuel related or injectors possibly. Both times in the last week when it has made it to 6k have been moments after start up (warm though) and then full throttle. Maybe it is the pump after all.

Anyway, that's enough of me throwing bits at it, it's going in on Thursday!

 

He did research on PH and found:

 

Just found some old posts talking about rev limiter issues....I'd definitely describe this problem as that rather than a misfire.

Weird how I've managed to get it to rev to 6k only twice and both times being soon after I've started it up from warm. Nothing spark related would allow this surely? It must be fuel??

Another find was the older post described the problem as existing under load, not in neutral. That turned out to be the coil. So for my scenario this makes me suspicious more towards fuel starvation.

Could the tank be contaminated?

A lot was expected of the visit to the TVR Centre but:

  

Took it to TVR Centre but as I guessed, I've done all the bits they could try there and then and I couldn't leave it today with them. However after that, a quick call to an ex Tuscan Challenge mechanic and he's pretty sure it's the fuel pressure regulator.

I've worked out a way to get the car to rev and not rev as it were. Anytime you start the car it will have a newly primed fuel line, this gives enough fuel pressure to reach 6k once or twice but after that the pressure reg is not holding enough pressure to get back up to 6k.

This is why I keep thinking it's cured, every time I try a new fix it's from startup with good fuel pressure.

Anyway, off to get the pressure tested now so will know for sure later today.

And so guess what:

 

It didn’t fix it.

I picked up a chavy adjustable one with gauge for £20, used for about an hour by some bloke with a Landy then he realised he didn’t need it so it’s as new. It's running at 44psi at idle with everything connected (didn’t realise about removing vacuum).

I just put it inline after the OE regulator which I've simply left plumbed in for now.

If you rev the car quite high the pressure drops a tiny bit (4psi) this sound right?

I've just been out with the cause of all this nonsense - my mate and his S2000 (a bit tuned too). I can keep him at bay and if I really try I'm a bit faster so in terms of power and enjoyment I'm happy and the car is super quick (to me) but this bad thing still happens at 5k or a little over.

I think all I'm left with now is ECU, fuel pump, wrong TDC mark on pulley (as on Steve Heath's Griff) - anything else?

I'd say it was just my car's particular rev limit but why then will it rev up to 6k after switching of and on again? 5k was it's limit it should always stop at 5k

Also, my fuel pump clearly works - it's always started from hot, cold or whatever and today I disconnected it while running to run the fuel out of the line so I could work on the fuel line and I clearly heard it running and then stop when I pulled the plug off BUT I rarely hear it prime, it does it now and then so I do know what it sounds like but most of the time including mornings I hear nothing but the car always starts.

So does the pump run at two speeds? It must do because sometimes I hear it audibly prime the line and other times it starts with no pump noise but it is still running.

Is there supposed to be a similar boost when full power is needed? IF so maybe the signal isn't getting through?

I checked the timing this aft and it's spot on. Really though I think it's fuel related. The engine runs perfectly otherwise, it just hits this wall though.

 

After all that rambling:

 

Well still not fixed but check this lot out.

Decided to inspect supposedly new fuel filter as I caught a glimpse the other day I thought it looked old. Went ahead and removed it. DATE: 30/05/05 - 6 years old according to the stamp on it! Now maybe it's been on a shelf ‘til I bought it in December – Don’t think so, this looked way older than three months and it was pretty blocked.

I don’t think they changed it even though I've got an invoice saying they did. So I picked up a new one made by Hengst, the difference in resistance (blowing) was vast. The old one totally empty of petrol felt pretty hard to blow through where as the new one was like blowing through a straw. Very suspect.

Second thing - get this, the non return valve in on the vac hose was round the wrong way! I've never touched it and again my invoice from back in Dec also included check and adjust timing - WTF!?

So I've got 8* Initial timing with vac disconnected and 40* total (3500rpm) with hose on. As it was (with non return valve wrong way round) It was something like 23* @3500 rpm.

Of course it feels much slicker from mid range onwards, definitely quicker but still this pigging 5k stuff is happening.

Imagine how much I thought I'd cured it TWICE today finding a blocked filter and non return valve back to front! But No

 

Much advice came through on PH and Steve appeared to try it all:

 

Yeah there is, the bible calls it a one way valve but same thing.

Yeah I know how to test the vac advance, had already established the mechanical side of things worked in there when I did the ign module, it was only trying the pipe sucking method that I found the one way valve was on the wrong way round.

Incidentally, anyone with lumpy cold running, check yours isn't the wrong way round too! I thought my idle was smooth from cold but now the advance can help out it's even smoother!

So just done a whole day in the car, got through just about a whole tank of V Power, driving hard. Rev limit thing now wont happen 'til nearer 5500!?

Weird.

Dyno the only way forward on that issue.

Had a blast today though! It's quicker than a Cayman!

 

He gave it more thought:

 

Been thinking about this today. It's got to be the ECU.

You can be driving along, take it to 6k, then it wont allow you to do it again - you can switch off and on again while coasting and she'll go to 6k once more but not again.

Something must be happening or at east the ECU thinks something is happening that it doesn’t like at 6k and every time I switch off and on again it's resetting it's self.

Might just be a faulty Lambda giving the wrong readings.

Going to use the tester very kindly sent to me by Mark (Blitzracing) anyway so should see something from that either way.

Get the car back from the bodyshop on Monday so will have a go next week!

 

Things beginning to become clear at last?

 

Bit of an update...

Had the car on a fault code reader and swapped for a known good ecu - no faults and other ecu did not solve it.

Cock!

Points me back in the direction of weak spark - there's not much left now! Could ideally do with swapping in a know good distributor or getting an HT check done to see spark voltage at high revs.

 

One problem leads to another:

 

Went to look at the distributor but battery was dead - fine it's been showing signs of dying recently.

Well, the old one is 7 years old so no wonder it's dead but I have to say the car spun over very well on the spare battery I hooked up which has got me thinking....

The high rpm misfire could have something to do with a weak battery - maybe that's why it will rev to 6k if you switch off and on again - the ballast resistor (I know they don't have an old style ballast resistor but, you know what I mean) will have just supplied cranking voltage to the ignition system and I'm guessing maybe enough left to provide adequate spark to rev to 6k...?

Couldn't get a new one today and had my pregnant wife with me in the car so 6k experimenting on spare battery was not going to happen! Either way I shall stick a new one on tomorrow and see what happens.

 

And then, at last:

 

I went to see V8 Developments and they cured it.

It turned out to be the ECU.

Something was telling it to go into a default mode which incorporates a 5,500 rpm rev limit. Every time I switched the car off and on again it would reset and the misfire/rev limit would be gone until I reved past 5,500rpm then from then on it would only go to 5,500rpm or there abouts. Sometimes after switching off and back on it would let me rev past 5,500rpm maybe 3 times before this default mode thing kicked in limiting me to 5,500rpm.

It was very strange and of course to begin with I didnt realise it was effected by me switching the car off and on again so to start with I tried all the obvious bits like Coil, ign module etc etc but as soon as I realised it went away by switching off and on again, all of the normal fixes kind of went out the window.

Anyway one more weird thing was that I did previously try another ECU from The TVR Center which did nothing but that was from a '93 car....Anyway, yesterday when I took the car to V8 Developments they tried their own spare ECU which fixed it...so I said hang on, why didn’t that other ECU from The TVR Centre change anything?

They were a bit puzzled to be honest! So they called Mark Adams who offered perhaps the best possible explanation which is that around '90 - '93 Rover changed the ECU's and that maybe TVR were still fitting the older chip into some of the newer ECU's meaning my car (a '94) and the spare ECU from TVR Centre both had effectively the wrong chip in the ECUs from new.

It all sounds quite far fetched I know but in all honesty even V8 Developments and Mark Adams were clutching at straws to come up with that synopsis!

But anyway! After many months on and off, fiddling and investigating it's finally cured.

Certainly this episode represents a most bizarre cause of a misfire/rev limit issue and if anyone was to have the same issue it will save them a lot of head scratching! The biggest clue was there was no backfiring, it was (as I now know for sure) an actual rev limiter kicking in but all to soon at 5,000rpm to 5,500rpm.

 

A happy ending.

 

A story of a difficult one