Problems at higher revs

[mr grumpy]

Having now had the car for 2 weeks I am now experiencing the second problem. This morning driving to work I opened it up a bit (normally only use 1500 -2000 rpm so far). Running at over 2500rpm the engine stopped accelerating or responding to the pedal. Lift of the gas - revs drop to below 2k then engine keeps running, but will not really accelerate and starts to get lumpy at about 2000rpm. Happened several times in a row - take it much over 2500 rpm and engine goes flat and won't accelerate any more - lift of and engine recovers at about 1500.
To date the following has been done:-
New coil
New Ignition amp
New distributor cap
New Rotor Arm
New HT leads
New temp sensor.
Cleaned stepper motor.
What can be causing this problem as I must have the only TVR that cannot break the speed limit. I have sold cars for lesser problems than this so I am getting very p*ss*d off.

[GreenV8S]

There's something severely wrong with it. If you are an experienced mechanic with access to the right diagnostic equipment you can probably fix it yourself without too much grief. Otherwise your options are keep fiddling with it and changing stuff until the problem goes away, this could go on forever since you may end up making things worse while you're at it, or take it to a TVR specialist who will say 'Aha, I recognise those symptoms, I'll check XYZ, yes it's Donald Ducked, problem solved'. This sort of problem often turns out to be caused by a simple component failure and the comnponents are rarely expensive. But the 'trial and error' route can end up being very expensive indeed.

>> Edited by GreenV8S on Monday 29th November 12:12

[woody_450]

Hi

Just had a thought, that sounds like the ECU has gone into limp-home mode to save the engine from damage, never had it in the TVR but I've experienced it before in an Audi.

Anybody shed anymore light?

Just thought I'd throw another spanner in the works...

I'd get it to a garage with some diagnosis equipment.

Rich

[Gavstar]

Air flow monitor? Mine had many of the components you mention replaced, but also needed that replacing. If you live near Crawley, I can recommend Austec.

[ian8542]

A faulty airflow meter would probably cause it not to run at all or run very rich.
Check the tune resistor.

[HarryW]

As Peter H said earlier, much easier and cheaper to get someone to look at it rather than diagnose by replacement, which can get a bit expensive, AFM's are at least £150 secondhand .

Harry

[david beer]

I agree with the tune resistor, mine was actaully in two halves.Mine would feel exactly the same and then at 3500 rpm it would clear. I have a code reader which told me, it would of taken ages to find it otherwise. If you would care to borrow it !

[Mr Grumpy]

Well I am totally confused. ON the drive home the car started OL in the car park but got worse and worse - wouldn't run run at all. It would start every time and would initally rev as normal but after a few seconds it would just completely die. Not much fun on the M25. I pulled of the M way and though I would struggle on on the A30. Nightmare getting to Egham. Then part way along egham bypass at about 50mph there was 1 more splutter then car now runs fine - if not smoother than before.

As the previous owner apparently let it run out of fuel just before I picked it up could this be air trapped in the fuel system (the rev counter kept indicating as the car coasted) or is it a symptom of something more sinister (read expensive).

[GreenV8S]

I still suggest you give serious thought to bringing in the professionals. But if you are determined to investigate it yourself, then in your situation those symptoms would have me looking for an intermittant fault in the electrical supply to the fuel pmp. One sanity check is that you should be able to hear the pump working when you switch the ignition on. As you know, the pump will only run for a second or so unless you start the engine, and the engine drowns out the noise of the pump. The fuel pump supply is moderately complex, but you could rule out a large part of the circuit by putting a fused feed straight from the battery to the fuel pump. If this cures the problem you know it is a simple electrical fault in the power supply, although it will still take some work to track it down.

The fact the tacho still works is encouraging as it suggests that at least the low tension side of the ignition is working. If you have a passive strobe that you can put in the king lead when the fault occurs this would give you a quick check that you have a good spark, eliminating a whole load of potential faults.

If you're reasonably familiar with the systems involved then you can track this sort of thing down methodically. However, unless you are familiar with them I still suggest you would be better off getting the specialists involved.