Engine starts to misfire when hot , then stops.

[GoodGriff500]

Hi All,

Ref: Griffith 500 HC 1997. Bought new has covered 12,500 miles. Had new ECU fitted 2007. I do about 1000-1500miles a year. It is stored in an air chamber with a battery conditioner fitted. Always serviced.

I forgot to put the battery conditioner on recently and the battery almost went completely dead with the alarm on. I had to charge it properly which meant removing the electrics from around the battery and then putting them back once charged. No big deal but not the best design by TVR.

Sometime after this I went for a drive and after several miles it started to misfire. Gradually this became much worse until it would not stay running unless at 3000plus revs. It then got worse, stopped and would not start again - the fuel relay is working. After an hour or so I tried to restart it and it fired straight up and was perfect for the journey home (20miles). I thought it was something to do with the battery charging which has reset itself.

However it repeated the same thing. Each time I have removed and put back the electrics just in case these were playing up.

Any help would be most appreciated.

[GreenV8S]

Is the spark OK, do you have the correct fuel pressure, are the injector duty cycles changing significantly when the problem occurs, is the ECU showing any faulty codes?

[Peter66]

It could be a bad battery. If it's not used much and a few years old it can go bad. It's typical for the symptom you described: wait a small time and than it starts again. Other issue is a bad earth connection. Best way to measure resistance between chassis and disconnected earth connector from battery terminal.

Good luck,

Peter

[GoodGriff500]

I did not disconnect the battery to charge it. Though I must confess it was on charge for almost two days as it did not reach the fully charged "green" light ever. I took it off charge and it had loads of power. Fitting the conditioner charger showed it as fully charged. Maybe the normal type charger has damaged the battery over the prolonged charge? How would this cause an engine to initially start and run fine, then over time start to misfire and then to stop altogether? The battery still having enough power to turn the engine for an extended period trying to start the engine.

How do I check the other possible causes mentioned i.e ECU? Should I call the AA to try and fix it or take it the TVR garage?

Many thanks

[GreenV8S]

GoodGriff500 said:

How do I check the other possible causes mentioned i.e ECU?

The simple answer is find somebody who knows what they're doing and ask them to diagnose the problem.

[tivver500]

Sounds just like the problem I had on my 98 Griff 500......
Started ok when cold then went to rat s**t when it got warm.
Fault was traced to the coil - it gave a spark but a very weak one. Easy to check - just undo the mounting bolts and give it a shake - if it rattles get a new one They're not expensive.
Happy Tivving