M.m.m.m.misfire

[lazyitus]

Right, here we go. Please offer as many opinions as you can. I have the most annoying intermittent misfire on my Griff 500.

Symptoms

Occassional misfire, hot and cold. After 1 minute or after 20 minutes. It takes its pick.

Normally under acceleration but not exclusively.

8 times out of 10 the problem will be cured if I turn the engine off and restart it. Only to happen again shortly after.

I can have this misfire 5 times in a 30 minute run OR zer0 times on an hour and a half blast.

I've (so far) done the following...

Had new HT leads
Had new Dizzy Cap
Had new Rotor Arm
Cleaned the Stepper

I love my car to bits which makes this even more annoying. Its like sleeping with the most beautiful woman in the world but her breath stinks every other time you sleep with her.

Please, please help me cure this (what surely must be a simple) problem.

Cheers
Lazy

Please go easy on the lingo. I'm not technically minded. At all.

ETA- A couple of independents have tried to cure the problem (mainly by doing the above) but have failed.

>> Edited by lazyitus on Tuesday 16th August 09:38

[Podie]

seasider said:

Loose connection HT/LT or in the footwell ECU/Fuse/Relay. or on the fuel pump

What he said...

[lazyitus]

Podie said:

seasider said: Loose connection HT/LT or in the footwell ECU/Fuse/Relay. or on the fuel pump What he said...

Have you both put this because you've had similar problems?

[Podie]

lazyitus said:

Podie said: seasider said: Loose connection HT/LT or in the footwell ECU/Fuse/Relay. or on the fuel pump What he said... Have you both put this because you've had similar problems?

Nope, (touch wood) not had this problem with mine, but know of a few people that reported similar symptoms.

Turned out to be the spade connector to the fuel pump in one case, and the fuse to the fuel pump in another.

Check the resistance of the HT leads to make sure it's not there, but other than that I concur with Seasider.

[lazyitus]

Cheers Podie,

That gives me something to go at tonight.



Any other offerings, folks?

[seasider]

Podie said:

lazyitus said: Podie said: seasider said: Loose connection HT/LT or in the footwell ECU/Fuse/Relay. or on the fuel pump What he said... Have you both put this because you've had similar problems? Nope, (touch wood) not had this problem with mine, but know of a few people that reported similar symptoms. Turned out to be the spade connector to the fuel pump in one case, and the fuse to the fuel pump in another. Check the resistance of the HT leads to make sure it's not there, but other than that I concur with Seasider.

What he said, apart from i'm not sure i know the same people

Another thing might be the resistor pack next to the coil...

[lazyitus]

seasider said:

What he said, apart from i'm not sure i know the same people Another thing might be the resistor pack next to the coil...

I take it that it might have been you, seasider?

[seasider]

lazyitus said:

seasider said: What he said, apart from i'm not sure i know the same people Another thing might be the resistor pack next to the coil... I take it that it might have been you, seasider?

Nope...
Don't think Paul knows about my loose connection

I fg hate electrical problems...

basically coz I'm st with electrics

[Podie]

lazyitus said:

seasider said: What he said, apart from i'm not sure i know the same people Another thing might be the resistor pack next to the coil... I take it that it might have been you, seasider?

Didn't know Seasider had experienced these issues... (actually, have you..?)

I talk to a lot of people and if they've had problems it's always nice to know what the fix was...

[griffter]

lazyitus said:

Right, here we go. Please offer as many opinions as you can. I have the most annoying intermittent misfire on my Griff 500. Symptoms Occassional misfire, hot and cold. After 1 minute or after 20 minutes. It takes its pick. Normally under acceleration but not exclusively. 8 times out of 10 the problem will be cured if I turn the engine off and restart it. Only to happen again shortly after. I can have this misfire 5 times in a 30 minute run OR zer0 times on an hour and a half blast. I've (so far) done the following... Had new HT leads Had new Dizzy Cap Had new Rotor Arm Cleaned the Stepper I love my car to bits which makes this even more annoying. Its like sleeping with the most beautiful woman in the world but her breath stinks every other time you sleep with her. Please, please help me cure this (what surely must be a simple) problem. Cheers Lazy Please go easy on the lingo. I'm not technically minded. At all. ETA- A couple of independents have tried to cure the problem (mainly by doing the above) but have failed. >> Edited by lazyitus on Tuesday 16th August 09:38

Can you smell fuel when it misfires? Does the engine want to stall, just flutter a bit or somewhere in between?

It could be anything:

duff spark plug(s)
duff spark plug extender(s)
coil
ignition amplifier
electromagnetic interference causing duff spark
sticky fuel injector(s)
sticky vacuum advance valve
sticky vacuum advance mechanism
duff fuel pressure regulator
blocked fuel tank vent valve / carbon cannister
blocked fuel pump
blocked fuel filter
fuel pump on the way out
dodgy fuel pump or ecu relay
dodgy earth
dodgy connection
dodgy wiring
dodgy sensor (afm / temperature / throttle pot / lamda etc...)
bent ecu
etc...

The symptoms sound similar to mine, and I've thrashed out most of the above to no avail. It must be one of the things I haven't tried then!!

Your options as I see them are:

1) Give it to a specialist to be collected only when the problem is guaranteed eradicated (£££)

2) Check/replace things bit by bit until the problem is eradicated (££)

3) Wait until it breaks down for good and then get it sorted (£).

[GreenV8S]

Misfire under power can be a sign of a weak spark. Intermittant nature of the fault also 'feels' like an electrical problem. Lost track of all the ignition bits you have changed but don't think you mentioned the ignition module?

[Ballistic Banana]

Lazy I have a spare module if your coming to the Growl I'll bring it with me for you to try?

[griff430]

I had what I thought was an electrical problem on my Griff, but it was eventually traced to a duff airflow meter. I took it to a TVR specialist, but he was stumped. I have a mate who works in a Rover garage, and he said he'd take a look. He did a straight swap with a Range Rover airflow meter, and it cured the problem. Put the original meter back on, and the problem reappeared. I ordered a reconditioned unit from ACT (very fast delivery!!), and the car has not missed a beat since.

Not sure if this helps, but if you can get hold of a spare airflow meter (or borrow someone else's for a couple of days, because they're easy to change!!), it may highlight the offending item??

Dan.

[lazyitus]

Griffter said:

Can you smell fuel when it misfires? Does the engine want to stall, just flutter a bit or somewhere in between? It could be anything:

I smell unburnt fuel, yes. Its stalls occassionally and it flutters in between.

Your list is massive so I'll try the easy things first.

GreenV8s and BB said:

Ignition module

I'll have to see what that is when I get home. I'll have a look in the bible. (Simon, don't think I'll manage the Growl this year unfortunately, cheers anyway)

Griff430 said:

Airflow Meter

Another 'easier' option. Cheers.


Thanks to all so far - I will systematically try the suggestions. I'm determined to sort this out once and for all.

Lazy.

[rfisher]

Check for ECU fault codes.

www.pistonheads.com/sales/48467.htm

[red griff 500]

Sounds suspiciously like ignition problems - Can't remember whther you mentioned coil, but try a different coil if you can borrow one.

Also, I recently had a misfiring experience which I solved by slightly adjusting HT leads - I would definitely recommend carefully looking at all ignition leads in a pitch black garage (watch out for those fumes) - it has to be so dark that you cannot see your hand a few inches away. Then spend a good few minutes looking for blue flashes - you'll need to occasionally shine a torch to find the area you want to look at. It takes about 5 minutes or so for your eyes to adjust - at first you see nothing, but after 5 mins you can see blue flashes all over the place (assuming they're there in the first place). You are not looking for "sparks", but "flashes". These weaken the spark. Locate the "shorts" which are causing the flashes and move the HT lead away from the offending item/surface.

It's worth doing just to eliminate it from your enquiries.

Oh, and I like your reference to the beautiful woman - brilliant analogy!

Good luck!

[simon.b]

Have you checked that the plug cap covers are not close to the manifolds.

One of mine was a loose fit and used turn and touch the manifold earthing itself. Have a look at the engine under load in a dark garage you should immediately see any shorts.

Cheers,

Simon.

[stringbag]

I think it is your coil breaking down. Is it leaking fluid?
You can always borrow one and see if that helps.
One thing to strike off the list anyway!
I think £10 borrowing the ECU fault reader might also be worth a bash.

[andy43]

I went thru a similar with my now written off precat - no-one, and I mean no-one, could suss out a dodgy idle prob, until it went in to Camco in Warrington - they sorted it, can't remember labour charge exactly but it was under £200, parts costs precisely £zero.
If you're at your wits end, give'em a try
They do a lot of Range Rovers and ECU recons, so the Lucas V8 is something they seemed to know inside out.
SFR have a code reader for the ECU, it's only 30 secs to get the fault codes out.

>> Edited by andy43 on Wednesday 17th August 18:49