Misfire Under Load.

[sir john]

The LS was laid up for a couple of months, August-dec, and has only done about 500 since. She ran faultlessly before but today there was a definate misfire under load, going up steep hills. It seems to happen at about 2000-2500 rpm. On a very steep hill i could feel it misfiring so i floored it. The old girl wouldnt pick up and go. She just wouldnt rev past 3500rpm. On the flat and motorway there is no sign of a misfire.

When i got a chance on the flat i floored her again. She kicked down and was off as if nothing was wrong.

In the past 12 months she has had 8 new spark plugs, new rota arms and disi caps. but somethong is amiss.

Im planning to have look tomorrow, but for now, any thoughts.

[steveskeggy]

You could try the leads, seeing as you have replaced everything else!

Apart from the leads, you could try the fuel filter:

http://www.lextreme.com/fuelfilter.html

Dont know if that article covers your car, but it should give you ideas.

It could be a perished pipe, have a look around the engine bay to see if there are any rubber pipes that look dodgy.

The fuel pump could also be the culprit.

Looks like this could be a fishing expedition for you.

[ROYT]

You could try the leads, seeing as you have replaced everything else!

Apart from the leads, you could try the fuel filter:

http://www.lextreme.com/fuelfilter.html

Dont know if that article covers your car, but it should give you ideas.

It could be a perished pipe, have a look around the engine bay to see if there are any rubber pipes that look dodgy.

The fuel pump could also be the culprit.

Looks like this could be a fishing expedition for you.

Also try looking inside the distributor caps for 'tracking' or damp or general wear...

[sir john]

You could try the leads, seeing as you have replaced everything else!

Apart from the leads, you could try the fuel filter:

http://www.lextreme.com/fuelfilter.html

Dont know if that article covers your car, but it should give you ideas.

It could be a perished pipe, have a look around the engine bay to see if there are any rubber pipes that look dodgy.

The fuel pump could also be the culprit.

Looks like this could be a fishing expedition for you.

Thanks for the link. I bought a fuel filter last time i serviced the old girl but didnt fit it because it looked like a faff. I still have it but the tank is full just now. So i will do that when ive exhausted everything else.

HT leads was my first thought though. As for perished rubber pipes: they all look good as nnew.

Im also gonig to get something called "air induction cleaner" or something like that.. A mechanic told me about it. Apparently its an airasol that you spray into the air intake.?

[Manc]

Forget all the above 1st, its usually the throttle body - http://www.lexls.com...rottlebody.html

It happened to me, it gets worse and starts happening when pulling away from lights or out onto main roads.... believe me!!!

Easy to do yourself in an afternoon at minimum costs... around £5 for some cleaner...

And at £5 its worth doing this 1st as sensors etc cost a small fortune and if you read posts, do not always solve the issue..

Half hour stripping the intake system down (like the p/s o-ring replacement..), unclipping the 3 accelerator cables and taking the throtttle body off (4bolts???),

half hour giving it a good spray & clean - the throttle body has thick black carbon in and you will see pin-hole nozzles that get blocked up - this starves your car of air & causes it to 'choke'

Try this 1st!!!!!

[steveskeggy]

Forget all the above Try this 1st!!!!!

Nice, love the attitude.

Its no wonder I hardly ever come on this site anymore.

[sir john]

Forget all the above Try this 1st!!!!!

Nice, love the attitude.

Its no wonder I hardly ever come on this site anymore.

Thanks for ALL the ideas. I appreciate both your responses (steveskeggy and manc) and opinions as to the likely causes and cures. Not forgetting Royt`s sugestion of course. Damp Disi caps are not good news.

steveskeggy; im sure manc meant no offence and i hope you continue to be active on the forum. Our community of enthusiastic owners who are interested in helping each other is extremely valuable to us all.

I didnt get time to look into it at the weekend but i will in the next couple of day; we are on a 660 mile round trip at the weekend.

Thanks again for all who responded.

[sir john]

Running out of time this week to get it into the workshop and follow uop on everyones advice etc but i was out in the LS seeing clients today and it didnt miss a beat. Ive given it a double shot of Redex today anyway and ill give it another double when i get to Suffolk on friday (she`ll be empty by then and needing a fill up).

[steve2006]

Could well have been damp in the ignition HT areas which has now dried out hopefully this will be the end of your misfire.

[sir john]

Hi steve. Hopefully you are right. If so, all i have to fix is the indirect steering habit and wondering sensation.

[sir john]

A quick update..

just back from the 660 mile weekend trip. 6 shots of Redex through the engine and still misfiring and low on power under load. I can just feel a slight misfire cruising down the motorway but it wont accelerate on the motorway as it should.

Looks like the Redex didnt work and a service and throttle body cleanout is on the cards.

Having said all that: its still smoother than any other car, even with the misfire :P