Common causes for Misfiring

[MCFADDEN]

What are the main things to check out that can cause misfiring problems ?

I am condsidering replacing my current plug leads for the Magnecor ones by ACT, not that I am sure this is the problem but they could do with replacing anyway as the existing ones look a bit tired & the extenders are a bit corroded on the outside.

Also took the plugs out this evening & they all look a bit on the oily side as if they are not burning the fuel cleanly.

At times very rough idle, erratic ranging from 850 to 2000rpm & started to miss badly even under acceleration.

It appears to be an intermittent problem as sometimes it runs very cleanly & pulls like it should.

Could it be the alternator not charging the battery enough, as I notice when the fans come on the amp meter drops to the top of the red zone. I have being guilty of letting the battery go flat, but it is on charge now.

What are the other main things to check out & is it likely to be any of the above?

ps - it has had a new stepper motor & plugs 2000 miles ago.

[angusfaldo]

McF

Corroded injectors can also cause a misfire. Though I'd have thought all your suggestions are way more likely to solve the problem.

AF

[colinb]

Could it be the flow meter on the air intake intermitent sticking

[Ballistic Banana]

ps - it has had a new stepper motor & plugs 2000 miles ago.

You'd be surprised how dirty the stepper gets and is so easy to clean its gotta be worth it.

As what AF said cant think of much else meself.

BB

[kevinday]

I suggest a look in Steve Heath's excellent bible. There are a long list of things that cause misfires, the stepper is the easiest to check so try that first.

[Beano500]

Plugs
Caps
HT leeds
Distributor
ECU connectors
Stepper motor
Fuel
Coolant level
Oil condition and level
Those main bl88dy great 80 amp fuses if they're cracked
All seem to have affected mine over the last 35,000 miles......

Phew - loads of possibilities really! It's a wonder they go at all really!

I am about four weeks (1200 miles) away from the next service. Apart from a general TLC session I have the feeling that my plugs could do with replacing. From 2000 up to the red line it seems to be storming, but from cold it stutters a little (foot on throttle gives an initial DROP in revs) and hesitation around 1500-1600. Also doesn't settle to idle so well and not taking off crisply. (Well, they all suffer from that little child school report comment: "doesn't play well with others" )

This sound familiar to others???

>> Edited by Beano500 on Thursday 6th March 08:57

[vodkakid]

on the air sensor (halfway up the big pipe on the right) theres a connector that plays silly buggers on mine, you have to give it a wiggle see if that works? did on mine1

[Podie]

Manifold crack?

[chibbard]

Anthony, I think i have the following in my garage from my old griff 500 to cure an engine missfire:-
1 Set of plug leads
1 Rotor arm
1 Injector
1 Air flow meter
1 Distributor cap
1 Rotor arm
All in workable condition. You are welcome to borrow them in order to sort out your problem. I also live in Essex by the way. Feel free to e-mail if needed.

[trefor]

If it's bad go get it tuned by a specialist. A Mark Adam rechip is very satisfying and turns the car into a much smoother beast low down as well as liberating power/economy etc.

Replacing part after part is not the proper way to do this.

Mind you, if your leads look old then replace them - they do break down over time. Do get plus extenders at the same time. False ecomony not doing so IMO.

T/.