Misfire, Please help!

[GreenV8S]

Is it a single cylinder misfire? If so, I'd start by checking for problems on the fuel and ignition components specific to that cylinder.

[GreenV8S]

Check the header temperatures to see whether there are any cylinder obviously not working. If that doesn't show it, pull the plugs and see what they tell you.

[Fat Griff]

What do you mean by header temperature? All the plugs are dry and but very sooty.

[GreenV8S]

Exhaust header i.e. the part of the exhaust pipes nearest to the engine.

[AntonyJ]

I think one way of doing what Pete is suggesting is to put a few drips of water onto each header to see which one isnt firing.

Pete?

[spend]

The one that is misfiring will be cooler (easy with an infrared thermometer - well worth £30 they can picked up for - a most useful tool ). Then simply check the ignition & injector on that cylinder.

With no thermometer, plastic cable ties, spit, burnt fingers will have to be used to judge.. Easy if there is no combustion at all, not so easy for an intermittent bang IMHO.

Dave

[Fat Griff]

I'll try and get hold of a Infrared Thermometer tomorrow. Thanks for all the advice, any other suggestions would be greatfully accepted!

[Pasco]

I have known the wires on the Airflow meter causing misfires if disturbed

May be worth checking them out

[wedgienauld]

A difficult one to answer without specific knowledge of your knowledge of such things and your car - but under the circumstances I'd try the following first. Remove your distributor cap and clean it and dry it. Remove each of the leads and clean and dry. Cloth and hair dryer. You don,nt want WD 40 inside the cap on the distributor inside. Most important; clean each of the points inside the distributor, which are contacted by the rotor arm, and remove any signs of electrolytic corrosion, (- white and becomes green in extreme case, here). I use a small pen knife. Be care not to stab yourself or damage the cap. Report back.

[blitzracing]

Fat Griff said:

What do you mean by header temperature? All the plugs are dry and but very sooty.

If they are dry and sooty, its likely to be firing, but running rich. The nearest I think for this is failed connections on the mass air flow meter. It will run very rich, and can be driven, but very rough.

[Pasco]

Up date please Hayden

[wedgienauld]

...yeah - finish the story....

[dumbfunk]

I had this after being caught in a vile European downpour.

About 6" up from the coil are a couple of diodes in line with the Low Tension leads. They're usually wrapped in crappy old electrical tape but if you unwind it you may find as I did that they are wet and corroded.

If so, clean em up and you're golden.


df

[Fat Griff]

Still working on it Guys!!!!!!! I work long days at work you know!

[wedgienauld]

[Pasco]

wedgienauld said:

[Fat Griff]

Getting There!

[Fat Griff]

Right!
I pulled all the ignition of the car and left the plugs out for a few days, put it back together with a new coil, rotor arm, dizzy cap, ignition amp and it now ran on all 8! Great! But it didnt want to idle and was really down on power?????!!!!!!!!!! It started to get worse and stall, but then i saw the light! Literally, the main Cat was glowing! Yep thats had it! All the f4rtin about running my baby with a misfire must of burnt the cat out! So the dead cat was replaced and it idled! But was still down on power after 4,000 rpm. My thoughts were now leaning to the AFM (Air Flow Metre) So tried running it with out it connected and guess what! It ran better on its default mode! So sourced a new 1 and she works and goes fine! So just a little bit of advice to any one that might want to Jet Wash there engine, its not a good idea! Thanks for all the tips guys!

[Big Ashy]

Don`t like the sound of a "glowing Cat", to me, that sounds like your ignition timing is out. Make sure your distributor is secure at the clamp and it doesn`t spin, its worth checking!

[Fat Griff]

The cat glowed because unburnt fuel was entering it, due to the misfire! But its all sorted now