Misfiring like a good un......

[Chris49]

Hi all,

Can some one give me a quick checklist for checking and resolving a misfire?

Happens all through the rev range and at all speeds.....

Any help would be great.

Thanks as always guys.

[matc]

I had this on my old car when I 1st got it, turned out to be a coil.

[robox72]

Loose wire on Air Flow Mass sensor ??? Happened to me on my '05 Exige

[delS1]

Mine was doing this (it sounded good actually) until a massive misfire then it wouldn’t start. Turned out to be a loose rotor arm and a very dirty corroded distributor.

delS1

[Lichtgestalt]

Had the same and for it was moisture at the coils and spark plugs (with a bit of corrosion)

[fergus]

also check that the crank signal isn't too close to an HT lead as this can cause enough interference to effect when the coil packs are firing...

[Gad-Westy]

Has it been out in the rain or washed recently?

[Chris49]

Gad-Westy said:

Has it been out in the rain or washed recently?

That was my first thought but she's been kept bone dry for a good week or so now.

[Gad-Westy]

Chris49 said:

Gad-Westy said:

Has it been out in the rain or washed recently?

That was my first thought but she's been kept bone dry for a good week or so now.

In that case, unless there is anything obvious, the first thing you ought to do is get the plugs out and have a look. If you find that one looks different to the others that narrows down the problem nicely. If they all look the same take a picture of them so we can have a look at the colour as it can tell you a lot.

[MadProf]

Yes,I'd agree,check you're plugs first,then HT leads are ok and connected properly.It's that old process of illimination game.

[wetny]

Mine had a good bit of moisture down the plug well. Usually plugs, leads, dis cap roter arm. Remeber not to over tighten the plugs if you get them out. Threads are soft.

[Chris49]

If I get the car over to a stealer will they be able to use some plug in wizardry to diagnose the problem?

Could save me a day of poking around!

[Gad-Westy]

Chris49 said:

If I get the car over to a stealer will they be able to use some plug in wizardry to diagnose the problem?

Could save me a day of poking around!

It'll depend what the problem is. The S1 diagnostic (does the standard car even have it, I know the 111s does) is fairly primitive. It'll probably tell you if a sensor has failed but maybe not tell you much about the state of the ignition system. Whip the plugs out and we'll try and give you an online diagnosis.

[mrssumner]

Gad-Westy said:

Chris49 said:

If I get the car over to a stealer will they be able to use some plug in wizardry to diagnose the problem?

Could save me a day of poking around!

It'll depend what the problem is. The S1 diagnostic (does the standard car even have it, I know the 111s does) is fairly primitive. It'll probably tell you if a sensor has failed but maybe not tell you much about the state of the ignition system. Whip the plugs out and we'll try and give you an online diagnosis.

The standard S1 111 does have a diagnostic facility ("Lotus Check" scanner tool), but it has two less functions than the 111S (just reading the service manual... I am sad...)

For a standard car it does:
PRE-TEST - check whether any faults have been detected since last pre-test
TEST - runs test sequence for various engine management components
LIVE DATA - enables current readings from various sensors to be displayed

[RobM77]

My cambelt slipped last month... it just sounded like a hammer drill through the rev range. No damage done thankfully.

[Gooby]

Isolate if it is ignition or fueling problems. This can be done in a basic way by smelling he zorst. If it smells of unburnt fuel then "probably" there is fuel being delivered. Run through the ingition circuit. Plugs, leads, coil and dizzy (both cap and rotor arm). If there is no resolution then try the temp sensors. (2 on a K series).

[Chris49]

One of the plugs was standing in about 1/2 an inch of water!!!

A dry and new plugs and shes all better!

[RobM77]

Chris49 said:

One of the plugs was standing in about 1/2 an inch of water!!! A dry and new plugs and shes all better!

ah... :-) that's a common k series problem. One of my friends sealed his plug cover on top of the engine with mastik to avoid that happening.

[Mr_C]

RobM77 said:

Chris49 said:

One of the plugs was standing in about 1/2 an inch of water!!! A dry and new plugs and shes all better!

ah... :-) that's a common k series problem. One of my friends sealed his plug cover on top of the engine with mastik to avoid that happening.

they can get a bit of condensation down the holes if you seal it too well though...