Misfire

[rip]

My Elan developed a misfire recently. It was fine on the journey out but after leaving it parked for about 20-30 minutes, it was missing 1 or 2 cylinders.
I have troubleshot this from the engine backwards..
The old plugs had been there 6 years, so I have replaced these.
When removing the leads, I found that No 1 had brokeen, leaving the connector on the plug. After a 2½ week wait, these have now been replaced.
I was confident that the broken lead was at fault, but when I tried it yesterday it was fine until I started it after leaving it 20 minutes. On the way home it was misfiring exactly the same as before. It had a brief moment of running normally, but this was only about ¼ second....so this suggests to me an ignition issue.
The coil packs are MSDs which were fitted in September 2008 & have covered 22000 miles.

Has anyone seen this before? It seems that I have to get the engine hot to replicate the fault then let it cool to work on it...so locating the fault would be a lengthy process.

[Dave Eds]

Time to phone Unlcle Gerald

[rip]

I had considered that, but I thought someone on here may have come across the same symptoms before.
I may as well buy a pair of MSD coil packs. If it turns out not to be them, then I will have spares.

[lotusflasherman]

I had a problem with mine that it ran fine when cold but then started missing when it got hot - but mine was missing across all 4. I eventually cured it by changing the Coolant Temperature Sensor that provides info to engine management system, not to be confused with the sensor that exists just to drive the temperature gauge.

When you've got the 'only running on 2 situation' have you tried removing plugs and putting back on HT leads and cranking engine to check which are sparking and which aren't? That's what I'd do to confirm whether it's electrical or fuel issue to start with..

[Rob P]

I'm assuming that you haven't had any fault indications thrown up? I've had engine misfiring a couple of times and eventually the car threw up a Code 22 issue which was down to the TPS. changed that out and all was solved, it did feel very much like an ignition issue when it first occurred and there wasn't the fault code to guide me
Hope you get it sorted I know what it feels like to chase faults round these cars

[dapinky]

In the absence of a definative answer to Phils advice above (which is always a good place to start), I'd suspect that maybe the multipin plug/socket for the injectors may not be making a good connection at all times.

Particularly as you will have disturbed them to some extent whilst changing plug leads.

Always worth giving them a wiggle to either cure or cause the same symptoms so you know where to direct potential repairs.

[dunnlor]

It's not clear to me that it's an ignition problem. I'd try to determine which cylinder(s) aren't firing. This may help to direct your attention to an individual cylinder, a fuel injector pair, or an ignition pair.

Tom

[rip]

Particularly as you will have disturbed them to some extent whilst changing plug leads.

But I only disturbed something after the initial fault.

Always worth giving them a wiggle to either cure or cause the same symptoms so you know where to direct potential repairs.

I agree.

[rip]

It's not clear to me that it's an ignition problem. I'd try to determine which cylinder(s) aren't firing. This may help to direct your attention to an individual cylinder, a fuel injector pair, or an ignition pair.

Tom

Easy to check the ignition except it only seems to occur when the system is hot, but fuelling/injectors are more difficult to check.
My first course of action was to look at the condition of the spark plugs, which is when the lead broke. They were consistent (& good) across all 4 cylinders although the fault had only just occurred.

I've not discounted the possibility that more use will help it, but I'm not placing too much faith in this.

[lotusflasherman]

Have you had a Check Engine Tell Tale light up indicating an error code or not?

When mine played up due to the wayward Coolant Temp Sensor I had no error codes - the Engine Management just thought engine was cold and supplied mixture for that, which was too rich for a hot engine so it ran very lumpy or stalled.

Are you sure yours isn't doing the same ... or is it running OK but on just two cylinders? I can't see how an electrical issue with coil packs or plug leads would come and go with temperature...

[dapinky]

....... seems to occur when the system is hot, but fuelling/injectors are more difficult to check.........

Who told you that?

Have you forgotten the great advice given to me many moons ago by the guru who is known simply as "Gerald"?

[rip]

....... seems to occur when the system is hot, but fuelling/injectors are more difficult to check.........

Who told you that?

Have you forgotten the great advice given to me many moons ago by the guru who is known simply as "Gerald"?

Must have missed this before. Easy test though.

Phil: some good points. No CEL & I've not hooked up the laptop yet.
Weird thing is that the engine starts from cold & runs fine when warm..until I leave it for a few minutes then try to start it again.

Maybe Elanscan will reveal something useful.

[GeoffSmith]

Weird thing is that the engine starts from cold & runs fine when warm..until I leave it for a few minutes then try to start it again.

Maybe Elanscan will reveal something useful.

Are you open or closed loop?

[rip]

Open loop.

[lotusflasherman]

Phil: some good points. No CEL & I've not hooked up the laptop yet.
Weird thing is that the engine starts from cold & runs fine when warm..until I leave it for a few minutes then try to start it again.

Maybe Elanscan will reveal something useful.

That is weird - and sounds irrational, therefore must be in electronics.
I think anything to do with computers is essentially female - uses fuzzy logic, does multitasking so does lots of things at the same time, none of them properly.
(Only joking ladies.)

Be interesting to learn what Elanscan tells you. I must get it myself some day.

[rip]

Update on this:
GST diagnosed a faulty injector on No.4 cylinder. It passed the basic test but they had some piece of equipment which gives it a more thorough test.
It seems that a faulty injector takes out its pair too. These are together in the firing order so I'm amazed it worked at all.

[Ian T]

Thanks for posting the cause - there are lots of open threads where I've found the problem either never got solved, or at least never got the solution posted.