Crossflow misfire

[John Ryan]

The last couple of times I have been out the same problem has occured.

 

Car starts fine, and runs really well for 15-20 minutes. It then starts to mis-fire quite badly, on any throttle setting. On Saturday, I thought the RAC were going to get a call.

 

It's on electronic ignition, and is not overheating, so I am thinking leads / coil, and I am going to order new ones. Has anyone got any other ideas?

 

What are the best leads to go for?

[Graham Sewell]

Last time this happened to me - it was the alternator going awol and causing the battery not to charge. Once the voltage dips below 11V the electonic ignition starts to fail.

 

Cheers,

 

Graham

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Low tech luddite - xflow and proud!

[Graham Perry]

The Coil might be breaking down when warm

[John Ryan]

Thanks Grahams!

 

I don't think it's the alternator, as the battery never goes flat.

[Graham Perry]

A couple of other things.

 

I have seen the coil lead to the dizzy also give trouble when warm.

 

A classic crossflow problem is the wires leading to the alternator where they run near the exhaust manifold. There are numerous cases in the archive of these breaking down internally due to the heat and causing strange things to happen.

[Horizontal]

Hi John,

 

As Graham said above, check the coil/dizzy lead. I had the same symptoms and after a lot of checking and replacements it turned out to be the lead only half connected at the dizzy. It had made a nice black and burnt mess inside the connection. Some days it would work perfectly, but over time it got more frequent.

Best of luck

Richard

 

Sylvia Silverstone on 45's

[John Ryan]

As the parts are fairly cheap, I am going to replace the coil and all the leads and see if that fixes it. I will also have a look at the alternator wiring at the same time.

 

Thanks for the pointers chaps.

[KeithT]

Please let us know how you get on.

My car was running fine then developed a misfire. Might run ok for a few minutes only. Cant find anything obviously wrong.

Have been experiencing intermittent starting problems and the engine has cut a few times (but not lately) so its off to Millwood next week and hopefully will be sorted.

 

[Setok]

A couple of things to check:

 

* If you have a master key, check if any of the cables are loose or disconnected. I wrongly assumed that if they were, I'd get no power whatsoever and thus did not bother to check. That was not correct.

 

* The cable from the electronic ignition. Check connections for corrosion and give them the scraping treatment.

 

After sorting those two things my own Crossflow has been running great!

 

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Kristoffer Lawson

[Steve C]

Do you have a rev limiter fitted? If so , i solved a misfire which occured at various changing points in the range as the lumenition limiter gave up the job. By pass it to test.

 

'Go on do that thing when your carbs catch fire'

[John Ryan]

Well, finally had a chance to fit the new coil and leads. Complete sod of a jod due to the carbs...

 

Result, still doing it.

 

(goes off to open bottle of wine)

[F355GTS]

John

 

The BDR will do this after 15 to 20mins when the Alternator wires/ connections become corroded/ dirty, it doesn't affect charge. Pull the plug on the alternator, thoroughly clean, brighten and tighten the plug connectors, then give it a go. If you have a Batt Master Switch it's important the connections are als ochecked/ tightened

 

Mark

[Paul Formston]

Hi John just a thought have you checked the tappet clearance as if the tappets close up when the engine gets hot it could hold the valve open and a misfire would happen esecially if you have got them set a little tight to keep the noise down 😬 Regards Paul

 

 

 

 

 

Edited by - Paul Formston on 29 Aug 2007 20:03:57

[Molecular--Bob]

Mine did exactly this, running ok till warm then missfiring and losing power to the point where it would hold no load at all, and it seemed to be a combination of things.

 

The fuel pump was pulling a partial vacuum in the tank, and eventually lost the battle and emptied the carbs, so i sorted a better breather, which helped, but didn't fully fix it.

 

Changed the coil,and plug leads, made no difference.

 

Had the carbs tuned, not much better.

 

Took it to a back street mechanic who at least knew what a crossflow was, who said that the exhaust tappets had closed a little and that the distributor had shifted due to not being locked, took 5 mins to reset and its been good since.

[John Ryan]

Update

 

Eventually I began to get paranoid about this misfire, as I thought I had changed everything that could cause it, as well as checking the timing and the tappets. Finally found out that the NEW coil I had bought from a reputable supplier was duff

 

So, yesterday I am on my way to Penn for the meet, car running really well, when the brakes started failing. I only just limped home before they went completely.

 

Bu**er