Engine "blip" - loss of power for a fraction of a second

[hanvyj]

I was driving recently and I noticed the engine looses power for half a second every now and again. It seems to get better and worse, at its worse it does it quite often and I can feel the car slowing. Sometimes it does it rarely.

Each time I can notice it as the car gives a little "jerk" and the engine noise lowers for a split second, then its fine.

It happened recently and the car refused to start soon after (ignition problem) after replacing everything except the condenser (spare used a few weeks ago) i got annoyed at having to change the cheap Chinese condensers every few weeks (and breaking down on motorways and other dangerous places) I put a new electronic ignition and coil in. I was planning on changing the plugs but was an idiot and only ordered one - so they are the same but only 6 months old.

The engine is a lot smoother now, drove it maybe 20 miles with no problem then suddenly it started doing it again, so I'm guessing its not ignition related.

I thought it could be a misfire. Any idea what it could be, and how to further diagnose the problem?

Cheers

[hanvyj]

Oh, and before it was fine the vacuum advance was knackered, its only started doing it since that has been replaced... Maybe nothing to do with it though.

[bmcecosse]

Does sound like a loose connection - I would put the old coil back on the car..........

[Chris Edgar]

I have been experiencing a similar problem...very occasionally the engine misses briefly...it may only happen every few days, maybe 2 or 3 times in one day,. I think more so when the engine is under a bit of load i.e. top gear up hill.

The dizzy is fairly new 45D, new plugs, all clean.
Connections seem good.
The coil looks as if it's been on for the life of the car though, so yesterday I swapped it for a coil I know is OK...no misfire since, but sometimes it would not do it every day anyway.

Time will tell, but I do suspect the old coil.

[hanvyj]

Does sound like a loose connection - I would put the old coil back on the car..........

I'll give the contacts a clean and put new leads and plugs on, why do you think I should put the old coil back in?

[bmcecosse]

Because...I would never have changed it in the first place...... " It's 'never' the coil "

[hanvyj]

Because...I would never have changed it in the first place...... " It's 'never' the coil "

Well its done now, and I have a spare for when it never breaks! Since its never the coil, there is little point in changing it back to the old one...

[bmcecosse]

Well no - I should say - " It's never the original coil " - modern coils fail horribly frequently........ Especially if you have been sold a 9 volt coil - intended for use on a ballast ignition circuit. Does your coil get hot??

[hanvyj]

Well no - I should say - " It's never the original coil " - modern coils fail horribly frequently........ Especially if you have been sold a 9 volt coil - intended for use on a ballast ignition circuit. Does your coil get hot??

I got this:

http://www.aseriesspares.co.uk/ignition ... _1107.html

with the new electronic ignition. I'll check next time I run whether the coil gets hot

[bmcecosse]

" High Output ". . . . Oh my.... can't see the voltage listed - my browser won't let me bring the page up. It's probably fine - but something is causing the ignition to drop out - and one time soon it may not drop back in again....

[hanvyj]

" High Output ". . . . Oh my.... can't see the voltage listed - my browser won't let me bring the page up. It's probably fine - but something is causing the ignition to drop out - and one time soon it may not drop back in again....

The reason I don't suspect the new stuff is because it did the same thing with the old distributor & coil... But yes, I am worried its going to get worse and cut out.

[Dean]

Have you eliminated the possibility it's fuel evapouration? We have experienced some warm weather lately, it's not related to the warm weather is it?

[hanvyj]

Have you eliminated the possibility it's fuel evapouration? We have experienced some warm weather lately, it's not related to the warm weather is it?

I haven't, does anyone know a way to eliminate this? I've noticed the fuel line going from pump-carb sits on the top of the engine, which can't be good... Other than trying to move that, is there anything else I could do?

It was fine last summer though, and there were some pretty hot days.

[bmcecosse]

Try a direct power feed to the coil to see if it still happens then. And a temp wire from coil to dizzy for the same check - but don't do both at the same time........

[hanvyj]

Try a direct power feed to the coil to see if it still happens then. And a temp wire from coil to dizzy for the same check - but don't do both at the same time........

Ok

[Chris Edgar]

I had similar symptoms to the OP.
Since changing the coil for a known good one on the 25th March, there have been no further misfires.
The one I used was a"PowerTrain", dated 1991..very colourful!

Often people mention the poor quality of "modern" replacement coils...can anyone suggest a reliable make/ source of good ones ?

[hanvyj]

Replacing the leads and advancing the timing seem to have fixed the issue.

[bmcecosse]

Thanks for coming back with that. It IS 'never' the coil........