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PostPosted: Sat Oct 20, 2018 11:19 am 
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Location: Wollongong
This is a problem I’ve been chasing for a while. It’s quite frustrating because it comes and goes.

For example I took the car for a 45min drive this morning and it ran really well apart from a very occasional miss. Then suddenly it started to miss and run rough/badly during acceleration. (Tacho stays steady) Then it comes good again. Then it got so bad it was doing it for about 15 min.


I swapped dissy caps, plugs and leads and still happened. Coil is new GT40. Electronic ign module is new. All connections are solid.

Compression is good on all cylinders. Plugs all look same and clean and light brown colour.

The mechanical advance on the dissy is locked and I’m running a black box. I’m really becoming suspicious of my “Stealth” advance unit not operating correctly.

I’m open to suggestions as to other things to check.

I’m pretty sure it’s not fuel related as it has a quite definite feel about it, like when you lose a lead or have a wet dissy.

I have a video of what happens and if I can upload it I will

Thanks in advance.

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PostPosted: Sat Oct 20, 2018 12:20 pm 
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Joined: Sun Apr 11, 2004 11:32 am
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phillb wrote:
Electronic ign module is new.


Don't mean a thing in this brave new world we live in...if you can bypass the module, do so to see if it is the cause of your problem :idea:

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PostPosted: Sat Oct 20, 2018 4:54 pm 
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I just fitted a brand new Bosch GT40 with a Chinese electronic dizzy and had an issue with misfiring under heavy load at 4000+... Switched back to the 40 year old no-name coil that was on the car before and the problem went away...

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PostPosted: Sat Oct 20, 2018 6:49 pm 
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I did mention a few years back that Bosch didn't recommend the use of the GT40 coils with electronic ignitions.


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PostPosted: Sun Oct 21, 2018 9:18 pm 
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Morris 1100 wrote:
I did mention a few years back that Bosch didn't recommend the use of the GT40 coils with electronic ignitions.

Well, I've been running my GT40R for 25+ years with a Pertronix ignitor, then a Pulsar dizzy, then an Accuspark Stealth black box.
It's still going. Australian Made Quality. :mrgreen:
I think the Bosch coil problems started when they moved production to China... :wink:

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PostPosted: Fri Oct 26, 2018 6:54 am 
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Convertible mini suggested it sounded more like a fuel supply issue. I had been thinking of replacing the old Ecco pump with a new Su unit. Swapped it over and took it for an extended drive and it seemed to behave.

Thanks Tony, fingers crossed.




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PostPosted: Fri Oct 26, 2018 9:34 am 
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If it does prove to be a fuel issue...check tank(s) for sediment, fuel filter and lines right up to the Carby(s)

[and then maybe pull top of float bowl(s) etc looking for gum and sediment etc]

:idea: :)

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PostPosted: Fri Oct 26, 2018 4:01 pm 
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Yeah Thanks. I had already replaced the filter. Tanks and bowls are clean. I’m running out of things to check actually.


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PostPosted: Fri Oct 26, 2018 4:52 pm 
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phillb wrote:
Yeah Thanks. I had already replaced the filter. Tanks and bowls are clean. I’m running out of things to check actually.
Sent from my iPhone using Tapatalk


Bad load of fuel then :(

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PostPosted: Fri Oct 26, 2018 6:17 pm 
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Some metho in the tank of my old camry cured missing when I got some bad fuel with water in the tank even after I'd drained the tank.

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PostPosted: Fri Oct 26, 2018 6:57 pm 
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fuzzy-hair-man wrote:
Some metho in the tank of my old camry cured missing when I got some bad fuel with water in the tank even after I'd drained the tank.


Yep...that's another possibility...

https://autoexpert.com.au/posts/qa/how- ... -fuel-tank

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PostPosted: Fri Oct 26, 2018 7:41 pm 
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Not burning? Something wrong with the fuel or something wrong with the spark.


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