75 Twin Spark misfire mystery - Alfa Romeo Forum
You are currently unregistered, register for more features.    
Thread Tools Search this Thread
(Post Link) post #1 of 4 Old 15-04-14 Thread Starter
Status: Thinking Giulietta QV...
AO Silver Member
Unkle Munkle's Avatar
Join Date: Mar 2003
Location: United Kingdom
County: -
Posts: 1,476
75 Twin Spark misfire mystery

Hi all,

Some time ago, the 75 developed an intermittent misfire. However, it was almost like the car was stalling and starting again - the rev counter dropped and it re fired in a split second. Not ideal though! Nasty kangerooing and very frustrating.

I checked the leads, replaced both coils and dizzy caps. I also changed both king leads with decent quality brand new leads (coil to distributor) and this seemed to remedy the problem.

However, after a few months off the road at winter, the misfire is back. Not as often. In fact, very intermittent but when it 'strikes' it's bad and you end up driving by the seat of your pants. Not sure what to do, where to look now. Getting really fed up with it. Short of replacing all the plugs, leads, both distributors, I don't know where else to look.

The car used to run like a dream and was a joy to drive. I'm ending up getting really hacked off with it and don't really have the time (and certainly not s to spend) sorting it out!

Something is failing somewhere. You would have thought, as a twin spark, that even if one 'bank' of electronics failed, the other would compensate but it appears not!

Any suggestions / ideas / obvious things to look out or try?

Rockin' all over the road!
Unkle Munkle is offline  
Sponsored Links
Status: -
AO Member
Join Date: Jan 2009
Location: United Kingdom
County: Surrey
Posts: 48
I would disconnect one coil module at a time and run it like that to see if you can work out which set the missfire comes from i.e. make it a "single" spark.
If that then shows up one set has the fault only half as many bits to check !
gary orchard is offline  
Status: Village Idiot
AO Member
Jim Spackman's Avatar
Join Date: Dec 2012
Location: United Kingdom
County: Cardiff
Posts: 365

Member car:

75 TS

Take a look at the multiplug that connects to the airflow meter. I had similar symptoms caused by dirty connections in here once. WD40 cured it.
Jim Spackman is offline  
(Post Link) post #4 of 4 Old 16-04-14 Thread Starter
Status: Thinking Giulietta QV...
AO Silver Member
Unkle Munkle's Avatar
Join Date: Mar 2003
Location: United Kingdom
County: -
Posts: 1,476
I think I've hopefully cured it. I discovered three HT leads were very loose over their respective spark plugs so could have been causing some sort of shorting out. The leads were quite taught too so I pulled through a bit more slack towards the engine and they are also being held down with the trim plate that fits over the top.

Seemed to be singing along nicely this morning so fingers crossed for an obvious and simple fix!
Unkle Munkle is offline  

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Alfa 75, RZ, SZ

misfire , mystery , spark , twin

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

For the best viewing experience please update your browser to Google Chrome