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Discussion Starter · #1 ·
Hello,

I've finally got my engine back in and everything working and it passed its MOT yesterday!

Still getting a random misfire though and am now beginning to suspect the dissy. This is a '93 MX-6 v6

Symptoms:

Idles ok but occasionally drops a spark about once every 10-30 seconds
Sometimes runs ok
Sometimes will idle fine, then when accelerating at low revs will only run on 5. If I lift off and try again often it picks up.
Is usually ok at high revs

What I've tried:
New dissy cap
New arm
New HT leads
New plugs
Reseating all cables
Checked timing
Checked codes - non showing except 69 which is for the fan/temp-sensor that I've not yet fitted.

I'm now ready to believe the dissy is broken but what should I try first I notice that RocSpeed sell two parts for the dissy. A "module" and a "coil pack" which should I try first?

Any advice gratefully received

It is so nice to go for a drive in a proper car - been stuck in a 323F for the past nine months....just not the same!

Cheers

Dom
 

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Have you checked the power coming out of your battery? Sometimes the wattage coming out isn't sufficient to keep a consistently powerful spark.

Ben.
 

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Discussion Starter · #4 ·
Thanks,

I'm pretty sure its not the battery. I've got a nice pile of good batteries...the current one is good enough to hold a charge for several months and then start an ancient bus - I've done this a few times - a six litre turbo diesel from '74 takes a bit of turning over and this battery is up to the job and gives a perfect reading. Also I did check the alternator a while back just in case and all seems well with that.

Like I say I reckon that the dissy is a bit weak and have heard that the 93-94 ones have issues-just not sure whether to go for the module or the coils....

Cheers

Dom
 

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I've just had very similar problems with my v6 , got over it by changeing the dizzy -cap from a cheap one to a good quality one . The cheapo had only done about 8k but was showing signs of "arcing" inside. The one we put on yesterday has made all the difference ( intermotor from probestore £25.99) .
 

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Discussion Starter · #6 ·
Hi lads,

I did some more testing yesterday. I went for a 300mile trip on back roads and gave it a bit of stick.

The mis-firing got worse after about an hour or so and stayed the same. When I got back I tried in desperation swapping to some very old used plugs. These are jap NGK ones with very fine platinum tips this cured the problem to some extent - just the odd misfire now but nothing like as bad as it was, just the odd mild stutter when going through 2-2.5k revs, with the other plugs and everything warm it was struggling from idle up to about 3.5k revs...

The other plugs were the Bosch +4 copper core ones. I had no problems with these in either my 626 2.0 or my 323F but this car must have issues. Again I reckon this is down to either the coils or the control module in the dissy - the rotor and cap are brand new and spotless no sign of arcing or whatever.

So I'd still really like to know whether to go for the coils or "module" as I can't afford a whole new dissy at £200!

Cheers

Dom
 

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theres a brand new dizzy listed for a v6 Probe on ebay for £75 buy it now. Looks like a genuine part and has the numbers so you can check compatability.
 

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Hi Dom

I know you don't think it's the problem but my money is on the battery efficiency. Your alternator may be at fault. Your symptoms are more drastic than mine but are the same with your 2k - 2.5k revs. I am using more efficient irridium plugs making the most of a battery working at 70%. They do miss but rarely.

My mechanic made it sound so simple when he told me what was wrong but it's something to do with the engine temp etc. When you start up you get no missing because the fuel is rich - easier ignition. When the engine has heated up the mixture is less rich and the weak spark sent by a less efficient battery leads to ignition failure.

I have 2 calcium batteries. I've used both at 100% effieciency but soon go down to 70% because of a faulty alternator.

Wouldn't faulty coils or modules be there all the time?

Elmer
 

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It's the Dizzy....infamous for this. I just changed mine in AUS off my 92 (93-94 in US). They fail due to heat from being attached to the head of motor! Change the rotten old thing & give yourself some peace & change Leads & Plugs too!!!! P.S. It is the Ignition Module/Modulator that fails from Heat!
 

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Discussion Starter · #10 ·
Thanks all, for the replies.

As I've said before I've tested and retested the batteries. I've got several from a 626, MX6 and a 323F all work fine in the other cars and will cold crank a 6 litre turbo diesel bus engine without breaking sweat!

Thanks for the ebay tip but I think I'll get a seperate module as it comes with a 3yr guarantee...

I'll get a modulator thing for the dizzy, shame the one on my 323F which is being broken for spares doesn't fit!

Dom
 
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