2005MY 4200 CC Misfire

M

Musto

Junior Member
Messages
37
Hello guys,

I have found your forum whilst searching for help with a sudden misfire on my coupe, I came back from the Silverstone classic, 700 mile round trip with no problems. Come to fire her up the next day to find what I think is a misfire, EOBD comes on, eventually followed by Slow Down message, which eventually goes off. I suspected an issue with a plug causing unburnt fuel to hit the cat, creating too much heat. Stripping her down to get at the plugs, I have found one that looks a little oiled up, which could be the misfiring issue. But more interestingly all the plug bores have a degree of what looks like engine oil in them, in some cases quite a lot, say a teaspoon full, one of the worst affected bores was of course the worst plug and the oil had reached up to the rubber coil lead. Is there an expert mechanic out there that could offer advice (other than replacing the seals which I will get round to) at the moment I am planning to simply clean the oil off, clean the offending plug and refit them all to see what happens.

Also I have been reading about your use of Denso plugs, how have you all found them.

I live in the frozen north and currently have my car serviced at JCT600 in Leeds, but I have just come across AutoShield south of Manchester, has any body got any experience of dealing with them.
 
lozcb

lozcb

Member
Messages
12,586
Musto said:
Hello guys,

I have found your forum whilst searching for help with a sudden misfire on my coupe, I came back from the Silverstone classic, 700 mile round trip with no problems. Come to fire her up the next day to find what I think is a misfire, EOBD comes on, eventually followed by Slow Down message, which eventually goes off. I suspected an issue with a plug causing unburnt fuel to hit the cat, creating too much heat. Stripping her down to get at the plugs, I have found one that looks a little oiled up, which could be the misfiring issue. But more interestingly all the plug bores have a degree of what looks like engine oil in them, in some cases quite a lot, say a teaspoon full, one of the worst affected bores was of course the worst plug and the oil had reached up to the rubber coil lead. Is there an expert mechanic out there that could offer advice (other than replacing the seals which I will get round to) at the moment I am planning to simply clean the oil off, clean the offending plug and refit them all to see what happens.

Also I have been reading about your use of Denso plugs, how have you all found them.

I live in the frozen north and currently have my car serviced at JCT600 in Leeds, but I have just come across AutoShield south of Manchester, has any body got any experience of dealing with them.
Click to expand...


Marios (Autoshield ) great guy , superb maserati knowledge and i mean all things Maserati , you be pushed to find better up north, there is also Millbrooke cars Sheffield they have a good rep

Re your misfire , could possibly be a coil pack breaking down , An sd/2 diag will tell you whats what


regards loz
 
Parisien

Parisien

Moderator
Messages
34,927
Hi Musto, welcome to our forum........can second Loz's recommendation great guys at Autoshield, plus the need for an SD type diagnosis.

Enjoy the forum and enjoy the car when sorted!

P
 
Emtee

Emtee

New Member
Messages
8,446
Hi Musto and welcome to the forum. Sorry to hear you're having problems, but as recommended above, a session on an SD2 tester sounds like it would be beneficial. I've been running Denso's for a year or so and they're fine; good price as well if you follow Parisiens thread on the topic.
 
BennyD

BennyD

Sea Urchin Pate
Messages
15,007
Musto, be advised that Whilst Marios is a fantastic guy he doesn't like non standard parts, so you will have trouble getting him to fit the Densos. Best you take it in, let him diagnose the problem with his tester and sort the oil leak. If it is the oil causing the problem with the plugs he may well not change them. You can then fit the Densos yourself using the handy guide in the tech section. BTW Marios will be away until a week on Monday but Russell, his mechanic, is holding the fort and will no doubt fit you in. Oh, and welcome to the forum!
 
N

nfm

Member
Messages
856
The seal failure is a common issue I think, MP Supercars picked up that a couple of mine had gone and replaced the full set.

Good luck with sorting it.
 
M

Musto

Junior Member
Messages
37
Latest update,

Just put the plugs back in no difference, warning light still on and misfiring. took them all out again. plug #8 front right still looked a bit dirty so cleaned it again and replaced, I also turned battery isolation switch off and on again. Turned the key, all eight fired up and no warning lights. Early days and will give it a few miles over the weekend before pronouncing a proper result, possible dirty fuel oiling a plug, but can't really see it.

Something that I did spot was the manual specifies NGK PMR8A but she has PMR8B's, bit like the missus really.

Anybody understand what the A or B represents, the NGK guide just says special which I take to mean which car manufacturer, everything else is the same.
 
Parisien

Parisien

Moderator
Messages
34,927
Phew...thought I was the nerd there for a minute Loz.......;).............................and I aint entirely sure just how much difference it would all make.....how would you measure the differences?


P
 
M

Musto

Junior Member
Messages
37
Doom and gloom, Started her up for a drive to Southport, no problems, all cylinders seem to be firing. But having set off all was not well, surging sensation and eventually engine warning light came on again, so returned home slowly, without overheating the cats and left it.

Will inspect #8 plug again tomorrow and may just change them all anyway, just to be on the safe side. But am now wondering if a lambda sensor has gone down causing over fuelling and fouling the plugs.

Spoke to a local Auto Sparks who did not recognise the term DS2 or DS3 for that matter, does someone have a clearer definition of the diagnostic system that has been referred to, is it Bosch, Marelli ? or something Maserati specific, can anybody help to define/identify this.

Also whereabouts do you plug it in.

Appreciate any help
 
Parisien

Parisien

Moderator
Messages
34,927
Musto, need to go to an indie near you, get hooked up, best way.

SD2/3 are the Maserati specific diagnostic kits....no other will do for a full diagnoses


P
 
M

Musto

Junior Member
Messages
37
Update, Having re-read another forum posting, I have ordered some new plugs (NGK PMR8B's £74 off eBay, as they were originally fitted by the factory) in the hope that they will cure the problem. If they do not, then I will arrange to have the diagnostic test, but not to keen on driving it 40 miles in its present state.,
 
Parisien

Parisien

Moderator
Messages
34,927
Yes, Musto, this has been mentioned before about non-original parts being fitted, only a change will tell.


P
 
Emtee

Emtee

New Member
Messages
8,446
Musto, I think the fault codes you need to have read are part of the generic EODB code range, so yes these could be read from an SD2/3 reader, but a generic reader from a decent indi should be able to point to the fault also? Just find a decent garage nearby and get them to run a diagnostic?
 
Maser Sod

Maser Sod

Member
Messages
1,965
Musto said:
Latest update,

Just put the plugs back in no difference, warning light still on and misfiring. took them all out again. plug #8 front right still looked a bit dirty so cleaned it again and replaced, I also turned battery isolation switch off and on again. Turned the key, all eight fired up and no warning lights. Early days and will give it a few miles over the weekend before pronouncing a proper result, possible dirty fuel oiling a plug, but can't really see it.

Something that I did spot was the manual specifies NGK PMR8A but she has PMR8B's, bit like the missus really.

Anybody understand what the A or B represents, the NGK guide just says special which I take to mean which car manufacturer, everything else is the same.
Click to expand...

Would always recommend running an ODB II scanner in to get a rough idea around the fault, e.g. if generated by the lambda sensors, saves just guessing ...

Pretty sure the faults will still be stored despite the battery trick.
 
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