Looking for your thoughts....

voicey · Apr 24, 2017

We must have crossed posts - sorry. Your fuel pressures seem fine so I would move on.

What are the fuel trims for each bank?

ttt0000 · Apr 24, 2017

voicey said:
We must have crossed posts - sorry. Your fuel pressures seem fine so I would move on.

What are the fuel trims for each bank?

We only have an OBD and google so cant tell atm.
A new O2 sensor was fitted by the Indy who supplied and fitted the clutch and did the service.
The Leanardo (sp?) only gave codes P300, P301, P302, P303. Low loaded home and working our way through as we eliminate the more obvious.
Thanks for your input.

Oxytorch · Apr 24, 2017

Was it the front O2 sensor that was replaced? Why was the O2 sensor replaced? Did he replace it on both sides or just one side? If replaced just one side, is the new O2 sensor on the same side as the misfires?

I agree with checking long term & short term fuel trims for both banks.

You could also try disconnecting the connector on the Evap purge valve after cel reset. By doing this, fuel trimming is disabled. If no misfires, it suggests a fuel trim issue. Of course, not recommended to run car for long like this. It will also trigger a purge valve code on 2nd start.

Contigo · Apr 24, 2017

I think the Pump is faulty now as that kind of explains the idle being fine but when the revs rise and the pump is asked to work harder/deliver more fuel it can't and in turn you get the misfire.

allandwf · Apr 24, 2017

Contigo said:
I think the Pump is faulty now as that kind of explains the idle being fine but when the revs rise and the pump is asked to work harder/deliver more fuel it can't and in turn you get the misfire.

Yes this, or a partial blockage in the suction side was my thinking.

spkennyuk · Apr 24, 2017

Might be worth taking the tank out and draining then at least you can inspect the tank for debris and start again with fresh fuel. I have no idea how easy that is to do on your car but at least it eliminates anything that may have been chucked in the tank while it was off the road.

2b1ask1 · Apr 24, 2017

No need to take it out but it may be worth finding out if these are petrol proof?

http://www.ebay.co.uk/itm/5m-6LED-Waterproof-USB-Android-Endoscope-Camera-Inspection-Borescope-HD-8mm-/262944372406?hash=item3d38b4b6b6:g:4eEAAOSwAANY7vqB

Contigo · Apr 24, 2017

allandwf said:
Yes this, or a partial blockage in the suction side was my thinking.

My mechanic said 100% fuel filter needs changing and it did cross my mind too.

mjheathcote · Apr 24, 2017

Could be wrong, but I believe there isn't a fuel filter on the 42/GS, why there isn't though I don't know!

CatmanV2 · Apr 24, 2017

Nothing not sure that this explains the pressure being identical. Unless we're suggesting that the pump can't maintain pressure at high flow

C

BuckRog64 · Apr 24, 2017

All logic points to a fuel system issue and I don't want to send you off track, but wondering if cause could be a faulty Crank Position Sensor.

Reason for suggestion is that I had a similar fault years ago (not on a Maserati) where car run fine for a while but would eventually start misfiring badly at higher revs when hot. Cause on mine was the CPS having been damaged (they are sensitive I understand) when removed to change belts.

I guess if car has been laid up for 6 months it could be fuel or electrical.

Contigo · Apr 24, 2017

Yep no fuel filter but a strainer in the fuel tank according to this thread. Ray have a read of this mate sounds very promising and identical to your issue.

Your fuel pressure is low too if this guy is to be believed.

http://www.maseratilife.com/forums/coupe-spyder-gs/12523-fuel-filter-fuel-pump.html

"Thanks for all the help. I finally got my Mas running great again. I was having mult. misfires. The left fuel pump was causing all my problems! We installed the new one at the cost of $250.00 and my Mas is running fine with no misfires or codes. Fuel press. should be between 50-55 lbs. Changing the pump was rather easy and took my mechanic and I about 1 hr for total job! Thanks again!"

ttt0000 · Apr 24, 2017

Thanks for all your help, input and suggestions really appreciated. Everything that doesnt work just takes us closer to a positive outcome
The O2 sensor that was replaced was the front on the right hand side.
Tonight we retested the fuel pressure. Under pressure, while misfiring and both rails were reading 45 (42 last night) so we are going to start on the sensors tomorrow night.
We are going to drop the exhausts and check the cats while we are waiting for the Infrared thermometer to arrive to check the heat pre and post cats.
Newton, loving the camera, going to order one of them anyway

ttt0000 · Apr 27, 2017

The pre and post Cat temperatures were reduced on the right so we believe its the Cats.
The good news is that the engine seems as good as we were told by several people

Contigo · Apr 27, 2017

The fuel pressure is low if the link I posted is any measure.

ttt0000 · Apr 27, 2017

Contigo said:
The fuel pressure is low if the link I posted is any measure.

Definitely still on the radar but they have def killed the cats so we will get them sorted first and then we can see whats next.
I am trying to download the Unidiag to give us more info as well.
Thanks

2b1ask1 · Apr 27, 2017

Still not convinced they are shot but if they are you may as well go for sports cats if you have to replace them, will do the job at a fraction the cost unless you go second hand.

StuartW · Apr 28, 2017

2b1ask1 said:
Still not convinced they are shot but if they are you may as well go for sports cats if you have to replace them, will do the job at a fraction the cost unless you go second hand.

Yes, good advise there. The sports cats are arguably better as they increase performance, they are cheaper than OEM and because of their construction, there is less risk of catastrophic damage to the engine if they did break up.

ttt0000 · Apr 28, 2017

2b1ask1 said:
Still not convinced they are shot but if they are you may as well go for sports cats if you have to replace them, will do the job at a fraction the cost unless you go second hand.

FTech suggested we look at the Cats but we hoping it was going to be a more common, cheaper option, we decided to start from scratch (plugs, coils, injectors, MAF, fuel pressure etc).
Having worked through these, all are working correctly. The thermometer arrived yesterday and the results are:
Engine running for a few minutes
R=180/30 (entry of Cat/exit of Cat)
L=150/100 (entry of Cat/exit of Cat)
Engine running for 10 mins:
R=320/200
L=290/270
The next job is to remove the Cats altogether as an extra check
I have spoken to Charlie at Prospeed and he can fit two new Sports Cats cheaper than standard Cats so that is a definite.
Will keep you updated, thanks for all your input.

ttt0000 · May 8, 2017

For anyone following this due to misfires, we removed both cats and refitted the exhausts. No misfires and no codes.
Thanks to everyone for their help, advice and any old posts, all of which have been used to diagnose and hopefully permanently fix.

Looking for your thoughts....

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