Ghibli gurus - please help with fault finding!

[Tipo 336]

OK... where to start, i recently installed a replacement engine into my '95 Ghibli. The transplant went smoothly, the car worked perfectly for 3 days and approx 80kms, it had excellent power.

Then, when i was driving the engine started to have an intermittent stumble / hesitation / slight backfire / low on power like an ignition issue or not firing on all cylinders.

When taking the car home, the engine cleared on two or 3 occasions back to normal, but would then would go back to the same symptoms.

Now that car will still start but has a low idle, smells rich, stumbles when revving.

So far i have done the following:

• I swapped over the 5 relays from the other side of the engine bay, cleaned and checked all sensor connections are tight, cleaned and checked fuse box.
• I checked all crank / cam sensor air gaps and adjusted shims to .6mm as specified.
• I checked crank and cam sensors with multimeter - all read 700 ohm
• I checked all coil packs, all read 700 ohm
• I then removed all spark plugs: Cylinder bank 1-3 are all even colour - slightly lean / grey but look OK, however cylinder bank 4-6 are all even colour but appear more black / rich - so for some reason this bank is running rich.
• I ohm test air intake sensors cold and hot, one sensor reads OK, the other is faulty, replaced sensor, no change.
• I ohm test water sensors - cold then in hot water - both read OK
• I replaced both Lamda sensors with new sensors, no change.
• I removed and cleaned MAP sensors with contact cleaner - tested ohms OK, although i have not yet tested to see if the MAP sensors hold pressure...

Next ideas to try.... any suggestions?

• I have not checked throttle position sensor - i will check this tonight, i will test resistance when manually opening the throttle? Could this cause this type of symptom?
• I have not tested fuel pressure reg / fuel pump / fuel filter or injectors - although does not explain why one bank has a different mixture to the other.
• I have not removed plenum to check for cracks (although unlikely vacuum related as symptoms were initially intermittent.
• I haven't done a compression test yet but i'm leaing towards a sensor issue or perhaps an ECU fault?

I have the car booked in next Wednesday for an inspection but i want to keep going to see if i can sort it out on my own as fault finding can get very $$$$!!!

Cheers! Mike

 

[outrun]

Hi Mike

These are some interesting symptoms and could be lots of things. I'd consider posting the same questions to Enrico's Maserati Pages and see if you can learn anything from there. There tends to be more owners of the older cars visiting that site and it is a wealth of great information. http://www.maseratighibli.co.uk/

Not to say that someone here can't help, they may well be able to. We'll certainly try!

Good luck

 

[2b1ask1]

How old is the fuel?

Unleaded has a 12 month shelf life; looks, smells and feels like petrol but won't burn even with a naked flame next to it!

Also if it has stood a while you may have got sediment/water into the system.

I'd be looking there myself.

 

[allandwf]

Does the ghibli have a pedal pot? My 3200 bogged down and seemed to lack power, it was the culprit.

 

[del mar]

I had issues with mine following removing the in take manifold. Mine was reluctant to start and started hunting badly whilst at idle. It turned out to be a combination of a damaged idle control valve ( I damaged it !!) this lives at the front of the intake manifold and a vacuum leak where it joined the block. It would run and perform well but idle was all over the place - very low to 2000 revs.

Good luck !

 

[Tipo 336]

Hi Mike

These are some interesting symptoms and could be lots of things. I'd consider posting the same questions to Enrico's Maserati Pages and see if you can learn anything from there. There tends to be more owners of the older cars visiting that site and it is a wealth of great information. http://www.maseratighibli.co.uk/

Not to say that someone here can't help, they may well be able to. We'll certainly try!

Good luck

Thanks for that, yes i have visited on several occasions, great site, too bad there isn't a live forum... it could be months before a post is made and replies come in! There is an active forum for these models in the Netherlands.. but little english on there.

How old is the fuel?

Unleaded has a 12 month shelf life; looks, smells and feels like petrol but won't burn even with a naked flame next to it!

Also if it has stood a while you may have got sediment/water into the system.

I'd be looking there myself.

Good thought... the fuel was only in the tank for 3 months, then i topped up with fresh fuel the same day i put the engine in. Next on the list is to check the fuel system.

Does the ghibli have a pedal pot? My 3200 bogged down and seemed to lack power, it was the culprit.

It does have a throttle postion potentiometer, although different to the 3200 version, it could be very well be the problem although i'm unlikely to get a new one in time for when the car is booked in.

I had issues with mine following removing the in take manifold. Mine was reluctant to start and started hunting badly whilst at idle. It turned out to be a combination of a damaged idle control valve ( I damaged it !!) this lives at the front of the intake manifold and a vacuum leak where it joined the block. It would run and perform well but idle was all over the place - very low to 2000 revs.

Good luck !

I did try cleaning out the idle valve, although the plunger did move freely, I doubt this is the cause, the revs are lumpy throughout the rev range, it currently has a steady, low but somewhat rough idle of approx 700 RPM when cold.

Thanks for the ideas guys, if i don't find it in time i'll report back with what the mechanic finds.

 

[jluis]

Check that both fuel rails receive fuel and that the pressure regulating valves are working properly.
One side running richer than the other could mean a problem with the rail regulating valve or fuel starvation in one of the rails

 

[Wally]

Check All ground-connections to chassis and the ecu-connectors especially if theyhave been disconnected.

 

[Contigo]

A duff Map sensor or inlet pipes connected incorrectly can cause this sort of lumpy idle or hesitation. On the 3200 if you have the same symptoms it could be a leak around the O ring at Plenum chamber or as Allan says a duff or failing pedal pot or even throttle body can cause stalling. Crank or TDC sensor is also worth double checking too!

 

[Tipo 336]

Good ideas guys, next on the list is to check the fuel pressure / fuel spray pattern at the injectors, all the sensors appear to be OK, i checked the throttle position sensor... reads 0.5v with throttle closed and 4.5 volts fully open, with no voltage spikes noted when moving the throttle.

If it's not a fuel pressure issue i'll probably just replace both map sensors for peace of mind... they resistance tested OK but may not be holding pressure properly.

Luckily most of these parts are quite affordable as quite a few 90's cars have the same sensors, such as Fiats, Alfas, Saabs, Citroens, Puegeots etc if you are willing to cross reference part numbers. Also, a good one to make note of is the Ford Sierra and Escort Cosworths have the same sensors as they also use a Magneti Marelli ECU...

 

[Tipo 336]

Well.. how about this, in a last ditch effort i decide to swap the new looking NGK spark plugs out of the new engine with the old champion spark plugs from my old engine.

Took it for a 30 minute drive, not one misfire!

The NGK plugs that came out of the new engine are heat rating 9 which might be a bit too cold for this engine? What is the correct heat-range spark plug for the 2.8?