Shock and Awe - 3200 Throttle Issues.

[urquattrogus]

I removed the scotch lock straight away and have 0.52 and 3.01 volts as pedal voltage readings, so that seems to be in order.

Thanks, will also post more pics, and have some other ideas.

now feel like I need a drink!

 

[urquattrogus]

Here are a few more pics:

Notice how the ones that run with other connector wires are not connected:





I am wondering if any of these pins are bad, going to extract and check them, for example the bottom lhs grey earth looks a bit suspect (although more so because I have been prodding it!)

I'm not even certain that the pins in the connector are in the correct sequence, should be, but who knows.



I also found this stray connector that was not connected to anything, I presume it's for an option I don't have like heated seats, or diagnostic connection to a controller - thought it might be worth mentioning.


I have ordered a brand new Bosch Pedal pot for the avoidance of any doubt. I would use the Davy one I have, and may still do, but I know that if I take the car anywhere they will point at that straight away.

It may seem piecemeal and hopeless that I'm trying to sort this myself, but at the moment I don't have many options!

After removing the scotch lock the car still develops an accelleration/light throttle stick after about 15 minutes of driving from cold.

Now when I stop it will even rev up indefinately when I put it into Neutral!

 

[Contigo]

They look exactly like mine did when I got my manual car. I sourced a used but mint connector from David Askew and bullet connected each wire to the existing loom.

 

[urquattrogus]

Thanks, but - the grey wires in that picture come from the same loom run as the rest. Mine Don't, as shown in the top picture.

 

[Contigo]

Yep it looks like yours have been removed and then two added from a different ground.

 

[boomerang]

Seen that before.
Important thing is, that potentiometer ground comes from the ecu.

Regarding the white/yellow connection: why should there be the risk of WOT?!
As soon as the resistor tracks start wearing, output voltages drop.
Both tracks do, or one stays put while the other is already going down.
If you connect the white and yellow wires in such a situation, some average value is obtained, in most cases still in range.
To bring the pedal pot in a WOT situation, one or both tracks should start wearing the other way around!
I do not see how a wearing track could cause a higher output voltage.
Till now, every worn pedal pot i have seen, showed output values below minimum treshold, not over max treshold.
But potentiometer ground should come from the same ecu, that is feeding and sensing the potentiometer, that's a fact.
If someone ever made a separate ground, strangest things could happen.

 

[urquattrogus]

Thanks - that confirms my suspicions.

Of course presumably the ground has been re routed because someone thought the old one was not good.

Now to establish where the new ground goes to and also whether the old one is good.

I agree that it needs to be grounded with the ECU - that makes perfect sense.

I may try running off the old grounds, although maybe those have been disconnected as they don't seem to lead to earth - I presume they should do? This was clamping the negative terminal of my multi meter to the nearby door hinge and then testing for continuity.

The new re re-routed earth wires went to earth, but the originals didn't. I will test again with a better earth connection, and maybe remove the ECU connector and check the two wires back to the pin.

With this and fitting a brand new throttle pot, hopefully I am getting somewhere - but I am not sure it will fix the elusive intermittent rev up on hot start original issue.

I ordered a new Genuine Bosch Throttle pot 0 280 752 029 for £353 delivered, arrived within two days. I have it in hand, all as it should be.

I thought that was pretty good...

 

[davy83]

There is always a risk of WOT, with electronic sensors, i agree its not a common failure mechanism, but i think the one you need to worry about is open circuit, if the pedal sensor output becomes disconnected from the ECU, the ECU input can float up to 5V, and cause WOT. I think this is why the original has two outputs so they would both have to fail at the same time for this to happen (redundancy). If you connect the white and yellow wires together, and one of them is already open circuit (wear, bad connections or dirt build up) then you are now in a position where if the one working output gets disconnected you might get WOT conditions.

Its not a definite that this will happen but its a fairly alarming possibility, and presumably Maserati thought it was a big enough worry to put a dual output sensor in there. I suspect the risk is higher on the 3200 because the connectors and the wiring are so poor.

Seen that before.
Important thing is, that potentiometer ground comes from the ecu.

Regarding the white/yellow connection: why should there be the risk of WOT?!
As soon as the resistor tracks start wearing, output voltages drop.
Both tracks do, or one stays put while the other is already going down.
If you connect the white and yellow wires in such a situation, some average value is obtained, in most cases still in range.
To bring the pedal pot in a WOT situation, one or both tracks should start wearing the other way around!
I do not see how a wearing track could cause a higher output voltage.
Till now, every worn pedal pot i have seen, showed output values below minimum treshold, not over max treshold.
But potentiometer ground should come from the same ecu, that is feeding and sensing the potentiometer, that's a fact.
If someone ever made a separate ground, strangest things could happen.

 

[Roberts Aerospace]

I don't like to point fingers, but Maserati Shed.

No finger pointing required, that was me. It's a pretty standard way of eliminating variance between the two outputs so that the investigation can move on to other things. It's not "bodging", it's methodically eliminating any possible causes or variances as part of a test programme. I can't speak for any of the other wiring issues that are mentioned above. It also cannot cause a WOT condition, or any of the other suggested disaster scenarios as there are two wear detection systems employed, only one of which is the "voting" system.

I spent a man week investigating that car and was, and am still, stumped, other than thinking that it may be ECU or gearbox related as the high revs are caused by an ECU request. Despite the huge amount of my time this investigation took, I only charged for the data collection and collation, and wrote off over £1000 of my time.

Every sensible suggestion made in this thread - and many, many more - has already been tried and checked under many different operating conditions. I wish Emblem good luck, and look forward to finding out the cause. It's going to be something very weird, a duff ECU, or maybe I just missed something - I am extremely good with these cars, but, I am just human!

Mike.

 

[Contigo]

No finger pointing required, that was me. It's a pretty standard way of eliminating variance between the two outputs so that the investigation can move on to other things. It's not "bodging", it's methodically eliminating any possible causes or variances as part of a test programme. I can't speak for any of the other wiring issues that are mentioned above. It also cannot cause a WOT condition, or any of the other suggested disaster scenarios as there are two wear detection systems employed, only one of which is the "voting" system.

I spent a man week investigating that car and was, and am still, stumped, other than thinking that it may be ECU or gearbox related as the high revs are caused by an ECU request. Despite the huge amount of my time this investigation took, I only charged for the data collection and collation, and wrote off over £1000 of my time.

Every sensible suggestion made in this thread - and many, many more - has already been tried and checked under many different operating conditions. I wish Emblem good luck, and look forward to finding out the cause. It's going to be something very weird, a duff ECU, or maybe I just missed something - I am extremely good with these cars, but, I am just human!

Mike.

Fair comments Mike, it's a frustrating job at times!!!!

 

[urquattrogus]

Agreed, Mike's invoice was very fair and it wasn't for lack of trying.

A degree of frustration sets in now - I will try to keep on the case and fix before September.

The fact that the earth wires have been re-routed/earthed differently (I think Mike only did the scotch lock part) means I must eliminate that first and try the original earth wires.

Tricky this, when I phoned Emblem they were adamant it could be one of 2-3 things, I tried to convince them that there is more to it, we shall see how it goes.

 

[Mott The Hoople]

For what it's worth Mike, this thread and others has helped convince me to bring my 3200GT to Maserati Shed in the near future. I'm getting a bit fed up with researching Maserati problems, buying parts and getting my mechanic mate to do most of the work every 1,000 miles or so. He's a German car specialist so he's never very keen - "built like a kit car" he says. I'm sure that everyone is either a German car person or an Italian car person at heart. My car is like my wife - a frustrating pain in the **** that I wouldn't be without. Marrying an Italian would probably be too much of a good thing! Best wishes, Steve.

 

[redsonnylee]

Mike did a great job on my throttle issues, it's been running the best ever since I had the car. Only wished I known about him sooner.

 

[davy83]

There is a re-work around the grounding of the pedal sensor on the 2001-2002 cars and i am wondering if this problem relates to that, the essence if it is that the ground connections from the pedal sensor are wired using very short wires direct to the ECU and not through the wiring loom. might be worth looking into this as you are running out of options. I presume you have checked the vacuum hoses and all the possibly air leaks around the plenum?

 

[urquattrogus]

There is a re-work around the grounding of the pedal sensor on the 2001-2002 cars and i am wondering if this problem relates to that, the essence if it is that the ground connections from the pedal sensor are wired using very short wires direct to the ECU and not through the wiring loom. might be worth looking into this as you are running out of options. I presume you have checked the vacuum hoses and all the possibly air leaks around the plenum?

That's very interesting. Mine was registered September 2001.

It looks like it was done with some care, the wires run across from the female throttle pot connector to the other side of the carpet where the bonnet pull is, I believe this is where the ECU also sits? Looks like a short run.....

Does anyone have any more info on this re-work??

I presume there was a service bulletin or campaign??

Yes I have checked the vacuum hoses, although maybe I should check again. I believe Grimaldi smoke tested the plenum and intake system, and two years 2,000 miles prior, Auto-shield changed all of the Plenum O rings.

 

[allandwf]

I'll have a look at mine, once I'm home. It is also Sept. 2001.

 

[boomerang]

What i do know is, that the LHD cars have a little white connector in these separate ground lines toward the engine ECU.
Posted a picture of that years a go.
It's under the carpet, near the footwell of the passenger. (LHD!)
It's a known trouble maker, we delete the connector and solder the wires.

What Davy says is correct; the Dutch Maserati specialist I deliver the contactless TB's to, told me this information and a German dealer who gets them, confirmed this info.
I know the new wiring was to be soldered, but I do not know exactly where the dealers/ specialists split the wiring/ made the connections to be honest.

 

[boomerang]

There is always a risk of WOT, with electronic sensors, i agree its not a common failure mechanism, but i think the one you need to worry about is open circuit, if the pedal sensor output becomes disconnected from the ECU, the ECU input can float up to 5V, and cause WOT. I think this is why the original has two outputs so they would both have to fail at the same time for this to happen (redundancy). If you connect the white and yellow wires together, and one of them is already open circuit (wear, bad connections or dirt build up) then you are now in a position where if the one working output gets disconnected you might get WOT conditions.

Its not a definite that this will happen but its a fairly alarming possibility, and presumably Maserati thought it was a big enough worry to put a dual output sensor in there. I suspect the risk is higher on the 3200 because the connectors and the wiring are so poor.

An active redundancy system is best of course.
Your thoughts where mine exactly, when I was busy solving throttle problems.
But I did a lot of " what if" teststing.
When you for example just for the briefest moment make a ground disconnection, you get a solid limp mode, not WOT.
As soon as the voltage rises above max treshold, 3.5 volts, you get limp mode.

All in all, I asked myself what I would prefer if the pedal pot occasionally tends to bring the car in limp mode;
The most unlikeliest case of wot, or the EXPERIENCED disaster of sudden loss of power, sitting between two other overtaking cars with 90mph on the highway!
It was due to the very quick and sound response of the guys behind me, that we did not end up in a major collision back then!

But, I do agree, a new or contactless pedal pot is giving the best of confidence you can find.

 

[urquattrogus]

 

[urquattrogus]

There you go, that's where my wires go, looks legitimate, straight from the pedal pot connector to the ECU Plug.

I am going to trying running another earth to the ECU and checking the wiring resistance etc.