My 425 isn't feeling very well.
Can you help? Please!

Any owner having a problem with their Maserati can send me details and I will publish these, together with any subsequent advice I receive, on this page.

Just drop me a line at


Even if I don't succeed in helping you with your problems; and I do try, it would help other Maserati owners a great deal if you could let me know how you managed to solve your problems. THANK YOU!


Iman in ? writes:-


Re: Maserati 425i (chokes and makes some loud shooting noise!)


It's great and nice to find a web page like this where people can get help for thier loved ones.

I have a 87 Maserati Biturbo 425i fuel injected. When I push the gas all the way down on low rpm power seems normal. On high rpm when turbo kicks in, no power.

The car chokes and makes some loud shooting noise if you know what I mean.

The turbo gauge reaches close to the orange line and I can hear them working fine; no leaks, no smoke. I was thinking maybe the fuel is not coming in enough, like a weak fuel pump which at a higher rpm doesn't push enough gas in.

I changed the fuel filter and no catylyst on the car.

Please let me know if anything might sound like a common problem.



David in the USA writes:-


Re: Maserati 425 firing order


I am looking for the firing order for a 1986 Maserati Biturbo V6 425, any help will be appreciated.



Peter in Canada writes:-


Re: Maserati 425 (applies to all Biturbos)

"Here's a question...I hope it does not make me out as a simpleton...

I re-set my mixture and idle as per basic instructions from Webber carbs and I trust the settings are right for the progresive carb on the 425. it seems to idle well with the plenum off (aprox 1200 rpm) but with the plenum on, it seems to idle lower and the idle in gear is rough, as if it were set too low but not a fuel starvation type of feeling. Does putting the plenum and filter box usually cause the idle to drop? Is this a sign that the design of the plenum (too small air intakes from the filter box) is causing air starvation? Should I increase the idle without the plenum to compensate? I don't want to play with the mixture if I can avoid it for fear of running too lean.

I also have a boost leak at the right side turbo (I see exhaust leakng out of the engine compartment) but I don't think that would cause the change in idle.

I'm happy to see Maserati models getting nice write-ups in the media but as they seem to get less mileage that the German performance vehicles. I hope the world fuel scare (manufactured or not) does not kill the demand. Thanks and have a good weekend.



Peter in Canada writes:-


Re: The Biturbo 425 'Gelato Express!

"Aaaah, will my Gelato Express ever run properly?

I purchase an auto 425 (4 doors) specifically to be able to cart my wife and two sons out to the ice cream shop in the summer. I fear this may never be. My silver girl friend, as my wife calls it, is in the garage. It starts well, thanks to tips from your site. It idles better, but the mixture is probably not correct and I am still looking for a schematic for the progressive carb to be certain I rebuilt it properly. I still don't get full boost and my right (Canadian side/pass side) turbo doesn't put out as much as the drivers side (I can feel the deficiency by putting my hands over the outlet tubes). I think I might have a leak at the exhaust to turbo pipe.

I am now finding large pools of oil under my car, even after a 10 minute idle. I don't see leaks at the oil pan and fear it might be the rear seal. Are there any other problem lines at the rear of the car that you think might be the problem? I have wiped the area under the oil pan and tranny clean but see oil dripping from the inside of the tranny area, where the timing indicator is. I don't see nay tranny oil.

Question: can the waste gate condition be checked with the engine in the car? I have tried to move it by hand but can't budge it (the drivers side with the wastgate valve pointing to the strut housing, the other is pointing to the block and I can't easily get in there). Would a vacuum pump help... will I see movement in the link by applying suction or should I apply pressure? I am not certain if the waste gates are normally in the closed position or open when at idle. What I read suggests they are closed.

Can the turbos be removed from the engine with the engine in the car?

I am truly sorry if these questions seem overly simple but I have tried to find answers to the above questions and can't find any. I have been struggling with this car since I purchased it from a smooth-talking liar about 4 years ago. I believe he had the boost tubes reversed...which is why the car felt swift..until my then mechanic corrected the connection. At this point, many tests have been done (cleaned all contacts, checked and changed many hoses, timing) and apart from having the mixture checked, I don;t know where else to turn. The boost was also this way after the mixture was set about two years ago during out compulsary emissions tests.




Reply from Andrea:-

Re: Biturbo 425 'Gelato Express'

"There is another possibility. At the rear of the engine, between the sump pan and the flexplate, you will find a banjo fitting which has two metal pipes coming from it. These feed the turbos with oil. A leak here is common and probably most likely to produce the quantity of oil in the time you suggest. Repair is fiddly but not difficult but be careful that you keep the thread in the block good because it can get expensive if you don’t. It could still be the rear seal however but if it is coming out that quick, the seal must have completely disintegrated.

The wastegates can be checked with the engine in situ. They should be closed when the engine is switched off. They can be checked either manually by trying to flick them against spring pressure on the rod, or with an air line down the pipe to each side gate, see if they will open and close. If one or both is seized in the closed position (most common), you would have enormous boost. If seized in the open position, then no boost. OR, the wastegate actually looks like a valve seat and can crack due to heat. This would also allow boost to leak away.

Yes they can but only if the exhaust manifold nuts all undo (unlikely). I would strongly recommend removing the engine to do work in the manifold/turbo area as it is relatively easy.

A good source of information and parts nearer to you is MIE Corporation in Seattle.



Geir in ?? writes:-


Re: Biturbo 425

Hello Enrico!

I am a happy owner of a Biturbo 425. I wonder if you have a wooden steering wheel suitable for this car? Perhaps you have an original watch too? In the car is only a cheap substitution that is not even working. Finally: if you have got these items, how much do you charge for them?

Kind regards,



Christian in France writes:-


Re: Biturbo 425

"Je vous écrie ce mail car je pense que d’après votre site internet vous semblé être spécialiste Maserati.

Je possède deux Maserati, une Ghibli 95 et une 425 Biturbo année 91.

Le problème concerne la 425. Ce véhicule a été arrêté 7 mois pour divers travaux de carrosserie.

Lors de la remisse en service de ce véhicule j’ai constaté que toute la planche de bord ne fonctionné plus (témoins batterie, jauge essence, compte tour, compteur km) les clignotant ne fonctionne pas non plus et aussi le bouton test, et apparemment le dégivrage vitre arrière ; seul fonction les quatre feux détresse l’éclairage tableaux de bort et témoins de phares.

J’ai teste le fusible pas de problème de ce coté le courant passé bien, et je ne voie pas d’où viens le problème.

Avez vous déjà eu connaissance d’un problème similaire et si oui m’indiqué comment résoudre le mien.

En vous remercient d’avance Veuillez agréer, monsieur, l'expression de mes sentiments distingués.



Re: Biturbo 425

"I am writing you this email because after viewing your internet site, you appear to be a Maserati expert.

I own two Maseratis, a 1995 Ghibli and a 1991 425 Biturbo.

I have a problem with the 425. This vehicle was laid up for seven months for various jobs on the bodywork.

After having got the car back from the body shop, I noticed that all the dashboard instruments no longer worked (the voltmeter, fuel gauge, rev counter and speedometer) the warning lights didn't work either as well as the TEST button switch, and apparently the heated rear window; the only switches that worked were the four hazard warning lights and the headlamps.

I have tested the fuses and there is current, so no problems there, I just don't know where the fault is.

Have you come across a similar problem before, and if so, could to tell me how to solve mine.

Thanking you in anticipation,

Yours sincerely,



Reply from Rossano of Repartocorse:-

Re: Biturbo 425 Central switches

"Per il tuo amico il problema elettrico dovrebbe essere nel cavo che alimenta la pulsantiera centrale, a parte l'hazard a tutti gli altri pulsanti hanno un cavo di alimentazione comune che porta il positivo, non sò se c'è un fusibile su questo, di solito sono a monte dell'interruttore, il problema potrebbe nascere dalla scatola di derivazione quella cosa nera da dove partono tutti i cavi dietro ai fusibili.

Comunque basta provare a togliere la pulsantiera e con un positivo diretto dalla batteria provare ad alimentare i pulsanti, se funziona basta trovare un altro positivo in abitacolo, mettere un fusibilie e ricollegare i contatti, spesso i carrozzieri nello smontare e montare parti di vetture senza volerlo tagliano dei cavi o creano cortocircuiti."

"For your friend the electrical problem would have to be the wire that supplies the central push-button switches. Apart from the hazard warning switch all the others switches are fed by a common wire that has a positive feed. I am not sure if this wire has a fuse of usual is to mount of the switch. The problem could originate from the fusebox, the black box where all the wires come from behind the fusebox.

However try to removing the push-button switch panel and with positive feed direct from the battery try connecting a wire to each push-button switch. If they work, find an alternative positive feed from under the dashboard and connect it to the switches and remember to add an inline fuse of the correct resistance. As often happens at the body shop, when taking apart and putting back together the panels, without realising it they can cut into the some wires creating a short circuit.



Craig in Australia writes:-


Re: Biturbo 425i interior trim


I have a 1989 425i with near perfect mechanicals and body, but the interior needs some attention.

I could have it re-trimmed to match, but would prefer to used original materials.

Do you know where to get the original Tan coloured vinyl used on the dash, doors and seat backs?

Many thanks.



Peter in Canada writes:-


Re: Biturbo 425 knock sensor!


Hope all is well. Now that Spring is here I am trying to get my carbed 425 back together. I removed the intake manifold last fall after rebuilding the carb...mostly because the previous owner's handywork was not to be trusted and I wanted to be certain the system was properly sealed for leaks and to replace some suspicious hoses.

I have remounted the intake, replaced the carburettor but when trying to start, it coughs and wants to spit up fuel. I am not sure if this is normal since the carb is bone dry or if I have mixed up some of the vacuum hoses. I can't find a proper diagram/illustration of the carb plumbing on the 425 model ( my three manuels have the other carb but nowhere can I find the progressive carb, ribbed plenum cover with carb throats that run up and down, not side to side as per most other Biturbo carbs.

The only two hoses I might have screwed up are the two that connect under the manifold's right side. One goes to the distributor advance and from the inside of the plenum, one goes to the back right side of the carb and the other goes to the back of the carb (towards firewall) beside the idle motor. I believe they are correct but you never know. Also, I have replaced the vacuum hoses with the closest diameter match but could one a bit too large or small cause an issue?


I am including a crude diagram. Hope it helps.


Reply from Andy:-

Re: Biturbo vacuum pipes

"The vacuum pipes will not cause a non-start or coughing carburetor. You should at least be able to start it. Are you sure you’re got your fuel pipes the right way round?



Peter in Canada writes:-


Re: Biturbo 425 knock sensor!

"Hi Henry.

Trust all is well.

I am putting the intake back on my 86 425 and have a few questions about the Biturbi knock sensor. There are 3 connections and I assume that one is for power, one ground, one signal to MABC.

So, is the knock sensor in the always "on" position, that is to say, when the engine is running normally, the signal to the MABC is on and the "knock" signal from the microphone stops the signal to the MABC or is the knock sensor "off" and only sends the signal if the microphone senses the knock.

In either case, do you or any members know the voltage or impedance of the signal from the third wire? If I know this, I should be able to measure the third wire output and cause the signal to open or close by tapping the sensor. Make sense? I believe my sensor is working fine and my valves are a bit tight as the boost will not go to the yellow . I am changing and sealing all of the gaskets and changing the hoses but really don't want to re-shim unless that is the problem.

And finally a quick question. How can one check the condition of the waste-gate with turbos on car?



Reply from Andy:-

Re: Biturbo 425 knock sensor!

"I am afraid that I have no info on voltage etc for the knock sensor. They are very reliable in my experience and any problems in that area seem to originate from the connection to the sensor which sits over the cam cover.

The valves would have to be seriously tight (and therefore requiring shim job) if they cut your boost down.

You can look at the wastegate seats if you take off the exhaust system and the wastegate housings, which is not that difficult unless the nuts are seized but better to check spring tension first, then air line them open and closed to make sure they are not seized.



John in ? writes:


"Hello to Enrico and all the other great Maserati enthusiasts that use this invaluable website!!

I have a 1986 425 that I am upgrading to fuel injection (from an '87 425i) I would like to know if there is anybody out there that has ever attempted to use 2.8-litre heads (with same-size intake valves) on the 2.5-litre motor. I do not know if the F.I. system can cope with the extra air flow. The rest of the system is to be stock, save for a 3" exhaust upgrade. I want it to be as reliable as possible!! Any advice or warning me off of pitfalls would be appreciated.

Again, thanks a million for the website. (I do have to say that I am jealous that so many of the great Biturbo era cars were only offered to those enthusiasts in the U.K.!!!)




Gerald in the USA writes:


"I am located in New Jersey USA, and I was wondering if there is any place that offers cheap replacement engines (running) for 1984 425 Biturbos...that may need minor work. I don't want to give the car up...the body is in great shape.



Reply from Enrico and David:-

Re: Biturbo 425.

"Hi Gerald,

I am afraid that being based here in the UK I do not know many sources for used engines in the US. There should be many. I know sources here in the UK and Europe but shipping costs would negate any savings you might make.

Is your engine fuel injected?

The link below is a guy called Lenny in California who I know has engines for sale.

Hope this helps.




Gerald in the USA adds:


"Thanks for the information i will give him a try....and no my engine is carb.



Peter in Canada writes:



I have an 86 425 with which will not boost past the halfway mark. It also idles a bit rough and eventually wants to sleep. Some background: It had boost during the test drive but after I picked it up (and did not boot it) the braking seemed to require some extra effort. could the previous owner have switched some vacuum lines to "boost" the boost? (sounds unlikely but after I started to examine the car in greater detail, i found many, many small hidden "fixes". The valve clearances are within spec. New timing belt. New aftermarket Cat. Muffler is flowing well enough. Good plugs. new wires and cap. Rotor seems fine.

I believe I timed the engine properly but the marks on the flywheel were a bit hard to read.

I removed the plenum (to check the fuel lines) and found that it idles roughly. Should a Biturbo in proper tune idle "smoothly" with the plenum removed?

The knock sensor sounds like the culprit but I followed a suggestion on one of the tech pages and disconnected the "w" hose from the cylinder on the firewall to see if boost improved (affirming a knock sensor problem) but it has not changed. I don't want to remove the manifold and sensor unless it is the problem due to the stupidly high cost of the intake manifold gaskets. I will be rebuilding the top end of the carb later on next week as I have the kit.

Any suggestions would be helpful.

Many thanks and let's stick together, e (ey!) Maserati fans!



Reply from Andy:-

Re: Biturbo 425.

"Sounds like two problems. The lack of boost could be down to the knock sensor, but it is unlikely to be the sensor itself as these are pretty reliable. Have you examined/cleaned the connector to the knock sensor, which is around the RH cam cover (black and white plastic). A poor connection here sometimes causes this problem. If you are worried about the timing, it should not be difficult to check - look for the PMS mark on the flywheel and time the cam wheels to it as per the manual. Also, have you reset the ignition timing since? Needs doing.

I would do all this before you delve into the carburettor too much, but yes, it should still idle smoothly with the plenum removed. You may have a partially blocked idle jet causing the rough idling so a general carb overhaul could also be a good idea.

Hope this helps,




Peter in Canada writes:


"Just a note. I have just submitted a request for help and thought I would submit a tip as well... as "payment" and "thanks".

The window cranking system on a Biturbo can be rebuilt fairly easily with NO new parts if necessary.

Carefully remove the motor and cable assembly. There is a bracket with rivets that holds the cable guide to a bracket. The cable is held in place with a "collar", for lack of a better word, that is pinched tightly around the cable. Gently pry this apart, remove the cable, clean it thoroughly, re-assemble with the cable in reverse.

Usually, the reason these fail is because dirt and grease get onto the cable and gums up the works. The sound you hear when you push on the switch and "nothing" happens is the gear skipping across the cable, eventually wearing out that part of the cable and then the window will not crank beyond that point up or down.

P.S. Do NOT grease the cables. Make sure they are clean and dry prior to re-assembling.



To enter Enrico's Maserati Pages CLICK HERE!

Copyright: Enrico's Maserati Pages - © 2000-2005. All rights reserved.