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Introduction to the Mitsubishi engine used in many 1980s-90s Chrysler vehicles

3 liter MMC V6Chrysler started using the then-new Mitsubishi 3.0 liter V6 engine in late 1987, when they had no V6 of their own — indeed, nothing between their modern four-cylinders and their aging V8s.

A clean-sheet design, the three-liter V6 was first used on the Dodge Caravan and Plymouth Voyager; shortly after, Chrysler designated it to be the standard engine on the 1988 Chrysler New Yorker and Dodge Dynasty. In both cases, it was used with the Chrysler three-speed automatic, which included an electronically controlled locking torque converter.

Chrysler introduced the 3.0 V6 as “an efficient, compact engine with remarkable performance and a host of high technology features. A dual-tuned intake manifold produces a broad, flat torque curve that assures the driver of powerful acceleration whenever he calls for it. The engine has one overhead camshaft for each bank of the large intake and exhaust valves for efficient engine breathing-an optical distributor-a single-module engine controller that electrically monitors and adjusts to every operating condition. The 3.0-liter V-6 also has an automatic belt tensioning system that increases belt life by maintaining proper tensions throughout the life of the belts. It also reduces the noise of belt-driven accessories.”

3 liter V6 engine

The company claimed that it was “Developed cooperatively by Chrysler and Mitsubishi Motors engineers,” but engineers have told us that the Chrysler contribution was essentially making the Mitsubishi engine work with Chrysler transmissions, fuel delivery, and control systems. On Chrysler vehicles, it used a three-piece, cast aluminum, dual-tuned, long runner intake manifold.

The head and intake manifold were made of an aluminum alloy; the engine had semi-hemi heads, a cast iron block and cam, forged steel connecting rods, a nodular cast iron crankshaft, four main bearings, hydraulic valve lifters, an oversquare design with a compact exterior, large 43 mm intake and 35 mm exhaust valves with squish areas on either sides of the chamber for detonation control, a cog-driven overhead cam, and cast aluminum, tin-plated pistons with steel struts.

Multiple-port fuel injection was used, with 36 psi of fuel pressure in 1987 and 48 psi in 1988; it ran on regular gas. Two injectors fired together, with the same controller, one against a closed valve and one against an open valve. Sequential injection with single injectors firing one at a time would be used starting in 1992. (The 2.2 and 2.5 liter engines would only have multiple-port injection when turbocharged; the standard versions made do with a single injector.)

The 3.0 liter engine displaced 181 cubic inches, with a bore and stroke of 3.59” x 2.99” and a compression ratio (in 1988) of 8.9:1. It has no parts in common with the 3.0 liter 90-degree V6 used in the Eagle Premier and Dodge Monaco.

In 1988, the 3.0 developed 136 h.p. at 4800 rpm and was monitored by the single module engine controller (SMEC, or computer) which used engine speed and manifold pressure to govern fuel delivery, ignition timing and idle speed. After appearing on the Voyager and Caravan, it was the standard powerplant on the Chrysler New Yorker and New Yorker Landau, its first passenger car use. At Chrysler, it would be used with a three-speed hydraulic-control automatic, a four-speed electronic-control automatic, and a five-speed manual transmission. 

Roger Lister's Guide

Roger Lister wrote:

I'm pulling info from many sources.  Dr. David Zatz and his ALLPAR site, my friend Rob Carter's 3.0 FAQ and his General FAQ, Gary Donovan's site, Paul Berkebile's site, James Dempsey and his Chrysler 3 liter mailing list, Rob Carter and I collaborated on the NEW Mopar minivan Homeworld, and my own personal research.  And many other sources and people and such.  Too numerous to mention.  Including several Chrysler service techs who shall remain nameless for their own protection... [Editor’s note: most links have been removed because, over time, they became invalid.]

This motor appeared for the Chrysler minivans in mid-1987, for the stretched minivans that became the Grands. This was built by Mitsubishi motors, altered to Chrysler's specs. From 1987-1991 it had multiple point fuel injection; in 1992 it went to sequential multiport injection. Like the 2.2/2.5 and other Chrysler V6 engines of the era, it used a Chrysler-designed "Speed/Density" computerized system to regulate fuel, which has a Manifold Absolute Pressure sensor to allow the computer to guestimate how much fuel to add. The fuel mappings in the computer were geared toward staying environment friendly, as opposed to performance friendly.

The Mitsubishi version was used in cars and trucks, including the 3000GT flagship, the Montero, and the Diamonte luxury sedan. The 3000GT started with the SOHC basic block and lower end, and with DOHC with or without twin turbos. As such, this basic motor could be had in flavors from 150 hp to better than 320 hp. All versions in the Mitsubishi lineup used Mass Air Flow computer systems.

For the remaining purposes of this discussion, I'll be referring to the SOHC version unless I specifically mention the DOHC or Twin Turbo (TT) models. (Turbo-3.0 information).

Different internal hardware for different applications

There appear to be two different versions of the Chrysler plenum with two lower intake manifolds; a different Hyundai Sonata version; and two different plenums and manifolds for the Mitsubishi vehicles, one for the truck/SUV, and one for the sedans and base Stealth / 3000GT.

There are also differences in the oil pumps and filter locations. Chrysler has a pump specific for its use, with the filter located on the "front" (as viewed with the hood open) of the block, while the Mitsubishi cars use a pump with the filter on the pump. Adapters altered the filter’s position depending on the application. Could such a pump be used on the Chrysler FWD cars or minivans? No, the right side halfshaft is in the way, explaining the difference.

In Chrysler vehicles, one lower intake manifold was used through to 1988, another used in 1989 and later; the PCV valve was moved from the valve cover (which is also different, for the same reason). The intake manifold was changed to redesign the floor and runners, smoothing the flow of air; and to be more compact to allow for lower hoodlines. The throttle body was also changed in 1989, with a smaller bore for smoother response. Exhaust flow restrictions were reduced at the same time by increasing the exhaust manifold outlet diameter from 2.25 to 2.5 inches, and a new throttle control system reduced effort and improved pedal feel, incorporating a self-locking cable for higher reliability. The air/fuel charge temperature sensor was dropped, that information now being calculated by the computer, and the EGR valve was dropped (in Federal cars).

Fuel rails changed around 1992 with sequential injection.

This motor has been used in Mitsubishi forklifts and other machinery. Those versions usually run on LPG or propane. It was also used in the Mitsubishi Raider — with a metric-threaded oil filter, unlike the New Yorker, Dynasty, and minivan version which used U.S. threading.

This motor is capable of handling much more power. It uses the same basic block, crankshaft (though in later years the TT version was Nitrile treated), bearings, and rods in SOHC and DOHC form. The main difference was that the block was machined to accept a 4 bolt main bearing cap, instead of the two bolt mains, and the pistons are different for the SOHC/DOHC FWD, TT and RWD SOHC motor. The Chrysler motor seems to have yet another piston. Clearances are basically the same though regardless of pistons or application. The DOHC heads will bolt on the SOHC block. So this is a way to generate more power, but then you need the whole computer and wiring harness from the donor car. Same thing if you decided to get the TT DOHC setup as well.

Mitsubishi trucks appear to have a different cam profile than cars, and Chrysler has different cam timing from the Mitsubishi versions. Since all the SOHC models used a distributor based ignition system, it would seem that the hot cam to get for minivans would be the one from the Mitsubishi Montero.  

(specifications).

 History of the 3.0 V6 in Chrysler, Dodge, and Plymouth vehicles

1987 was the first year of the 3 liter in the minivans.

1988 saw the 3 liter motor introduced in the Dodge Dynasty car chassis. (Jason B. notes that 1988 and 1989 3.0 engines did not come with EGR because they met emissions standards without it.)

1989 shows a revised intake plenum to allow for lower hoodlines for the AA bodies (Acclaim/Spirit/Lebaron Sedan and Chysler Saratoga), the AP bodies (Shadow/Sundance), G body (Daytona) and J body (Lebaron Coupe and convertible) cars. Exhaust manifolds were changed from 2.25" output, to 2.5," coinciding with the increased exhaust housing sizes for the turbo 2.2/2.5 motors and the TBI 2.5. The throttle body and throttle control were also changed.

1990 saw the introduction of the roller cams; cam timing seems to have added a little duration for intake valve opening, while a slight decrease in exhaust valve opening, presumably related to the roller cams. A molded epoxy coil was mounted on the intake; the computer shut off fuel at redline (6,300 rpm with manual, 6,000 rpm with automatic). The intake manifold lower casting was modified for the PCV system, so that the PCV valve went into the lower manifold (in the 1990+) rather than the neck of the plenum. The earlier heavy, iron tube plenum (usually with 52 mm throttle body) was replaced by a lighter aluminum-alloy plenum with a center deivider and 46m throttle body. In 1996 this would be changed again, to a 56 mm throttle body.

1991 Chrysler started development of the planned (but cancelled) turbocharged 3.0 liter for the IROC Daytonas. The belt routing and the belt itself were changed, and an extra free pulley wheel was added.

1992 seems to have made an improvement in horsepower, but at the expense of torque. This change appears to be as a result of using the SMPI as opposed to the MPI system. Rob Carter and others suggested that the switch to SMPI was to increase fuel mileage, since each injector fired only when needed, making metering more exact and keeping the fuel atomised.

In 1993, Jay Storm reported, “the valve guides were redesigned to not drop down, causing skeeter-killing spy smokescreens.”

Transmissions and swaps

The A670 and A604 automatics share a common right side extension housing.  This housing includes the bearing and seal for the right side of the differential.  The A604 was the only transaxle offered for the AWD minivans.  If you were to unbolt the extension housing from the the 3 speed automatic (A670), you could then bolt in the adapter for the AWD Power Transfer Unit.  Then, bolt in the PTU and there you have it, power transmitted to the rear of your A670 equipped vehicle. 

(Since then, Roger learned from a Chrysler transmission service tech that the five speed extension is indeed different, though the A413 and A670 have the same extension housing. The automatic and manual vehicles do use the same half shafts, but the differential bearings and differentials themselves are probably considerably different. This means a five-speed manual-transmission AWD V6 minivan would be hard to set up.)

Benjamin Hook has transplanted the equal length setup from the C body New Yorkers into his 3.0 5 speed P body.  All K based cars except the vans share common half shafts in their given years. The minivans seem to have stronger shafts than the cars, but otherwise appear to be the same length.

A lot of auto parts stores will only carry one axle and claim they work with the vans and the cars.  Autozone lists the same part number for most front wheel drive Mopars.  The L body used unique axles, as well as the Neons, Cloud cars, and vans starting in 1996. Also, there are different shafts whether you have have antilock brakes or not. Factory part numbers for the vans shows a different shaft than for the cars.

According to two Chrysler mechanics I'm in touch with, the A543 5 speed can be mated to the 3.3/3.8 motors. It seems that the major difference for the 3.0 and 3.3 bell housings is the "cutout" on the 3.0 version for the water inlet from the radiator. Other than that, they appear to be the same.

Why not use a 5 speed in a 3.3/3.8 vehicle? The 3.3/3.8 motors were primarily used in the C body and S body vehicles. The C body included the Dynasty and Fifth Avenue and then stretched out for the New Yorker. Buyers were not expected to want manual transmissions with these luxury-looking cars. Likewise, only base models of the minivans with 4 cylinder motors got manual transaxles. The 5 speed wasn't offered for the V6 models, even though it was available for the G and P bodied cars. It seems that Chrysler didn't think V6 owners would want to shift for themselves.

A handful of folks on the 3 liter list have already replaced their A604 automatics for the A543 5 speed. (John Mitchell says the transmissions cannot be swapped. Harvii says they can..)

Swaps with Mitsubishi trucks (Neal Sandstede)

I used information from your site to repair my 1993 Mighty Max (also sold as the Dodge D50) 5-speed manual, 4WD truck. The truck had 185k miles and showed smoke so it wouldn’t pass the Colorado emissions test. I pulled a 3.0L from a 1989 Plymouth van with 105K, missing the water pump and front plastic covers. Even though it was a cross-fit engine it looked the same. The oil filter was in the wrong place so I found that the left motor mount of the Mits engine would cover the filter attachment boss on the Chrysler and used the original Mits oil pump. Using a handmade gasket between the mount steel and the block, oil flows correctly and there are no leaks. The bolt holes for the Mitsu mount align with the Chrysler filter attachment boss holes, but you have to trim the motor mount some to get the dipstick to fit. Interestingly, the flywheel fits the Chrysler version and the transmission input shaft carry bearing (idler bearing) is integral with the flywheel so no problem existed there.

At first I used the cast cam sprockets from the Mitsu but found that somehow the Mitsu sprockets are not centered on the Chrysler cams. The cam drive belt would alternate between too tight and too loose and made a repetitious noise like one or more of the lifters was faulty. I finally found the problem after using a stethoscope and noting that the noise was accompanied by a movement in the heater supply hose! I changed to the stamped Chrysler cam sprockets and eliminated the problem. It was difficult to comprehend how the timing belt survived this torture but it seems to be fine.

I used the Mitsu injectors and plenum, distributor, starter and motor mounts. The oil dipstick ended up being on the driver side instead of as in the Mitsu on the passenger side.

The truck seems to have a little more power, gets a little better fuel economy and passes emissions. I can easily accelerate from 30 mph in 5th , the truck will go over 100 mph (if you are brave enough to keep it up) and get about 27 mpg in mixed, but mostly highway driving.

Salvage yards wanted over $900 for a rear-drive engine from a Montero and I got the Chrysler engine for less than $100.

Some other comments:

  • The engine is a zero-interference engine; that is if the timing belt breaks, no damage to the valves.
  • When aligning the cam timing marks it should be noted that the right bank sprocket (from the rear) will stand precariously on the top side of a valve while the left bank sprocket will sit stable with all valves closed. No information about this trait is in your website, the shop manuals, or any other references. The valve timing belt tensioner is simplicity itself.
  • When installing the plastic timing belt cover, note that the oil slinger plate on the crank goes counter-intuitively outside the cover.

The only down side is that the engine idles at about 1100 rpm, which I think is too fast. So far I haven't been able to find out how to slow it down.

Credits, thanks, and needs

I'd like to thank Robert Carter III, Robert Hassler, Adam Baubach, Paul Berkibile, Drew Beck, Jay Storm, James Dempsey, Ron Adair and others IN NO PARTICULAR ORDER! Without the 3.0 list, and the subscribers to it, this information wouldn't be available in 1 location. Shoot, without those that have access to Factory Service Manuals, lots of this wouldn't be here. Also, I'd like to thank the folks at Ventura County Montero club for the FSMs and Haynes manuals on line for the Montero AND Conquest (2.6 turbo), and the folks at Club DSM for the 1993 3000GT motor FSM. All these references have been extremely valuable, and could lead to other development for us as well. Certainly helps us with alternate parts (higher compression pistons and cams with different timing values).

As I get more information, I'd like to add the factory turbo info as a block. Also, I'd like ANY motor/manifold/plenum information of the Hyundai Sonata, the industrial (forklift) version, and anything anyone might have that could be of help for others. Even international versions of the motor including Export versions of our own Chrysler 3.0 liter V6. Thanks for reading.

Keep in mind, I am NOT an expert.  This is the research I have done on my own, and now increasingly, with the help of others.  I know for a fact it is incomplete because I don't have access to some information others may have.  I do know that this IS the beginning of a FAQ for the 3 liter mailing list.  If anyone wants to add anything or use anything, please, let me know, and give proper credit if it comes from a book.  Getting more power from the 3 liter motor is a common goal for many of us.  We have many bright people coming on board to help us out.  This is a work in progress...

Also, for the short term, until this is more complete, I'll be showing others’ inputs in red and my additional and new comments in blue...

Vehicles equipped with the 3.0 liter engine (Rich Hutchinson)

  • Caravan/Voyager and early Town & Country (quickly replaced by 3.3)
  • Spirit/Acclaim/LeBaron sedan (replacing turbo-four)
  • LeBaron coupe/convertible (replacing turbo-four)
  • Daytona (replacing turbo-four)
  • Sundance (Duster)/Shadow (replacing turbo-four)
  • New Yorker AC body - until 1990 (replaced by 3.3)
  • Dynasty (replaced by 3.3)
  • Hyundai Sonata
  • Various Mitsubishis

More 3.0 liter engine repair notes

Fuel injectors (from Jason Beneteau)

To test for a bad injector in 1989 New Yorkers, take a 3 foot vacuum hose and install a Tee connector into the middle of it for fresh air to come in. Then run the car until it is warmed up all the way (coolant fan turns on 2 times), then take off the upper intake. Next you will turn the fuel pump on for a minute and after that hook the vacuum hose up to an exhaust gas analyzer and stick the hose 5-6in down each of the runners. If the Hydrocarbon readings are over 100ppm then you have leaky injectors and need they need to be replaced.

I had to deal with long start ups for years and I could never figure out what was wrong until I came across this TSB. All of my hydrocarbon readings were 1500+ppm. Since I put new injectors in my fuel mileage has increased 6 mpg from 18 to 24, and it starts up fast every time.

Stalling when stopping (Ron Wirth)

See fuel pump replacement (minivans)

I have owned and repaired five 1988 Dodge and Plymouth Vans (Caravan and Voyager) over the intervening years totaling some 400,000+ miles in aggregate. Three had stalling problems at one time or other when coming to a stop. No codes, no temperature correlation, no weather effects.

I ran into an independent garage owner and race car builder one day who seemed to be quite familiar with the stalling as I described it. He suggested that the fast idle servo was sticking (tight clearances in the cone valve area) due to the smog debris. He was right!

I had heard of that sticking before in connection with gasoline varnishes or deposits, which I dismissed because I knew that no gasoline was in the the throttle bell area; but the deposits, deposited in the valve by smog passages that share the valve passages, act in a subtle way, likely affected by combinations of moisture and temperature, in a stick/slip kind of way. The result was seemingly random and frustrating, as it would manifest itself at the most awkward moments, like in the middle of an intersection waiting to make a left turn.

The stalling ended immediately after solvent cleaning the fast idle servo as I indicated. (Don't get solvent in the motor actuator). (Also see replacing the fuel pump)

Water pump (Tyler)

I had the misfortune of having to replace a locked-up water pump on this 3.0. I restore cars for a living, and knew I should replace the cam and crank seals, realizing.....I don't want to do this again!

jurkka wrote: One does not need to open all the bolts. The water pump comes off after removing the 7 bolts that have the 12mm head. The 10mm bolts are not to be removed before water pump is out of the engine.

You noted the bracket that needs to be removed at the top of the water pump housing, usually requiring the removal of the intake manifold. I came to that conclusion as well, taking note that the bolts were restricted by the thermostat housing, unfortunately being part of the manifold casting.

I loosened the two bolts on the rear head as far as I could, and totally removed the bolt that met the water pump casting. I had a lucky break at this point realizing I could easily "bend" that small bracket up, giving me access to that top 10mm bolt. (It was a tight fit using the 1/4 inch ratchet version of the 10mm, but it was just enough to spare myself the grief and anguish.)

Warning: one reader wrote, “[Don’t bend that bracket up —] I bent the small bracket, and now the bracket doesn’t fit!”

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