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

Chrysler started using the Mitsubishi 3.0 liter V6 engine in late 1987, when they had no V6 of their own, just a pair of four-cylinders (2.2 and 2.5) and the 318 and 360 V8s. They introduced it as “an efficient, compact engine with remarkable performance and a host of high technology features. Available on Voyager models only. 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.”

The company also claimed that it was “Developed cooperatively by Chrysler and Mitsubishi Motors engineers... the result of a clean sheet of paper approach to engine design and three years of development work.” 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 to provide a broad, flat torque curve.

Features included an aluminum alloy cylinder head and intake manufold; semi-hemi heads; cast iron block and cam; forged steel connecting rods; nodular cast iron crankshaft; four main bearings; hydraulic valve lifters; oversquare design; compact exterior; large 43 mm intake and 35 mm exhaust valves; squish areas on either sides of the chamber for detonation control; 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.

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 should not be confused 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 (it would go up!) 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, it was featured as the standard powerplant on the Chrysler New Yorker and New Yorker Landau, its first passenger car use. In its first uses, it was teamed with automatic transmissions witih electronically controlled lockup torque converters.

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.]

I've done a fair bit of research into the variants of this motor. This motor appeared for the Chrysler minivans in mid 1987. Was included with the introduction of the stretched minivans that became the Grands. This motor was built by Mitsubishi motors, and was altered to Chrysler's specs. Our version is a multipoint fuel injection motor, and was later upgraded to sequential multiport injection. It uses a "Speed/Density" computerized system to regulate fuel, which has a Manifold Absolute Pressure sensor to allow the computer to "gauge" how much fuel to add. Not too bad of a system, but not real performance friendly. And the fuel mappings in the computer are geared toward staying environment friendly, as opposed to performance friendly. Check the links for power ratings by year and model...

1992 seems to be the magic year for the swap from MPI to SMPI. Look below for more info on the changes...

The Mitsubishi version of this motor was used in cars and trucks, including the 3000GT flagship. This motor was available in their Montero and trucks as SOHC, and also in their Diamante sedan and the base level of their 3000GT, again as a SOHC. The 3000GT also was available with the basic block and lower end, but with DOHC and 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.

Nick Boers had started to use the plenum and intake from the Hyundai Sonata version of this motor for HIS turbo project, but finally fell upon a reworked stock one like the rest of us are using. (Click here for more turbo-3.0 information from Allpar).

Different internal hardware for different applications

To mention intakes and plenums... There appear to be two different versions of the Chrysler plenum with one lower intake manifold. Then there is the Sonata version. Then, there are two different plenums and manifolds for the Mitsubishi vehicles. One each for the truck/SUV and one for the sedans and base 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 located on the pump and various adapters are used to alter the filters position depending on application and whether there is are turbochargers used or oil coolers. Could such a pump be used on the CHrysler FWD applications? No, the right side halfshaft is in the way, explaining the difference.

There are indeed 2 different lower intakes for the 3 litre in Chrysler vehicles. '87 & '88 and '89 and newer. The major diffrence is the mount for the PVC valve in the intake. In '87-'88 the PVC valve mounted in the valve cover. I have both in my posession. The older style in my van and the newer style sitting on a shelf in the basement. This also means 2 diffrent front valve covers too.

I also know of 3 diffent styles of exaust manifolds. I have 3 diffrent styles in my posession. One 2.25" and 2 2.5". Were there more. I'm not sure.

There were also 2 diffrent fuel rails. The older rails supposedly flow better than the newer style. Circa '92?

Now for even more confusion. There is evidence that this motor has also been used in Mitsubishi made forklifts and other machinery. Obviously, those versions are seriously different, as they usually run on LPG or Propane fuels. Since this basic motor is used in such applications, that tells me that it is a strong and reliable motor. And I've even seen a DUNE BUGGY (8 seats even, can you say "Minivan of the Dunes"?) with the industrial 3.0...

This motor is very capable of handling a lot more power than it has stock. It uses the same basic block, crankshaft (though in later years the TT version was Nitrile treated), and bearings and rods. 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. Or for that matter, the whole motor.

It also appears that the trucks got a different cam profile than the sedans did. Also, the Chrysler version has distinctly different cam timing from the Mitsu applications. Since all the SOHC models used a distributor based ignition system, it would seem that the hot cam to get for us (minivans) would certainly be the one from the Mitsu Montero/trucks. I ask out loud for the first time, but for the untold countless times in my head, why didn't Chrysler offer some of this stuff? And why is there such a vast difference between the Mitsu application motors and ours? Is this due to the different computer applications?

(Check out the specifications page for more).

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

1987 was the first year of the 3 liter in the minivans. I'm Not sure how long it was in production for Mitsubishi.

1988 saw the 3 liter motor introduced in the Dodge Dynasty 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 {overseas}), the AP bodies (Shadow/Sundance), G body (Daytona) and J body (Lebaron Coupe and convertible) cars. Also, exhaust manifolds were changed from 2.25" output, to 2.5". This coincides with the increased exhaust housing sizes for the turbo 2.2/2.5 motors and the TBI 2.5.

1990 saw the introduction of the roller cams. Also, adjusted cam timing seems to have added a little duration for intake valve opening, while a slight decrease in exhaust valve opening. Why?

1991 doesn't seem to have anything of real interest. Though I believe this is the year Chrysler started developement of the planned (but cancelled) turbocharged 3.0 liter for the IROC Daytonas...

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. Anyone else have an idea in this matter? Rob Carter and others suggest that the switch to SMPI was to increase fuel mileage over the older system. Each fuel injector in the SMPI system has its own "driver" as opposed to paired injectors per driver in the MPI setup. The Single Board computer (SBEC) seems to have code written for fuel efficiency but some additional power worked its way in there too. Still not enough though... Also, Robert Hassler has switched his turbo motor back to MPI. This motor runs on the stock computer... Hmmmm, at up to 10 psi boost, he seems to be giving Ricers and Rustangs fits...

Drew Beck has an excellent chart on applications for the minivans.

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. What is the significance here? Um, well, 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. But wait, if it fits the A670, what about the A413? I'm looking into that, anyone interested in finding the power limits of the AWD drivetrain with a turbocharged 2.2/2.5 four banger? Wouldn't an AWD launch be fun?

(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.)

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 halfshafts in their given years. So there you go. The minivans seem to have STRONGER shafts than the rest of 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. Of course 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. I have a list of compatible shafts/bodies that I'll include in a later revision...

According to not one, but two Chrysler mechs I'm in touch with, the A543 5 speed can be mated to the 3.3/3.8 motors. Waiting for confirmation for the 3.5... But it seems that the major difference for the 3.0 and 3.3 bellhousings is the "cutout" on the 3.0 version for the water inlet from the radiator. Other than that, they appear to be the same.

So, why not use a 5 speed in a 3.3/3.8 vehicle? Well, 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. Yes, this chassis is generally regarded as a luxury vehicle. As such, Americans NORMALLY prefer to be caudled and pampered in their luxo-cruisers, meaning, they don't want to be bothered with shifting, so a manual transaxle wasn't an option. 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. So much for forward thinking.

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. We will investigate.)

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:

I suppose everyone knows that 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 extant in your website, the shop manuals or any other references. The valve timing belt tensioner is simplicity itself.
One other note, 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 developement 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
LeBaron coupe/convertible
Daytona
Sundance (Duster)/Shadow
New Yorker AC body - until 1990 (replaced by 3.3)
Dynasty (replaced by 3.3)
Hyundia Sonata
Various Mitsubishis

More 3.0 liter engine repair notes

Fuel injectors (from Jason Beneteau)

In 1989, Chrysler put a lot of bad injectors into the 3.0Ls. The injectors will tend to leak which floods the engine and will cause extremely long startups. On 1989 New Yorkers, Chrysler decided not to put a test port for a fuel pressure gauge to plug into on the fuel rail so it is difficult for the average person to find this out.

According to the TSB, you have to 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 needto 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 milage has increased 6mpg from 18 to 24, and it starts up fast every time.

Stalling (from Ron Wirth)

I've read many notes and postings regarding Mitsubshi 3.0 motors with a chronic, but intermittent stalling problem when coming to a stop. No codes, no temperature correlation, no weather effects, but it seemed tied to the fast idle servo located in the throttle body, which I had looked at before and saw nothing unusual. Starting with the new 1988 Caravan, 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. I even placed a pressure gauge in the fuel line in an attempt to blame the fuel pump. I broke a transmission trying to get a stalling motor going on ice and I have to admit that I never really knowingly cured this annoying characteristic until now.

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. His hint galvanized me to take another look at the servo. He suggested that it 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. Wow, was I wrong in dismissing. 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 stik/slip kind of way. The result was seemingly random and very frustrating, as it would manifest itself at the most awkward moments, like in the middle of an intersection waiting to make a left turn.

It's been several months since the stalling. It ended immediately after solvent cleaning the fast idle servo as I indicated. (don't get solvent in the motor actuator). I hope this is helpful.

By the way, I change the Caravan in-tank fuel pumps by first making sure the tank is full, then I carefully cut through the floor pan just above, and centered over the fuel pump mounting position on the tank, using a Moto tool cutting disc, being careful not to cut too deeply and damage the rubber fuel lines below the area. Don't use a reciprocating saw. And, of course, don't use the grinder either if you smell gasoline anywhere around the tank area. Advise doing job on level ground.

The section, approximately 6" x 6" is then discarded and replaced with a fabricated, overlapping steel panel, that gets sealed and screwed down over the service port. Changing the fuel pump then becomes a piece of cake, with little or no danger of exploding fumes, like one would encounter taking the tank out of the vehicle. The in place, full tank, produces very little fumes from the small surface exposed through the fuel pump mounting portal, making the whole procedure far safer and much quicker than the traditional tank removal. (I did the latter twice before coming up with the floor access method.)

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!!! I noticed the passage where you were telling of 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. What I did was.....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 myself 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. Just a thought!!!!