converting a V6 into V4

I would like to know if it's possible to convert a V6 3.8L engine into a V4 2.5L?

If I disable 1 pair of cylinder (example 1 & 5) by removing spark plug n°1 et 5, and by unplugging 1 and 5 injectors? It should work?

It'll remove compression, injection, and ignition on these cylinders, for reducing the fuel consumption.

Can this damage the engine, or making it run roughly?

Another question, when V6 engine start, did all the pistons working? Or just 2 or 4?

At start-up, all pistons should be working.

If you disable the #1 and 5 cylinders, you are removing every third power stroke. The engine will run quite roughly.

Removing the spark plug is not the best way, because, if you did so, the piston's movement would be shoving air in and out of the hole very quickly. This would introduce frictional losses and fuel-sucking drag due to air pumping loses. Also, unfiltered air would be introduced into the engine, causing excessive engine wear; and it would be very noisy.

The best way would be to remove the intake valve pushrod from those cylinders.... thus the air trapped inside the cylinder would work like an air spring, it would absorb energy upon compression but return it upon expansion.

Also you need to come up with a way of holding the hydraulic valve lifter in it's bore (to maintain oil pressure) but keep it away from the cam lobe (so it does not bounce out.)

Also, you would have to unplug the appropriate spark plug wire and fuel injector.

Doing this would give the ECM fits. You would get the 'Check Engine' light on and the ECM would throw several codes.

The car would be SLOW.... imho slow enough to be dangerous and unusable for highway driving. The engine would have less power than a V4....... due to the excess frictional drag of 2 extra cylinders. It would feel more like a V3.5 :)

Frankly, this idea of disabling cylinders for better fuel economy has been around for decades. I have a 1981 Cadillac (parts car) with such a system..... and mine worked very well, even though these engines developed a bad reputation.

Several new cars use such systems these days with great success. However, these cars all have the ability to reactivate all cylinders very quickly when full power is needed. Your idea would not allow this... leaving your car (imho) slow, unsafe, rough and miserable to drive.

Thanks for this info.

This afternoon, I removed 2 plugs of the same coil, but the engine shake and stall when I release the accelerator.
I was wondered if I make something wrong. So I put the plugs back.

But I will defetitively not do that again. It'll use more fuel, like you said. And it seems complex with the valve...

I agree with MagicRat. You'll still have the friction of the extra two cylinders without the additional combustion to support it. It would be the same as if you replaced the 3.8 with a 2.5L four cylinder and kept your foot on the brake while you drove.

Engines are also timed to fire evenly. In a V6, there is ignition every 120 degrees, so it pulses evenly over the full 720 degrees of rotation in the cycle. A 4-cylinder fires every 180 degrees. If you disable two cylinders on a V6, it will operate like; bang, bang, rest, bang, bang, rest.

Not only will it be hell to program and very hard on the engine, you probably won't gain any mileage. That vehicle needs a certain amount of fuel to be burned in order to propel it based on weight and many other factors. If you disable 33% of the cylinders, you'll end up using 33% more accelerator to accomplish the same driving style which negates any gains. Add in the fact that you're dragging along the dead weight of two cylinders not doing their share of the work and you'll probably lose mileage big time.

There might be a logical alternative. The 2.3L four cylinder was used in many of the same vehicles that got a 3.8L. You might look into a swap.... or look into a diesel vehicle :)

The reason why I asked this, it's not only because I want to save fuel.
My engine just blew 2 days ago. It make a very hard metallic sound, misfire and stall sometime.

I think it's either the valve or the piston. I'm not sure if it's all the pistons, or just 1 or 2.
So my car is undrivable.

It's why I wondered if something is possible to let run only the cylinder that work properly, and disable the others. I've no choice other than finding a solution, if not, I'll be obligate to scrap my car. It'll be too bad, cause everything else work on the car.

I don't know if you've a better solution to save my car.

The reason why I asked this, it's not only because I want to save fuel.
My engine just blew 2 days ago. It make a very hard metallic sound, misfire and stall sometime.

I think it's either the valve or the piston. I'm not sure if it's all the pistons, or just 1 or 2.
So my car is undrivable.

It's why I wondered if something is possible to let run only the cylinder that work properly, and disable the others. I've no choice other than finding a solution, if not, I'll be obligate to scrap my car. It'll be too bad, cause everything else work on the car.

I don't know if you've a better solution to save my car.

For our other members, here is the thread serge saati is referring to:

http://www.automotiveforums.com/vbulletin/showthread.php?t=958880

I think that, without an accurate diagnosis of the malfunction, it's a waste to consider such a conversion.

Have you priced-out a good, used engine for this vehicle.... or a rebuilt one? Frankly, if the rest of the van is in fine shape, a rebuilt engine will be cheaper than buying another van in the same condition.

Yes, beside that, the van is in full working condition.
But a used engine replacement cost 2000$ with the labor. It takes a lot of times to do that.

A used Windstar 99 in good condition cost about 1500$.

Read my last post there: http://www.automotiveforums.com/vbulletin/showthread.php?t=958880

What do you think?

Now, it works great a constant speed, but stall at stop, unless I keep my foot on the accelerator while I brake.

I have brought your last post here, because your link does not seem to work
It's funny, I let the engine idle during 5 minutes, I rev up at 2000rpm sometime, the noise have reduced a lot.

Then I make a test drive, at cruise speed in city (30-40mph), the engine didn't make noise at all! It's strange, but good. Maybe the valve stop moving?, I don't know.

But when I come to stop light, the engine want to stall, I put in Neutral, I push gas so it keep that way, when it's green light, I push brake and accelerator in same time, I put Drive and I release the brake. So it go w/o stalling. But it jerks.

The engine misfire alsmost 90% of the time in this 10 miles (30 minutes) test drive.
I check the code, I got only the P0301 code and also the old classic 171/174 code which is normal for a Windstar 99-03.

So only cylinder 1 misfire???? Very strange.


So my question is: It's possible to make the engine run with only 4 or 5 cylinders, instead of repairing the valve? Well, I guess it's a valve problem.

So the engine will not stall anymore.

When I removed the plugs n° 1, there's oil deposit in it. So I guess, oil leaking through the valve to this cylinder, it's why it misfires.

So if I make the engine works with the plugs n°1 removed and connect the plugs wire to GND, so that current will flow to plugs 5, engine should work fine?

because I can't afford a valve or piston reparation, it's more than the car value.

I really feel like in 60s decade working with old combustion engine. Exept that I have automatic transmission. I wish I could have a clutch, it'll be easier to drive, instead of put N and D at each red light. It'll stop jerking.

Try all - new park plugs, or at least change the oil-soaked one. And no, you do not have to ground a plug wire thats been removed.

Compression test is a must at this point. That will tell you if this engine is worth saving or if its scrap time. It could be something as simple as a loose injector wire, bad plugs, bad wires, bad coil; all of which can be fixed for under $50 if not free.

Labor is what is going to kill you. Plan on 10-12 hours at least. The shop will probably charge you $75-90 per hour. The mechanic gets $20-30 of that. Advertise on craigslist that you will pay a fair $25/hr for 12 labor hours to any mechanic that wants to do the work. That just saved you $660. The shop will also mark up the used engine about 30%, so call a junkyard and get it yourself. Used engine for $500, $600 in labor... bingo.

Compression test is a must at this point. That will tell you if this engine is worth saving or if its scrap time. It could be something as simple as a loose injector wire, bad plugs, bad wires, bad coil; all of which can be fixed for under $50 if not free.

Labor is what is going to kill you. Plan on 10-12 hours at least. The shop will probably charge you $75-90 per hour. The mechanic gets $20-30 of that. Advertise on craigslist that you will pay a fair $25/hr for 12 labor hours to any mechanic that wants to do the work. That just saved you $660. The shop will also mark up the used engine about 30%, so call a junkyard and get it yourself. Used engine for $500, $600 in labor... bingo.

It sounds a good idea, but are you sure that a mechanic will able to remove the engine without the special hydraulic machine that we found in a shop?

It sounds a good idea, but are you sure that a mechanic will able to remove the engine without the special hydraulic machine that we found in a shop?


If your really keen, you can move an engine with anything.
I've done an engine install before using some rope and a block of wood :icon16:

It sounds a good idea, but are you sure that a mechanic will able to remove the engine without the special hydraulic machine that we found in a shop?

These hydraulic engine lifts can be rented by the hour, for not much money. All one needs is a smooth hard surface (preferably paved) for the lift to roll on. If you are swapping the engine in your back yard, on grass etc., a sheet of thick plywood will do.

I'd suggest an engine swap. A used engine at a junkyard usually doesn't cost anymore than maybe 700 at the very most if its stock. If your even a half decent mechanic you can do it yourself. I would consider myself far below an average mechanic and I was able to do it. It took me about two weeks but only because I was taking about numerous parts that I had never worked on and some never knew existed. However I did it and it worked fine. Another suggestion would be if you rent a engine hoist, the day you rent it should be the day that all you have to do is unbolt the bolts that hold the engine itself in(i don't remember what they are called, told you im below) and then pull it out and drop the other in and bolt it back down.