Engine Turning the Wrong Way -- Counter-Clockwise

[Mark The Homer]

I've got a new Tacoma with a 4.0 L engine and a manual six speed trans.

So, I'm parked on a fairly steep incline pointing down. Nothing is in front of me. It's in gear and the parking brake is on. I start it up, release the parking brake, and, since I've got the clutch in and I'm in neutral, I begin rolling down the hill at, say, 10 mph. Being the smart guy that I am, I don't touch the brake -- instead I use the engine to maintain a slow speed down the hill. So, with my hand on the shift knob, I let my foot off the clutch gradually, and the engine grabs the trans fairly smoothly.

I proceed down the hill to the bottom. I travel maybe 100 ft. I'm not touching any pedals. Engine is firing fine. I don't touch the gas pedal or the brake. When I get to the bottom of the hill, I push the clutch pedal to the floor and brake. As I'm doing this, I notice the engine sounds a little funny. It's running a little rough. And at that moment, the horrible realization comes over me of what I just did.

I was in REVERSE.

As I'm thinking about this -- and starting to feel kind of sick, the engine is sputtering for another ten seconds or so. It's running, but weakly. And then it dies.

It's then that I begin to fully understand what just happened. My engine's crankshaft and flywheel was spinning COUNTER-CLOCKWISE. BACKWARDS, if you will.

So I turn the ignition, still feeling sick, and praying for it to start, and it does. But there's this loud hissing sound now.

Turns out, one of the vaccuum hoses blew off. Instead of sucking air, it blew air, and blew the hose right off. And it's running rough.

So I take it into the dealership.

Service manager: "We're you fiddling around with those hoses at all?"

Me: "No, sir. Nuh uh." I give him a perplexed look.

Service manager: "You weren't pulling on any of them for any reason?"

Me: "No. Not at all. Why?"

Service manager: "Because your vaccuum hose came off,", he explained. "Very unusual. In fact, we've never had that before."

Me: "Hmm." I shrug.

My truck is good as new now.

What happened was, my truck is a six speed. And when they designed the shifting mechanism, they put the reverse all the way to the left and up. And first gear is ALSO all the way to the left, and up. So, after driving standards all my life, I had my hand on the shift knob, confident that it was in first. But it wasn't. So, by releasing the clutch while in reverse, I forced the engine to spin backwards. And it ran backwards.

I wonder if anybody has ever heard of something like this happening before.

[wantarace17]

not doubting you but i have never heard of an engine rotating counter clockwise

[DeanCollins]

It's in what gear? If you were in reverse the engine would not have be spinning backwards obviously. even if you were in a forward gear, I don't see any harm being done. transmissions don't like sort of thing, like towing a car with the driven wheels trailing.

the vacuum hose probably popped off when engine was shaking back and forth at low rpm, stuttering.... no big deal. btw most engines do spin counter clockwise (when viewed from the front) normally

[chomerics]

Umm, your engine could not run in the other direction, the timing of the piston firing would be all messed up, and it could not run.

The gearing of reverse is taken up in the transmission, and not the engine. the hose popped off when the engine was struggling and straining the trainy

[Pete]

I've seen diesel engines run backwards a few times. Pretty funny actually when it happens.

[IONTOP]

Wow, I don't know about that shift placement. My reverse is all the way to the right and down, barely right of where 6th gear would be if I had one.

Does your car not have a reverse lockout? In order for me to get into reverse I've got to pull up on something on my shifter, to prevent exactly what you did...

But then again in my car, if you "accidentally" put it into reverse, you'd probably be trying to get it into the nonexistant 6th

[twa]

Umm, your engine could not run in the other direction, the timing of the piston firing would be all messed up, and it could not run.

The gearing of reverse is taken up in the transmission, and not the engine. the hose popped off when the engine was struggling and straining the trainy

One of the rare times I agree with you.

Does this mean we are wrong?

[Mark The Homer]

Umm, your engine could not run in the other direction, the timing of the piston firing would be all messed up, and it could not run.

First of all, there's no doubt the engine was running in the opposite direction. What else could it have done? Did you read my post? I was there. If the truck is moving forward in reverse gear with the clutch out, the crank has to be rotating backwards. It was doing all this, AND it was firing.

Secondly, I'm not a mechanic, but I do have a very basic understanding of how an engine runs. And it seems to me, in my simple mind, if it's rotating backwards, then the timing would also be backwards, so it should fire. But as I said, it did stutter and stammer and finally die after sitting in neutral for about ten secs.

Wow, I don't know about that shift placement. My reverse is all the way to the right and down, barely right of where 6th gear would be if I had one.

Does your car not have a reverse lockout? In order for me to get into reverse I've got to pull up on something on my shifter, to prevent exactly what you did...

Yes, I'm not happy about the Reverse placement either. And this isn't the first time I've accidentally put it in reverse thinking I was in first. The thing is, it was parked in reverse gear -- so it was already in reverse when I started moving forward.

Anyway, I told this story to a good buddy of mine up near Boston (ex Redskin fan and now a Pats fan, the poor dumb ****) who is very mechanically inclined. He didn't doubt my story at all, and said he knows of old boat engines in the 20s and 30s that would sometimes, if the flywheel was positioned at just the right spot, it would start, then compression would force it back, and those engines would sometimes continue to run rotating the wrong way. You had to then shut it down and restart. But he never heard of it happening in a modern engine.

[Ghost of]

No homo but that's why I don't mess with standards. Especially with these hills 'round here in Seattle. Rain+steep incline downtown+10 cars behind you not giving you space+standard=your ass.

[chomerics]

Secondly, I'm not a mechanic, but I do have a very basic understanding of how an engine runs. And it seems to me, in my simple mind, if it's rotating backwards, then the timing would also be backwards, so it should fire. But as I said, it did stutter and stammer and finally die after sitting in neutral for about ten secs.

All automobile engines are four stroke engines (well, not all, but the one you are talking about is since you are not talking about a rotary or a diesel). In a four stroke engine, the piston goes through 4 stages. . .

intake

compression

combustion

exhaust

Your piston runs through 2 complete rotations to complete one cycle. . .

Now, here is why it is impossible. If your engine was running in reverse, the engine would go through the following sequence. . .

exhaust

combustion

compression

intake

http://auto.howstuffworks.com/engine1.htm

You can look here for a working schematic. . .

Do you see the problem? Your combustion stroke comes directly after your exhaust stroke, so you have no fuel mixture in the chamber for ignition. In essence, you fill the chamber, exhaust it and you go through one cycle of nothing.

You have to remember your camshaft is going in the same direction as your engine, so it HAS to follow this order, there is NO POSSIBLE WAY to run an engine in reverse in spite of what you may think.

What was most likely happening to you was that your car "running rough" was your clutch plate getting grown down to nothing. Moving in reverse would want to cause the engine to move in reverse, but of course, it would not run, so it would either strip out the gears in your transmission or go to the weakest part of your drivetrain, which is your clutch. You probably burnt the crap out of your clutch, and that is what caused the car to "run rough" and blow apart your vacuum system.

Either way, you can not run an engine in reverse, it is physically impossible to do so because of what I just mentioned. . .

Anyway, I told this story to a good buddy of mine up near Boston (ex Redskin fan and now a Pats fan, the poor dumb ****) who is very mechanically inclined. He didn't doubt my story at all, and said he knows of old boat engines in the 20s and 30s that would sometimes, if the flywheel was positioned at just the right spot, it would start, then compression would force it back, and those engines would sometimes continue to run rotating the wrong way. You had to then shut it down and restart. But he never heard of it happening in a modern engine.

A boat engine is a 2 stroke engine, and it is a completely different setup then on a modern gasoline engine. A boat engine CAN run in reverse.

I also want to add that I have an advanced degree in mechanical engineering, so I know what I am talking about. I have been around engines my entire life, rebuilt them from the ground up, bored out cylinders, and done just about every mod imaginable.

I am not trying to show you up by any means, but instead just telling you that what you think happened did not actually happen. It gives you a little bit more knowledge in the inner workings of engines, and hopefully you appreciate it when you learn something new

If you want to know why a 2-stroke engine (boat outboard, lawnmower, weed trimmer etc) CAN run backwards, I can answer that as well for you

[Mark The Homer]

In a four stroke engine, the piston goes through 4 stages. . .

intake

compression

combustion

exhaust

Your piston runs through 2 complete rotations to complete one cycle. . .

Now, here is why it is impossible. If your engine was running in reverse, the engine would go through the following sequence. . .

exhaust

combustion

compression

intake

http://auto.howstuffworks.com/engine1.htm

You can look here for a working schematic. . .

Do you see the problem? Your combustion stroke comes directly after your exhaust stroke, so you have no fuel mixture in the chamber for ignition. In essence, you fill the chamber, exhaust it and you go through one cycle of nothing.

You have to remember your camshaft is going in the same direction as your engine, so it HAS to follow this order, there is NO POSSIBLE WAY to run an engine in reverse in spite of what you may think.

What was most likely happening to you was that your car "running rough" was your clutch plate getting grown down to nothing. Moving in reverse would want to cause the engine to move in reverse, but of course, it would not run, so it would either strip out the gears in your transmission or go to the weakest part of your drivetrain, which is your clutch. You probably burnt the crap out of your clutch, and that is what caused the car to "run rough" and blow apart your vacuum system.

Either way, you can not run an engine in reverse, it is physically impossible to do so because of what I just mentioned. . .

A boat engine is a 2 stroke engine, and it is a completely different setup then on a modern gasoline engine. A boat engine CAN run in reverse.

I also want to add that I have an advanced degree in mechanical engineering, so I know what I am talking about. I have been around engines my entire life, rebuilt them from the ground up, bored out cylinders, and done just about every mod imaginable.

I am not trying to show you up by any means, but instead just telling you that what you think happened did not actually happen. It gives you a little bit more knowledge in the inner workings of engines, and hopefully you appreciate it when you learn something new

If you want to know why a 2-stroke engine (boat outboard, lawnmower, weed trimmer etc) CAN run backwards, I can answer that as well for you

Okay. Well, it certainly sounds like you have a better understanding of what is going on than me. And you're better educated too.

Study what I am about to say and try to follow me here:

When a 4 stroke engine is running, the piston is moving up and down like this: It moves up. Then it moves down. Then it moves up. Then it moves down.

So, if the crankshaft is turning clockwise, the piston moves like this: It moves up, then down. Then up, then down.

If the crankshaft is turning counterclockwise, the piston moves like this: It goes up, then down. Then up, then down.

Either way the crank rotates, the piston goes up, then down. Doesn't matter which way the crank turns. Am I right?

I understand what you are saying in regards to the camshaft. And I agree something seems weird.

Your idea that the engine was strong enough to grind the steel in my clutch plate all the way down that hill rather than stall out is interesting, but not really realistic, is it? Besides, if it did that, I would have smelled burning steel.

My engine is a VVT-i engine. Maybe this explains the difference between your argument, which I think is in regards to a purely mechanical engine, and this one.

Toyota writes:

In a conventional engine, the valve timing is fixed at a compromise setting, which is applied to different driving conditions - from idle through to sporty driving. ... However, with VVT-i, inlet camshaft timing is varied according to your needs.

Here's a link:

http://www.toyota.com.au/fuelefficiency.html

This may explain why my engine was able to run in the wrong rotation: The computer made adjustments in the inlet camshaft timing which enabled the engine to run.

Then it finally stalled. When I started it back up in the correct rotation, it still ran rough. The service manager ran the codes and told me it was running lean due to the vacuum hose that had come off. They purged the system, reconnected the hose, reset the codes, and I am good as new.

[bschurm]

not doubting you but i have never heard of an engine rotating counter clockwise

I thought they only did that in the Southern Hemisphere.

[ZoEd]

All automobile engines are four stroke engines (well, not all, but the one you are talking about is since you are not talking about a rotary or a diesel). In a four stroke engine, the piston goes through 4 stages. . .

intake

compression

combustion

exhaust

Your piston runs through 2 complete rotations to complete one cycle. . .

Now, here is why it is impossible. If your engine was running in reverse, the engine would go through the following sequence. . .

exhaust

combustion

compression

intake

http://auto.howstuffworks.com/engine1.htm

You can look here for a working schematic. . .

Do you see the problem? Your combustion stroke comes directly after your exhaust stroke, so you have no fuel mixture in the chamber for ignition. In essence, you fill the chamber, exhaust it and you go through one cycle of nothing.

You have to remember your camshaft is going in the same direction as your engine, so it HAS to follow this order, there is NO POSSIBLE WAY to run an engine in reverse in spite of what you may think.

What was most likely happening to you was that your car "running rough" was your clutch plate getting grown down to nothing. Moving in reverse would want to cause the engine to move in reverse, but of course, it would not run, so it would either strip out the gears in your transmission or go to the weakest part of your drivetrain, which is your clutch. You probably burnt the crap out of your clutch, and that is what caused the car to "run rough" and blow apart your vacuum system.

Either way, you can not run an engine in reverse, it is physically impossible to do so because of what I just mentioned. . .

A boat engine is a 2 stroke engine, and it is a completely different setup then on a modern gasoline engine. A boat engine CAN run in reverse.

I also want to add that I have an advanced degree in mechanical engineering, so I know what I am talking about. I have been around engines my entire life, rebuilt them from the ground up, bored out cylinders, and done just about every mod imaginable.

I am not trying to show you up by any means, but instead just telling you that what you think happened did not actually happen. It gives you a little bit more knowledge in the inner workings of engines, and hopefully you appreciate it when you learn something new

If you want to know why a 2-stroke engine (boat outboard, lawnmower, weed trimmer etc) CAN run backwards, I can answer that as well for you

Wait a minute, Chom you're a gear head? I see you in a totally different light. Major cool points. :applause:

Being a bit of a gear head myself I don't see anyway possible for an engine to run backwards. Impossible if you ask me.

I do have a good story though. A guy driving a dodge mini-van pulls up in front of my building one day on base, this was about 10 years ago. Van is running like crap, knocking, sputtering, smoke bellowing out of it. He turns it off and jumps out saying it wouldn't shut off. I told him to pop the hood so I could take a look. By this time this van sounded like it was about to explode, the entire van was shaking. I immediately started pulling wires trying to get this thing to shut off. The ignition was off, I pulled positive battery wire, coil wire, plug wires everything, damn thing was still running. Then I noticed the exhaust manifold was glowing a red color. It was so freaking hot because of a blocked up catalitic converter it was igniting fuel in the cylinder causing the engine to keep firing. No spark needed, this thing was a freaking bomb ready to blow and since it had a mechanical fuel pump she just kept on firing until finally due to the heat she locked up. I've never seen anything like it in my life.

[HOF44]

I know in the old days of NASCAR a few teams decided to set the engine up to rotate counterclockwise. Doing this caused the torque to pull the car down on the left side which made it grip better for cornering. It was outlawed when discovered.

[jrockster21]

What are you doing using your clutch to take you down the hill anyway? Throw that sucker in neutral, and use the brakes. Brake pads are cheap - a new clutch or transmission is not.

[jrockster21]

Found this - maybe the VVT timing works in such a way that this can happen:

It was discovered long ago that there was an advantage of triggering the ignition spark several degrees of crankshaft BEFORE TDC. Otherwise, the maximum pressure only develops so long after TDC that the piston has dropped and less pressure and force are created, as described above. This spark advance situation causes the interesting effect that an engine begins building up combustion pressure BEFORE TDC, which actually would have the effect of making the engine rotate backwards! Some early engines had a serious susceptibility to this, and many people who used early crank starters (before electric starters) were seriously injured when the engine kicked backwards.

.

.

.

If an engine were intended to run at a constant speed with a constant load, it would be possible to fine-tune the exact best spark advance angle. However, vehicle engines must be able to go from idle to maximum performance rather quickly. There are many other engine conditions that also affect the amount of ideal spark advance, such as the relative richness of gas in the mixture and whether the air intake path is restricted or open. All these things are important for the following reason. When the ignition spark occurs substantially before TDC, a significant combustion pressure starts to build up even before TDC. If the engine was not already spinning, this could act to make it rotate backwards! Only the momentum of the crankshaft and flywheel makes it overcome this backward torque to get past TDC when good things start to happen.

http://mb-soft.com/public2/engine.html

[DeanCollins]

I My engine's crankshaft and flywheel was spinning COUNTER-CLOCKWISE. BACKWARDS, if you will.

"In this drawing, we are looking at the end of the crankshaft, and the crankshaft is going to rotate counter-clockwise. Therefore, at this moment, the crankshaft is pushing the piston upward in the cylinder, and it is currently half way up. This is during the stage called Compression, where the gas-air mixture above the piston is getting compressed by the upward movement of the piston."

All automobile engines are four stroke engines (well, not all, but the one you are talking about is since you are not talking about a rotary or a diesel). In a four stroke engine, the piston goes through 4 stages. . .

intake

compression

combustion

exhaust

Your piston runs through 2 complete rotations to complete one cycle. . .

Now, here is why it is impossible. If your engine was running in reverse, the engine would go through the following sequence. . .

Chom your logic is good but in reality there would be enough unburnt fuel left in the cylinder head to fire. It doesn't matter which way the engine is rotating (counter clockwise normally, clockwise is opposite) when the piston is headed down to bottom dead center the vacuum created would suck fuel into the cylinder head and even if the fuel left through the exhaust valve and into the exhaust manifold the vacuum would pull it back into the cylinder (running backwards) timed poorly mind you but in time to be ignited. The result would be a violently shaking and random knocking ( from detonation) barely running and perhaps backfiring mess mechanics call "dieseling". Anyone ever turned off the ignition of an overheating engine and watch it continue to run to their shock and horror? Anyone who has installed engines has experienced this when the distributor is mistakenly placed 180% out of proper timing, or the spark plug wires are one or two locations off in respect to the distibutor cap, or just in the wrong order all together with regard to the firing order. But you would be amazed at how far off and how many of these things could be wrong at one time and the engine somehow can still run because there is fuel and spark.

[twa]

Dammit ,I knew agreeing with Chom was trouble. :laugh:

[Pete]

After giving it some serious thought, I'm still tossed up on this one. Fuel injection pulse and spark are triggered by crank position. The signal produced by the crank sensor would be identical rotating in either direction, so you would still get fuel and spark at the right time.

The thing that I'm stuck on is, with the diesels that I have seen run backwards, they were sucking air in through the exhaust, and pushing the exhaust out the intake.

Have to do a little more thinking on this.

[DeanCollins]

After giving it some serious thought, I'm still tossed up on this one. Fuel injection pulse and spark are triggered by crank position. The signal produced by the crank sensor would be identical rotating in either direction, so you would still get fuel and spark at the right time.

The thing that I'm stuck on is, with the diesels that I have seen run backwards, they were sucking air in through the exhaust, and pushing the exhaust out the intake.

Have to do a little more thinking on this.

got to admit I haven't replaced an FI motor yet, I've never lost one. You bring up an interesting point about the air intake on an FI engine being able to exhaust (running in backwards) with the fuel charge coming from the injectors.

[bpoch]

You guys are going way to deep for this. The transmission is going to control the gearing between the engine and axles. Your engine is only going to crank and run in one direction, like other said before the time would be all off and it just wouldn't work.

The gearing in the transmission is what is going to reverse the ways your tires spin not the engine.

[DeanCollins]

You guys are going way to deep for this. The transmission is going to control the gearing between the engine and axles. Your engine is only going to crank and run in one direction, like other said before the time would be all off and it just wouldn't work.

The gearing in the transmission is what is going to reverse the ways your tires spin not the engine.

read marks post again, he was going forward with the transmission in reverse

[RLeVan]

Found this - maybe the VVT timing works in such a way that this can happen:

If it works anything like Honda's V-tech, it's computer controlled advance/retard spark in conjuction with a variable cam. The cam itself has two profiles actuated by hydraulic pressure; a fuel saving profile between 0-4,500rpm, as well as an aggressive profile between 4,500-8,000rpm. As engine rpm increases along with oil pressure to the cam rail, the more aggressive lobes slide into place and take over.

My guess is that your engine thought twice about running backwards, blew the vacuum hose, and sputtered until you let the clutch out when you came to a stop. In the meantime, your clutch took the brunt of the force as well as the pressure plate but it shouldn't be too bad being that you didn't travel all that far.

The odd part of this is, you would know if your engine was running backwards, kinda like a bucking bronco.

[chomerics]

Okay. Well, it certainly sounds like you have a better understanding of what is going on than me. And you're better educated too.

Study what I am about to say and try to follow me here:

When a 4 stroke engine is running, the piston is moving up and down like this: It moves up. Then it moves down. Then it moves up. Then it moves down.

So, if the crankshaft is turning clockwise, the piston moves like this: It moves up, then down. Then up, then down.

If the crankshaft is turning counterclockwise, the piston moves like this: It goes up, then down. Then up, then down.

Either way the crank rotates, the piston goes up, then down. Doesn't matter which way the crank turns. Am I right?

I understand what you are saying in regards to the camshaft. And I agree something seems weird.

Yes, you are right, as far as the engine is concerned, the piston goes through 2 complete strokes and it does not see a difference in cw or ccw rotation because it is linear motion. . . but, as I mentioned before, the timing will be completely messed up as it would be firing on an empty cylinder. The problem lies in the camshaft, as it is directly connected to the crank. The engine will fire slightly before TDC (on most models). I believe this is to maximize power, but I can not remember.

The problem is that there is no fuel in the cylinder to ignite. Someone mentioned that there may be enough residual fuel to actually fire, but I am skeptical to say the least. I would venture a guess that you would not have nearly enough fuel to fire the cylinder (if you did it would mean that you are wasting most of the energy during normal operations, and a much leaner fuel could be used instead.)

Your idea that the engine was strong enough to grind the steel in my clutch plate all the way down that hill rather than stall out is interesting, but not really realistic, is it? Besides, if it did that, I would have smelled burning steel.

It isn't steel in a clutch, but a clutch disk which is the weakest force. The clutch disk (which is what people usually say is the clutch) is a material similar to what break pads are made out of, and it is meant to give and wear. In this condition, you can give enough force to cause the clutch disk to slip even when fully engaged.

My engine is a VVT-i engine. Maybe this explains the difference between your argument, which I think is in regards to a purely mechanical engine, and this one.

Toyota writes:

In a conventional engine, the valve timing is fixed at a compromise setting, which is applied to different driving conditions - from idle through to sporty driving. ... However, with VVT-i, inlet camshaft timing is varied according to your needs.

Here's a link:

http://www.toyota.com.au/fuelefficiency.html

This may explain why my engine was able to run in the wrong rotation: The computer made adjustments in the inlet camshaft timing which enabled the engine to run.

Then it finally stalled. When I started it back up in the correct rotation, it still ran rough. The service manager ran the codes and told me it was running lean due to the vacuum hose that had come off. They purged the system, reconnected the hose, reset the codes, and I am good as new.

I read the link, and what they are talking about is an electronic injection system which is computer controlled. The computer will monitor the engine's performance, RPM level an speed, then adjust the fuel mixture and timing accordingly. The thing to understand though is that the computer will still only fire on the same stroke, it just varies the position of the piston when firing. It would not take into account something like an engine running backwards, i could be wrong, but I can not for the life of me see a computer firing during the exhaust phase, which is what would be needed for it to work.

Now, the difference in what pete said in Diesel engines is true, a diesel can run backwards. This is because they do not require spark plugs, and they fire on compression only. If this was indeed the case, then the exhaust and intake air would be reversed.

Now that I think about it even more, I think with the CC on the car, the engine would not get enough air to ignite as well. The converter would act as a restrictor and decrease the volume of air needed to fire.

[IONTOP]

If it works anything like Honda's V-tech, it's computer controlled advance/retard spark in conjuction with a variable cam. The cam itself has two profiles actuated by hydraulic pressure; a fuel saving profile between 0-4,500rpm, as well as an aggressive profile between 4,500-8,000rpm. As engine rpm increases along with oil pressure to the cam rail, the more aggressive lobes slide into place and take over.

I really hate the V-tech engine... I mean, if your customers want power, give them power, if they don't want power give them an engine without power... I'm tired of all the ricers everywhere sayin "You would've been toast if I had hit my V-TTTTTTAAAAAAAAAAKKKKKKKK sooner"