During shutoff engine starts backup backwards

[02stu]

Here's an odd one, every now and then when turning my car off the engine spins to a stop and then right after stopping it starts in the reverse direction for about 2 seconds. You can imagine how terrible the timing chain sounds. It also blows a significant amount of exhaust through the intake. Obviously this is very bad for the engine the electronics etc. what do you guys think it is? Leaky injectors? If you're doubting me like my local car guy friends I can insure you that you put it in first gear and the car will go backwards.

[bigwave]

Seen this with a 1 cylinder diesel marine engine, but never with an i6.

[slammin_e28]

Google "Dieseling"

As for the running backwards.....I have no clue.

[rmiddendorf]

Okay, I'm in for the analysis on this one. I've always wondered why this didn't happen more often actually.

Edit: read this:

http://forums.off-road.com/jeep-short-w ... eling.html

[al525i]

Major buildup of carbon in combustion chamber creating a glow plug that ignites the leftover fuel/oil in your cylinders

Or possibly wrong spark plugs staying too hot

Not leaky injectors as they would likely create a fire in the intake in this scenario.

Does it burn much oil?

[Mike W.]

I would think leaky injectors along with carbon buildup. I mean it's got to have fuel to burn to do anything, right? With a complete fuel shutoff, it's not going to fire under any conditions.

[Cactus]

Do an Italian tune up.

[86GT635]

Do an Italian tune up.

Seafoam/distilled water would do it too, wouldn't it?

That's gotta sound crazy, never heard of a m30 doing that. I'd be really worried about breaking timing chain guides.

[rmiddendorf]

Do an Italian tune up.

Seafoam/distilled water would do it too, wouldn't it?

That's gotta sound crazy, never heard of a m30 doing that. I'd be really worried about breaking timing chain guides.

I was also thinking I'd might go in and refresh those timing components if this car is a keeper. Plastic breaks.

[al525i]

I would think leaky injectors along with carbon buildup. I mean it's got to have fuel to burn to do anything, right? With a complete fuel shutoff, it's not going to fire under any conditions.

'

IF its indeed running backwards, its almost certainly not an injector problem (as the intake valves become the exhaust in this scenario.)

I've seen engines do the same thing before if they were terribly worn and they would actually draw oil by the rings in the pistons and combust that. (a scary proposition if you can't cut it off and have actually seen an old detroit diesel burn all the oil out of the crankcase then seize up from a lack of lubrication when it broke the supercharger quill shaft.... (an extreme case for sure though)

sounds like you need to get a bore scope in there and check the internals for carbon buildup.

verify the spark plugs are correct as well.

[Grande Royal]

I would think leaky injectors along with carbon buildup. I mean it's got to have fuel to burn to do anything, right? With a complete fuel shutoff, it's not going to fire under any conditions.

'

IF its indeed running backwards, its almost certainly not an injector problem (as the intake valves become the exhaust in this scenario.)

I've seen engines do the same thing before if they were terribly worn and they would actually draw oil by the rings in the pistons and combust that. (a scary proposition if you can't cut it off and have actually seen an old detroit diesel burn all the oil out of the crankcase then seize up from a lack of lubrication when it broke the supercharger quill shaft.... (an extreme case for sure though)

sounds like you need to get a bore scope in there and check the internals for carbon buildup.

verify the spark plugs are correct as well.

X2 on the Detroit diesel running backwards. Not too nice, can't stop them unless you choke off fuel or air.

[wkohler]

That was used as the basis for a Car Talk Puzzler.

[Gustav129]

Never heard of a feul injection engine dieseling. Only carbed cars where the butterfly valve can't close all the way.

But in the world of auto mechanics, nothing is impossible, only unlikely.

[a]

I would think leaky injectors along with carbon buildup. I mean it's got to have fuel to burn to do anything, right? With a complete fuel shutoff, it's not going to fire under any conditions.

'

IF its indeed running backwards, its almost certainly not an injector problem (as the intake valves become the exhaust in this scenario.)

I've seen engines do the same thing before if they were terribly worn and they would actually draw oil by the rings in the pistons and combust that. (a scary proposition if you can't cut it off and have actually seen an old detroit diesel burn all the oil out of the crankcase then seize up from a lack of lubrication when it broke the supercharger quill shaft.... (an extreme case for sure though)

sounds like you need to get a bore scope in there and check the internals for carbon buildup.

verify the spark plugs are correct as well.

This.The glowing carbon detonates the mixture early The charge blows back out the still open intake valve. It isn't running backward

[athayer187]

I agree with the assessment that you've probably got some nasty carbon buildup causing hot spots. I disagree that it must be fuel that is helping the combustion though.

How much oil do you burn?

Reason I ask is I've seen an M50 diesel and have enough oil bypassing the rings that the only way to stop it from running was to dump a fire extinguisher down the intake (Lemons Race in NJ last year).