Intake Manifold Explosion

I ran into a problem yesterday. I was driving down a highway in the Netherlands in my Dodge Charger RT when I lost all throttle control. The Electronic Throttle Control warning light came on and I coasted to a safe spot on the side of the road. The car stopped running almost immediately after. I tried to start the car. It would turn the engine over but wouldn't start. So, I called for a tow.

After I got the car home, I did some research online. I had problems with my battery over the last two months and I wanted to rule that out as the cause for a low voltage reading causing the ETC to malfunction. I put the battery on the charger overnight and went back to start the car in the morning.

This morning, I hit the start button. It was the same cranking noise for about 2 seconds and then there was a loud BOOM! Smoke started to billow out of the engine. 

I made sure there was not a fire but I found some pieces of plastic. It appears that the intake manifold exploded from the bottom.

I am not sure of the root cause. I think that the Throttle Body is not working, so I will have to order a new Intake Manifold and Throttle Body. Unfortunately that will take weeks to have it shipped from the US (and expensive). 

Does anyone know if a malfunctioning throttle body would cause the intake manifold to explode? My guess is that there was a build up of fuel that ignited, but I haven't narrowed it down yet. Possibly a bad PCV valve somewhere. Maybe I need to sleep on it and get past the emotions of seeing it explode this morning. 

yikes... seems like the root cause is a timing issue though, only way to get fire in the intake is to spark when the intake valve isn't closed.

this is coil on plug right? not a wasted spark ignition?

It is coil on plug. What would cause the timing to go off to make that happen? I didn't change or adjust anything from stock.

Part of me is worried the internals are messed up. The valves look ok looking in from the top after removing the manifold. But that doesn't tell me that much.

Time for a compression test....

Once upon a time I washed the engine compartment in my '71 Chevelle. I also decided to respray the air cleaner lid. When I got through I ran the engine to dry it off, installed the air cleaner top and shut the hood.

Several hours later I went out to move the car. It cranked and cranked and BOOM a huge cloud of smoke enveloped the car. I literally did a Duke Boys style exit leaping out of the car - forget opening the door! My next door neighbor came running out of his house.

It turned out paint fumes from the lid were trapped under the hood and they made it into the left turbo muffler and ignited inside the muffler. It was split apart. The muffler guy said he had never seen one do that.

It even blew a hole in the ground under the muffler - no grass, just dirt. Lesson learned!

I don't want to be that guy, but I'd say typical dodge nonsense. If the timing got off that far on a COP ignition system I'd blame the electrics. Something about a history of failing ECMs and really shady wiring systems. If the failure was mechanical I'll be shocked. Good luck. The car looks great though. Dodge has that going on for sure. 

5 posts..  It took 5 posts and I had to come clean up for you guys..

I've always wondered with the plastic intake manifolds if this would be an issue.  I was suprised that they don't have a pressure relief popoff but I guess they probably are cheap enough, and this is rare enough that adding a $.25 part to every car doesn't make sense. 

I bet either you had a spark related misfire prior to the etc failure or a hung/failed injector. Either lead to an overfilled cylinder causing the backfire.

It does not help that the plugs on the hemis have a 30k service life still.

Compression test the engine. I also suspected you've bent a rod from the backfire.

Similar thing happened to a coworker’s SN95 Mustang back when it was new.  In his case, driving along on the interstate, steady speed, BOOM.  Hole in the plastic intake and a dead engine.  Seemed to be a not uncommon experience at that time on those V8 engines from what Ford dealer told him.  Repaired under warranty, then happened to him again a short time later.  He sold the car shortly after incident number 2.

I'm guessing you lost something that makes the engine run, but not fuel delivery.  The intake had a bunch of raw fuel that evaporated, creating a lovely combustible mixture, which was then lit by the next bit of fire availabile.  Problem is, you kinda need to replace the intake to figure out the problem that caused you to blow your intake manifold up, which may then explode before you figure out the problem, and so on.

As an aside, I once repaired the distributor in a 1975 Volvo 244, and the single spark created by turning the key on (not even cranking) lit the fuel in the exhaust, which peeled the front muffler wide open and lifted the car a few inches in the air.

I didn't poo hardly at all, but everyone else in the building sure came running to see whether I had.

Too much nitrous. Did you have Harry get you two of the big ones?

nocones said:

5 posts..  It took 5 posts and I had to come clean up for you guys..

 

I've always wondered with the plastic intake manifolds if this would be an issue.  I was suprised that they don't have a pressure relief popoff but I guess they probably are cheap enough, and this is rare enough that adding a $.25 part to every car doesn't make sense. 

All intake manifolds are designed with a specific backfire test that in theory should have prevented this issue.  I second the others on ecu driven issues causes the spark/timing to be out.  I believe these heads are prone to dropping valve seats but this doesn't sound like that issue.

I think the throttle body completely died, which caused the car to stop running and the ETC light to come on. Then I was not able to start the car, but that didn't stop me from trying several times. I think that by trying to crank the car so many times without it starting dumped fuel into the intake, which sat overnight. On the first try in the morning, it ignited and blew the intake manifold.

Of course, this is all a guess at this point. I am going to spend some time inspecting parts and checking things to see if I can find anything wrong. I am debating a visual inspection of the pistons with a scoping camera before I do any compression tests. I will check the push rods as well and look into the valve seats if possible. I may have to remove the heads to fully check everything but that would take even longer to get replacement head gaskets here.

I may just visually inspect what I can, check the push rods, and then reassemble with a new intake and throttle body on it to see if it starts. 

I have seen the same thing happen on waste spark ignition systems if there is a fuel injector leaking. You can get spark during the overlap period and if there is fuel vapor, poof! You are coil on plug from what I remember about these engines so it may be a bit more complicated to diagnose. I have seen this happen twice on the COP VW 24v engines but both were pretty sketchy electrically and I chalked it up to shorts in the harness.

I would be very surprised if this explosion did any internal damage. Fix the ignition issue and replace the manifold. Then start it up. 

New intake and throttle body came in today. I switched over the parts from the old intake, including the fuel injectors/rails. I installed everything and the car still does not start. 

The good news is that there is a check engine light on now. We have codes!

P0013 - Camshaft position actuator
P0340 - Camshaft position sensor

So, I have to order two new parts. Once they are in and the car starts, I will change the oil. Time to wait another 7-10 days.

Well, that's a good start.  

Someone already established you have to have a valve open or leaking for combustion to travel up into the intake manifold. 

Someone also mentioned these heads have been known to drop valve seats. 

They also used to be known for broken valvesprings. I dont know if that was 'fixed' by this year but a broken valvespring would do the same thing, leave a valve not fully closed.

The point about wasted spark during valve overlap is really interesting and something i had never thought of before. These engines use a semi-similar system in that they have two plugs running off one coil, but both plugs are in the same cylinder and AFAIK the only spark occurs during the compression stroke as normal. 

If you don't want to just pull the valve covers right away I would start with a compression test. It's vaguely possible that a sensor or electrical problem resulted in some freak spark event but you wouldn't be able to test that without running the engine again, taking a chance of blowing up the new manifold. If it's a mechanical issue you have a good chance of finding it without cranking the engine which would be the 'better safe than sorry' approach to this. My .02.

In reply to Vigo (Forum Supporter) :

You make a good point and I did think about that. I have been going back and forth about taking the valve covers off to do a visual inspection. Maybe I should just do it and remove doubt.

Also, if the camshaft position sensor is bad, wouldn't it throw off when the coil packs give a spark? It may have been off on timing, which could have caused this as well. At least that is what I am thinking.

tedroach said:

In reply to Vigo (Forum Supporter) :

You make a good point and I did think about that. I have been going back and forth about taking the valve covers off to do a visual inspection. Maybe I should just do it and remove doubt.

Yes ^^^ and compression test.

tedroach said:

In reply to Vigo (Forum Supporter) :

You make a good point and I did think about that. I have been going back and forth about taking the valve covers off to do a visual inspection. Maybe I should just do it and remove doubt.

Also, if the camshaft position sensor is bad, wouldn't it throw off when the coil packs give a spark? It may have been off on timing, which could have caused this as well. At least that is what I am thinking.

Does the code say the signal is missing, or it's in the wrong spot?  Those things have timing chains, right?

5.7 V8, correct?

Does this engine have variable cam timing? Cam position actuator code leads me to think so. Be aware that the cam position sensor and or actuator may not be bad. If the timing chain jumped a tooth, valve seat dropped out, or the actuator is hung up with oil gunk, it will throw the code for being outside the expected range of operation. 

As has been said before, a compression test with the fuel pump disabled would be a good idea to rule out mechanical issues. 

TheRyGuy said:

Does this engine have variable cam timing? Cam position actuator code leads me to think so. Be aware that the cam position sensor and or actuator may not be bad. If the timing chain jumped a tooth, valve seat dropped out, or the actuator is hung up with oil gunk, it will throw the code for being outside the expected range of operation. 

Wiring issues are another frequent cause of sensor codes.  Ideally you want to hook up an oscilloscope to the sensor output and see if the waveform looks correct before swapping parts, but if they're cheap and easy to get to then...

In reply to Streetwiseguy :

The code says: P0013 - B Camshaft Position Actuator Circuit / Open Bank 1. The car was running perfectly fine and smooth up until the engine turned off. Which leads me to believe it is electrical. The intake explosion is something that was created after that. 

It is the 5.7 V8

In reply to TheRyGuy :

It does have the VVT, which is why I have to replace the actuator. I believe the actuator failed which they are notorious for, especially in high mileage. 

I am heading out of town for a week, but when I get back I will remove the valve covers for a visual inspection and then perform a compression test. This will give me an indication on where I am at.