My 05 NA has blown two intake manifold out . Both times were preceded by big backfire. I’m wondering if the crankshaft position sensor is defective and could cause this backfire?

You can see the hole just above the hose

 

From my 12 years on this forum, I'd say no. MANY CPSs have failed, none caused that, what they cause is the engine to quit.
Keep in mind, the ECU still knows where the cam is, as there is a sensor on that as well, so it's not like the loss of the CPS signal means the ECU is going to fire plugs randomly.

In fact, if the sensor fails enough for the ECU to light the CEL, it will also stop firing plugs (and, I assume stop firing the injectors).

 

Do you have any thoughts about where I might look for causes for these backfires? I have another manifold on the way but I really would like to find the source of the backfire?
After the backfire I have code po101, not surprising with a hole in the front of the manifold.
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Parts already replaced:
New fuel pump
New fuel filter
New injectors
New plugs
New air filters
New MAF
I’ve ordered intake manifold and gaskets. This time around I’m replacing the crankshaft and camshaft sensors too.
I would like to have a list of all reset procedures. I know about the battery reset and throttle reset. Are there more?

 

Default Re: Crankshaft Position SensorDo you have any thoughts about where I might look for causes for these backfires? I have another manifold on the way but I really would like to find the source of the backfire?
After the backfire I have code po101, not surprising with a hole in the front of the manifold.
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Parts already replaced:
New fuel pump
New fuel filter
New injectors
New plugs
New air filters
New MAF
I’ve ordered intake manifold and gaskets. This time around I’m replacing the crankshaft and camshaft sensors too.
I would like to have a list of all reset procedures. I know about the battery reset and throttle reset. Are there more?

 

You didn't replace WIRES when you did plugs? I tried that once, never again any car that needs PLUGS needs WIRES.
I learned that LONG ago. Changing Cam and Crank sensors is NOT a bad idea anyway, I just dont'[ think that's the issue.

I mean, to blow a hole in the INTAKE manifold? That sounds pretty extreme, back in the day, we had cars backfire a lot, never did damage like that.

No, no other reset procedures. I would ask, "backfire" or "misfire"? THis just seems very odd to me.

 

I did replace the wires, neglected to mention that.
I don’t know which way to go here. I’m going to replace the manifold again and try to get it running again but I’m nervous about not knowing what is the root cause. I will check the vacuum lines real close also. I would call it a backfire, it was literally a really loud bang accompanied by a cloud of blue smoke.

 

Have you looked in the service manual under the DTC index ? You will probably get a more definitive answer to your problem with a scan that does more than check generic OBD II codes; There has to be some indication when you get into the saved DTC in the cars memory. The MAF and throttle are controlled by the PCM. and the RCM is in the circuit as well. All need to be checked out. A decent independent Mercedes shop would be a good place to start. Your problem is more than replacing simple parts. Good Luck.

 

I believe it is possible an injector was sticking causing an over rich situation at detonation. That is the only cause I can think of. I don't understand how that much excess fuel might get into the intake though. You might speak to Rob at Needswings or Josh at MSS and get their feedback.

 

How many miles on the car, maybe it is a burnt valve. The cause for ignition has to come from somewhere.
What was the time difference between the occurrences? How does the car run between these events?

 

it was several weeks and more than a hundred miles (maybe two tanks of gas).
it ran great, smooth idle between occurences.

 

pizzaguy, where are you located and do you work on these cars for other people?

 

Burned valves have been mentioned here. Several weeks have elapsed between the fest an last incident. The car ran great and smooth. If it were a burned valve wouldn’t it have caused the first explosion and wouldn’t I have noticed a burned valve after I replaced the blown manifold the first time?
what about the purge valve sticking?

 

You've given little info on the car, how you would have seen a burnt valve I cannot imagine. Something ignites the fuel and the only thing I can think of is the combustion chamber leak.
Good luck.

 

By “noticing a burned valve” I mean in the way the engine ran, sounded. I’m so sorry

 

I know the Crossfire has two plugs and three valves per cylinder but I'm not sure of the function of the third valve.

 

2 intake and one exhaust valve per cylinder

 

Thanks I think that might mean one bad intake valve might not equal a rough idle .

 

Shouldn’t I try to get someone to do a computer analysis (NOT A DEALER!)before I disconnect the battery and I take this apart again?
You are in Bentonville, do you work on these for other people? I live in Russellville.

 

Did you read post #7
independent European car shop. Your car can be scanned as a Mercedes 2003 SLK 320, R 170