I am experiencing a problem with my 2005 backfiring when I go to start it. When I turn the key it will sometimes start right up with no issue at all and run great but sometimes it continues to crank without starting and all of a sudden it will backfire and not start. It seems like it is getting fuel and no spark and when it finally gets spark the fuel is ignited and BOOM it backfires. When i shut the key off and go to start it again it usually starts right up without backfiring. Anybody else ever come across this? My neighbors get kind of touchy when i go to start it at 4am to go to work and it backfires.

 

i suspect the camshaft position sensor
https://www.needswings.com/camshaft-...n-sensor-bosch

 

I thought the same thing and changed it but the backfiring still happened. I got another because I didn't trust new parts and again it did the same.

 

everyone limited and srt should carry a spare RCM so swap that it may solve your problem. i read of a manual trans car backfire , swapped rcm solved it,,, then put his original and no backfire,,,, Loose connection.

 

The original rcm was sent out to get checked and repaired so it didn't solve the problem. I got a new one and that didn't solve it either.

 

I'm having the same issue. Cam & crank sensors replaced & rcm ... Did you find out what the problem was on your car?

Chris

 

I would think if the fuel is loading up and then being ignited, it might be a coil issue, spark plug wire issue or spark plug issue.
You can check the back of the coils to see if they are cracked. If they are cracked they might be grounding out on the valve cover.
Using a scanner might be the best way of finding out what it is. If you don't have a scanner, any large auto parts place will do it for free.
If the scanner doesn't recognize the Crossfire, enter it as a 2003 Mercedes Benz SLK 320.

 

Thanks for the reply.
There are no fault codes
Interestingly - it doesn't happen all the time, sometimes it starts perfectly. If it does crank, backfire, and eventually start then it runs perfectly afterwards.
I noticed yesterday that if I lightly press the accelerator pedal whilst it is cranking then it starts right up and runs fine.... Now I'm thinking intermittent vacuum leak maybe ..

Chris

 

Fuel injector could be leaking.

 

It can also be caused by a defective EGR valve or collapsed hose. All of the hoses are getting old and soft.

 

As the OP writes "crank, backfire, and eventually starts" How would a defective EGR valve cause a backfire? It should be completely closed during starting, opening only after car starts: open or closed, how would that cause a backfire on a cold engine?

A leaking injector will run fine when car is running as any excess gasoline is vaporized, but at start up there will be a bite of unburned gasoline in the cold cylinder or intake/exhaust just waiting for its chance to ignite. He also says the car "eventually" starts. The car isn't starting right off the bat because the fuel system has not come up to full pressure as it has leaked completely down to zero by the leaking injector and the fuel pump has not had sufficient time to bring the fuel rail up to full pressure; Thus the car hesitates to start, but fuel in leaking cylinder can ignite causing backfire.

At least that's my theory and I'm sticking to it until proven wrong. I'm wrong a lot; Just ask my wife!

 

I have had the same problem for over 8 years and no one has been able to diagnose what is causing it. I had the RCM, crankshaft and camshaft sensors replaced as well as the fuel pump and filter. I was thinking it could be in the ignition switch because if I VERY QUICKLY release the key, it starts. Any help from the forum would be greatly appreciated.