So last week I am on vacation and decided to take my girlfriend out to breakfast in Palm Springs. 75 mph with an empty freeway and all of the sudden I felt the car surge and then nothing. I glanced at the instruments and saw my speedometer dropping while I am trying to accelerate. Check Engine light flickered on then pow...it started back up and no furrther problems until this morning.
I was driving to work today with heavy traffic driving about 30mph and the engine dies. I had to coast through the 3 and 4 lane to the shoulder and while coasting, I put it in neutral and started the car with no further mishaps. I have had issues of it stalling at a light or stop sign but now it is stalling while driving. Is this the dreaded Crankshaft Position Sensor?
I have a 05 Roadster with 53,000 miles.

 

I had that happen and it was the cam position sensor.

What codes did you get with the check engine light?

 

What is the code that set the light? There is your first clue.

But it CAN be the CPS, they usually act up at high temperature (that is, after the car is really warmed up) and sometimes the car won't start until it cools 20 minutes or more.

Get the code, and maybe order a BOSCH CPS (don't settle for a generic one, you'll be chasing weird stuff for weeks ...) They are easy to change.

Yea, CPS is the first guess. I carry a spare in my trunk - haven't needed it in 95,000 miles but many do.

 

Witchal...No Codes. I took it in to the dealer and they found nothing wrong. So they have tried to replicate the same and of course the car will act perfect for them.

 

If the light came on, there IS a code. You can stop by Autozone and they read codes for FREE.

 

Pizza guy...you say easy to install? I have rebuilt engines before but that was in my younger years with no back trouble. Is this thing way down into the engine compartment with easy access?

 

Waaaaaaaaaaait a minute -what do you mean it FLICKERED?

That is not a code being set, that sounds like poor power/ground to the PTCM to me. How old is the battery? How do the battery terminals and cable clamps look, are they clean, tight and neat - or loose/corroded/filthy? How does the connection of the ground cable to the chassis look, is it all green and messy?

Please don't tell me "the dealer tested the battery", just tell me how OLD the battery is. Bad batteries in these cars cause all sorts of stuff to happen that no one can explain.

 

I am thinking it's not the CPS now. But the CPS is at the back of the engine block, driver's side, it senses a magnet on the flywheel.
Lean over the brake master cylinder/servos to see it in 'bell housing' at the back of the engine. THere are threads here talking about changing it - super easy.

 

Everything happend so fast that I say it flickered. But keep in mind, where I sit in the car, the steering wheel blocks view of the check engine light so as I glanced at it...it was on and off that fast. Hard to explain if you know what I mean. All I knew is that I was happy then I was pissed LOL.
Battery terminals are as clean as your dinner plate. The car is spotless. The Dealer told me they thought it was new. But, I will have to check on the battery age as it was in it when I bought it used 2-1/2 years ago. I will report back on the age.

 

Also, pulling the Relay Control Modules out and resoldering all of the relay pins, etc. would be a VERY good idea. The "engine control relay" feed to the PTCM may be the cause here. That relay powers part of the PTCM and all contacts on the RCB are known to go bad in time.

There is a thread here on the RCB fix. The RCB (and other modules) are in the black box next to the battery. The RCB is the one closest to the center of the car, it unplugs easily. You can take it to any radio / tv shop and have them resolder every point on the board for $10 to $30.

I think you have intermittent power to the PTCM. I'd almost bet money on it. That, or the battery is getting flaky.

 

The CEL does not go on and off that fast, not when there is a code!

No, the PTCM is having problems and I BET the PTCM is not the actual problem - it is POWER to the PTCM, that is what I'd bet.

Yank the RCB and look at it, I bet you see cracked solder around some of the relay pins. That, or the engine control relay is bad/pitted/dirty/worn armature - etc. Again, there are threads here about this. Gotta get back to work.

Search "RCB" and Relay control board. You will see that this is very common.

 

Pizzaguy, I just came in from checking the engine and the battery does not indicate the year in service. I have to go home and pull out the service records and see but it may be time for a new one...not too sure. I will "process" all the info from you guys today and see where it takes me. Hopefully not back to the dealer as they said they do not see too many of these Crossfires so they do not know what they are doing most the time.
Your info is very helpful. I just want you to know, if you're delivering pizza in your XF, I am driving to Cumming, GA and slapping you around LOL.

 

Stay away from dealers. Find an independent shop that knows MBs.

 

+1

And i will almost 100% bet this is the RCM (Relay Control Module). I had the exact same symptoms. There is a guide on how to fix it in the TSB / How To section of the forums.


Do not take it to a dealer, they will just start replacing random parts until they figure out it is the RCM. When and if they figure that out they will replace with another one that will break again in 20 - 50 thousand miles as well as charge an arm and a leg for it.

Anyone can fix an RCM with 15 minutes of time and $20 at radio shack.

 

Thanks Alex...I will check into that as well. Lots of good info here. Looks like I am getting dirty this weekend.