Before I give up and take the car up to the local independent Mercedes shop . . . I'm seeking assistance here. I've completed several mods and repairs including replacing the supercharger (because of a damaged electo magnet plate from when my 62mm Karmen pulley malfunctioned and ultimately grenaded), replacing the intercooler with a brand new Rudy intercooler, replacing the engine wiring harness (because a rat decided to move into my engine compartment and chewed through the wiring going to the coils on the right side of the engine), replacing the intake manifolds with the Needswings aluminum intakes. Now that I have everything back together I have one remaining issue that I can't seem to track down . . .

When I first start the car it runs very rough, the engine does not seem to be getting enough airflow and there is a strong smell of unburnt fuel. Giving it throttle the engine falls flat and there is a strong sound of the engine trying to suck air. This situation usually does not throw a CEL or code and if I feather the throttle and get the car warmed up a bit, it starts to run great. Occasionally this situation WILL throw the CEL and trouble code P0105 (Manifold Absolute Pressure Circuit malfunction).

On the SRT6 the Manifold Absolute Pressure sensor (MAP sensor) is mounted to the bottom of the intercooler snout, right? I've checked all the wiring connections and they seem to be fine. Is there a fuse for the MAP sensor system? If so where is it?

I've found several threads that describe the same symptoms as what I'm having but their root problem turned out to be coolant leaking into the intake system from a faulty intercooler. I don't have a coolant leak.

Any thoughts on what I might look for?? THANKS for any advice . . .

 

I found this test for a MAP sensor, there may be others.

 

Dave, Thanks for your effort to assist . . . After weeks of taking things apart several times, rechecking connections and putting things back together again, I believe I finally solved the problem. I did a throttle body reset and that seems to have fixed it. Apparently the MAP sensor circuit and the throttle body communicate with each other to coordinate the fuel input based upon throttle position / air intake. It seems that they were just out of sync. Keeping my fingers crossed . . . Will know better after a few more cold starts.

 

I hope that turns out to be the fix. I've always suspicioned that there are a lot of little Germans in there all running around talking to themselves.

 

I am dubious that will solve the problem, it seems strange that the system would somehow go to a condition that caused the CEL to come on.

 

Well you're right Dave, The problem is still there. I have to give up on a DIY repair. I HATE it when I can't fix something myself.

I'll be taking it up to JR Benz in Miami (that's where Rudy comes down to do some of his V8 swaps and where Jim gets his V8 Crossfire work done). They really know what they are doing! I'll have them track down and fix my MAP sensor circuit issue and also swap out the rear differential for the 3.27 gear WaveTrac differential that I have been waiting to get installed.

I'll come back to post here on the cause of the MAP circuit malfunction issue.

 

How do I find the MAP Sensor on my SRT-6? It stumbles when I press the gas pedal from a standing start, but once it gets going it seems to run ok. I am going to replace the plugs and wires this weekend, as it's just a few hundred miles from hitting 100K.

 

The MAP sensor is mounted to the bottom of the intercooler which is mounted underneath the supercharger. Not easy to get at and almost impossible to change without removing the supercharger. I seriously doubt that is your problem unless you are getting a trouble code that indicates to look at the MAP sensor circuit.

In this photo you can see the mounting location in the left front of the pictured intercoolers near the snout(s).

 

[QUOTE=RED DOG;866323]The MAP sensor is mounted to the bottom of the intercooler which is mounted underneath the supercharger. Not easy to get at and almost impossible to change without removing the supercharger. I seriously doubt that is your problem unless you are getting a trouble code that indicates to look at the MAP sensor circuit.

Well, I hope it isn't my problem but I am getting P0135 which is the MAP circuit. I'm going to change the plugs and wires tomorrow as it's just about to hit 100K miles. I will check all my electrical plug connections and look for any leaks.

 

OK, so what was the problem?

 

Strange but true . . . I have no idea what was wrong! I started the car up one morning and it was running fine. That issue has never shown up again (and I hope to hell it doesn't). Then I found the issue with my 62mm supercharger pulley slipping at high RPM and I installed a new 65mm pulley. EVERYTHING is great now! I'm actually starting to enjoy the car again and I'm driving it more often than ever! Just need to tweak the sound system and thinking about doing something with that river of silver on the center console.

 

Navigation system in it? Have a feeling I'll pull the trigger on this when it's road trip time in my roadster..

 

Hi Greg, Were you heavily into the alcohol when you posted this? It seems to have nothing to do with this thread . . . LOL

 

[QUOTE=ROB311952;866338]Well today I erased the code, and installed a dozen new NGK Iridium plugs and Bosch wires. While I had things apart, I checked all the vacuum and electrical connections I could get to, cleaned the throttle body and the K&N filters. Tightened up a few fasteners here and there as well as clamps. Had to remove/replace the belly pan to retrieve the sockets, etc. I dropped doing all this.

Cranked her up, and the idle speed had gone back up where it belongs and idling smoothly. Took a for a ride making a quick stop then quick start which was causing it to stall before. This time pulling hard and smooth with no jerking like before, and even broke the tires loose on a rolling start with no hesitation. Glad I don't have to deal with a MAP sensor replacement after hearing I would have to remove the supercharger for that! You'd think they could have used a little plumbing and found a more accessible place for it. Anyway, now 99,600 miles and counting.

Next on the list is replacing the turn signal/multi-function switch which has become intermittent.

 

One of us?

 

As long as it is done professionally that would be good. Covering it with a river of tacky plastic not so much.

 

One word Bob : hydrographics

 

Yep or a respray in black ala Beaner.

 

Yep . . . I think Hydro dipping is the way to go. Looking into that now . . .