Going out Saturday morning at VIR for my first session, exiting pit lane, and just about when I crossed the start-finish line I hit the gas and the car lurched and went into limp mode. Was the first time it has ever happened. I had no idea what was happening, but just hoped I could get around before the field lapped me (which did not happen).

Anyway, got 3 codes:

• P1688-electronic throttle control monitor level 2/3 mass air flow calculation
• P0107-manifold absolute pressure sensor circuit low
• P1106-manifold air pressure too low at engine stop

which has caused me to focus on the MAP sensor. I made a video of the MAP sensor voltages. They seem reasonable, but I am no expert and do not know what voltage should be at specific RPMs. When I hook up my scanner it is telling me the manifold absolute pressure = 0. It is almost like there's no signal getting to the ECU. The sensor itself looks fine - looks brand new.
I also removed the TMAP sensor and cleaned it. Had some oil residue on it, but upon a reinstall nothing changed. I have not checked voltages on the TMAP sensor.

Is manifold pressure a valid PID (parameter ID)? I.E., should I be seeing a number there on the scanner? If yes, it would seem that is my problem.

Any help would be greatly appreciated. Video here:

 

Well, it was not the MAP sensor. That would be too easy. I took the right-side horn, SC bypass valve, intercooler, and throttle body off today. The idea was to just check it out and see if I could see anything obviously wrong. Did not find anything obvious. Put it back together and got some starter fluid with a plan to spray around vacuum lines to try and detect a leak when/if the idle changes. The problem is the car has to idle to try that, and it will not idle now. It will start each time but I have to keep revving it up or it stalls out. So, actually the issue seems to be worse. I could at least get an idle last weekend - should have tried the spray then.

 

P1688 + limp mode happen to be the two major tells for the infamous crankshaft pulley separation problem. The other one is the smell of burning rubber which you may have missed being at the track where it is everywhere.
Do you know if it is the original one to the car?

 

I tried to find you but I had two students and I was running around a lot, but you must have already left, I carry spare map & tmap sensors in my bag!

those symptoms could still be bad map or tmap

 

Thanks for the replies!

I have an ATI super damper that was new in 2020 and does not have many miles on it, probably less than 10k. I put the car on the lift today and removed the front, right wheel and the wheel well lining to get a closer look. The belt looks fine and the pulley as well. Here's a video:


The car was idling okay, so I also sprayed starter fluid in and around vacuum lines and fittings looking for a vacuum leak. Sprayed a lot of it. Also followed the vacuum lines to the rear and sprayed around those. No change in idle. I also sprayed around the plastic air intake that goes from the throttle body to the supercharger. It appears the supercharger side of that air intake piece does not bolt on, which is a bit 'suspicious' but when I sprayed it I saw no change in idle.

I pulled the scanner out again and was trying to clear codes to see if that made a difference. I got the CEL to go out, but it came back on. At one point I got a new code P1125. This code has to do with the throttle position sensor and is interesting since I also had a P1688-electronic throttle control monitor level 2/3 mass air flow calculation. I may need to look at the throttle position sensor.

 

Seems like if you had a big vacuum leak there would be a lean code thrown at some point.

There is a vacuum line going to the throttle body.along with the electrical connector of course. And speaking of throttle body and P1125...

 

Thanks! I will look around for some links on how to test the throttle body. I found a lead on motoringalliance.com where they talk about testing potentiometers. The butterfly valve felt fine when I moved it, but I realize that doesn't mean all is good.
New throttle body is $250 - I'd hate to buy a new one and find out I don't need it. Can get a used one for $50-$100 on ebay, but if that's my problem, I'd like to get a new one anyway so that'd cost me $50-$100 for the test.

FS: R53 Throttle Body (motoringalliance.com)

 

So I have had similar issues to you but they have only been intermintent. I shut the car off for 5 seconds and start it up again with the code disapeering. Sometimes it hits like a brick wall and I get it 5 times in a row but then it doesnt happen for about 6 months (or everytime I say I'm gonna sell the car) I guess my car has feelings. I have not replaced anything related to this code on my car but even the same fault code can have different solutions. But back to the point, that vacumm line running to the throttle body is not a vacumm line. If you go to the engine modified section and look for the larger BMW 760li throttle body thread (i'll link it below) apperently thats just a vent and people have left it to vent to air. If anything I would upgrade it to the 760li throttle body for some extra power if it really is the throttle body.

https://www.northamericanmotoring.co...le-body-4.html

 

throttle body has 2 sensors inside for self checking.. If you are doing trackdays you need to switch to the 760il anyway

Did you change both map & tmap sensors?

 

is the 760li throttle body a direct change over or do you have to do other modifications

 

also what year 760li throttle body should i get because i am having the exact same issues with my 2006 mcs and i tried changing it out with my friends 2002 mcs manual throttle body and the issues got wayyy worse so i think i may just get a new throttle body. the wierd thing is that I think the previous owner of my car replaced the throttle body because it says 2020 on the side of it doesnt mean it cant be broken but it does mean that it could be something else. not sure what else would cause the throttle position code tho.

 

it has no vac line for the evap system and you need a newish rubber boot or its a bear to fit on

 

ok what should I do with the old Evap line then?

 

I deleted it off all my cars