Hi all,

I have a 06 MCS that starts and runs fine but has trouble when the engine gets warm and it is put under load. I will start from when I got this Mini back in March 2017...

I totaled my nice reliable stock r53 and got this as a cheap replacement. I knew why it was cheap, looks like a front end collision occurred at some point in it's life. Two days later SES light comes up for the "ambient air temp sensor". cleared the code and it never came back.

The car had no power steering when I got it. Put in a pump and it was all good. I suspect the old pump just died but I know i have read about some people who's steering pump died and it was related to a much more complex electrical issue.

Anyway, code cleared, power steering equipped I hit the road making a commute of 150 miles/day in that car. I always noticed at highway speeds the engine would be sort of jumpy and buck occasionally. Well, one time this buck put me into limp mode while on the highway. Pulled over and stopped. The engine still ran but idle was very rough. Killed the engine and looked at the belt and whatever i could check roadside. Without me doing anything it started back up fine and continued my driving just as before. Had the SES light on, don't remember the exact code it was but someone on-site with a code reader read it as something throttle body related.

So since it was running fine I ignored the problem like any idiot should lol. I did continue to experience the surging/bucking at highway speed but just slowed down a bit when I felt it coming on.

Well in late June the same thing happened and it went limp. Feeling confident that killing and restarting would do the trick i shut down, restarted and began driving. THIS time i did not make it far before it did it again, and it was at much lower speed this time. Tried a few more times and same result. Got towed home... code was P1688 only

The car has been pretty much sitting since then. I did some poking around and found f the wrong size belt and wrong heat range plugs were in. Previous owner who installed the pulley did not change the plugs and used a belt one size too big. Corrected all that and the car ran better, but still bucking under load. I have changed throttle body, crank pulley, belt, plugs, coil, wires. Tested the BPV and that operated as it should. Bucking happens mostly on hard accelerations, regardless of what speed or gear. Happens around 3200-3400 RPM.

It is worth noting that I can start it upo and drive around the block a few times just fine. The issue is ONLY PRESENT WHEN THE ENGINE IS WARM!

Wish i had more codes or could explain better. Thinking it might be the T-MAP sensor but don;t know how to verify except for replace and pray. I have a whole parts car to play with for only the next month then it has to be sold so if i need to pick parts now is the time!

List of mods (that I am aware of):
-15% SC pulley
-Alta Intake
-new NGK plugs (heat range 7), new coil, new wires
-ST coils
-Wilwood brakes
-short shift kit

Current suspicions are: T-MAP sensor and just a good tune?

Any suggestions would be greatly appreciated! This is sort of a rush post so I will add more details later. Thanks!

 

Oh and i forgot to mention the throw out bearing is on it's very last leg. Actually amazed it hasn't blown yet. Maybe that could be related but i doubt it this seems like a mix ratio problem. You tell me...

 

P1688 is a mass air flow issue. If you have not already done so suggest you to a P1688 search in the Stock Issues/Problems section, will see a few threads on the issue.

On the back of the coil, cylinder 3 is the driver side and 4 is the passenger side. Pull the plug wire off and see if there is rust on the steel electrode.

 

I'll have to do more research on the P1688 code, its been awhile since I really dug into this.

Another thing to mention is at idle rpms bounce between 700 and 900. Is that a sign of an air/vac leak?