I know there have been a million threads on the elusive codes 1171/1174.

Before trouble shooting MAF, O2 sensors, upper air gasket, air intake or anything else, you might try this. See pic.

On the passenger side of the upper air intake on non secondary air D2's, there is a metal nipple with a rubber vacuum cap on it. It is right under the vacuum tube to the power brakes and vacuum hose to the valve cover breather. (See pic)

I have had my D2 for over 350,000 miles and have had to replace this vacuum cap every 20-40,000 miles when the 1171/1174 codes appear.

This vacuum cap dry rots and at first you get the codes, then misfires, then rough idle as the vacuum leak gets bigger.

I keep a pack of these in my Rover parts box. Just a few bucks at any auto parts store.

Hope this helps your 1171/1174 frustrations.

Thanks

 

Kinversand, this is a WONDERFUL, proactive post! And I see it's your first post here! Welcome, and thank you.

I posted in the last month in response to someone's problem thread about this port and the need for it to be capped, but hopefully your thread will save someone from needing to sift through lots of other threads.

And if anyone is wondering where to get a vacuum cap, just go to any auto parts store. No need to order. My local Advance Auto Parts sells them individually for 29¢ each.