91 525i with new MAF won't idle.

I have a 1991 525i that is out of commission. It was having problems starting in the cold and during the last cold snap (5 deg F) would not start at all. Finally got it started when it warmed up but it would not stay running and it was backfiring badly on low and high RPM. Stomp test showed 1215. Cleaned the MAF, did some work on the boot with electrical tape on the cracked port near the manifold, to see if there was any improvement. There wasn't. Disconnecting the MAF helped some, but not much.



I ordered a new boot/hose (MAF to manifold) and a new MAF. Installed those last night. Some improvement. Then I found that the connector on the hose under the manifold was not connected. It looks like the clip is broken off. Part #9 in this diagram.



http://ift.tt/1DE49uj



I can't find a good picture of the hose but it is a short hose that seems to go in opposite of the manifold where the air intake is located. For now I pushed that hose back into the opening. (Will order that part today). The backfiring has gone away on both high and low RPM. But it still won't idle on it's own. If I disconnect the MAF it will idle and run fine. Actually drove it around the neighborhood for a few minutes with the MAF disconnected - no problems. The second I reattach the MAF it dies.



I am stumped on what to check/change next.



1. Is it possible the new MAF is bad? I cleared the codes with stomp test ran it for a while (before I found the bad hose connector) and the 1215 code came back .

2. Could O2 sensors be causing a problem? Should I just order and replace?

3. Other things to check?





Thanks for your advice!!



Steve

91 525i with new MAF won't idle.