Cold start RICH mixture

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  • snaponbob
    Noobie
    • Oct 2014
    • 34
    #1

    Cold start RICH mixture

    Just did a complete M20 rebuild. ALL vacuum and coolant hoses are new. New rubber parts in the intake tract. Everything (all those common loose/worn fittings) sealed at and around the throttle body. At cold start the engine runs very rich. AS it warms up, it gets better. ICV tests good and the internals are moving freely. A meter valve in the air box is free. TPS is good. Both coolant sensors are functioning properly. No CEL (and it does work). Once the car warms up it smells a bit rich, but runs okay. At this time, the car is not tagged so street driving is not an option. (Waiting on a windshield.)

    Thoughts?
    Tags: None
    • ak-
      R3V OG
      • May 2009
      • 12422
      #2
      This is normal.

      1991 325iS turbo

        Comment

        • snaponbob
          Noobie
          • Oct 2014
          • 34
          #3
          "Normal" to the extent that the car will not idle without help for at least a minute? This is a stone stock un-modded M20, and if is not a little rich at cold start !!!

            Comment

            • hooken m
              E30 Mastermind
              • Sep 2010
              • 1537
              #4
              subbed
              Originally posted by evandael
              a car is a car. call it a dildo, i'd still drive the hell out of it.

                Comment

                • snaponbob
                  Noobie
                  • Oct 2014
                  • 34
                  #5
                  Originally posted by hooken m
                  subbed
                  What?

                    Comment

                    • dnguyen1963
                      R3VLimited
                      • Nov 2011
                      • 2648
                      #6
                      Originally posted by snaponbob
                      What?
                      He wants details...and follow this thread.

                        Comment

                        • snaponbob
                          Noobie
                          • Oct 2014
                          • 34
                          #7
                          Sorry, I am lost. I described what I have in the first post, AK says "normal" for a car that will not idle at all on cold start, hooken m says "subbed", and THAT means he wants DETAILS ????

                          Ask, I answer !!

                            Comment

                            • ak-
                              R3V OG
                              • May 2009
                              • 12422
                              #8
                              Originally posted by snaponbob
                              Sorry, I am lost. I described what I have in the first post, AK says "normal" for a car that will not idle at all on cold start, hooken m says "subbed", and THAT means he wants DETAILS ????

                              Ask, I answer !!
                              lol. You didn't specify in your original post that it wouldn't idle! I was just saying that cold starts are always a little rich while the o2 sensor warms up.
                              But yeah, now that you mentioned it won't hold idle.. that's not normal.
                              hooken_m is just saying he is now subscribed to your post, so I guess he has the same problem.

                              What insures you that the coolant temp sensor is working properly? You said sensors, but should have only one that reads temp for the ECU, unless you have an m20b27(?)
                              Did you replace that or maybe replace it with the wrong one? Leaky injector?
                              Last edited by ak-; 11-05-2014, 05:34 PM.

                              1991 325iS turbo

                                Comment

                                • snaponbob
                                  Noobie
                                  • Oct 2014
                                  • 34
                                  #9
                                  GOT IT. Sorry for the important omission. D'OH !!!

                                  Posted this at E30Tech as well. Interesting results.
                                  http://www.e30tech.com/forum/showthread.php?p=1385973#post1385973

                                    Comment

                                    • snaponbob
                                      Noobie
                                      • Oct 2014
                                      • 34
                                      #10
                                      Update ...

                                      Not yet. Checked the cold resistance at the DME plug. I am "seeing" the sensor at 3500 ohms. So, no wiring issues.

                                      Then I hooked up mt SnapOn "brick" to look at the data stream. Engine cold, shop is 52 degrees and so in the coolant temp.

                                      The reason I am COMPLETELY focused on cold start is that it is SO rich that it is washing the bores and blowing oil smoke. After a minute or so, and some revving, the smoke goes away and it is willing to idle. After it shows some movement on the temp gauge the engine runs fine, but the exhaust smells rich. I have dealt with a couple 2.5s (an M20 and an M50) with failed (open) injectors, and this is not THAT. They may be leaky, but they are closing.

                                      Bentley directed tests of the ICV indicate IT is functioning properly. Need to see if there are tests for the AFM. Weird.

                                        Comment

                                        • packratbimmer
                                          E30 Fanatic
                                          • Dec 2009
                                          • 1331
                                          #11
                                          Have your injectors been cleaned in the last 25 years?

                                            Comment

                                            • snaponbob
                                              Noobie
                                              • Oct 2014
                                              • 34
                                              #12
                                              Hell, probably not !! I bought the car for cheap to flip it. It was clearly rust free, and completely stock with nothing missing, and a nearly flawless interior. As soon as the work is done (including a rather important windshield), I will get it tagged, throw some Sea Foam in the tank, and start driving it. If necessary, I will send them out and have them REALLY cleaned. However, update to follow.

                                                Comment

                                                • snaponbob
                                                  Noobie
                                                  • Oct 2014
                                                  • 34
                                                  #13
                                                  So, after checking the DME temp sensor AT the DME plug, I hooked up my SnapOn "brick" to look at the data stream.

                                                  Intake air temp --- check
                                                  Coolant temp ---- check

                                                  Started the engine. Trash !! As it seems to do. Nothing standing out on the data stream. Once I cleared its throat a little, I started monitoring what there is to look at on the data stream. As it warmed up past 140F coolant temp, the RICH data started to change as the O2 sensor came on line. It DID throw a code 10 O2 control code which I cleared and continued. Once up to 170F coolant temp, the O2 sensor was switching, TPS and AFM data was following activity of the throttle as I "blipped" it some, and the code did not happen again. Idle smoothed as it warmed up, too. All I can "assume" is that I am missing something about this engines "cold" habits.

                                                    Comment

                                                    • digger
                                                      R3V Elite
                                                      • Nov 2005
                                                      • 5995
                                                      #14
                                                      how does it run without the O2 when hot/warm?
                                                      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                                                      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                                                        Comment

                                                        • snaponbob
                                                          Noobie
                                                          • Oct 2014
                                                          • 34
                                                          #15
                                                          Have not tried that. Explain, please.

                                                            Comment

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