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M20 runs excessively lean

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    M20 runs excessively lean

    Hey guys, get cup of coffee and sit down for a good read. I really didn't want to post about this because it's been covered at least a million times. Probably two million times. BUT I'M LOST!!!
    A quick background on the motor. I rebuilt it over the winter, top and bottom end. The cylinder head has a bimmerheads 274 cam, the whole head was built by them. (great guys by the way) It has bimmerheads tune and 17lb injectors. This is the exact setup they recommend. So the injectors, tune, and cam should be working in harmony. I also swapped a manual transmission into the car. Lightweight flywheel and performance clutch.

    Here are the symptoms.
    1. It will not idle no matter what. Even if its life depended on it. (it should fear me at this point)

    2. It runs fine if I hold the throttle at about 1000 rpm. Let off and just wants to die and sounds like its about to drop a cylinder out the bottom. (timing?)

    3. It starts EVERY time like a dream. But shortly dies if I don't give it a little gas.


    5. After two or three hard pulls, it becomes the most unresponsive pile. Any throttle above 3 grand and it sputters and wants to die. If you hold the throttle down (full throttle) it will sometimes jerk back alive and go full throttle as it should. Or just kinda jerk around.

    6. The check engine light does come on after some hard pulls, Usually doesn't come on until a minute or so of driving. It throws a 1222 code. Which tells me I'm running too rich or too lean

    Here is everything that I've checked.

    1. I re adjusted the valves as bimmerheads recommended, it ran much better as they were pretty tight. (But these symptoms are all after i did the valve adjustment, the car was just completely undrivable before.

    2. I've checked the plugs to make sure I wasn't running lean. The plugs look like they've been washed clean. So I must be running rich.

    3. I checked the resistance on the wires. They seemed to all be in good shape. (but I'm going to take it out at night and look to see if I see any sparking between wires)

    4. I pulled off the crank sensor and inspected it. I was told it's pretty much impossible to check these things. So I ordered a new one and it should be here wednesday.

    5. I checked for power on the throttle switch, ICV, and crank position sensor. All seemed to check out ok? But in saying that, I can't figure out how a multimeter is supposed to work.. I think I'm too dumb. If anyone could explain which terminal is supposed to show what voltage that would be great.

    6. I clean the ICV and inspected it. I can hear it buzz when the ignition is on so it should be just fine. I noticed the fitting that goes from the ICV hose into the throttle body was a bit loose. But I sealed it up. No change in idle.

    7. I know the fuel pump works just fine. The car sometimes runs good as long as you're driving and not idling or putting in the clutch to down shift. I also forgot to unplug the fuel pump relay when I was first cranking the motor for oil pressure (first start up) and it built up enough pressure to start leaking out of the fuel filter. oops. At least I know it works.

    8. I've checked for vacuum leaks with starter fluid around the common vacuum leak points. No change in idle. (I have to hold the throttle at 1000 rpm or it dies)

    Things I'm going to check,

    I'm going to do a compression check tonight because I'm afraid that the rings aren't sealing properly. This is obviously an extreme case. I would get a lot of oil on the plugs if this were the case though right? (I'm not getting any oil on plugs)

    I ordered a crank position sensor just in case. ONE THING TO NOTE, there was a leaking coolant hose right above the sensor. So it was soaked in coolant. I cleaned it and inspected for any cracks in which coolant could go in. Didn't find any except for where the wire goes into the sensor. Maybe coolant got inside the sensor?

    I'm going to ground the motor to body of the car with a jumper cable. I read somewhere that it's possible the motor isn't being grounded correctly. There is indeed a grounding wire already but maybe its not doing its job? (can you feel the desperation of a college kid during finals week now? :D )

    My thoughts
    I don't think that it has anything to do with leaks in the vacuum system due to it running fine at partial throttle (1000 rpm) and the fact that it doesn't seem to sit at high idle or come down in idle super slow (like a vacuum leak would cause) It did before but after sealing the ICV i can't say its done it again. Though I haven't driven it much due to it just not working.
    Once, when doing a test run, I accelerated up to about 4 grand and it cut out hard, like suddenly there was no spark.

    I'm pretty convinced it's something electrical, like the cranksensor. But it starts just fine every time. All these symptoms happen when the car is cold or warmed up. It doesn't make a difference.

    I actually feel bad posting about this. It's been covered so many times. But I've done the normal checks that people say and so far nothing. Someone once told me that it could be the alternator due to the crazy electrical system these cars have. Has anyone heard that before?

    Anyways, this car ran just fine before I swapped the trans and rebuilt the motor. It just leaked oil like a sieve. the timing belt had snapped during previous ownership but it was repaired with new pulley and belt. While the car ran just fine when I bought it, I figured a rebuild was in order. (I was right, the head was ruined. why do broken things run better than nice new things?)

    Any suggestions on things to check? I've got my uncles coming over tonight to see what they think. I'm thinking a bad tune thats running it so rich it doesn't have a chance to breath.
    Last edited by Dillon; 04-18-2018, 01:49 PM.

    #2
    Gotta remember that even light throttle the vacuum goes down quite considerably. and by half throttle the vacuum is basically zero. Idling is the most difficult thing for an engine to do. especially one with an air flow meter. you are using minimal air, so the air flow meter is operating in its lowest position. so any vacuum leaks have a huge effect on the air metering. I would be looking very closely for any vacuum leaks. Even a hose clamp that is tight but not tight enough will make the idle shit and maybe even not idle at all. There are a million threads on potential vacuum leak locations as you mention, have a google around. You want zero vacuum leaks.

    The other thing to look at is the Throttle position sensor (TPS). the TPS has an idle switch and a wide open throttle switch. unplug the TPS, get out a multi meter and operate the throttle by hand. using a bit of trial and error on the 3 pins you should be able to find which pins are the idle switch. the TPS has some adjustment in it, you want the idle switch in the TPS to operate just as the throttle is closed. its not unheard of for the TPS and idle switches to be broken (mine did). In fact it may be the cause of your check engine light.

    Which is another thing, google how to get the codes from your ECU and find out what that check engine is flashing for.

    Comment


      #3
      Hmmm..... Ok I'll double check all that. It makes sense that it could be a vacuum leak. But it would run lean if it was right?
      My uncles both came and checked out the car and they came to the conclusion that it was running wayyy to rich. We pulled the plugs after running it for a couple minutes and low and behold, the plugs were wet with fuel and it smelled like very rich running engine. So I'm thinking the tune must be not quite right for the high altitude that I'm at.

      Comment


        #4
        Did you figure out what your check engine light is?

        A dodgy coolant or air temperature sensor could well be your check engine light and your running rich issue. ECUs do funny things when they don't the signals they are expecting.

        Comment


          #5
          Ok yes, I was able to get the code to work. It gave me a 1222 code. Which I looked up and found that it was the Lambda Control 1 code.

          In order to get the code, what I did was took it out for a drive and hot rodded the thing around for about 2 miles so that it would show up. Then I checked it.

          So... the code tells me I'm either running too rich or too lean. Which would explain the bad idle, and it should explain the bogged down behavior that I'm getting. Which now that I drove it again, this is how I THINK its happening. When I first start it from a cold start, it will drive around town. (still bogged down and smelling like fuel though) but it will pull all the way up to six thousand rpm just fine. But after a couple runs of doing that it flashes a check engine light and falls on its face like I explained earlier. So tomorrow I'm gonna do the same thing and see if it repeats itself.
          I'm thinking a fueling issue. Either from the tune or something. Do you know if Bimmerheads accounts for altitude? Because I'm a good 3 or 4 thousand miles higher than california. Which makes a HUGE difference in terms of tuning.

          Also should note that my MPG gauge shows like 10 miles to the gallon... Very bad.

          Comment


            #6
            Oh and yes, about my temp sensor, it doesn't quite hit the middle. Its a little colder than the middle. Would that make a difference?

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              #7
              So I've checked around the throttle body to see if I have any vacuum leaks. There is no increase in idle when I spray starter fluid around any of the common vacuum leak areas.

              So I'm thinking that it is the tune. Does anyone here mess with tunes at high altitudes?

              Comment


                #8
                Originally posted by Dillon View Post
                Because I'm a good 3 or 4 thousand miles higher than california. Which makes a HUGE difference in terms of tuning.
                So how did you get your E30 into orbit? Any photos?

                Comment


                  #9
                  An engine generally loses about 3% of its power for every 1000 feet in elevation. I'm at 5300 feet here in New Mexico and you can definitely feel the 16% power loss because of the thinner air. I always thought that the AFM had an altimeter and the computer adjusted the fuel trim for higher altitude.

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                    #10
                    Originally posted by E30-325iS View Post
                    So how did you get your E30 into orbit? Any photos?

                    Man I don't know how I didn't catch that.

                    I'll have photographic evidence tonight.

                    Comment


                      #11
                      Originally posted by RobDog View Post
                      An engine generally loses about 3% of its power for every 1000 feet in elevation. I'm at 5300 feet here in New Mexico and you can definitely feel the 16% power loss because of the thinner air. I always thought that the AFM had an altimeter and the computer adjusted the fuel trim for higher altitude.
                      So I spoke to the tuner and you're right, the AFM will work to adjust for altitude, not the tune.

                      So after some more investigative work, I found that my throttle position sensor isn't making that click noise when you press down the throttle. Would an incorrectly adjusted tps sensor screw with the fueling?

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                        #12
                        So I've taken the throttle position sensor out and cleaned it. I put it back and made sure it was adjusted right. So far I've got no where. Still won't idle and it still will throw a check engine light code 1222.

                        I'm at a complete loss. I'm going to put the old BMW chip in to see if it will make the fuel mixture a little more rich. Maybe that way I won't feel like I'm blowing the motor up.

                        Comment


                          #13
                          I have always made the assumption that if the engine light is on you start your diagnosis with the oxygen sensor, or emissions system circuit.
                          My son has the 1987 325e, 2 door, 5speed
                          I daily the 1989 325i, 4 door, 5speed

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                            #14
                            Hmm... Well I guess I could order a new o2 in. The problem is that mine is brand new.

                            I put the old chip back in and it idles, but it idles just over 500 rpm. I pull the plugs and their white. So I'm really too lean.

                            WHAT IS GOING ON!!

                            to top it all off I can't get the coolant system to bleed correctly. I'm about done with this car.

                            Comment


                              #15
                              Ok... So after more looking around the car I've made an interesting discovery. I unplugged the while the car was running and it died. Then I started it back up (with out connecting it) and it idled just fine. I didn't drive it around or anything. But it idled nicely. What on earth does this mean? Is there a way to test the MAF? I have a multimeter if anyone has the specs.

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