The m20b20 in my e21 has been converted to run l-jet (assumed from e30) and now that I've got it running it's having some issues.
Idle is 2000 cold and 1500 warm.
Seems to misfire/ run lumpy at low revs.
Seems to run very rich.
Where can I go about troubleshooting?
It feels like a car missing a lambda sensor and like its set to a max fuel safety setting but I have no lambda sensor!
L-jet m20 running issues
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alschux
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Re: L-jet m20 running issues
Recently converted to l-jet on my M10, and had problems with over-fuelling to start with. Things to test are the cold start valve and the temperature sensor (thermo time switch) which controls it, and the temperature sensor for the ecu.
You should be able to test these with a multimeter and a pan of water on the cooker. Will try and dig out some of the specifications for testing, but the thermo time switch should be either 8 seconds or 12 seconds closed (cold start fires) and after that open (cold start valve stops firing.
You can also try unplugging the injector wires and seeing what the cold start does on its own. It is enough to start the M10 and then the car will die after a few seconds. Also check the wiring to both.
You should be able to test these with a multimeter and a pan of water on the cooker. Will try and dig out some of the specifications for testing, but the thermo time switch should be either 8 seconds or 12 seconds closed (cold start fires) and after that open (cold start valve stops firing.
You can also try unplugging the injector wires and seeing what the cold start does on its own. It is enough to start the M10 and then the car will die after a few seconds. Also check the wiring to both.
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Jeroen
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Re: L-jet m20 running issues
Good suggestions to start with, temp sensor for the ECU is a known suspect, and you may need a different ECU as there are versions with and without lambda control (O2 sensor). What P/N ECU do you have? Did you do an exhaust gas analysis? Adjust the AFM while monitoring the CO value?
Regards/groeten, Jeroen
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alschux
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Re: L-jet m20 running issues
I would leave the AFM adjusting screw alone, as it really only affects the idle. The screw allows more air to flow around a bypass route (not metered by the flap), but as soon as the flap starts opening under load, the effect of this bypass route becomes negligible.
Re: L-jet m20 running issues
Thanks guys.
Did a bit of reading on the adjustments of the afm, because the idle is different hot and cold I thought that pointed towards the temp sensor working.
Had a little look at the afm and found this-
Not exactly bmw standard sealing!!
I got the car with a failed head gasket and think it could have been tampered with to try and overcome poor running.
I'm going to hopefully borrow a working afm to test and will work from there
Did a bit of reading on the adjustments of the afm, because the idle is different hot and cold I thought that pointed towards the temp sensor working.
Had a little look at the afm and found this-
Not exactly bmw standard sealing!!
I got the car with a failed head gasket and think it could have been tampered with to try and overcome poor running.
I'm going to hopefully borrow a working afm to test and will work from there