I recently bought a 1989 240DL sedan, my first car, and two weeks later the check engine light went on. I tried to adjust the idle by turning the red nut attached to the throttle cable. Found out that was a mistake. Checked the on board diagnostic and got these codes; 1-1-3 2-2-1 2-3-1. Not sure what to do next. Please advise.

Sorry I don't have tips on the specific trouble codes.
However you CAN look in the brickboard 700/900 FAQ. There's a table of code meanings. Your system is LH2.4
Whenever I look up those codes for one of these, the info I get is:
"The mixture is too rich or too lean, but the computer can't tell you which it is". Which I find moderately helpful, and that's putting it charitably.

JKot is right in that there should be a bit of slack in the throttle cable when it's released.
The manual that you need is Bentleys.
I've seen it available on Amazon and also from fcpgroton.com.

Adjusting the throttle cable where the cable meets the pulley wheel is only to ensure that the throttle plate comes to rest in its maximum closed position when you take your foot off the gas, with a bit of slack in the cable. The throttle position switch (tps) also needs to recognize the closed throttle and should click when that position is reached. If it doesn't, the tps itself is adjustable. It's mounted on the side of the throttle towards the firewall. The TPS has oval holes; you loosen the screws/nuts and slide it a bit to get the adjustment right. Usually if you didn't change it, you won't need to. But of course anything is possible.

With the throttle plate fully closed with your foot off the pedal, idle speed is maintained by the idle air controller which is a servomotor operating an air valve. The computer regulates that valve to allow the needed amount of air to bypass around the closed throttle, to maintain proper idle speed. The computer measures air flow (air mass meter) and also exhaust gas (oxygen sensor) and that way provides the right amount of fuel to match the air. There's really no idle speed adjustment on the '89 and later - the computer is set to allow air flow to keep engine at about 700 rpm or so.



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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.

I played with the adjustment several times, cleared the codes, pulled the 25 fuse and the light hasn't come back on for about 4 days....knock wood.

Thanks for the good information Sven. The thing that's confusing us is that the light didn't come on before we played with the adjustment and it's running so well right now. I'm not getting a click when I move the pulley either. Should I disconnect the battery and see if the light comes back on? I cleared the codes

Sounds like you have a good one. Nice year. You didn`t mess up the injectors. The one thing that could have happend after you adjusted the cable is that you didn`t return it back to the propper idle setting. Make sure you have a little slack in that cable. With engine off listen for a faint click sound coming from the throttle position switch (that is mounted on the right side of the throttle body) as soon as you turn by hand the cable spool which is located on the left side of the throttle body . If there is no click then you need to make adjustments. A Chiltons manual from advance is a handy thing to have . Some of the simple things to check would be vaccum hoses,spark plugs,plug wires,cap and rotor, flame trap,fuel filter and air filter. If there is no change there are more things to check like cleaning the idle air control motor . Run a tank of good fuel injector cleaner with next fill up. As a note the service engine light comes on every 3500 miles or so to let you know the oil is due for changing . The check eng. light is the one from the on board diognostic system. You probably already know this but some may not . I hope this helps . How many miles are on the clock? These things run just about for ever and are great cars if taken care of. Disconnect the battery to reset the codes and try again after checking those things . Hope this helps . Right back . Larry

So over the weekend I tried the re adjust the idle. Still can't hear any clicking sound. Cleared the codes and pulled the 25 fuse by the battery. drove it to work and back about 10 miles ...no light. Went to the store last night and light came back on. I'm waiting to get the Bentley's manual before attempting some of the other fixes. I'm only getting two codes now instead of three. Both are pointing to the fuel mixture (too lean ...too rich).

Hey Larry,

Thanks for the advice. My son bought this car with 91K miles for 900.00. It's in pretty sweet condition, two owners who apparently took pretty good care of her. Unfortunately neither he or I know much about mechanics. The light wasn't coming on until they played with the cable so I think that's the problem. We'll try those things you suggested and go from there. I'll let you know how we make out. Thanks again.

DISREGARD

1-1-3 Fuel injectors.

2-2-1 Heated Oxygen Sensor(Rich mixture/part throttle).

2-3-1 Lambdfa adjustment.

By the way, the car seems to be running great other than a little rough idle at stops. I haven't checked the gas mileage. Did I mess up the injectors by turning the throttle ?