Hey, I have a 91 740 thats having startup/idle problems hot or cold. Ive read through some of the previous posts but havent resolved the problem. It seemed to start after I recently replaced the belts and spark plugs. I made the idiot mistake of not disconnecting the battery and I arc'd something when handling the alternator wiring. No fuses were blown but the headlights would no longer work. After testing I decided to rig a wire from the light switch to the lighting relay as that seemed to be where the break was but that I couldnt find. Anyway, after doing all that, now the damn thing has a hard time starting and even harder time staying started. When cranked, it will bounce up and down around 1000 rpm very sluggishly and with alot of chugging, but if throttled, will die and not want to start. I read in some older posts about switching radio suppression relay?? Not sure if I have that. I also sprayed cleaner in the throttle body, but should I remove it and clean? If so, will I have to replace the gasket? Could I have fried something with the control unit with the alternator incident? I really dont want to spend shop money..plz help.

William

 

Oh yeah, is there a way to read a malfunction code on the 740 or does it even have this? I also have an exhaust leak at the manifold to head. The bolts are burnt and orange. Is there a trick to removing them effectively and could this be causing the starting and idling problems?

 

Ok, so I found the diagnostic box in engine compartment and testing according chilton online manual (only manual I can find). First off, how do I tell what EEC system I have? I plugged the no. 2 hole for fuel injection and pressed the button once and at first nothing happened but then it started flashing rapidly and continuously. I unplugged and tried again and got a 1-2-2. I tried several time to repeat the procedure but mostly it wouldnd flash or respond at all. Is my control unit fried?

 

Anyone? EEC type for B230F? Also forgot to mention alot of belching and backfiring with idle probs.

 

That could have damaged the ECM.
http://www.troublecodes.net/Volvo/
See if this link helps explain any better.
The connections at the Diag plug are A1=transmission A2=Fuel system A3=ABS A5=TCU/CEM A6=ingition system A7=combined instrument B2=cruise control B5=SRS B6=power seat
All might not apply to your car.
See if this helps any and let me know.

It might be a good idea to remove the throttle body and clean it good.Also clean the idle motor.Replace the throttle body gasket when you do it.

 

Ok, I have a few questions

- How do I tell what EEC system I have? ie Regina, Bosch etc.
- Is there a diagnotic check for the ECM unit?
- There is apparently no air temp sensor, only the amm ..so why do I get a 122 code signifying
the air temp sensor.
- What is the best way to check the O2 sensor?

Thanks

 

Regina ignition has a square coil.
Im not really sure how to test the control module.
The air temp snesor and the mass flow meter are the same thing.
To check the o2 sensor put a multi-meter on the single green wire from the O2 sensor.Pull the boot back and set the + side of the meter on that wire.Put the negative side to ground.Then start the car the voltage should go from 0 to 1 volt and go up and down.