Hi everyone. I just signed up here as I am helping a buddy of mine with his 1990 240, non-turbo. I am not a Volvo guy, so I thought I'd draw on the knowledge of the experts in here.

Anyway, the car was running fine, and then all of a sudden it won't idle....It'll start and run, although very rough, if you keep your foot on the gas, but as soon as you let off it stalls.

Buddy already did some research and replaced the Idle Air Control (IAC) valve with a used unit, and installed a new MAF sensor. Problems continued so that's when I started working on it.

If I unplug the MAF the car will run, and stay running, but the idle is way high, the car runs rough and backfires. Plugging in the new MAF the car reverts back it is original symptom of stalling immediately if you let off the gas. IAC makes no difference if unplugged, nor does unplugging/plugging the throttle position sensor.

Maybe the new MAF is a dud? What other things can I check, and how? The fact that this came about suddenly has me thinking it's a sensor/engine management issue.

Any help, advice or instruction is appreciated.....it's freezing out and this engine bay is seriously greasy, so tinkering with this really sucks.

 

Do you have OBD1? Check for codes, MAFS failure should throw a code. Cheap "new" MAFS are often bad, yes. Check, swap the Ignition Amplifier, on the left inner fender. That may cause what you describe.

 

I am not sure, but I think it does have OBD1. Is there anything unique about pulling codes on these, or just standard OBD1 fare? Anyway to check the ignition amplifier? I don't have another one to swap it with...

Thanks,

 

The OBD1 module is in the upper aft port side of the engine bay, small black box the size of a salt shaker. Pop the top, plug in the little electrode on the side into plugs 2 and 6, one at a time. Hold the black button for 3 seconds then let go, and it'll blink back at you like morse code. 1-1-1 means all clear. If it blinks other sequences, write them down and post them here or look them up in a manual, and that'll start you down the path of troubleshooting those codes.

 

pin 2 has the ECU (fuel injection) codes, while pin 6 has the ICU (ignition controller) codes.

after reading the codes, hold the button in for 10 seconds, and it should clear them. the ignition should be be on but the engine not started when you read the codes.

everything you could possibly want to know about it
https://www.volvoclub.org.uk/faq/EngineOBDCodes.html

(in addition to reading the codes, there's some test modes that cycle various actuators for testing, like the electric fan, idle control valve, EGR valve, etc)

 

Very helpful, thanks guys. I am away right now, but when I am back in a few days I'll get back on it.