I think I'm getting gas back in the oil again and the plugs are fouled. Going to go change the oil, filter then pull the plugs and unplug the MAF sensor. After this I think I'm going to through in the towel have have a Volvo Mechanic look at it. This 240 is wearing on me in a bad way.

 

I'm back ...

Switched back to old MAF that was on the car originally. I'm no longer getting getting gas increasing the level of oil in my motor!! Nothing appearing on my oil stick anyway and does not smell as foul as it had in the past.

Low idle 550-600 remains.

The NGK plugs I used did foul again after about 2 1/2 weeks about 300 miles driven. This creates rough starts until finally it will not fire up from cold start. I changed them again tonight and the car started right up again and initially idled rough but after taking it for a drive the warm starts was fine and idle remained at 550 to 600 rpms.

Battery died twice the last two days prior to plugs going foul but I dont think it is related.

Thinking of dropping this off at a Volvo shop but really don't want to spend a ton of cash on the car. However, I'm running out of patience on trying to figure this out with basically replacing parts. The odd part is once I get this 240 running it drives well down the road and freeway.

This 240 has plenty of power and not blowing any black or blue smoke. I get a little white smoke at cold start and things do smell to be running rich. Tired of this issue ... looking for help as I we like the 240 but I'm starting to think it has too many issues to track down.

Thinking I will go back and try to run codes again and see what I get.

 

My first thought is to check for exhaust leaks and make sure your O2 sensor is working well. Either of these issues can cause mysterious driveability or idle issues. Also, a bad O2 sensor can very easily push your fuel economy lower.

 

a LH2.4 car will usually throw a OBD code if the o2 sensor is bad, or if air leaks are significant enough to throw the 'lambda' out of balance.

 

I've come to realize that with our cars, what usually should happen, doesn't always happen. See, when my exhaust sprung a leak in a very audible way on the highway, the next stoplight I came to, my car was idling extremely rough. Only a few days later, on one occasion when my car nearly stalled at a light did my car set a code telling me that the O2 sensor was reading as too lean. I fixed the leaks and my idling issues disappeared.

Additionally, if your O2 sensor has failed in that it always thinks your mixture is running fine, then you would again potentially have a problem.

But yea, I still recommend checking for exhaust leaks first.

 

Back again ... I tossed in the towel and took the 240 to a volvo mechanic. He tested o2 sensor, fuel pressure, check for air leaks, injectors and timing belt slip. He said he felt narrowed it down to replacing needing to replace ECU and or MAF. Since the car is not worth much I decided to pick it up and look for parts.

Mechanic said 02 is working but something is telling the car to run rich. It is getting about 8 to 10 miles a gallon at the moment but I find it amazing how nice the vehicle drives down the road. I'm running the universal Bosch 02 sensor from IPD.

I need stop the car from running so rich. I'm sure I am about a week away from fouling spark plugs again due to rich fuel mixture. What would you guys do next? I hate to just buy a new MAF for $300+ on a $1,000 to $1,200 car if I dont know 100% it is a fix. The maf I had picked up from a wrecking yard months ago seemed to assist in fuel dumping in the engine oil which is why I went back to the original MAF that I am using now.

Next steps?
Pick up a used ECU off Ebay or wrecking yard?
New aftermarket MAF off Amazon?

Looking for help!

 

running too rich is often a sign of air leaks in the intake or exhaust.

 

Pierce I took it to a Volvo mechanic who checked for leaks and found none.

 

if the Engine Coolant Temperature (ECT) sensor is bad (or has connection/wiring issues), the ECU and ICU can think the engine is cold and run it too rich. simple test, get the engine hot, park, unplug the ECU, and measure the resistance at the harness plug on pin ?? to ground...

See this explanation, Engine Sensors and the 'diagnosing ECT' section a few pages down...

so, I'd suggest removing the right passenger right side kick panel (the liner just forward of the door hinges) before warming up the car, also pull the ECU plug and inspect it with a bright flashlight, inside the plug you should see the pin numbers molded... pin 13 is the ECT, pin 5 is ground. now plug it back in, start the car, drive it 5-10 mins to get it to full operating temp, back to base, shut off car, pull the plug, read the ECU resistance, and it should be about 200-300 ohms when the engine is still hot, and go up when the engine cools off.... Should be like 2400 ohms or so at 70F, and 6000 ohms at 32F (freezing, if your place gets that cold). or something in between if its inbetween.

be careful not to mangle the pins when ohming them...

 

New Bosch ECT had been installed over a month ago

 

Even though the ECT is new, check it through the wiring at the ECU. If there is a broken or bad connection through the wiring Pierce's method will verify it.

 

'new' doesn't always mean working. the wiring can cause as much of a problem as anything, its worth testing.

 

Thanks everyone for the feedback on this.

I first went with the Volvo mechanic advice and replaced the ECU. I looked under the passenger side panel and found the Pink ECU 0280000561 which I understand has common issues. I found an ECU online for $45 with same number but a white label and plugged it in.

Smell of the rich gas scent is gone. Check engine light is no longer on. It has been almost a week of driving and no issues. Driving the car is feels so different and drives amazing. Idle remains a little low like 650 but other than that I'm very happy. Vehicle has gone from 8mpg to 17mpg (City with very short distance driving).

 

ahhh. that suggests the cold start valve control output of the ICU was stuck 'on' (grounded)... which yeah, would dump too much gas in all the time.

 

Fuel pump check valve
Or the gas pressure regulator valve