1991 240 DL Terrible Gas mileage and exhaust smells l

[jessica8527]

Ok. I just bought what would be my dream car. I love my Volvo, but as a woman purchasing an older car, I sort of feel that I'm at the mercy of my mechanic. When I drive it smells of fuel and smokes from the tailpipe. Also..which is even worse, is that I filled it up with gas and only got 120 miles out of the entire tank! Now, the mechanic replaced the throttle position sensor and also the temp. control sensor. I don't see any leaks from the car and he said the hoses were intact. Whoever had this car kept a record of things done and it seems that cleaning the throttle body happens nearly every other month at around 15 years of age and that doesn't seem right to me but it tells me that whatever the issue, he thought this would fix it. Flame trap was cleaned when I had the previous listed sensors replaced. Now, tomorrow I have an appointment to replace the O2 sensor and I'm wondering if this could even be the problem. Any ideas? Also, I noticed when rev the engine (Was checking to see if it smoked) soot comes out of the tailpipe. Please help.

[lummert]

I'd suggest checking the fuel pressure regulator.

[rgk]

First things first: You are at the mercy of your mechanic only if you lack knowledge, never simply because you are a woman.

Gas smell and a smoky tailpipe are indicative of a rich fuel mixture (i.e. more fuel than desirable or necessary mixing with air in the combustion chamber). A number of things could be responsible for this, including (but not limited to) bad fuel pressure regulator, leaking injectors, a leaking cold start valve, a bad mass air flow sensor, a bad ignition module, or a bad oxygen sensor. A leaking fuel line can also cause a gassy smell.

One thing you can easily check on your own is the fuel pressure regulator. Google 'volvo 240 fuel pressure regulator' to see what it looks like, then find it on your engine (it's usually smack-dab in the center). Remove the vacuum hose going to it, and check for fuel inside that hose. A properly-functioning regulator will NOT have fuel in that line. Put the vacuum hose back after inspection.

Your mechanic should have tested and confirmed that the throttle position sensor and coolant temperature sensor were indeed bad before changing them, and not simply changed them to see whether that would fix the problem. I hope he or she got the resistance values for those parts and determined those values to be out of specification. Those specifications can be found in a Haynes repair manual and on the web. Other parts, such as the oxygen sensor, can be tested in a similar fashion.

There are other resources across the web to help track down the causes of a rich mixture, but unfortunately this is one of those things that can be caused by many different possibilities. Try googling 'why is my car running rich', 'rich mixture', 'rich fuel mixture', 'gassy smell', and other similar keywords.

Here is one I found: http://www.brickboard.com/RWD/index.htm ... show_all=1

Additionally, I would check to make sure that the smoke coming from your tailpipe is indeed due to a rich mixture, and not a more serious condition, such as coolant or oil seeping into and burning in the combustion chamber.

[tryingbe]

O2 sensor could cause the problem you're describing. Any check engine light?

[jessica8527]

Yes. Check engine in since I purchased it.

[jessica8527]

Ok guys..had to O2 sensor replaced today. I love the fact that my volvo mechanic shows me stuff that he is doing so that I can see what to look for and learn what it going on. The sensor was a universal instead of what the car actually calls for and the person that put it in rigged it up and it looks bad where he connected wires. When he pulled the sensor out it was covered in black soot (the same stuff that was coming out of my tailpipe) completely clogged and burnt looking. He put a new one in and instantly the fuel smell was gone. I'll keep you posted on the gas mileage as I haven't calculated it since I fueled up last. Thanks for the support. I love this site.