1995 Volvo poor gas mileage

christi49W · Post by **christi49W** » 14 Jun 2014, 18:37

I have a 1995 Volvo 940 wagon that I love, but about two years ago the gas mileage dropped from about 28 mpg down to about 14-17 mpg. I just replaced plugs, plug wires, cam seal, timing belt and tensioner, water pump, belts, hoses, fan clutch in an effort to get mileage up. Any other suggestions? The fuel gauge also has a mind of its own. It never goes to full but goes to about 4/5 when the tank is full. One time I start the car and it is 4/5 and the next time maybe 1/4, then back up to 4/5, then maybe 1/2. Suggestions please? I replaced the fuel pump about a year and a half ago and the guy thought maybe the float was sticking. Thank, Christi

lummert · Post by **lummert** » 14 Jun 2014, 22:37

Check the fuel pressure regulator vacuum hose for gas smell. If you smell gas the diaphragm is most likely leaking fuel through the vacuum hose.

christi49W · Post by **christi49W** » 15 Jun 2014, 03:45

Have done all of that plus smoke test. Thanks

93Regina · Post by **93Regina** » 15 Jun 2014, 18:33

christi49W wrote:1995 Volvo 940 wagon...gas mileage dropped from about 28 mpg down to about 14-17 mpg.

I'm not familiar with B230FD engine, but I think there are two systems on this engine:

1. EGR Valve

2. Pulse Air system

Both systems fail with time, but I suspect EGR valve if stuck open would affect fuel mileage. Here, is a generic take on both; myself, I'd get a shop manual.

Also, I hear if air system fails, it may take out AMM; I know nothing on this topic, but both can be Googled.

christi49W · Post by **christi49W** » 15 Jun 2014, 19:21

Thanks for the input. The car actually runs pretty good but occasionally runs a little rough the first few minutes. I will probably start at EGR.

christi49W · Post by **christi49W** » 16 Jun 2014, 12:12

One more thing. I passed the emissions test for license plates and from I've read, the poor emissions from a clogged egr probably would not have allowed the car to pass. Is that correct? If so, other ideas, please. Thanks.

93Regina · Post by **93Regina** » 16 Jun 2014, 15:31

christi49W wrote:passed the emissions test....28 mpg down to about 14-17 mpg

There would seem to be a paradox here; 14-17 (highway mileage) would suggest a rich mixture, or fuel being dumped overboard. Emission machine was defective, old boy let you slide, and/or something like EGR caused vehicle to pass.

I assume the ignition system is Bosch, which uses MAF/AMM and O2 sensors.

I understand function of a Pulse Air system, but I assume O2 sensor is downstream of this air injection system. A O2 sensor, when old, can skew the voltage when sent to ECM, but I assumed newer ECMs/ECUs with OBD-II evaluated O2 sensor performance, which on OBD-I vehicles, they did not. If O2 sensor(s) have not been changed in last 80k miles, then change them.

But, some ignition systems have default fuel tables, and will use them when a malfunction happens; but I have no idea how 1995 Bosch handles this.

On older Bosch systems, if MAF/AMM was bad, engine would idle up/down, and extra fuel would be burned.

Regardless, both EGR and Pulse Air system needs to be examined; I do know those EGR systems will plug up, and/or valve stays opened/closed.

If yours is OBD-II, do those $100.00 scanners work?

An open EGR valve would be passing exhaust gas into intake, which would affect overall fuel mileage, but I'd ask one of those emission testers about how this might affect an emission test (not the person who did yours).

93Regina · Post by **93Regina** » 16 Jun 2014, 20:02

christi49W wrote:1995 Volvo 940 wago 28 mpg down to about 14-17 mpg

I assume your lockup torque converter is working? Around 45 mph with easy throttle, it should lockup, and RPM may be around 2,000 RPM or less

Someone pushed OD button, and forgot to push again, or is relay broke, or is OD solenoid broke?

christi49W · Post by **christi49W** » 17 Jun 2014, 04:53

Thanks. Will check OD. I had a new shifter unit put in and OD unit after that. It's kind of hard to pinpoint exactly when this started but the egr hasn't been touched for at least 70 K and maybe longer.