9 replies to this topic

[rims421]

My wife and I both drive 94 850 turbo wagons. I have been getting bad gas milage with mine the last few weeks.
I normally get around 23- 25 mpg. But it has dropped to around 19 mpg. I had an exhaust leak from the front flex joint where it bolts up to the turbo. I thought it might be the problem so I replaced the whole cat assembly with a Bosal setup ( $500) The MPG did not change. I checked the diagnostic unit and have no codes. I noticed that the car was not reviving up on startup like it used to. Normally when I would start the car it would rev up to around 15 - 18 k and then idle down. Now it just starts and runs around normal idle.
I have also noticed that the exhaust does not smell right. It is hard to describe but it is not normal.
When I pull it in the garage and shut it off I can still smell it when I get out. I had tuned up both cars last year when gas prices were crazy. (plugs, wires, air and fuel filters, I replaced the rear o2 sensor about 70k ago.
Checked for vacuum leaks and could find none.
My question is since I have two identical cars I can swap parts between to diagnose the problem where should I start?
I was thinking maybe o2 sensors or maybe MAF unit.
What would you guys do? My car has 232k my wife's car 188k.
Any ideas would be greatly appreciated.

[JVC]

rims421, on 21 November 2009 - 12:44 AM, said:

Normally when I would start the car it would rev up to around 15 - 18 k and then idle down.

I have also noticed that the exhaust does not smell right. It is hard to describe but it is not normal.

15-18k?! Theres your problem... you just blew your motor starting it because it revved that high...

did you put race gas in it?



seriously though, cat could be toast which is causing the bad smell, then the o2 sensor got all messed up and is making it run rich causing low mileage.

[rims421]

The car ran poorly with the old cat and did not change when I intalled the new cat.

[Korruption]

How many miles are on the car? Does you know how much boost it is doing? Perhaps it has a boost leak.

Doh... sorry... missed the mileage in the first post.

[jdlc]

rims421, on 21 November 2009 - 12:44 AM, said:

My wife and I both drive 94 850 turbo wagons. I have been getting bad gas milage with mine the last few weeks.
I normally get around 23- 25 mpg. But it has dropped to around 19 mpg. I had an exhaust leak from the front flex joint where it bolts up to the turbo. I thought it might be the problem so I replaced the whole cat assembly with a Bosal setup ( $500) The MPG did not change. I checked the diagnostic unit and have no codes. I noticed that the car was not reviving up on startup like it used to. Normally when I would start the car it would rev up to around 15 - 18 k and then idle down. Now it just starts and runs around normal idle.
I have also noticed that the exhaust does not smell right. It is hard to describe but it is not normal.
When I pull it in the garage and shut it off I can still smell it when I get out. I had tuned up both cars last year when gas prices were crazy. (plugs, wires, air and fuel filters, I replaced the rear o2 sensor about 70k ago.
Checked for vacuum leaks and could find none.
My question is since I have two identical cars I can swap parts between to diagnose the problem where should I start?
I was thinking maybe o2 sensors or maybe MAF unit.
What would you guys do? My car has 232k my wife's car 188k.
Any ideas would be greatly appreciated.

It could be you're running rich, not rich enough to trip the cel YET but wasteful fuel-wise as you described. If this is so, the tailpipe should be darker than usual, or if your paint color is light, the area will darken noticeably in a short period of time. I know, I have a white wagon

If you have not replaced the coolant temp sensor (CTS) for the last 100k, you may want to start there - faulty one will cause rich condition.
You usually replace the t-stat while you're in there. Could be tricky to get them torx bolts, so be careful not to strip them by using quality T40 torx. Then get new bolts #986228 from the dealer. And would be good time to flush the coolant before winter sets in, assuming you have not done so in the last two seasons.

CTS/t-stat/bolts are inexpensive parts and are PITA to get to, so not worth switching form your other car.

Because you have turbo cars, getting to o2-sensor is a bit of a challenge too, with the intake on the way to the o2 connectors.
Unless you have <100k on your front o2 sensor, you may just consider replacing it imo.

GL, and if you should need cooler lines and want to save some $$$ (check my sig) , pm me.

[TryingBe]

Lower gas mileage is to be expected in colder weather and winter blend of gas is different than summer time.

[BananaRep]

TryingBe, on 21 November 2009 - 03:12 AM, said:

Lower gas mileage is to be expected in colder weather and winter blend of gas is different than summer time.

That does not explain the smell in the exhaust he mentions.

Maybe try to switch the MAF from your wife's car. That's pretty easy to do.

[rims421]

I think I will try the MAF and see what happens.
I will also go over all the vacuum lines again just to be sure.
The funny thing about it is that right before the milage dropped I was getting above normal MPG 25+.
I noticed on start up the engine would rev up a bit more than usual before dropping back to normal idle.
Both of these cars would always rev up a bit before dropping back to normal idle RPM.
Now mine starts up with no additional RPM's.

Very interesting don't you think

[rims421]

Replaced front o2 sensor and it seems to be much better.
I checked my old service records and found it wad almost 150k miles on it.
Gas milage went up and idle at startup is back to normal.
Thank you for all your input.

[7 VII 7]

How about a tune up?