I bought a 95 bonneville SSE 3.8L about a month or so ago, Ive been having milage problems from the get go. At first it was getting 7 MPG. Now I went across town and (1.6 Miles) and Back and It ate up over 1/4 Tank of gas. Can any one help me figure out what the problem is.
Also, I put shoes in, bled all the breaks. and they are still spungy. Is their a computer deal that needs to be reset? they were spungy before aswell.

Hows the power? Got any balls?


It sounds like several things could be wrong, including an O2 sensor and possibly a plugged up cat (you'd notice SEVERE power loss)



Do you have any check engine lights?


Have you done a tuneup and changed the plugs and wires air and fuel filters?


Changed the O2 Sensor lately? if so what brand did you use? There are known issues with the bosch o2 sensors on your year btw.




To answer your brake question, its hard to say, if they are spungy you most likely have air in the system, you need bench bleed them since the car has ABS.....It could also be something is failed such as the master cylinder, but I would count on air being somewhere in the system, many shops will bleed the brakes for next to nothing.




You can reset the PCM (computer) by taking off the negative battery cable and leaving it off overnight, the next day you will drive the car, it will be slower at first as it needs to "re learn" the parameters and tables.

But I'd start with a full tuneup, fuel filter is cheap, air filter is cheap, plugs and wires, are cheap, you dont need anything fancy.

If we have a check engine light we need to figure out WHY....






Also, there are MANY members in MN...aka MNbonnevilleclub.com , I'm sure someone lives nearby that can help you out if we dont get it figured out here.

No Power Loss, Ive never had a car with ABS. How do you Bench Bleed? The car was a drug taskforce car and I dont know anything about the past owners. I havent done a tuneup. I was wondering if the mass airflow sensor would be the issue? I had check engine lights, I pulled a chime fuse, put it back in, I havent had any sense then. I had a check engine, air bag, and security comming up.
The Air Filter is fine, Plugs and wires, I havent checked.
Is the fuel filter on the line like some vehicles ive delt with in the past?
So the O2 sensor would kill the power for sure? Ive herd of that being a common GM problem.

Dylan,



Before I say anything else, your car should be able to get 30MPG+ on the highway and 20MPG+ in the city.



Big variance on these, I normally get around 19mpg in the city waiting in traffic a lot. I also have a big ol supercharger and a paralyzed foot so my foot sometimes gets stuck on the gas.


As far as bench bleeding, there are automated systems at most repair shops but you can do it yourself, for information go to google or go here:

http://www.advance-auto.com/english/...0020701bm.html

As far as power goes, your car should be as fast as this car:

http://www.bonnevilleclub.com/forum/...t=mystery+3800

the video is here:

http://media.putfile.com/Mystery-380014

thats a 95 SE.....bone stock



The maf usually does not cause major power loss, You can clean the maf, but be ready to replace it if you break the sensor, they can be costly from a parts shop, so having a spare from a Junk Yard is a great idea.


To clean the MAF, you need some q-tips, some isopropl rubbing alcohol and some distilled water. I usually do a 50% alchohol mixed with 50% distilled water, mix as best you can, now remove the MAF, you will notice 2 electrical wire looking resistor things. You need to VERY carefully clean those without bending them with the q-tip. Let dry for 1 hour before reinstalling.




The fuel filter is a 10 minute job. I had never done it before and it took me 20 minutes.

1. bleed off fuel from the fuel rail with a towel or something, dont get fuel on the engine, thats bad.

2. once pressure is relived, remove gas gap or loosen it

3. look underneath the car on the passenger side near the kickpanel or near the fuel tank, its inline with the fuel lines, just pop the plastic connectors off and swap the new one in, replace gas cap and crank engine a few times it should fire right up.


OK, if we have CHECK ENGINE lights on your car we are sorta in trouble. You have an OBD-1.5 compliant car, so that means you CANT get it scanned for free at autozone.... I'd try to do all the basics before paying $40-$60 to have your GM dealer scan the car. I'd start by replacing the plugs and wires, as if they are original you could have an issue with a misfire or tons of other problems.

Your EGR valve can be removed and cleaned with throttle body cleaner, I'd do this, it may not help much but is worth a shot.

Since we are on the topic of throttle body cleaner, lets just remove the throttle body and the TPS, MAF and IAC and clean the sucker, make sure you have a throttle body gasket from the dealer before you attempt this, as the gasket nearly always gets destroyed in the process of removing the TB.


Airbag lights are a problem, I'd let someone who knows what they are doing fix this, seriously.

Security light can be several things, where the car is still starting every time its hard to say, but I'd focus on making sure the check engine light never comes back and the car is getting normal MPG and having normal power.


I'd reset the PCM as well, as I described in my other post.

Make sure you replace the O2 sensor with an OEM delco O2, others are known to have problems, several members have experienced very quick failures with the bosch O2 sensors..avoid them.

Finally, please click on PROFILE at the top of this page and go to SIGNATURE and put your car in there. That way, if you have questions in the future, we know what kind of bonneville you have

Mileage being that bad, I'd suspect a fuel leak.

I agree with that. To use that much fuel, the car would not be running well at alll. Check for leaks.