So, stock my car is rated at 25/31 mpg. Its modified with performance exhaust, header and a CAI. My mpgs haven't changed too much cuz of that but they did go up. But recently my city mpgs have gone down to about 22/3. Highway miles are the same so far. My power has gone down a bit as well. So there are a few factors that I'm wondering someone could identify anything based on these things:

First is my distributor. I had done a tune up and replaced the cap. Unfortunately I over-torque and the screw snapped. It went a while not sealed on that particular spot. If the cap is not sealed completely can that lower MPGs without making an obvious difference in my engines behavior?

My exhaust- I put it in myself and had a few issues with it being sealed correctly. I searched throughout the points where it connects while it is running and could not feel any exhaust escaping nor could I see any wet spots from leaks. Is there something I did not notice that could be costing me MPGs?

My brakes- I've been having an issue lately... I had bad pulsing when I brake in the steering wheel and pedal and changed the rotors. Same problem occurred and I changed the problem bearing. The other one had been replaced a while before. I still feel pulsing when I brake and the steering wheel is shaking as well. But its not just when I brake now, it is not too obvious but I can feel it a bit when I drive too. Is something off that could create resistance when I drive?

Sounds like my cars a mess right now but it runs fine, I've just noticed with my Ultra-gauge that it has gone down lately.
Im gonna clean the EGR, throttle body and replace the PCV valve just for standard maintenance but is there anything going on that I'm missing?

Also- for the brakes, I welcome any answers as to what could be going on with that too, theres a small detail bout that too with my issue.
When I replaced the bearing I put the caliper and bracket back on. The pins didn't go in the correct spots though. The L and G pins were reversed. I tried putting the bottom one where it is suppose to go and it would not go in far enough to be screwed in. In the reverse spots they fit fine though. Could them being reversed contribute to this issue?

 

If the cap is not sealed completely can that lower MPGs without making an obvious difference in my engines behavior?
Response: No, the cap is vented to allow oil that may enter to drain

Is there something I did not notice that could be costing me MPGs?
Response: exhaust leaks can cause problems, however this usually sets a code, but in some cases engine may add fuel trying to balance a perceived lean mixture.

My brakes- I've been having an issue lately
Response: Dragging brake rotors can cause poor gas mileage. New caliper pins, caliper boots, and new rotors may be necessary.

Im gonna clean the EGR, throttle body and replace the PCV valve just for standard maintenance but is there anything going on that I'm missing?
Response: New air filter, clean or replace PCV, new spark plugs, depending on mileage a new O2 sensor may be indicated.

good luck

 

Ok,

I already changed the plugs and I have a new K&N filter. The o2 sensors were both replaced not too long ago as well. Ill look into new caliper parts.

Thanks,

 

I've heard of cold air intakes becoming too restrictive due to too much oil on the filter. I've never had one and don't think much of them.

Is everything hooked up that formerly connected to the air intake?

good luck

 

Yes, everything is hooked up.

 

Hey man check your PM's

 

What about my spark plugs? I replaced them recently and thought they were pregapped. If they're off by a little will that affect my performance and MPGs?

 

Tire pressure and alignment can also effect MPG in a big way, so make sure your tires are good and your car isnt pulling to one side or the other.

 

I've given in and am going to the mechanic on monday about my tires and brakes. So maybe an alignment will be in order.
I just gapped my spark plugs, they were all pregapped but at about .43/2 but my car should be at .44. The engines running a bit smoother already now that I adjusted them. Nice to see a result like that so easily. That never happens with my car :P
I read that you can gap them .01" more for better economy and performance. That the specifications are set for cases in the future where a car would need tuning or is in bad shape. Anyone hear anything about that?

 

Do you know how small 1/100" is?