Finally Passed Smog!!!!!!!

[92VXHatchguy]

Im so relieved that this VX has passed smog. I was able to get my new plates finally, because the personalized ones that it came with needed to go!

Here's my readings:

15mph
RPM: 2357
CO2: 14.8
o2: 0.0

HC
Max:138
Average:31
Mine: 34

CO
Max: .84
Average: .10
Mine: .05

NO
Max: 859
Ave: 237
Mine: 131

Result: PASS

25mph

RPM:2208
CO2:14.8
o2: 0.0

HC
Max 112
Average:20
mine: 17

CO
Max: .73
Average: .09
Mine: .04

NO
Max 798
Average: 199
Mine: 140

Result: PASS

Now the only problem i'm having is that im still getting between 25-28 mpg.
Compression was check on all 4 cylinders and they were all good. EGR was good. I had a new cat installed below the stock cat, so I'm running with 2 cats right now. At first the NO was high, so it was recommended to put a new cat in. After it was installed, the car passed. What can I do to get better MPG?

[GasSavers_JoeBob]

Good for you! Now I gotta find the time to take care of the Cad...

[mkiVX]

if its a five wire change your o2 sensor.
bump up those tire to 45 psi minimum

[monroe74]

You already know this, but I just want to confirm that something is very wrong.

There are about 26 VXs in the garage here, with gaslogs. In aggregate, hundreds of fills have been reported. The number of times anyone has ever reported a fill under 30 mpg is very close to zero. There is one car that reported these two fills: 28.98, 26.57. Another car reported this fill: 29.22. I can't find any other VX fills under 30 mpg. So your situation is pretty unusual.

Typical overall mpg, taking into account all the VX gaslogs here, is about 45 mpg.

There are all sorts of pretty obvious things to check, but I have a feeling that it's probably a combination of factors. I'm also optimistic that the problems will be easy to fix.

[monroe74]

Some ideas about things to check.

Are the sure it's a VX engine and transmission? Is it CA or Federal? Have the proper ECU and O2 sensor?

Does the car start quickly and idle smoothly? Is the idle speed correct?

What size are the tires? Pressure? Original wheels?

Is the engine warming up properly? Thermostat working right? (Chances are the problem is elsewhere, because this would probably have created smog issues.)

Check the timing? Proper plugs? Rotor, wires?

Any signs of an exhaust restriction? You can check this by putting a rag over the exhaust. Be careful.

Are any brakes dragging? Lift the car and make sure the wheels spin freely. Does the car coast well? Are the tires wearing evenly? Any signs of bad alignment? Was the car ever wrecked?

If you engine has a lot of carbon deposits, some kind of top engine cleaner might help (e.g. Seafoam).

Check the accessory belts? A/C belt or alternator belt too tight, or a bad bearing in the accessory creating drag?

Check the valve clearance? I wonder if the valve timing is right. Could it be the belt slipped a notch?

Check for a vacuum leak? Check for proper fuel pressure? Fuel filter not clogged?

I'm sure I forgot some things.

[kamesama980]

you DO have multiple cat converters now. maybe the 1st one was buggered and you ought to have replaced it instead of adding to it. would go along with fixing your trouble simply by adding a cat.