So I've started to have a whole host of issues with my g recently. Its a 2004 6mt. Bought the car earlier this year and some of this has happened since I got it, some is new.

To me it seems like the car is running stupid rich almost all the time. Since I got it, on cold starts/wot pulls/free standing revs, if I have the climate control on the entire cabin reeks of gas. Not sure if its a cracked manifold or something else? Over the past few weeks, a worsening problem I've had is bucking under moderate acceleration. Pulling away from a light trying to accelerate, if I give it 50% or more throttle the whole car bucks pretty bad. Once it gets over 3500 rpm it usually stops, but its somewhat consistent. It's not a 'one gear too high to accelerate' kind of bucking either. Sometimes it will just stutter once and other times I have to let off completely for it to stop.

Ever since a few days ago, when the car is at operating temp it takes probably 3x the time it normally would to crank. Cold starts just fine, but if I just go inside a store for a few minutes and come back, usually 5-6 seconds to crank when before it was maybe a second. If its not totally warmed up it won't do it either. Left it for 30-40 min and the temp gauge was probably 3/5ths of the way to operating temp and it started fine. And lastly, the gas mileage. This has been an always thing. I've gotten as low as 12 mpg, and the highest that I got driving conservatively entirely on the highway was 21. But usually.... its 15 or 16 mpg driving normally, or 14 if I really beat on it. I know people say these cars get bad gas mileage but is it really that bad? I have absolutely no idea if any of these are related.

This car was and still is beat up as ****, 10 owners and wrecked 4 times. God knows the last time any kind of maintenance was done to it. Three of the calipers wouldn't budge when I got it and it was missing 3 quarts of oil, if that paints a maintenance history picture. I plan on doing simple **** like cleaning out the k&n filter, cleaning off the maf and the throttle body, and putting new plugs in it because with the condition of the rest of the car I wouldn't be surprised if they have 80k+ on them. Just want to know if these are related in any way, and if there's anything else that I should check. Thanks.

 

For the fuel smell, check the small EVAP hose on the backside of the throttle body/plenum, and the fuel lines run along the rear passenger side of the engine compartment.
For the bad fuel mileage, 6 months ago my knock sensor harness was bad (read: vermin chewed through it) and I had p0327. I was getting 15-18 around town prior, replaced the harness + knock sensor, now I get 17-19 around town. 25+ on the freeways. Your cats also could be clogged. Cleaning the MAF is a good choice. On that note, make sure you aren't over-oiling the K&N, when I worked at AutoZone we had a customer who kept having MAF's fail. I ripped out his air filter, and it sure enough was a K&N that was *dripping* oil. I personally don't like the K&N filters. They don't seem to filter very well, every car I've had or seen one on leaves the intake pipe dusty, whilst paper filters leave it clean as a whistle.
As others will say, the spark plugs tell you exactly how the engine is running. ONLY run NGK or Denso. Make sure when you clean the throttle body you are VERY careful, its a sensitive unit. FYI you will probably need to do and Idle-relearn afterwards if it was super dirty prior.

 

If you smell fuel in the cabin you're leaking gas, find the leak.

Next pull the plugs, pretty sure you'll find the culprit along the way, either a damaged coil pack, oil in the spark plug well tube, or fried/worn plugs.

Personally I'm on the K&N bandwagon but you have to know how to reoil the filters or you just cause problems. After you use the cleaning solution and dry the filter 100% (protip you can hang the filter in front of a shop fan/box fan and it will be 100% dry in about 20 minutes) spray a generous coat of oil on both sides of the filter element and then LET IT SIT FOR 24 HOURS ON A PAPER TOWEL. I use like 2-3 layers of paper towels under it, just let it sit overnight. Excess oil wicks into the paper towel leaving just the right amount on the filter.

Run the filter for a week then remove and clean the MAF because there will almost always be a little oil splatter on it and it's good practice to clean the MAF yearly which lines up with the air filter maintenance. I've been doing this method for 25 years since these filters became popular, I've gotten pretty much everyone I know (that uses K&N) to use this method as well and I've never heard of anyone run into problems doing this.

 

Should've clarified, its an exhaust smell not a raw fuel smell. I checked the evap lines and they all seem connected and uncracked from what I can see. Super annoying when I need to have the defroster on and it smells like the exhaust is routed directly into the cabin.....

As I expected, all the plugs looked very old and very dirty, and cylinder 3 spark plug tube had 3-4 inches of standing oil in it, cylinder 5 had maybe a half inch. Took the plugs out, cranked it over to blow all the oil out, put new plugs in, replaced a coil that was taped together and it runs a whole lot better than it did. It hasn't done the long crank since either. Will have to report back in a while to see if gas mileage changes.

I cleaned the maf again a week after I did the filter when I took the intake back off. Project Farm made a great video showing just how much a K&N lets through vs just a regular filter, but it came on the car and it makes all the right noises so I'm not worried. Its not like I'm taking it anywhere dusty or dirty, I can barely make it out of parking lots without scraping the front bumper lol

 

More like "It's not like I'm sprinkling a cup of flour over my filter". They do just fine for real-world environments not whatever that sprinkled flour test crap was lol.

As for the leaking spark plug well tube seals, that's probably your culprit. Just pull the coil packs and plugs again in 10k miles and see how much oil is pooling. That oil causes havoc on the spark once it hits a certain level.