Onyx_Black_Z28

iTrader: (2)

Hey guys, recently purchased a 2002 Z28 Camaro with 21k miles. It was bone stock when I purchased it at Carmax and I have since added an SLP lid/new filter. Below is a picture of my gas gauge and trip meter. Trip meter was reset before I left the gas station on the last fill up. This has been consistent the past few fill-ups.



My driving is light to moderate at the most. I typically shift at about 2k rpms. Any thoughts? I'm not expecting Honda Civic fuel economy, but 10-12 MPG on conservative driving is a good bit worse than I expected.. and definitely worse than other friends with f-bodies. Is this consistent with what the rest of you are seeing?? Any feedback is greatly appreciated.

Mr. Sir

I can only assume it's not as "stock" as you think, and not in a good way. Look at the tune, and check the a/f tables. Honestly that's worse than some carbed vehicles.

lemons12

iTrader: (71)

I assume you are a manual?

Even a H/C 410 gear manual car would get better than that with fairly aggressive driving.

Codes?

Onyx_Black_Z28

iTrader: (2)

Mr. Sir, it is definitely stock. It was apparent looking under the hood/underneath the car that nothing on this car has ever been touched. It had the original EVERYTHING - didn't even look like the air filter had ever been changed. I actually work at Carmax where it was purchased, and they won't sell anything that has been more than lightly modified (more than a cat-back/intake, anyway, which this car didn't have). Which makes the awful mileage all the more baffling.

Lemons12 - you are correct, M6. Forgot to mention that. No codes - the engine runs/pulls great, just like any other stock f-body I've been in.

lemons12

iTrader: (71)

plugs
plug wires
o2s
fuel filter
injectors
mass air flow

Just a few things that I would look into... Hooking it up and scanning it wouldn't be a bad idea. I have seen cars have codes and no "SES" light coming on.

Onyx_Black_Z28

iTrader: (2)

Plugs and plug wires are definitely on my list of tune up items, along with the fuel filter. Do you know of any signs that demonstrate the O2's, injectors or MAF have issues if no codes are present upon scanning? Or am I just stuck with the same diagnostic procedure found in a dealer handbook?

lemons12

iTrader: (71)

Usually a bad maf or o2s would be pretty easy to notice.. Loading up would be the biggest thing. It would clear up higher up but 2000-3500Rpms would be very rough.

Scan it first, then go from there.

Again, both of these should show their self fairly easily if there is a problem. Diagnosing a bad maf (if the normal signs are present, which you say the car is running fine) is as simple as unplugging it and seeing if it clears up. You would have to replace yours... Used they run 20-40$ on here... And lt1 MAFs are interchangeable. Finding a buddy that would is in a situation to let you borrow one for 3-4 days would be perfect.

o2s? Replace them.. Not much else you can do. You can buy them off here used for usually 30-50$. I *might* have a set I will sell cheap if you end up getting here. I will have to double check the shop though.

You could take the injectors off and inspect them.. You can get stock injectors for roughly 20-45$ on here used.

I would scan it then look into plugs/wires/fuel filter first... They are cheap and easy. Then go from there.

Onyx_Black_Z28

iTrader: (2)

Lemons12, that is fantastic information. Because the car is 10 years old and doesn't look like anything other than oil/filter changes have been done, I'll probably end up replacing all of the above items you mentioned (with the possible exception of the injectors). I will post back results as soon as I've had a chance to scan/replace a few of these items. Thanks so much for your time.

lemons12

iTrader: (71)

Glad I could help, definitely report back with updates... Your update could point in a direction to solving an issue, even if it doesn't fix it. Or you could replace everything, give updates, and it still not be fixed.
Not funny, but its what happens with cars! LOL

Mr. Sir

I really can't think of anything that would have such a profound effect on fuel economy. Far too much fuel is being injected. If the maf and o2's are working correctly, It's most likely the fuel system. Scanning it will probably reveal the problem.

lemons12

iTrader: (71)

It is either a mechanical fuel issue or a computer issue (the computer thinks you need more computer). There is nothing else left.

It could be something as simple as having a hole in a line or something, who knows. Just have to see what you can find out once you dig in.

Onyx_Black_Z28

iTrader: (2)

I had an Mr2 turbo several years ago that drove great but would get zero extra power under full boost.. it was the strangest thing. I replaced half the parts on that car and saw ZERO difference. Here's hoping my new Camaro is different!!

RikkiTorment

I'm also thinking what was stated above, check the plugs and wires. The stock wires can be somewhat difficult to tell if they are secured on the plug. I also ran Champion plugs for a few months, absolute worst mistake I have ever made in my entire life. Another thing is you can clean out your throttle body too, could possibly help.

And does your car pull as hard as I should, any power loss?

Blk98Vert

iTrader: (2)

Definitely do a basic tune up. I went from 230 miles per tank to 300 with just plugs/wires, synthetic oil/gear oil, catback, lid and K&N filter

01ssreda4

iTrader: (96)

I would lean towards 02s or a bad MAF.

remauto1187

iTrader: (1)

Tuneup? On a car with 21k miles that is equipped with wires, plugs, etc. that will go a min. of 100k miles. That would be throwing money out window. Definitely pull the plugs and see what color they are. While you have them out run a compression check. Just like they said above, it would not be a bad idea to look over your tune to see if has been messed with. Scan computer for codes to see what gremlins you have. Doubt the injectors are stuck open otherwise you would smell gas while engine was running and would eventually hydro lock.

_JB_

iTrader: (33)

The newest F-body is 10 years old now...

lemons12

iTrader: (71)

Yea but it only has 20K miles on it...

sjsingle1

iTrader: (1)

check the ENTIRE pcv hose......a hole or a rip will give you a vacuum leak........every rubber piece on f bods is rotted after 10 yrs

Onyx_Black_Z28

iTrader: (2)

I haven't dyno'd the vehicle to confirm the power it is making, but it feels plenty fast. I had a manual 05 Mustang GT a few years ago and this definitely feels faster. I can't imagine it's supposed to be any faster than this stock!


You do 300 miles a tank?? That would be fantastic. I took the car to about 170 miles today before fill up - had to put 14.5 gallons in it to fill it up. Works out to 11-12 mpg. I'll definitely try everything you mentioned.

I'll check that out - thank you!


Remauto1187 and _JB_ thanks for your feedback. I do have to agree with _JB_ that those items do probably need to be replaced - Even though I only have 21k miles, I am about 8 years past the point it's recommended to replace those in the maintenance schedule. I don't have HPTuners or any kind of scanning equipment yet, so checking out the A/F ratio and codes will have to wait until I have access to those something to that can provide that information. I'll be surprised if there is something so major wrong with the car that a compression test would yield poor results. I definitely don't smell gas and the car runs great - if it ran rough or anything, I would have simply returned the car within the 5 day return policy rather than try and hunt down issues. I don't do a ton of driving, so it took me a week to burn a full tank of gas.. go figure.

Great feedback, I'll check that out.

Thanks again everyone - you have all given me a number of leads to follow up on. I will report back once I've had an opportunity to try some of these things!