red 95 z28 lt1

hey guys im kinda new here just bought a 95 z28. i have a little problem here. i am getting 10 to 11 mpg on the thing when i think i should be getting at least 16 mpg. i have to fill up every 130 miles (aprox) the engine runs fine no problems just had automatic trans rebuilt. no ses light, no unusual noises. the car has 116k miles but the engine has 37 k miles (new motor) only thing i can think of is o2 sensors. only mods i have is a moroso cai 1800 stall converter, airfoil, and hypertech power programer and a 160* power stat. i dont know what things were swapped on the new engine from the old except the pullys. thanks for your help in advance.
-frank-

RedRyder518

I would definitely change the O2's, especially if they are origional. When you had the engine replaced, are you sure they put new spark plugs back in? When mine was replaced, they used the same old sparkplugs because they are supposidly the platnum tipped and should last 100k, but that is way too long I think for them.

cals400ex

i would make sure your not getting any codes. some codes will not pop on the ses light. yes, o2's need to be changed. if plugs/wires are bad, change them out also. try changing the fuel filter because if that is the factory one, you will be getting bad fuel economy.

red 95 z28 lt1

if i decide to change the plugs which ones should i get? same with wires assuming i will do headers in the near futue. ill change the o2 sensors first. what kind should i get? i work at an auto parts store so i can get things at discount. also are they hard to change (o2 )

SS Mark

130 miles to a tank is more like 8-9 mpg, but Im sure you dont reun it dry evertime so it will be a little more than that. Tuneups help alot, check plugs/wires, timing, clean air/fuel filter, new o2 sensors, should do alot for your car.

-Mark

Thebeast431

I am not sure where you consider a full tank to be. But I fill my tank up when my gauge reads a 1/4 tank, which in actuallality is about 1/8 tank, I get 160-180 miles when I reach that point. I would take off the Hypertech crap, it is probably robbing you of hp and mpg. Just use it for the stat and forget the rest. O2's are a biggy and also exhaust leaks, maybe a clogged cat and/or muffler.

Travis

Lost

As said above, if your o2's are failing then you will get a code.. however your ses light may not turn on. So, I suggest you get your car scanned for free at autozone to see if you have any codes.. I wouldn't just replace the o2's and hope that's it because they ain't exactly cheap. Also check/replace plugs with ngk tr55 (that's what most, including myself use - they are copper not platinum) check/replace wires too.. and change out the fuel filter. A clogged cat would also kill gas mileage but you'd notice a power loss too..

Beyond that I guess you could have a leaky injector.. I dunno. Anyone know how to check/diagnose a leaky injector? How common is that problem with these injectors?

HTH

You should be able to get more than 16mpg city.. even if you're ragging on it a bit...

Terran2k

good luck man, there many posts out there with this same prob. such as myself. 150/tank. plugs/wires/fuel filter didnt help me, shooting for o2's...let us know how things go

cals400ex

i don't believe autozone can scan a 95. the connector should fit in the car but i believe no codes will come up unless you have a 96 or newer computer. i think the cable needs to be different for 95 and previous years for autozones scanner to work.

lituplt1

When I first got my Z, my mileage was terrible. Turned out to be a lead foot. Once the cops get to know your car, your mileage will go way up, trust me.

HungryT/A

It's a very common problem on the stock ones. Depends on the quality of fuel. A common sympthom (sp?) is a very strong gas odour in the car. Unbolt the fuel rail, (4x10mm bolts) lift off the rail assembly, place it on a rag, and turn on the ignition, but do not start the car. You'll be able to see the leaking injectors!

Good luck!

red 95 z28 lt1

yesterday i went to autozone and had it scanned and there was a link error and it wouldent work (they used the obd 2 scanner) i told them that the computer had hypertech power tuning installed and they told me to bring the computer back to factory settings and it may work.
also yesterday i went to start my car and it took a little longer then normal. it did it through out the whole day. it also did it when i started it and it was running for about 5 mins and it then i went to start it again after shutting it down to see if it would take longer and it still did it. my guess is that it may be fuel related also when i was leaving school i noticed a whining/buzzing noise from the back of the car it was very noticeable it sounds like the fuel pump priming when you turn the key in the on position. i am going to change the fuel filter next week and see if that does any thing as far as gas mileage or buzzing noise. also i want to check the fuel pressure i never did this before im guessing i have to connect the fitting to the fuel rail somewhere.? what shoud the fuel pressure be and should the engine be running when i do it?
also if the fuel pump is bad how much $ do they go for and where exactley is it located? i havent been under my car yet.
thanks and sorry for the long description

cals400ex

the fuel pump will be a tough one. the pumps are located inside the gas tank. these will usually cost a couple hundred bucks. i don't think the autozone scanners will work on obd 1 cars.

red 95 z28 lt1

its obd 2 i believe. and does any one know by the part # if it is obd 1 or 2 or new or old cuz i went to the chevy dealer and they said if the ecm is old the number would be 1227730 and if it is new it would be 16198262 but i forgot to ask them if it these numbers were to tell if it is obd 1 or 2. or if it was replaced or not (as far as new and old) i checked my ecm out and the service number was 16188051 and it had another number way below that that read: 16209471. sorry if i keep throwing more problems into the situation but i just want to make sure im changing or fixing the right thing. your help is greatley appreciated. thanks in advance

Lost

obd II came out in '96.. yours is a 95 so you've got obd I... and that won't work at autozone.. my bad.. I didn't even think about that. I guess there is an upside to having obd II