Hi all,

just joined this forum to get general help. I just bought an 87 iroc 5.7 tpi which is my very 1st car and its honestly going to be a project. i just got it back up and running, previous owner had nothing done correctly on it from misc. engine work wrong starter and completely half assing the electrical. Ive been driving it to and from work which is 14 miles round trip and i expected it to waste gas but not as quick as it has. i did the research and saw that it gets from 12 to 16 mpg and rightnow mine is at the 12 mpg level any ideas on what i can do to increase this?....

thank you all!

 

-First off, make sure it's tuned up with good plugs, wires, etc.

-After that intake and exhaust mods will help as long s you don't kick it all the time.

-Proper tire inflation is critical

-Make sure the tourque converter is locking up

As i think of more I'll post em up if they aren't covered by someone else!

and.... WELCOME!

 

Thank you Boss. I am going to take the tuned part as my next move. See what i get from that. My mechanic told me the exshaust system was actually nice it has a flowmasters which makes it sound like a have a T-rex under the hood and the smell of gasoline it realeases really gets on the nerves of those prius drivers....hahaha....

Thank you!

 

Is the check engine light staying on? If so, pull the trouble codes.
If you're smelling gas, you may have a damaged fuel line, an injector problem, bad 02 sensor in the exhaust manifold, or some such. Those would sure explain the bad MPG.
And where did you get 16 MPG from? The original window sticker should have showed about 24 MPG for highway.
If you have 3.27:1 gears, or more, you should be in OD any time you're above 30 MPH. That should be about 900 RPM with the converter locked.

 

Check engine light is off.
Yes sir Def. smelling gas everytime i stop and wait for a light, and also when im warming the car up....so i will look into these 2 things.(thanks a million man) i got the 16 from an iroc website (dont really remmember i was just doing searches)....
Wish i could read my RPMs but the only thing working in my dash is the MPH...the fuel level gage ive noticed that when i accelarate it goes up and when i brake it goes down. It does mesure the gasoline when correctly when i fill it up and it gradully goes down but i really dont have much trust in it right now.

Thank you for knowledge!

 

would you guys happen to knwo what the correct mpgs would be for this car?

 

Should be around 16-17 city and 24 highway...thats what my car got on average. Depends on how you drive and such.

I'd do what others have mentioned...check the engine over and make sure its in top running condition. Replace any old sensors that may not be functioning correctly. O2 sensors, verify no exhaust leaks, no vacuum leaks, make sure you have good spark plugs/wires, coil, and ignition module. Basically freshen up all the running components and see where that gets you.

Then you can work on tuning the chip for more mileage if you want. You can lean it out for better highway performance.

 

Thank you sir...knowledge of where the mpg should be at helps alot. once fixed doesnt sound so bad at all. i just got the car and i do plan on working from the inside out. My mechanic did tell me that who ever was working on it before did a wtf job! and not in a good way. im just saving up some money before i can take it back to him so he can start on this current list that i am building... thank you for the input!


Much appreciate it!

 

your gas guage goes up and down when starting and stopping because gm didn`t put baffels in the tank untill a few years later. my 87 is like that too....a real pain in the ***, but if you don`t stare at it while driving around you don`t even notice it after a while

 

About the fuel slosh: I love it. Why? Because I had a Mercury that once ran out of gas going up a mountain, and a nice old guy tow-strap towed me to the top, but his pickup overheated. Guess what? I had gas going down.
It seems the Mercury pump was in the front of the tank, and that's dumb. It seems ours is in the rear of the tank, so if you run out of gas going up the mountain, then you really are out of gas.

 

Also check where the fuel filler neck goes into the tank - is the neck loose? Mine leaks when then tank is full, I suspect it might be a couple mpg worth. Follow the smells and you should find the leaks.

 

Tune up is a great start and I would also replace the fuel filter, done this on my GTA had great results

 

Of all the f bodies here none get better than 17mpg average, that's:
87 5.7 IROC, 88 5.0 IROC, 88 5.7 IROC, 88 5.7 GTA and a 89 5.7 GTA. All are tpi coupes, only one (the 5.0) is a five speed, the rest are autos. The autos all are 3.27 axles, the 5.0 has the shorter of the 9 bolts 9forgot exact ratio think it's 3.48)

I don't see how anyone can get 21mpg out of these.

 

Top off your tank, set your tires at 35 psi, get on the interstate, set the cruise control at 65 MPH, and travel until your tank is empty. Then top it off again, and note how many gallons that took. Divide that into the number of miles you travelled. If you don't get 24, then replace your 02 sensors, and repeat. If you still don't get 24, then sell your cars and buy a new Hyundai.

 

I know after all my mods... T5 <> 3.73 ... I was getting 25MPG
and no where near stock... and my tuning<<<<

 

i get 20

 

I have a 305 and I've gotten 12/13 mpg in town and 15/16 mpg on the highway from day one. I've done everything in this thread and it didn't fix it at all. I've pretty much come to the conclusion that I need to get new fuel injectors, but I don't have the money for them since I'm going off to college next fall and I have to pay for it myself.

So if you do all of the stuff mentioned above and you still get crap mileage, look into changing out your fuel injectors.

 

I just did a trip from the Oregon coast up to Bellingham Washington, and averaged 19 mpg at about 65 mph with a bunch of stuff in the car. The motor is a 305 with a carburetor. So with EFI I could easily see these cars getting 20+ MPG

 

My 87 350TPI gets 16-18 town and 24 on the highway. Always has. I've had her from 112k and up to the 150k she has now. And yes, i can get that going 75mph down the interstate all day long. So those are definitely doable numbers. I had a 86 305 TBi that got 30mpg, consistently.

 

Check the catalytic converter if your exhaust smells really rich. It may have been gutted by a previous owner.

And I get 17 city+highway combined & have hit 21 on strictly Interstate Highway, on my 350 TPI.