Geo Storm Gas Milage Improvement?

Hello, I am new to this forum, but I made an account cause I need some help with my friends 1991 Geo Storm

He wants to improve the gas mileage on it cause it’s pretty terrible, and he was talking about putting a cold air intake on it, I told him he’d need to get it tuned to make it actually work.
Can someone help me out, would a cold air intake work, how would you mount it, how would you tune it, I don’t really know much about this car, and I was hoping someone would.

First of all the cold intake is a waste of money . This is an old vehicle and what kind of mileage does it actually get . Also since you say you don’t know much about the vehicle and you are on the web asking you would be wise to tell him to talk to a good shop. This is a case where no good deed goes unpunished .


A Geo Storm should be capable of excellent mileage. The first step is to examine the driver and the driving.

Does the driver accelerate at full throttle and rush up to red lights to slam on the brakes? Are they a left foot braker who rides with their foot lightly on the brake pedal?

What kind of driving is being done, is it short trip city driving and do they idle their car a lot or maybe let it warm up for 20 minutes while they drink another cup of coffee?

Then the car, are the tires properly inflated, the brakes and the parking brake checked for dragging? Is the wheel alignment way out of spec?

Do a compression check on the engine, if the compression is bad, no amount of tuning will help.
Is the transmission or clutch slipping?

Are the fuel injectors dirty, it the engine operating at the right temp and is the check engine light on?

A dirty air filter will hurt your power, not necessarily your mileage.

A properly designer cold air intake can give you a little more power, but if you use it it would actually drop your mileage.

New plugs might help, but only if they are needed.

In short there is no secret magic answer.


He just bought the car and it’s been sitting for roughly 5yrs and has a total of 260k miles on it, and the tires were one thing we were thinking it was, they’re in horrible condition, dry rotted, and his driving definitely isn’t the cause.
The radiator fan kicks on like every 3-7seconds really loudly as well.
He was having issues with the rpms we changed out the idle control sensor.

28 year old disposable car with 260k miles? And on top of that it sat for 5 years? It should have been disposed of at least 5 years ago. IMHO Any money put into this thing is money wasted. As a matter of fact the money to buy it was money wasted. Sorry but those are my thoughts.


i bet all fluids need changing. But first do a compression test. If the engine is worn out no need to spend any more money on it.


What kind of fuel economy is it currently getting?

That’s not going to improve the fuel economy and no he won’t needed to get it tuned.

All bests are off. It’s impressive that the vehicle is even running in light of this information. There could be (and probably are) half a dozen things wrong with this vehicle.

Is it overheating? Does it only do this when the A/C is on?

When that vehicle was new and in perfect mechanical condition, it could be expected to eke-out a bit more than 24 mpg, if driven very carefully. After almost 3 decades and 260k miles–with unknown maintenance–it would almost surely not do as well with gas mileage.

As others have asked… What type of gas mileage is he getting from this re-badged Isuzu Impulse?

With a car that old, and with that many miles on the odometer, I think that the OP’s friend should be focused (in this order) on the following things:

Have the engine compression-tested.

If its compression is reasonably good, then he should have all of the 90k/180k maintenance procedures done, and should have the dry-rotted tires replaced before they lead to a catastrophic traffic accident. That may improve the gas mileage… a bit.

If–as I suspect–the engine’s compression is poor, then he should start searching for his next vehicle, as this old, tired car is not worth spending the money for an engine overhaul.



Setting for five years means rotten fuel in all the lines that will take a while to clear , Should have put new tires on as soon as possible and at 260000 miles that is a lot more miles than most Geo vehicles lasted. This person is driving around on dangerous tires and he is worried about this unknown fuel mileage . Good Grief.


Not everyone has the ready access to cash to go out and replace a vehicle just because it’s underperforming. We should keep that in mind when we cavalierly tell people to junk a car and get a different one.

OP, you never defined “terrible” gas mileage. What, specific, mpg is he getting?

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… and, let us not forget that most Geo models were re-badged Toyotas, but this particular one is a rebadged Isuzu. Isuzus were never noted for the same type of longevity that Toyotas are, and after 3 decades/260k miles of use and unknown maintenance, the long-term prospects for this vehicle are not good.

The owner of that vehicle should focus on immediately replacing the tires, and on keeping it running, rather than on gas mileage.


A stuck thermostat can kill your fuel economy, so that’s worth checking in addition to the things listed above.

Yet he is considering adding a performance air intake kit!

Because you can get one for less than $100 (especially if you make it out of cpvc) and there’s a lot of marketing BS out there that claims it increases fuel economy in addition to adding horsepower. Now that we’ve told him CAIs don’t live up to the hype, he doubtless won’t advise his friend to do it. :wink:

I hate it when someone asks a question and then after we answer, they reveal the pertinent information that makes the answers irrelevant.

If it sat that long and was recently thrown back onto the road… What considerations have been taken with the braking system? Are the rotors rusty? Calipers sticking? There will definitely be something wrong with the brakes if you just jumped in this car and began driving.

I would be looking there first and foremost. The mileage doesn’t work in your friends favor here either… But the brakes man… the brakes and rotors do not take well to sitting 5 years and they will not function properly if no attention is given to them. They could be hung up at all times which would kill your mileage right quick.

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Make sure to turn the rotors or replace them. People love to look at them and think oh they look fine.

Sorry I haven’t replied to any posts, I’ve been extremely busy lately, haven’t had much time. He bought the car thinking it had 50k on it but the odometer was reset, and in the certain conditions of the car he wouldn’t be able to argue it. He had the breaks and rotors replaced shortly after getting the car. The engine doesn’t seem to be over heating, the radiator fan just kicks on really loudly after a couple seconds pass, the tires were one thing we thought about in consideration.
We don’t know the exact gas mileage but me and him drove probably about 2 hours the one day and blew through an entire tank of gas. I told him to track his miles upon filling the car, and the difference between refill and do the calculations to figure the ball park idea of the mpg.
A compression test would probably help, to get some information, thank you for that suggestion to everyone who suggested it instead of just saying junk the car, even though I personally tell him how bad the car is, he still wants to try with it.
The car definitely does still have life, and if everything is figured out I wouldn’t be surprised if he can get another 30k atleast out of it.
I suggested his Throttle Body, or Fuel Pump was a suspect based on his rpms randomly spiking, but he came to the conclusion that it only spikes like that when it’s really hot out, so I’m not too sure anymore.
He also has another issue were the throttle will basically stick, and he has to keep the brakes held while at a stop cause the car is trying to move forward.
He ordered a short ram intake pretty cheaply and also a fuel pressure regulator pretty cheaply, we’re probably gonna change those out and see what happens.

I’m having some issues with my car as well but it’s stuff I know how to fix so we’re both kind of in an interesting situation, except my car is an FRS, and my issue being my suspension shocks, and I need new sway bar links and the place I bought a new set from sent them to the wrong address.
Also I ordered the wrong wheel studs for my car.
I included this information to kind of let you know that I’m not 100% clueless with cars, I’ve also changed my clutch, did a new exhaust pipe on a previous car an alternator, rewired a couple head units, my career is a generator mechanic in the USAF, went to school for it primarily troubleshooting issues with mechanical and electrical systems, so I do have credibility in this area.

Sounds like you mostly have him on the right track. Just gotta wait till he does the real mpg test. If you drive it hard enough, it’s not terribly difficult to go through a tank in 2 hours, so that could still be within normal expectations.

I’d also make sure the throttle cable is free and doesn’t bind anywhere, including where it attaches on both ends. As for the rev spikes, sometimes low coolant can cause that, so double check that the level is proper and it’s properly bled. I don’t think it would be the fuel pump.

The short ram intake will do nothing for you except make the car louder and slower. You should tell him to return it, it’s a waste of money.

I assume this is an automatic transmission?