Major Tune Up Input
 

My 1994 SL1 has horrible gas mileage and only a fraction of it's stock HP. I know what I need and I am looking for input for anything I can do to increase power and fuel economy.to see what others say.

What should be serviced or replaced on my Saturn to improve the HP and fuel economy? Note it has over 305K miles, has been severely neglected and not getting any tune ups years over due IF it even got any in the past 8 years minimum.

A tune up with new plugs, wires, PCV valve and air filter and breather elements along with a good cleaning of the throttle body should help the mpg. As far as power increases go, you're SOL. These are not hot rods. DO NOT waste your money on a cold air intake. I don't care what anyone tells you, they do NOT increase your horsepower. All they do is make a lot of noise and your mileage will actually go down because you'll like to hear the sound when you punch the accelerator to the floor. WASTE OF MONEY.

I do not want more than stock horsepower. My poor engine only runs maybe at 65% of stock horsepower. I want to see if I missed anything that can improve fuel economy and restore lost horsepower.

Don't forget the fuel filter. That can have a big impact on overall power. If the car burns a bunch of oil, you won't get much power out of it due to worn compression rings.
Edit: That auto trans isn't helping anything either.

beat me to it.

What's the compression across all four cylinders?
Also, how are you measuring/guestimating hp output?
Throw in the front 02 (not a normal part for a tune up but makes sense here given car's history).

But do the compression check first w loan a tool from autozone or similar and post results.
There's no point trying to tune up a vehicle that needs an engine refresh

Go to junk yard.
Buy DOHC.
Rebuild.
Swap.


Onto the serious answer now.


What about looking into swapping the cat as well? We all know that can hurt performance and mileage. Not cheap to do, but may be worth it. Especially high mileage.


Only if the compression test checks out.

Very nice responses. Above and beyond what I was looking for. However, I agree with everything, but I will only he doing the ones that take little time. Its a fact my engine needs an overhaul, but with my schedule and my only work area being an auto parts store, I can't even replace the head gasket which I need to do.

I have a list of about 20 parts my car needs that I can do within my resources. All possible were purchased from Rockauto.

Once I get a place to do major work, I am just rebuilding the engine first then the transmission.

So again, assuming everything is bad (pretty much true sadly) what can be replaced or serviced in under an hour with the proper tools without a car lift?

I will post my list soon of everything I have written down that my car needs.

Here is a long list of things my poor Saturn needs. Reading my previous post, If there's anything I missed that I need to check replace or clean or anything else, please let me know. Again, assume everything is bad because they mostly are.



Clean/Replace Idle Air Control Valve
Replace Spark Plugs
Replace Air Filter
Clean/Replace EGR Valve
Replace EGR Valve Gasket
Replace Thermostat
Replace O2 Sensor
Clean Alternator Cables
Replace Ignition Coils
Replace PCV Valve
Replace PCV Valve Hose
Replace Air Intake/Charge Temperature Sensor
Check Vapor Canister Purge Valve
Test/Replace Manifold Pressure Sensor
Replace Coolant Temperature Sensor
Replace Fuel Injection Pressure Regulator
Replace Spark Plug Wires
Replace Gas Cap
Replace Intake Manifold Gasket
Replace Fuel Injector O Ring
Replace Valve Cover Gasket
Replace Oil Filler Cap
Replace Transmission Dipstick
Clean Throttle Body
Clean Intake Manifold
Clean/Replace Clogged Fuel Injector

I am going to prioritize your list and add 1.
At 300,000+ miles your rings are going to be worn out.

1: check your compression.
2: replace spark plugs, they will be out for #1
3: replace the air filter
4: replace the pcv valve and hose
5: Now is the check engine light on?
6: The rest is done only if needed.
7: Don't replace coils until they die
8: Wires are always a good idea, but if it runs on 4 cylinders it can wait.
9: Sensors should be changed if they are bad
10: Gaskets should be replaced if they are leaking.


Clean/Replace Idle Air Control Valve
Replace Spark Plugs
Replace Air Filter
Clean/Replace EGR Valve
Replace EGR Valve Gasket
Replace Thermostat
Replace O2 Sensor
Clean Alternator Cables
Replace Ignition Coils
Replace PCV Valve
Replace PCV Valve Hose
Replace Air Intake/Charge Temperature Sensor
Check Vapor Canister Purge Valve
Test/Replace Manifold Pressure Sensor
Replace Coolant Temperature Sensor
Replace Fuel Injection Pressure Regulator
Replace Spark Plug Wires
Replace Gas Cap
Replace Intake Manifold Gasket
Replace Fuel Injector O Ring
Replace Valve Cover Gasket
Replace Oil Filler Cap
Replace Transmission Dipstick
Clean Throttle Body
Clean Intake Manifold
Clean/Replace Clogged Fuel Injector

To be honest with you, I wouldn't put that much money into a car that age with that many miles. I'd just find a nice, used Saturn with 100,000 miles or so on it. Craigslist if full of them.