1991 K1500, fuel economy

[otis24]

I have a 1991 Chevrolet K1500, 4.3 V6, automatic transmission. I just made a highway trip and have done some town driving. Oil has been changed by the p.o. Every 1k to 1500 miles. Spark plugs were changed about 17k miles ago with Champion copper plugs. Fuel economy based on a rough guess is about 13 mpg mixed driving. I had hoped for better MPG. What can ai do to improve fuel economy? Thought about Bosch Iridium plugs and new wires. Any other suggestions?

For better or worse, i'm in the midst of an Auto-rx cleaning and will starr the rinse phase as soon as I receive my Fumoto valve.

 

[dishdude]

Sounds about right for a 24 year old fullsize 4x4 pickup! I don't think there is much you can do to improve that mileage.

If the PO changed the oil so frequently, why are you doing an ARX cleaning?

 

[xxch4osxx]

Ya, I think that is about the most you will get out of it for fuel milage. Just drive it easy is about all you can do.

 

[Pontual]

FSC

 

[zrxkawboy]

I would replace the O2 sensor if it hasn't been done. Also, it never hurts to clean the intake system (throttle body, etc).

 

[clinebarger]

Adding a few degrees to the base timing helps. Low compression TBI engines respond well to more Ignition Lead.

Unhook the EST Bypass Connector (It is located near the distributor, The wire is Tan with a Black Stripe)
Using a Timing Light adjust the timing to 4 degrees BTDC (Advanced). Reconnect the EST Bypass, Disconnect the battery to clear the EST code.

Good stock Ignition parts is all this engine needs, platinum/iridium plugs will not return any MPG gains. Though I'm not a big fan of Champion plugs in anything but Chryslers & Briggs & Strattons.

Installing a Heated Oxygen Sensor helps a lot, I'm sure there are several write-up's on the internet.
You will need a 3-wire Heated O2, Matching connector, Run an Ignition Hot & Ground for the heater circuit & of course splicing your O2 signal wire in.

You would be surprised how much your truck runs in "Open Loop", Installing a Heated O2 will allow 100% "Closed Loop" operation when the engine is warm. And achieves Closed Loop faster after a cold start.

At the trucks age, The Gasket under the throttle body needs changed, Check all vacuum lines, There are not many....MAP sensor, PCV, & Evap purge.
Intake Gaskets would be a good thing to do in the near future, People usually wait for Coolant leaks, But Vacuum leaks form long before that.

Good luck!

 

[otis24]

Originally Posted By: dishdude
Sounds about right for a 24 year old fullsize 4x4 pickup! I don't think there is much you can do to improve that mileage.

If the PO changed the oil so frequently, why are you doing an ARX cleaning?


This was a short tripper, 1k miles per year. Looking down the fill hole, it looks like a lot of varnish. Had I realized the valve covers were so easy to remove, I would have done that. In addition, the PVC was gunked up. Therefore, I used Auto-Rx as a prcaution. Figured it couldnt hurt.

Will use PYB after I drain it followed up by a High Mileage oil for cleaning.

 

[Pop_Rivit]

It's a 24 year old 4X4 pickup. As has been stated earlier, that's about right for that type and vintage truck.

 

[zzyzzx]

Sell it and buy a Cruz.

 

[hattaresguy]

That's about all they get.


We run a lot of those trucks the funny thing is an 04, 05, 11x2, and a 12 get all maybe 1-2 mpg better around town. Chevy didn't improve them notably until the 2014's.

Buy a 2014 you will get about 16-17 around town!