Buy a 91 GMC 1500, poor millage

[turbogui]

Hi, i have buy a used 1991 Chevrolet 1500 4WD 350 whit 280 000km.

I have bad fuel millage, like 10 mpg. For 100km on highway and no town i have used like 25 liters.

I probably need a tuned-up. Air filter is new. The exhaust pipe look very black inside...indicated a rich condition i guest.

I plan to : put new plug, cap, wire, O2 sensor and do timing check. I don't have the base timing number...somebody have it?

EGR Valve seem to not work too.

Any input and timing number?

Thank

[junior3382]

Get the timming fixed and replace the plugs, wires o2 sensors and everything you planned. Also, I would run a can of carb or injector cleaner through the engine. the can goes in the gas tank with a full tank. However, you may want to consider testing the compression on the engine. I suggest this beacause of the black sut you see in the tail pipe. With mialage like that, and age, the engine may be tired and need more than a tune up.

i hope it works out for you..

Good luck

[turbogui]

Thank for the reply.
A tune-up is the way for now but like you suggest.
At this milleage, a rebuild must be done to ensure good perf/millage.

[junior3382]

Most places would discourage you, however, I have found that spark plugs that have more than one contact like the splitfires or the bosh platinum plus 4's halp increase mileage dramatacally. Upgrade your wires to better quality, change the fuel filter and consider a higher octyane gas. these will help.

I have a friend that has a camero, and he did all that I just suggested and he brought his 350 up from 11 mpg to 19 mpg. it should work....

[chevyguy]

Spark plug only deliver spark, not increase it. Splitting the spark doesnt help anything. Sorry but too many people believe this add hype. Not saying all this together wont help , but replacing used plugs with new ones is always a great idea, but to replace good plug with splitfires and expect better fuel mileage, no. Spark will travel the path of least resistance. i have a sparlk plug tester i have proven it many times, these plugs are advertised to split the spark, well its simply not true.

[0425004x4]

Change out fuel filter on frame. The first sign of clogged filter is poor mileage. Use a delco or wix filter only do not use fram for it because the filter media is poor and they flow poorly new and sometimes cause the engine to code.

[junior3382]

My experience has shown that better quality spark plugs run more effeciently. I had a pontiac that I tried to prove it to myself. the 5.99 dollar preamo's vs the .49 cent cheapo's did produce better gas mileage. Now weather or not the spark was greater or not, they still run more effecient. However, every one has their own experiences.

Anyways, checking your fuel filter is a great idea, that could help a great deal too.

[chevyguy]

try as you may, voltage is voltage. It doesnt increase by trying to split the spark. I have a shop , we use them when the customer askes for them. never seen any results from just the plugs.