Lately the MPG have gone to the crapper. 6MPG in the city just doesnt fit the budget very well. Thought it might be the MAP sensor. Whats the volts to this sensor vs manifold vacuum? I have replaced the o2's and temp sensor and nothing changed.

Truck is a 1996 1500 5.9. Any help will be helpfull.

 

What brand O2 sensor did you get?

Did you reset the PCM after you replaced them?

Truck blowing black smoke?

Have you checked the plenum?

When was the last time the truck had a tune up?

Air filter?

 

OK this is what i got when i tested my MAP sensor with a vacuum pump. Key on got 4.89v and the other wire got 5.03v? 20 inches vacuum i got 2.27v and 5.03v? Iam guessing the 5.03 is the power to the sensor and the other is the transmit wire just dont have a good understanding and how a known good MAP should be?

 

Everything is new and from the dealership. Whats a plenum?

 

Ok found out what the plenum is. I do not use much oil betwen oil changes can it still be bad?

 

Possibly.

Did you reset your computer after doing the tuneup?

Something is screwed up if you are getting that bad of mileage even after the tuneup.

 

I'm having the same issue.

This next week she's going to get Hughes plenum fix (I can see some oil in there but hardly any - but NOT consuming any oil), kegger mod, Accel tune up kit, Cloyes timing set, new waterpump, new Goodyear serpentine belt, Goodyear upper and lower hoses, bypass hose, electric fan conversion and new Bilstiens all around.

I read in some threads guys are replacing IAC's but the dealer said "if it aint broke don't fix it"? On that note and O2 sensor - can I get some opinions here as well? See mod's below (the typical ones). I'd like to save the $120-$130 towards my 1.7 rollers if the other's aren't needed. I have 106,xxx miles.

Man if I could see 13+ mpg I would be one happy guy!

 

Use a mechanic's stethoscope and put it on each injector while the engine is running (Be careful!), you should here a click each time it fires. if it isn't clicking, it could be stuck open and leaking gas the whole time. Long shot, but it's possible.

I'd lean toward blown plenum or bad pre-Cat O2 sensor.

 

What elevation are you at ? It can sku your readings as those don't look correct.