94 suburban engine problems

[atvaddict]

hi, i have a 94 gmc 3/4 ton 2 wheel drive sub with the 350. Its got about 140K miles on it. It cranks what seems to b quite a lil bit before it starts, and we put all new plugs in it, wires are fine. We also put a new O2 sensor on it. The problem is it just doesnt have any balls. gas milage is poor like 8-10 mpg...and it just doesnt run strong at all. It also uses alot of oil..but we cant figure out where its going, since it doesnt leak out, and doenst smoke at all. Anyone have anyideas to what might b hindering it..or maybe its just ready for a new motor?

thanks

 

[atvaddict]

anyone?

 

[the cork]

Try fuel filter and pvc valve,

 

[HarryH3]

Is it always hard to start, or just when the engine is cold? If it's the latter, try switching the key "on" for a couple of seconds before trying to start the engine. This will let the fuel pump repressurize the system. Our '94 Sub starts much easier if I do that. But if it's been driven within the last couple of hours or so it will fire up as soon as I bump the starter.

The oil probably is burning, it just isn't bad enough yet to create a smoke screen. A quart every 1,000 miles or so won't be obvious at the tail pipe.

Ours gets 10-12 mpg in town and 12-14 on the highway.

 

[atvaddict]

hmm we'll have to try that key trick. i dont know what the pvc valve is but ill look into it

 

[darkshadow]

it is the plug with the vac lines hooked to it in your head covers

 

[Fierospeeder]

im assuming you have worn piston rings or cylinder wall which is causing blow by. The pcv introduces the gases and the oil back into the engine to be burnt.

It is possible that the engine is worn and it doesn't have a great compression to get the fuel compressed and heated.


I would do a vacuum check or a compression check and see the results.


You can rule out the o2 sensor on the cold start issue. Your injectors maybe clogged which isn't giving enough of a fuel mixture for a cold start. Coolant temp sensor is another option, stuck egr, clogged filter or cat.

 

[4xcrazy]

I have 220k on my 350 in my Burb, with no starting problems, the only problems i had was when the fuel filter was plugged or when the pump was dying out, i would definately check the fuel pressure.

 

[goldwing2000]

Yeah, I was going to say it sounds like the fuel pump is taking a crap. Possibly a leak in the system somewhere. Check the filter and check the pressure.