99 K1500 sub: motor problems

[noJeepshere]

My dads 99 GMC Suburban (350 vortec 4 speed auto 4x4) has an annoying engine problem. It stutters and stumbles and in general runs poorly. Having just drove it, anything over 1/2 throttle makes it stutter, anything less, and it runs ok. Cruising down the street, flooring it will make it shift (slowly) to first and then just hang out there. Nothing more. My guess is the fuel injectors being dirty, but have no way of being sure. I will pull the spark plugs pretty soon to see what they look like, and post a pic for the world to see.

Thanks for any help guys.

 

[sweetk30]

few points on the 96-2000 vortecs.

dist cap/rotors heavy corrossion build up.

dist gear wear out and cause 20-30* of play in dist to cam gear. requires replace of dist. and check reman units for sh!ty fix at the 2 hold down bolt holes for the cap. thay brake off and love to glue them back on. and thay do a bad job at it. setting timming will require a gm or top of the line scanner. as no crank point on front of engine.

ONLY use ac delco factory plugs in them.

55-60 psi is the pressure needed for the fuel system.

ever change fuel filter. ? could be about pluged. and dont twist off the rusty lines at the filter. 16mm line wrench and 20mm wrench for filter body required.

and fire it up at night and pop the hood and look for fire works. possible bad plug wires arcing all over to ground.

is the check engine light on ? even if no scan it and look for stored codes.

let us know from there. happy hunting.

 

[noJeepshere]

few points on the 96-2000 vortecs.

dist cap/rotors heavy corrossion build up.

Relatively new cap/rotor/wires/plugs, mid-range stuff, Bosch plugs (I think)

dist gear wear out and cause 20-30* of play in dist to cam gear. requires replace of dist. and check reman units for sh!ty fix at the 2 hold down bolt holes for the cap. thay brake off and love to glue them back on. and thay do a bad job at it. setting timming will require a gm or top of the line scanner. as no crank point on front of engine.

How do I check that?

ONLY use ac delco factory plugs in them.

55-60 psi is the pressure needed for the fuel system.

Looking for a fuel pressure tester to find out.

ever change fuel filter. ? could be about pluged. and dont twist off the rusty lines at the filter. 16mm line wrench and 20mm wrench for filter body required.

Changed at the same time as the ignition parts

and fire it up at night and pop the hood and look for fire works. possible bad plug wires arcing all over to ground.

Nope

is the check engine light on ? even if no scan it and look for stored codes.

Yeah, lots of them- P0101 P0171 P0452

let us know from there. happy hunting.

That's what I got so far.

 

[sweetk30]

FOR THE LOVE OF GOD DITCH THE BOSCH JUNK.

thay cause lots of running problems in the vortec motors.

like i said ac delco gm factory plugs only.

pull the dist cap. then twist the rotor by hand . if there is a lot of slop you prop have bad gear. .

 

[sled_dog]

P0101 is a Mass Air Flow, not enough airflow code. P0171 is a Bank 1 lean code. Sounds like the engine can't meter fuel properly because it doesn't have the right input readings. Bad fuel pressure could very likely be helping the issue.

Check the fuel pressure, Vortecs are real pressure sensitive, and 55-60 is a good number for them. Check the MAF for dirt. And check the air filter, it could be clogged and not letting enough air to the sensor, though that wouldn't explain the lean condition, stranger things have happened.

If all that checks out, take it to a shop. You need a pro scan tool or a scope to diagnose the MAF properly. And don't clear the codes before you take it, it makes their job harder.


I have Bosch wires and cap and rotor at the least on my 97, no issues. Forget what plugs I have though.

 

[noJeepshere]

I bought a can of mass airflow sensor cleaner (didn't know it existed) and that seemed to do the trick. It runs much nicer now. It had codes for both banks lean, so the whole motor wasn't getting enough fuel. Plugs looked like they had a bit of oxidation (no surprise there) but weren't worn too badly.

Found a fuel pressure gauge, 57 lbs idle is what it read, so the pump seems ok.

 

[sled_dog]

Good to hear it was simple.

That Mass Air Flow sensor cleaner has only been out for like 2 years. I haven't bothered to learn what is different about it really. I have used other solvents on them with no problems. But I make sure to blow them off right after I spray them off.

 

[noJeepshere]

The only thing I could tell about the amf cleaner is that it evaporated VERY quickly, like, almost as soon as I sprayed it, it was gone. Liquid spray never reached the ground. Otherwise, it smelled like starting fluid.