mistaake

Hey guys. Somewhat proud? owner of a 96 Yukon (aka Tahoe)...

Specs:
5.7L Vortec 350 Gas V8, 4L60E Auto Trans, 4x4, 114K miles.

I've had these issues since buying it from the used car dealership. It was $2400 so within that price range it was hard to find something in better condition.
I'm trying to round up solutions to all of the problems I'm having and would love some troubleshooting assistance. I won't mention the minor stuff like mild slipping trans, very forgiving breaks, and play in the steering wheel... oh and the 4wd doesn't work at all) Thanks in advance for any help

Issue 1:

Smell of coolant when driving, from inside cabin and outside standing next to or in front of the truck. No noticeable drop in coolant level. No overheating. No drips/leaks of coolant or any fluid in parking spots.

Issue 2:

Long version: Vehicle idles rough and seems to be shaking (barely noticeable, didn't feel it during test drive, just thought it was bumps in the road) when driving at any speed, especially when going 75-80 and accelerating on highway. Also low power. It drives like it has a V1 but is a V8 If I wanted something that was slow and got lousy gas mileage I would have bought an older Ford 5.4 V8!! No CEL/codes. Oh, and it gets like 12MPG average. Would expect a bit better. 15-17?

Short version: runs rough, loss of power, poor fuel economy

So far we've replaced cap+rotor (ACDelco parts), spark plugs (took out but set aside ACDelcos that were in it that looked to be in good condition and put in Champion double platinium, no change at all). During replacing cap the coil wire broke so I replaced that but didn't replace other wires which look to be in good condition and are Bosch. Ran a bottle of generic fuel injector cleaner through the tank. No improvement.

+++++++++

So here's what I think. I think it's got either a leaky lower intake manifold gasket (the dex-cool in the system looks ancient disgusting and like mud), the fuel injector spider needs replacement, the timing is wrong, or more than one of these problems.

I've attached a screenshot of the scantool output. The igntion timing is always at around -20. I don't know if this is the same as "cam retard timing" that I've seen YouTube videos on but my scantool doesn't seem to have that option. That's why I'm wondering about the timing being off?

Thank you for any advice; I'm afraid that one of these issues will leave me stranded somewhere at the worst possible time or could be a safety issue (inhaling coolant smell can't be healthy lol). Yet this is my only working car and I depend on it every day. Oh and I can't afford to get it professional fixed. If I can provide any more info I will!!!

Scotiapilot

Cracked heads is a vortex mainstay. YOur description is spot on with the typical cracked V-head.
Dexcool does NOT mix well with exhaust or combustion and thus you are seeing the dexcool GOO!
They usually crack from the center exhaust seat to the coolant crossover. This is what you are smelling. Until that get fixed the computer is reading all kinds of wacked out stuff and then throwing in corrections to deal with it.


The best thing about the vortex is that popping off the heads and replacing with magnafluxed rebuilt ones is that it is easy as pie. It is to me anyway.

mistaake

Well, I flushed the coolant with new Dex-cool. The smell is worse now.
Are you sure it's cracked head not lower intake manifold gasket?
I want it to be the easier one!

Here are some pics - as you can see it leaks on one side not the other - if this is even the same leak?? Still thinking heads or intake gasket?

Thanks,
Michael