2000 Chevy Astro Issues 2WD

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Hello All,

I have been doing the work on a 2000 Chevy Astro for a family member it has roughly 130k on the clock.. It currently has two issues.

1# I pulled a P0101 Mass Air Flow (MAF) Circuit Range. Tried cleaning it with MAF cleaner, no dice.. the vehicle does have two drive-ability symptoms that I believe are related.. sometimes it will hesitate when taking off (never experienced this, but the driver has.) When you try to go WOT, the engine will rev very harshly but will start slowing down(I have experienced this with a clogged cat, but do not believe this is the case). When operating the vehicle with the MAF unplugged, it gains all of its power back.. however the transmission shifts very harshly..

- Is this a confirmed bad MAF? Could there be more underlying issues?

2# Non-visible coolant loss.. are the LIM gaskets the suspect here? Similar to the GM 3.1/3.4 I always thought it was only those two engines, but do not know if it affected any of the others.. are there any other common coolant leaks on these vehicles? I do not see any Anti-freeze in the oil, and no oil in the anti-freeze.. Maybe(hopefully) its a leaky hose/radiator I am not seeing.

If I end up having to pull the intake manifolds and heads.. what kinda job am I looking at.. pretty difficult and pretty expensive?

Let me know your thoughts, thanks!
 
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Sometimes what can happen is you get a vacuum leak behind the MAF, and that cause cause a MAF error code, and poor driveability. Blast any possible leak point with carb cleaner and listen for changes in RPM. MAF sensors do often need replacement on vehicles with over 100,000 miles. I would also think about your oxygen sensors as another possible problem.

If you suspect that the cylinder heads are the cause of coolant loss, You should get an item like the Lisle Block Test Fluid kit.

Intake manifold gasket leaks are very common on 4.3 engines with spider injectors. I wouldn't be surprised if that is what is happening.

Having a leak at the heads or intake could cause that vacuum leak as well. Burning engine coolant can foul an oxygen sensor quickly.
 
Clean the throttle body, and change spark plugs first then continue troubleshooting. I would try cheap maintenance items first and see if it makes a difference. Change pcv too.
 
I would bet on the intake gasket. Mine let go right at #1 cylinder, it was at the top, right where the intake, head and valve cover all come together. Was very hard to find until it got worse, was loosing coolant and would smell occasionally when warm but that was it. I eventually took the AC compressor off before I found it.

If that gasket is compromised I could definitely see the possibility that both are related. There isn't a tone of material around the intake ports on that gasket.
 
What you describe is a bad MAF. Check the plumbing after the MAF for any cracks or splits.
You may or may not have bad intake gaskets, it sounds like a common enough problem but that doesn't rule out other sources of leaks.

I would suggest pressure testing the system with a dye additive added to the coolant and testing the cap.
If its not external i would suspect the manifold gaskets before the head gaskets as your not describing typical head gasket failure.
Generally if you have a HG coolant leak you know it and it usually worsens quickly.

From what i can tell these are not that bad to do the manifold on, regular hand tools and a few hours should get it done.
 
You're right Trav, it's not a really that bad, just a bit awkward being a van. An extra set of hands to set the manifold back in place was the only non-regular hand tool I used.
 
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