I have a 85 Suburban with the 6.2. It just recently started have a loss of power and a huge jump in black smoke out the tailpipe. The dealer wants a ton of money just to look at the thing. Any idea as to the problem(s). Thanks for your input.

When you title the post "Blow By" it makes us all jump to conclusions that this post is gonna be about excessive blow by. As in compression that gets by the piston rings and ends up in the crankcase, that can be seen by opening up the oil filler tube with engine running..

Anyways, thats beside the point. I think that what you're getting at here is that the burb is fogging mosquitos with a black smoke. Am I right here?

Some thing to clear up excessive tail-pipe smoke would be to check your air cleaner, a dirty air filter will return the results you're seeing. Black smoke really means more fuel than the engine can possibly burn, therefor lack of air. Another thing that usually causes black smoke is the EGR system. If you own a 1500 series or "10" series 1/2 ton truck/burb/blazer than you have a 6.2L thats got an EGR valve. The EGR valve and system can malfunction causing exhaust gasses to enter the intake manifold and essentially smother your air supply with hot preburnt combustion gasses. This system is orignally supposed to work on low load situations, but at full load, the EGR system isn't supposed to be working.

What you can do to test this, is find the hose outside of your aircleaner and unplug it from the EGR solenoid, found on the Driver's side valve cover near the firewall. Go for a test drive, see if it quits smoking. If so, then you'll need to splice that hose, cut the hose in the middle (what's outside of the aircleaner) and connect one end back to the EGR solenoid. From there, find a couple bolts/screws that fit SNUGLY into the hose, to block passage of vacuum or dirt getting into the hose. The EGR will be blocked then, well it will prevent vacuum from the solenoid from opening the valve.

I also believe this is probably an egr issue. But I would go one step further and remove the 2 bolts that hold the egr valve to the intake manifold and remove for inspection. I have seen these valves fail to the open position allowing exaust gas to enter the intake under all conditions, creating loss of power and black smoke due to unburned fuel. If you find the egr valve has failed open, simply make a block off plate to replace it on the manifold, seal it with high temp silicone. Let us know if this helps.:grd:

Thanks for your information. I will give it a try and let you know how it worked out.

I noticed that both of you didn't advise replacing the EGR unit if it was the problem. Any particular reason(s)?

.Thanks again.

EGR is there as an emission control device, but it generally hurts the way the engine runs and clogs up the intake runners with soot and rob's power. Even the military knew they didn't want it and that is why all of the military vehicles, including the blazers don't have egr and thus have more power on tap with the heavy duty emission package. The heavy duty emission package generally had about 15 more horse power, no egr(free flowing intake) and a little more fuel.:eek:

If you own a 1500 series or "10" series 1/2 ton truck/burb/blazer than you have a 6.2L thats got an EGR valve. C/K 20/2500 series trucks also came with C code engines equiped with EGR valves.

I think it actually has to do with GVWR rating. up to 8500lb GVWR was C code engines, beyond 8500lb GVWR was J code no matter what truck series.
non government truck wise anyways.

Yes, thats true, I was just making the point that all the 1/2 ton 6.2's did have them. Most of the 3/4 and up didn't. I know the 2500 series G-vans, that have the 5 lug wheels have an egr valve. and some trucks, I've got an 82 8 lug 2500 series truck that is supposed to have an EGR engine in it. But thanks for the pointer!

I did what you said and it worked great. Thank you very much!!!!!!!!!!!

It saved me alot of money by not going to the dealer, you guys are awesome.