2 Items: Dead miss; Buzzing noise

[Vaughn MacKenzie]

Got two separate issues I have questions on. . .
#1 My buddy's '84 Blazer recently developed a dead miss (or pretty close to it) on one of the cylinders and I have no idea if it's an injector or pump problem. It happened suddenly and while it's not that obvious at idle it shakes noticeably at all RPM. What it feels like is there is a bit of fuel going into the cylinder and it's fairly smooth at idle but as fueling is increased the miss increases, like there is no change in the fuel going to that cylinder. What do you think? How hard is it to swap out a pump? Are they very expensive to replace or have serviced? For starters I recommended he pull the injectors and pop test them. There is no smoke from the exhaust other than a very slight haze at WOT and a bit of blue first thing in the morning, like normal.

#2: on my '82 (as well as most 6.2 Blazers I've seen) there is a loud irritating metallic buzz at around 1000-1100 RPM which seems to be coming from the injection pump area, like it's a loose bracket. What's causing the noise and does anyone have an idea how to shut it up? I know with the high compression all sorts of noises & buzzes appear at various RPM but this particular noise seems fairly typical.

Anyway thanks all, Vaughn

[More Power]

Miss: Loosen one injector fuel line at a time - at each injector, looking for a possible bad injector. This is like looking for a bad spark plug in a gas engine. If you go through all eight and can't identify a bad injector, you may need to look at the valve train for something like a broken valve spring or defective rocker.

Buzzing: Look for two closely spaced injector fuel lines touching one another, or an injector fuel line touching some other engine component. These lines are supposed to be rubber isolated from one another and from the other engine components (except pump and injectors :D ).

Jim

[Vaughn MacKenzie]

Jim, thanks for the tips, will check it out

[bmiszuk]

Vaugn, my Suburban had a strange vibration also at certain speeds. It turned out to be a missing bolt on the A/C compressor. Check for missing or loose bolts. It sounded like it came from the injector pump area but turned out to be the A/C bracket.

My '93 6.5 developed a solid miss one day at any speed. It turned out to be one of those little plastic buttons that holds the rocker arm in place. You problem sounds a little different but I thought I'd give you something else to check tongue.gif

[Vaughn MacKenzie]

Well after fiddling around with my rig tonight I wasn't able to chase down the 1000 RPM buzz, which I can feel when I put my hand on the engine. But driving around afterwards it's really loud so I'm thinking it's coming from underneath somewhere.

I have another issue I discovered with this beast tonight. . . looks like the Banks turbo has a bad oil seal 'cause it mists oil vapor out the compressor outlet when idling. There's a coating of engine oil all over the system between turbo and intake manifold. Not good, I shouldn't drive it 'til I get the turbo fixed.

Vaughn

[john8662]

For the misting oil vapor question I have to ask how much blow-by the engine has when you have the engine up to operating temperature and remove the oil filler cap?

The reasoning behind this question is that the CDR valve has plumbing that goes into the air filter housing, which basically sucks the blow-by out of the crankcase to be burned in the engine. During it's passage into the clean air side of the airbox, the vapors go into the turbocharger. So, if you've got an engine with lots of blow-by, then it's probably not the oil seal in the turbo.

For the 1k sound, it could be the engine, but it could also be the torque converter mounting to the flexplate problem that I recently found on my rig, etc.