Diesel Suburban: Black smoke

Normal.....acceleration with wide open throttle will do that. It's running rich when you do that so the soot has to go somewhere.

I don't believe it's normal. That's a 6.5 turbodiesel. Mine never blows black smoke under full acceleration. I'd look for a turbocharger wastegate problem. More than enough air is supplied with that engine, when it's running normally, to combust the fuel at full throttle. Mine's a '93 with full mechanical wastegate controlled by exhaust back presssure. That '97 engine has the wastegate controlled by a computer.

Garrett Fulton

I'd look into possibly the FSD showing early signs of failing. In the heat of summer, my '98 Tahoe 6.5TD tends to blow black smoke during hard acceleration but it does it much much less in the cold of winter (the new remote FSD/cooler is still in a box waiting to be installed...).

As for "wide open throttle," it's more of a description of what is being attempted: diesels are throttle-less engines -- hitting the accelerator pedal simply increases the amount of fuel being injected. During accelration, as the turbo spools up to bring the boost pressure to 7 psi (around 2300-2400 rpm), there should be gradually less black smoke/soot, as Eightupman has stated, hence, check for proper operation of the wastegate. If the black smoke bothers you, there are diesel fuel additives that really work.

Have the turbo unit checked out -- pretty expensive to replace.

Make sure your air filter is clean, too.

Good luck and enjoy if you buy it!

I understand that the diesel is throttle-less...I jest kept it to a more common term. One day when I was explaining that very same thing about a diesel "throttle" to someone, he joked and said..."So if a diesel does not have a gas pedal....does it have an air pedal?"

Well, I called one of our locaL GMC dealers and talked to the service guy there (regarding black smoke on acceleration) and it was a most interesting talk. Basically the men said he sees these 6.5 diesel engines every day (for repair that is) and it is not a very good performer in his book, expensive repairs, problems of various kinds, he pretty much recommended against this engine. If I wanted a diesel I should go with the newer Duramax diesel or the proven gasoline engine of any year.

Is this something owners in this group can confirm??

Uwe

I have a 95 GMC Sierra 3/4 ton. The odomoter shows 433,000 plus and the

6.5 turbo diesel actually has 263 thou on it. It runs great, pulls my 31 foot fifth wheel anywhere I want to go. Probably not as fast up hill as a D'max, Cummins, or Powerstroke. But it still runs and good. I'd buy another if I needed it. Few problems and decent mileage.

George V.

Other than the FSD issue with heat, lines to oil cooler leaking, one alternator replacement, it's a good engine, not a racing vehicle but reliable at everything else we've used it for. 22 mpg on the highway on a

4x4 weighing in at 6450 lbs, it's much better than any diesel I've seen, pre-Duramax. Just went over 160k miles.

As for "throttle," I STILL describe accelerating/decelerating as throttling up/down, "stepping on/off the gas." I tell my kids that I have to stop to get "gas."

interesting

Unless your truck has been tweaked for full out race, "stack blowing black as coal" shouldn't happen. Could be minor issue or major.

126k is low on a disel if it had been properly maintained. I hit 486k on mine, traded it off, just saw it the other day its up to 600k and finnaly getting tired.

snippage

Uwe, your local service guy is just wrong about this. My first diesel was an '85 6.2 that I put a Banks turbo on. Had 238,000 m. on it and ran fine with no problems. Gave it to my oldest son, 16, and he rolled it and totaled it inside of two months. My '93 3/4 ton p.u. with the 6.5 turbo is up to 200,000 now and has been dead reliable. I bracketed the wastegate spring to increase boost a little and put an aftermarket freer flowing exhaust on it. Plenty of performance for my needs and around 21 miles to the gallon. I've got several friends with this same engine and have yet to hear anyone complain of any serious problems. The only real problem I've had on the '93 was the contacts on the oil pressure switch that control the electric fuel pump eroded and caused low voltage to the pump. And hard starting. There's a service bulletin from GM on this and an improved press. sw. to fix this. Just my opinion, but that service rep. is wrong.

Garrett Fulton

Well, I guess we all have experiences with one or two or even several cars, but what made me listen to this service guy is that he comes in contact with more cars in a day than I probably did in several years.

But he still could be wrong.

So I went to the J.D. Powers website, they rank service records of trucks, and there my 'car to be' had two stars out of five for mechanical reliability. There was no one star I could find, I guess that would be a lemon.

I never owned one of those cars and have no reason to badmouth them, but if someone looks at all this info one wonders.

Its statistics, it doesn't means your car is not great, and maybe even the one I looked at could be great, but overall there seems to be a less than desirable record.

Uwe