Hello everybody. I've been hanging out for about a year and have learned a lot. Up until now I've not had any problems with my '01. She's blowing gray smoke at idle and upon accelerating and has been doing this for a couple months. It was not doing this when I bought the truck a year ago. Here are some particulars. Any input would be appreciated. Thanks.

Mileage: 123,000. Purchased 1 year ago with 82,000.

Injectors and water pump replaced at 62,000. Had injectors checked last week by good local shop and all are within specs - none even marginal.

Has clean K&N air filter and has not been over oiled as it was smoking before & after cleaning plus I have been using these filters for 25 years and know how to maintain them.

Clean MAF with MAF cleaner at every oil change.

No engine codes.

Coolant level has stayed at proper level for at least the past two months. No coolant leaks. No oil in coolant either.

Oil level stays at the proper level since purchase. No coolant in the oil either.

Have been buying diesel at different stations. Have been using about 3oz MMO diesel supplement at every fill since purchase of truck.

Ran a can of Sea Foam through and engine still smokes.

Meticulous oil, oil filter and fuel filter changes. Have been using RotellaT 5w40 since purchase and Purolator fuel filters.

Any ideas on what I am missing? Or is this normal? I called my local GMC dealer and he said they were busy and it would be a week before he could look at it.

Did you happen to get the injector balance rates from the dealer? Has your filter been changed since the smoke started? Is the exhaust smell a strong, almost make your eyes water smell? Where you located?

Don't have the balance rates from the shop. This is a local garage I have been going to for many years and I trust them completely (I have a towing business). In the Denver area. Yes the exhaust has a very strong odor. Also it smoked before and after changing the filter. Oh and there are no mods.

Changed the oil today myself and very close to 10 qts came out including what was in the filter.

Based on filters and all other things you mentioned. I am pretty sure it is Injectors. I was told by a very reputable diesel repair shop that balance rates needed to be within +/- 3 per cylinder. Here is what I have learned though. These balance rates are a balance rate of adjacent cylinders.

For example, these rates look within spec (Under 3)

#1 /-2.58
#2 /2.89
#3 /-0.17
#4 /1.63
#5 /-2.17
#6 /1.17
#7 /-2.11
#8 /1.59

However, when you measure it as the difference between sides, #1 and #2 are close to being out of spec.

+2.89 #2 #1 -2.58 Difference of 5.47
+1.63 #4 #3 -0.17 Difference of 1.80
+1.17 #6 #5 -2.17 Difference of 3.34
+1.59 #8 #7 -2.11 Difference of 3.70

I asked where you’re from to see if someone close by, could scan for you and post your rates.

I will get those balance rates. One other thing I've noticed is a fairly loud chattering type noise coming from the left side of the engine I think. There is no consistency to it, but when it's doing this, the engine rpms surge slightly.