I know these 2 topics have been discussed to death on here, but I have a question regarding my personal vehicle and these 2 items. My SUBURBAN has never started worth a crap, and I don't think the milage is as good as it should be either. It was suggested to me by texas diesel guy to do an optic bump on mine in another thread regarding cold starts. My question is this, everything I've read on this says it will give you more throttle response and more smoke on throttle snap with improved throttle response and will give a rough idle if you go to far. My 6.5 already will put out a cloud on throttle snap(moving or in neutral), great throttle response and a touchy pedal and a rough idle to boot. I was going to do the optic bump, but if rough idle is a concern then I'm already going backwards. My idle is not real rough, but it is rougher than other 6.5's I've driven and seen. Also my TDCO is at -1.2 right now according to the readout of a snap on MT-2500(haven't been able to check it with a tech 2), an OTC GENISYS gave the same reading. From the receipts I have on the truck the previous owner took it back several times after pump replacement to be re-timed. Should I try the optic bump? Or get the IP retimed with a tech2? I haven't read on here where the error in the snap-on was still there in the OBD1's or not regarding TDCO. The slightly rough idle has been there since I got it, and I'm still having the idle flare problem(now it will do it in neutral, drive or reverse).

What is actual mileage on truck?

What brand of fuel r u using, and where is ur usual refueling station(s)?

I've got about 172,000 on it now, I've tried just about every brand of fuel out there and none of them really make a difference. It's always been hard to start since I've had it, and the guy before me took it back several times after pump replacement to have it re-timed(I'm assuming for this condition). Just wish it would start a little easier. I've changed out the CTS here last week and that got rid of my whitish grey smoke on start-up, but I've still got blue smoke on start-up. I was just trying to get opinions on the optic bump and timing since all of the benefits of doing it with the exception of better starting I don't need, and I already have a slightly rough idle and a fair amount of black smoke will come out under load if I get on it.

rough idle could be caused by a dripping injector(s). Add injector cleaner to your next tank and see if it helps. The bump definitely helps starting. Anticipate things getting a little louder, but you won't know for sure until you try. You can always go back if you don't like it.

I run LUCAS in every tank, it helps a little for the idle but mainly helps the milage. It has always been this way to my knowledge, I've had it since 153,000 and am now a little over 172,000. I get better milage now thanks to the LUCAS, but it still has the rough idle. It isn't real bad, but seems worse than it should be. I was wondering about timing though because I read in here where others had there timing off and had poor starts and there engines seemed quite. Well mine is pretty quiet for a diesel, I can park next to a D-max and hear it over mine. Just trying to get info on this. I'm going to try it tommorrow, would have done it today but rained all day here.

I would suspect the injectors also. Your description of your 6.5 sounds identical to mine, right down to the rough idle and fuel mileage that seems less then the "norm" around here. My injectors are original as far as I can tell, and I have near 150,000 miles on it.

I would suggest new timing set AND injectors - both are way past GM suggested limits to retain functional Inj Pump timing and operation.

I tried the optic bump today with mixed results. The first time I did it I moved the lockplate instead of the sensor(woops:o:), less throttle response lower EGT's and less boost down low but more up high:confused:. So I came back and reread canadianriggers post(with pictures, gotta have pictures:cool:), realized what I did and moved it the other way. Took it and drove it, all I can say is holy crap(G-rated version). The throttle pedal is BEYOND touchy now, and smoke oh at the smoke:ro) :evillol: (there are some very unhappy people out there right now). It runs now with the about the same power it had with the hypertech chip, just more smoke without the extreme exhaust drone(thank god, I couldn't stand the exhaust with a chip). It still has about the same idle if not smoother:confused:, but the starting seems to be worse. I haven't cold started it yet, but warm starts take longer. The engine turns over quicker now than before, but it still is slow to start. It actually started better when I went the wrong way with it. I think I'm going to leave it alone for awhile and see what it does, but I was hoping for better starts.

Accordig to the picture that Texas Diesel Guy put in Canadianrigger's post about optic bump, mine must have already been bumped because right now the lockdown is almost flush with the side of the sensor(and I didn't move it much).

I would suggest new timing set AND injectors - both are way past GM suggested limits to retain functional Inj Pump timing and operation.
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When we "bump" the timing it really is VERY small. IIRC 1mm=1deg. Just bumping without the Tech II won't change the over all timing. The TDC Offset has to be done also.
-1.50 to -1.94 is really the sweet spot. I believe after 75K the injectors really don't owe you anything. Old injectors don't spray well. This spray can hamper performance, cold starts and fuel mileage.
When you launch hard if the smoke doesn't clear up after the turbo catches up somethings wrong. You could accept a slight gray haze in the head lights behind you untill you lift your foot. If everything is working good it might push you into the seat back.:ro)

It will definately push me into the seat back like it is right now, I did the relearn with the pedal after I did it and it did make a difference in how it ran. I drove it without doing it and then did it, made a difference. Once the turbo comes in it is a dark greyish haze about like I had when it was chipped. It's the initial throttle snap that makes the smoke. I went alot less than 1 mm in the bump, I think somebody may have done it before me. My question is why did it make it worse on startup, but when I went the wrong way it started dramatically better almost instantly? This is why I included the part about TDCO in the question.

At the risk of repeating myself -

I would suggest new timing set AND injectors - both are way past GM suggested limits to retain functional Inj Pump timing and operation.

Don't EVEN imagine that the timing set was replaced with the Inj Pump - or the injectors - unless it's on the work order sheet.