Northstar Engines and System Technical Discussion Discussion, Blue/black Smoke only after Idle in Cadillac Engine Discussion; Hey guys...so I've been reading a lot about smoke on the site here, but I'm still not convinced I have ...
Hey guys...so I've been reading a lot about smoke on the site here, but I'm still not convinced I have a solution to my problem. When I sit at a stop light for a good 60 secs or longer and then take off, I get blue/black smoke just for a second or two. Any suggestions on what's causing this? My oil consumption is 1qt every 1-1.5k miles which does not appear to be excessive and the engine does not burn any coolant so I *HOPE* I don't have a headgasket problem. One post said replace the fuel pressure regulator which they claimed was "easy" but where exactly is this part located? Several other posts say that WOTs cure smoke problems, but I get into enough I think. I haven't done one of the "2nd gear only WOTs to 70mph" but I suppose I could try a couple of those on the interstate tonight after work. Any suggestions would be greatly appreciated.
The secret to the WOT is to keep it in 2nd gear take it up to 6 grand and let it back pedal to 4 grand and repeat 2 to 3 times.
It will clear the carbon off the pistons going to 6 grand and letting it back pedal to 4 grand will shake the piston rings and take the carbon off of them.
You will probaly see a reduction in oil consumption too.
And maybe and increase in mpg.
Just remember to look ahead and behind for those in society that give tickects for that.
Blueish smoke out the exhaust would mean that you are burning oil. But since you are only losing a quart every thousand miles, which is completely normal, I don't think its that. Definetly sounds more like carbon build up, there is a write up in the tech tips section about cleaning your throttle body, this might help a little. I wouldn't worry about headgaskets yet. Im not sure a fuel pressure regulator would have anything to do with it, but i may be wrong. It is extremely easy to change and will be on the top right hand side of the engine, right before the fuel rail. Theres also a write up for that in tech tips.
A bit of blue smoke after idle and/or startup is a classic symptom of valve guide seals. There's a lot of vacuum at idle, and oil more easily gets sucked down into the valve seal. When you take off, that excess oil gets burned off quickly and you notice a puff of smoke. Valve guide seal problems are almost unheard of with these engines, but there are going to be some out there I'm sure. This is nothing any WOT procedure can help you with (if it IS the valve guide seals). This is a mechanical breach and can only be fixed by replacing the seals. A high mileage type oil may help, but I wouldn't count on a quick fix from oil alone.
jadcock A bit of blue smoke after idle and/or startup is a classic symptom of valve guide seals. There's a lot of vacuum at idle, and oil more easily gets sucked down into the valve seal. When you take off, that excess oil gets burned off quickly and you notice a puff of smoke. Valve guide seal problems are almost unheard of with these engines, but there are going to be some out there I'm sure. This is nothing any WOT procedure can help you with (if it IS the valve guide seals). This is a mechanical breach and can only be fixed by replacing the seals. A high mileage type oil may help, but I wouldn't count on a quick fix from oil alone.
see, some of us know what were talking about. I woulda never guessed vavle guide seals.
OK...so a little bit of follow-up. At lunch I went out and did a couple runs up 6000rpm in 2nd gear, engine brake back to 4000rpm and then floor it back to 6000rpm (its pretty impressive that the car can do 90mph in 2nd gear!!). After that I went and got a sandwich and didn't see any smoke after sitting at traffic lights so it appears like hammering the throttle *MAY* have taken care of the problem. I'll keep an eye on things this weekend and keep ya all updated.
Following the WOT instructions from PhantomCadillac appears to have taken care of my problem. I was driving around all weekend and didn't see any smoke under any circumstances. That's a relief since the car has 145k miles on it, but is still running GREAT and I don't feel like dealing with a major problem right now.
Automobile(s): 2002.5 F55 STS, 2014 Explorer XLT 4WD
MD Eastern Shore
Re: Blue/black Smoke only after Idle
Appears that a little WOT work may have cleaned things out a bit. In regards to rpm vs. speed, remember that a small engine needs to maintain higher rpm for power delivered (normally aspirated). The N* 280 C.I. engine is a small, sophisticated engine. Bigger than a riceburner 4, yes, but a lot smaller than some of the 400+ c.i. stuff out there. An old drag racing axiom was "There ain't no substitute for cubic inches". It was true in 60, and it's true today. Witness the proliferation of HUGE crate engines.......Wait 'till someone takes a RWD late STS and stuffs a 572 into it........(Yeah, I know.....off the thread, but it's fun to dream....)
Yea...I'm pretty sure it was still in 2nd since the needle on the tach only dropped once. It does shift into 3rd gear eventually even though the shifter is in '2'. Does the computer override the shifter to protect the engine from too high rpms?
Automobile(s): White Diamond '03 DHS (with DTS floor shift)
Re: Blue/black Smoke only after Idle
Now you guys have me doubting myself. You may be correct. I'll have to pay more attention next time I do it. Yes, regardless of shifter position, the trans will shift to protect the engine. Try putting it in 1st one time and nail it. It will shift into 2nd in no time at all.
Ranger, try it on your DHS. 2nd gear should be good until about 92-95 mph (depending on the exact shift point that your car has). 1st gear on your car should be good to over 50 mph (6000 rpm in 1st = 51.6 mph). Again, that's only for LD8 powertrains (3.11 final drive).
Theoretical maximum speeds-in-gear for LD8 (3.11), assuming 6000 rpm max:
1: 51 mph
2: 93 mph
3: 152 mph
4: 224 mph
Theoretical maximum speeds-in-gear for L37 (3.71), assuming 6500 rpm max:
1: 46 mph
2: 85 mph
3: 138 mph
4: 203 mph
That's right, both cars have a theoretical top speed of over 200 mph, if the engines were strong enough to push the cars to redline in 4th gear.