: Blue/black Smoke only after Idle



digitalcaddie
05-04-07, 11:20 AM
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.

PhantomCadillac
05-04-07, 11:28 AM
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.:D
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.:yup:
And maybe and increase in mpg. :sneaky:
Just remember to look ahead and behind for those in society that give tickects for that.:banghead:

misfit6794
05-04-07, 11:36 AM
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.

jadcock
05-04-07, 12:26 PM
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.

misfit6794
05-04-07, 02:42 PM
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.

digitalcaddie
05-04-07, 04:10 PM
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.

Ranger
05-04-07, 06:30 PM
Have you read the Technical Archives at the top left of this page regarding oil consumption?

BTW, you are not in second gear when you reach 90. The shifter may be, but the trans has shifted to third, then goes back to second when you back off the throttle.

digitalcaddie
05-07-07, 01:38 PM
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.

jadcock
05-07-07, 03:51 PM
BTW, you are not in second gear when you reach 90. The shifter may be, but the trans has shifted to third, then goes back to second when you back off the throttle.

Actually, he is still in 2nd gear at 90. On an SLS, or any LD8 powertrain, 2nd gear is good to about 93 MPH (2nd = 5943 RPM at that speed).

The same RPM (almost 6000) on an L37 powertrain is only 78 MPH, however.

Submariner409
05-07-07, 05:44 PM
:thumbsup: 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....)

digitalcaddie
05-08-07, 03:38 PM
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?

Ranger
05-08-07, 04:04 PM
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.

jadcock
05-09-07, 08:01 AM
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.

Ranger
05-09-07, 11:06 AM
I tried first gear once just to see what it would do. The engine winds up to 6000 RPM pretty fast and shifts well before 50 MPH.

jadcock
05-10-07, 02:11 PM
Larry, the previous owner of your DHS must have slipped a 3.71 transaxle in under ya. ;)

My '97 SLS would wind out to about 50 in 1st. I can verify that over 90 was attainable in 2nd as well.

I'd be interested to know what your DHS tops out at in 2nd gear.

Ranger
05-10-07, 07:40 PM
It should be the same as an SLS.

jadcock
05-11-07, 06:57 AM
It should be the same as an SLS.

Right...which is why I'm curious as to why yours is different.

Your tire size is 225/60R16 right?

Ranger
05-11-07, 11:40 AM
Yeah, I have the OEM tires. Maybe mine is not different and I am confused.

digitalcaddie
09-27-07, 03:34 PM
OK...so to follow-up on this post after a couple months and 8k miles later, I'm still getting big puffs of blue smoke after sitting at idle for long periods of time. I've been doing my wide open throttles (no tickets yet) but the problem is not going away. So how much of a pain is it to replace valve guide seals? Does this involve pulling the engine or is that a repair that I (or my mechanic) can do with the engine still in the vehicle? I just fixed a couple other problems without spending much loot so I'm thinking I'd like to try to get the thing running perfectly and then drive it for another 100k. '97 SLS w/ 153k

I might try a high mileage oil at the next change, but I hate paying the higher price for that stuff when the engine eats a qt every 1500 miles.
Please let me know what you guys think.

dhm37
09-27-07, 06:50 PM
d'caddie,
I had smoking in '98 w/150K miles. I had put in new rings, so vacuum was high, and sucked in lots of oil around valve stem seals. You will need to drop the engine to make it easy to replace the seals. Hold the valves up with air pressure through spark plug hole. Biggest problem I had was making a little tool to pull the old seals out (couldn't seem to find a tool to do it), so made one out of CB radio antenna (small stainless rod material).

When I compared the hole in old seal with new one, the reason for leaking was clear. Now it is a like a new engine, with new seals, new rings, and new bearings,etc. No smoking, even after backing down from high RPMs or coming down a mountain into Denver.

Ranger
09-27-07, 10:11 PM
Hmm, I would have thought replacing valve seals was doable without dropping the engine.

digitalcaddie
09-28-07, 03:12 PM
OK...so I can't drop the engine myself...I don't have the tools. I could pay my mechanic to do this, but is it worth it? I know there's not supposed to be anything in the chamber besides air and fuel, but whats the worst that can happen? If the problems gets to be excessive aka there is smoke all the time, then that is the point where I REALLY have to do something, right? And I'm assuming that if a fair amount of gunk builds up in the chambers, I'm going to start losing power, right, which would be another indicator that I really need to attend to the problem?

I guess I can live with the smoke at the current levels and continue adding more oil. My oil consumption is still only 1 qt every 1-1.5k miles which isn't too bad. Let me know what you guys think.

dhm37
09-28-07, 03:48 PM
Hmm, I would have thought replacing valve seals was doable without dropping the engine.
.
I have done one set of heads not mounted to block, and another set on the block but cradle out of body. I sure would not want to do the job (especially the rear head with the engine in the car. Doable, maybe, but I wouldn't do it.

digitalcaddie
12-26-07, 04:43 PM
So to follow up on this post again, after tracking my oil consumption its in the 400-500 miles per quart range which seems to be pretty high and is worse than I thought. After reading the oil consumption article in the Tech Archive again, the guy states that if you've got blue smoke out the back end, then you have a problem. So if I'm going to replace valve guide seals is that something I should take to the stealership? My mechanic is a guy who works on cars out of his barn and he's pretty good, but if he has to drop the engine, that's a lot of moving things around/a lot of work for a guy who doesn't work on cadillacs every day. Any opinions here?

Ranger
12-26-07, 05:41 PM
And the WOT did not help any? Valve guide seals don't seem to be a very common problem. I would guess stuck rings before valve seals.

digitalcaddie
12-27-07, 02:49 PM
WOT did not cure the problem. I think it reduced the amount of smoke (although that's a tough one to measure since its not like I'm sitting outside the vehicle watching myself drive away) but it hasn't eliminated it. Could also just be a placebo effect. I do know that my oil consumption is 400-500 mi per qt which is on the high side and I'm seeing blue smoke out the exhaust after sitting at stop lights.

Ranger
12-27-07, 05:30 PM
If you are seeing blue smoke, you are consuming LOTS of oil. How much WOT did you do?

Douglass Harroun
12-28-07, 12:02 AM
I found many stuck rings and two pistons with broken lands recently in my '98 STS with 175,000 miles. Was using a lot of oil and smoked on WOT. Did a lot of WOT's- did not help . All fixed with new pistons and rings. Didn't touch the head, Did time-cert it. No bore wear. Put the rings in dry, no hone. Runs really good now.
Doug

Crown Vic Owner
12-28-07, 02:41 AM
This thread has been leading me DOWNWARDS of all i know



For gods sake, i have NEVER heard of a n* having bad valve seals, and i have read ALOT here.