Blueish smoke on slight decel.

[PSD_Mike]

I have a 92 7.3L with Headers and Dual exhaust (trying to sell it so it's not in my sig). It has started doing something weird and hopefully someone will have an idea about what it is.

What I see happen is Blueish (maybe somewhat white too) smoke out of both pipes (and a bit rough running) when one of two things happen. The Auto Trans has an issue shifting into 3rd and sometimes when it doesn't want to shift and i hold it steady at 2500 waiting for it to decide to shift, the truck runs a little rough and I get the smoke. I also see this same thing happen if I am cruising on the HWY, start down a slight hill, and have to lift the throttle slightly (lifting fully does not cause the smoke). Both of these conditions are light load and higher RPM. If I press on the pedal fairly hard, I get almost no smoke.

I think the compression is good as it starts real quickly (easy).

Ideas?

[Squid63]

Sounds like the timing may be slightly retarded. I've had similar issues on mine, and advancing it a couple degrees made a huge difference. There are many posts on here regarding timing, so you should be able to find what you need.

[DaytonaBill]

Headers???

I would be very interested in those, it seems that would be a good thing to put on my '92 IDI...

I think you should check for bad valve stem seals, have you noticed an increased oil consumption?

Then again, I could be barking up the wrong tree (has happened before...).

[cdnsarguy]

How full is the engine oil.........run it at or just above the minimum mark..... check 10 minutes after hot shutdown........ As stated could be valve oil seals......

Getting any flashing light on the OD switch....... check for codes or reset the FIPL. Do a google search for FIPL reset with my name.

[PSD_Mike]

Originally Posted by DaytonaBill

Headers???

I would be very interested in those, it seems that would be a good thing to put on my '92 IDI...

I think you should check for bad valve stem seals, have you noticed an increased oil consumption?

Then again, I could be barking up the wrong tree (has happened before...).

Yep, headers. I don't know where you are, but I bought them from a guy that makes them near Seattle (Stan's Headers - found him on the internet). I had dual 3" exhaust put on too. Then I took it to a fuel system guy and he turned the pump up about 10%. I have just over $1000 in the exhaust system. It's pretty cool, but I really love the truck in my sig!

I do believe it is using more oil than it had been. I sold the truck to a guy a year ago who didn't finish paying for it, so I got it back. When I did, I found that it only had about 4qts of oil left in it (stupid jerk). Before I sold to him, I had noticed the same phenomenon when cruising down the hwy with a toy hauler - again a slight downhill and no load throttle. So it may be worse now, but was doing it before.

How do you check for valve stem seals? Can that be fixed without pulling the heads?

Thanks,

Mike.

[PSD_Mike]

Originally Posted by cdnsarguy

How full is the engine oil.........run it at or just above the minimum mark..... check 10 minutes after hot shutdown........ As stated could be valve oil seals......

Getting any flashing light on the OD switch....... check for codes or reset the FIPL. Do a google search for FIPL reset with my name.

Since I am trying to sell this thing, is there any bandaid if it is the seals?

I don't get any OD light flash - never have. I had it in the Trans shop and they pulled the codes to diagnose the Trans - never mentioned any other issues, but maybe they wouldn't have. I don't have a reader and again, since I just want to get rid of it, not sure I want to spend much time on this. Maybe I should just part it out .

[cdnsarguy]

I do not know of a bandaid solution........ replacing the valve seals, if that is the problem, is not that hard a job if the prospective buyer has suitable mechanical knowledge and tools.

Do you have a lead to a picture of the truck...........or a listing for sale.

[Snotzalot]

Blue smoke on deceleration is usually valve guide seals.

[PSD_Mike]

Originally Posted by Snotzalot

Blue smoke on deceleration is usually valve guide seals.

OK, but the interesting part is that it doesn't smoke on decelleration (completely off pedal). It smokes when at higher RPM (around 2k) and no load steady RPM. Even seems to miss a little then (run rough).

[cdnsarguy]

How old is the CDR valve...... check my photo link for pic if you need it.

How old it the fuel pump.........

[goinbroke2]

Guys, the reason a GAS engine smokes on deceleration is because the vacuum is high. On a diesel (which has no throttle plate/restriction/vacuum) there is no increase in the vacuum when you take your foot off it, so it won't suck oil past the valve seals because of it.
Besides, even a gas engine that does have bad seals will smoke worse with no throttle on decel than part throttle decel.(because the higher vacuum)

First thing I would do is
1) replace fuel filter, if it still does it,
2) check return fuel for bubbles indicating a vacuum leak on the suck side of the lift pump
3) check lift pump pressure at 2500rpm (could be weak spring or bad valve) if pressure is low then change lift pump.
4) check injector pump output pressure.
5) Check injector blow off pressure, inj could be "leaking" a little or have a bad/weak spring

There is other things, but that's enough to get you started.

[Burdizzo]

I had this problem with mine a few years ago. Tweaking the IP toward the passenger side of the truck a few degrees cleared it right up. and the mileage went up 1-2 MPG too.