Tons of BLACK smoke all the sudden.

[tcrawfo]

My '95 Suburban, which now has about 175,000 miles on it, all of the sudden is blowing a lot of black smoke under most acceleration conditions and lacks power.

This condition seems to have started when I was pulling a trailer (not too terribly heavy) up and over Sardine Canyon near Logan, Utah. During that pull, the check engine (or service engine soon) light came on but I haven't seen the light since.

I've searched a bit and have read a few posts indicating that it may be any of the following:

Turbo Boost Solenoid
Tubro Boost Sensor
Wastegate control Solenoid
Wastegate Actuator
Wastegate Valve

As is sometimes the case with too much information, I'm more confused now than I was when I started.

Can anyone help clear up my confusion as to what I should look at first.

Thanks,
-Troy

[DmaxMaverick]

It could be any of the above. Fortunately, they are easy to check. Just search the forum for each phrase.

Also check the vacuum pump and vacuum lines. A line could have cracked or come loose.

Good luck!

[markrinker]

Since you have gauges, it should be apparent if you are getting appropriate boost to match the fuel. How many lbs are you seeing under acceleration? Tow? Cruise? What are your EGTs doing in relation to the boost?

[David Brady]

Can you check the code? It would be helpful to know what made the light come on. Do the manual check on the waste gate control, with the engine running you shouldn't be able to move it.

[jeffscarstrucks]

I had a similar problem about a month ago. My 93 sucked the air filter right up against the air inlet(near new filter too!). I know a 95 uses a different style filter housing but don't overlook the obvious like I did! Good Luck, JEFF

[tcrawfo]

Thanks to you all for the information. I'm confused on one more thing. Based on some of the responses I've received, and other posts I've read, I think my problem may very well be with the wastegate solenoid. However, when I go to gmpartsdirect.com, I only see wastegate actuator and wastegate valve parts listed. Is one of these two just a different name for the wastegate solenoid, or is it something entirely different?

If anyone can provide me with the actual GM part number for the wastegate solenoid, that would help me greatly.

Thanks much!
-Troy

[tcrawfo]

Ok, here's what I just learned while on the phone with my local dealer.

The part is actually listed in their computer as: Turbo Wastegate Regulator Solenoid Valve part number 1997227, price $35.55.

One more question regarding the current condition of my Suburban. I need to get it safety & emission tested before month's end. Does anyone know if this black smoke condition will cause any problem with the truck passing the emission test?

Also, is this an easy part to replace? Although I have a bit of experience, I'm not a real wrench monkey like many of you.

Thanks again!
-Troy

[MTTwister]

Troy - the solenoid should be a rinky dink little valve unit on the Drivers side, on top of the valve cover. There are 2 hoses on it - one From the vacuum pump,( ~20" vacuum) the other to the Waste Gate "actuator" on the turbo (~ 15" vacuum). The solenoid also can get cruddy - and wd-40 has been known to help clean it out.

People have had problems with the wires, and the connector that goes to the solenoid, also - you might try the 'wiggle' test on that connector to see if a wire failed prior to popping for the $$ for the solenoid.

You could wire the waste gate closed to get you through the emissions test - a real last ditch approach- you still have 5 days before the end of the month... smile.gif

[DmaxMaverick]

Two things will fail a Diesel smog test, both of which you have. SES light and smoke.

You could wire the wastegate closed, which will eliminate the smoke. Temporarily, it won't hurt anything, as long as you don't flog it or tow.

The SES light. Unless you disable the bulb, you'll have to get the PCM to think the problem is fixed. If you've been in the dash, and can do it easily, just pop the bulb out for the test. This should get you by so you can get the problem fixed at your soonest convenience.

[moondoggie]

Good Day!

Black smoke means (99.9% of the time) insufficient air, most commonly caused by wastegate system problems. Your boost gauge should be telling you the story here - I'd bet your boost is gone. Most often this is caused by the wastegate system.
</font> Check vacuum @ vacuum pump: &gt;= 20 inches;</font> Check vacuum @ wastegate actuator: 3/4 of vacuum measured at vacuum pump (assumes engine idling)</font>Most of your problems will be found by testing the above. I can't imagine guessing about whether the wastegate solenoid is bad or not, it's so easy to test. ;)

Good Luck & Blessings!

[tcrawfo]

I went ahead and replaced the Turbo Wastegate Regulator Solenoid Valve (GM part #1997227) and unfortunately it didn't fix my problem.

As soon as the truck needs/wants power, my boost drops from about 7 lbs. down to nothing and that's when the black smoke just pours out....those poor cars behind me.

In order for me to check the vacuum pressure as many of you have suggested, do I need a certain type of vacuum pressure gauge, or will any work. I don't own one so I'll need to go make a quick purchase during lunch today.

Can anyone be specific about which vacuum lines I need to check, how much pressure they should have, and what to do if the pressure isn't adequate?

Thanks much!

[BobND]

You could tie the wastegate lever shut with some mechanic's wire, and then drive it, without abusing it, to see if the smoke is gone. Then, you'll know for sure it's a wastegate actuator system problem.

Check for system vacuum by tee'ing into the line that crosses over the engine from the vac pump to the solenoid bank. You'll be looking for 15"+ of vacuum.

A simple $14.99 fuel pump/vacuum tester from an auto supply store should be sufficent.

If the vacuum pump is doing it's job, check the wires within a couple of inches of the wastegate solenoid by tugging on them to check for the copper strands being broken inside the insulation by flexing and vibration. I have seen this a half-dozen times, twice on my own vehicle.

One of the wires feeds battery voltage to the solenoid, the other leads back to the ECM, which pulses the solenoid by connecting that end of the winding to ground. The duty-cycle of the pulse generated by this grounding controls the level of vacuum to the wastegate actuator. If ypu have access to a mechanic's stethoscope, you can actually hear the solenoid pulsing.

Also, the plastic tubing from the vac pump to the solenoid bank, or from the solenoid to the wastegate actuator may have a hole worn in it from vibrating against other parts, or even the wastegate actuator itself may have a hole in it's diaphragm.

[tcrawfo]

I bought a vacuum/fuel pressure tester during lunch so I'll test that out tonight. What would explain why I have boost originally and then it just drops off suddenly when I need it the most?

Also, where exactly do I check the pressure? There are two vacuum lines that connect to the boost solenoid, do I test for adequate pressure at each of them?

Thanks!

[MTTwister]

tcrawfo -

Hmmm good question, now that you mention it.
Have you checked all your vacuum tubes back and forth? - they snake all over the place - could have rubbed a hole that might only leak or collapse under 'stress' ( probably not) .

However - it might be electrical - if not the connector to the solenoid - then possibly for the baro sensor on top of the intake manifold. ( hey guy's - whatda think?)

That's the dealie that get's the Boost Fooler mod connect to, and It might be flaking out. Not sure how you test that, or why it would cut boost on demand. Wiggle the connectors - at least you'll feel like you're doing something.

1st check for vacuum at the turbo waste-gate tube. That will tell you final vacuum to the waste-gate. If you got ~15# there, then your pump is obviously working. You could splice a tee in that line - run the gauge into the cab and see what happens when you drive it. ( uh - vacuum will probably go away. )

Pump line goes to the vac solenoid - one of those 2 will have vacuum.
For the non-EGR engines - that's it's sole purpose in life - to power (suck on) the waste-gate.

[BobND]

The vacuum source line to the solenoid tee's off from the line coming from the vacuum pump, so that will have the 15+" of vacuum, if the pump is working, and there are no leaks in the SOURCE side of the system.

The vacuum on the side of the solenoid leading to the turbo wastegate actuator will vary between full source vacuum, when the computer is allowing full boost, and near zero vacuum, when the computer wants the wastegate fully open.

Another possible problem could be a bad MAP pressur sensor on top of the upper part of the intake manifold.

This sensor reports manifold pressure to the computer, and when the max pressure the computer will allow for the other operating parameters is reached, the computer slacks off on the vacuum to the wastegate actuator, allowing the wastegate to begin to open. A flaky MAF sensor could confuse the computer into backing off on the boost prematurely.

You can look at the MAP numbers, and wastegate solenoid duty cycle, if you have access to a scan tool.

[tcrawfo]

Sorry for asking so many questions here....

If I end up needing to resort to wiring the wastegate open as has been suggested, how exactly do I do that?

Can anyone help?

-Troy

[MTTwister]

Troy - you want to wire the waste gate closed - open allows the exhaust to by-pass the tubo, hence no( well less) boost.

The rod between the vacuum can on the turbo housing and the waste gate acutating lever pulls the waste gate closed when vacuum is applied. you would want to wire the lever in the closed position - ie with the rod sucked up into the vacuum can.

[BobND]

Simply take a length of wire and tie the lever arm on the wastegate in the direction it is held be vacuum in the actuator.

Caution... do this for testing only, and don't get on it too hard, as you will have uncontrolled boost.

[tcrawfo]

I'm very embarrassed to admit that my problem ended up being a very dirty and quite clogged K&N air filter. Once I cleaned out the entire air box and replaced the air filter (the K&N wasn't salvageable), the truck is running much better and without black smoke. I'm usually so thorough with these basic maintenance items but have obviously overlooked the air filter.

As a maintenance/precautionary type thing now that I now a lot of dirt may have entered the engine, what should I do to minimize the negative affects of my recent situation?

Any suggestions (including reminding me how stupid I am for not keeping the filter clean), are welcome.

-Troy

[BobND]

I think you'll find, if you're not real gungo-ho about regularly servicing your K&N, that an OEM or WIX deep pleated paper filter with foam pre-filter will hold a LOT more dirt bore becoming severely restricted.

[BobND]

Scratch "BORE", replace it with "BEFORE"!

[MTTwister]

Hey Troy - at least it was a easy fix! Maybe hard to find, but we always seem to start with the thought that the dang thing's imploding. Enjoy the day!

[tcrawfo]

Thanks for the advice BobND. The filter I bought to replace the bad K&N was a Fram that had the pre-filter foam. You know one other thing I hate about a simple air filter service on this truck is how difficult it is to even open and close the filter box. I don't know if mine has become warped or what, but it is a bugger to get on. Has anyone else experienced this?

-Troy

[BobND]

Check the overall thickness of the filter... depth of the pleats between what you have and an OEM or WIX filter. I don't know about the FRAM, but there are other "will-fits" out there that appear OK, but are a LOT thinner, (MUCH less filter material surface area), and therefore will plug much quicker.

I found this out the hard way... I got stuck with one such filter, which quickly plugged, got torn out of it's foam rubber mount, and sucked into the turbo elbow, dumping some of it's dirt in the engine in the process.

[DmaxMaverick]

Just say NO to Fram!

[tcrawfo]

DMaxMaverick, what brand air filter do you recommend? I think I'm going to shy away from the lifetime (serviceable) filters so I can just simply replace them as needed instead of having to clean and service them.

Any recommendations from those of you not running K&N's?

-Troy

[DmaxMaverick]

First choice is the OEM (AC Delco), and watch your restriction indicator for the need to change it. Second choices are Wix, Baldwin, Hastings and the like. Stay with a "commercial" brand filter. Walmart won't have anything on my list of options.

Another note:
Don't try to "blow out" your disposible filters to "clean" them. All you will do is force fine dust particals into the material, and either cause it to fail by plugging, or colapsing. There's nothing wrong with "shaking" them out, but don't use shop air to try to clean them. The best advice it to leave it alone until you replace it. GM was kind enough to equip your truck with a filter-minder, which will work exactly as it needs to if you monitor it.

[JohnC]

I've found the Fram air filter for the early 6.5's (the flat one) works fine and is easy to find. I wouldn't use their oil filters, though...

(Their fuel filter is fine too, after all it's made by stanadyne...)

[jonflies]

Had the exact same indications and changed the air filter to a fram because the old one was filthy (and had the same trouble fitting the filter into the box) but changed the solenoid and the boost pressure sensor. I was on my way out of town and couldn't wait to see which one was actually bad. Fortunately my neighbor works for a chevy dealer.