turbo troubles

[derekja]

I think I'm having turbo problems. Here's the sequence of events. I have gauges in the truck, so where I give boost pressure that's where it's from.

The truck has always tended not to give me any boost when the engine is cold. I presumed that to have been a computer setting or something, but the failure events lead me to wonder if something else is going on.

Three days ago, I drove the truck for about an hour and didn't see any boost pressure at all on the gauge until I drove up a big hill and all of a sudden boost came on to about 5 psi. Prior to that I heard some roaring that I couldn't completely identify (sounded almost like the fan engaging, but louder and a bit different timber, and, of course, the engine was cold, so I wouldn't have expected the fan to be engaged, although it had been sitting in the direct sun.) Driving home boost pressure was normal (again 5 psi.)

Today, a similar thing happened. I headed out, engine cold, and climbed a big hill and had no boost. Didn't hear the roaring of the other day. Warmed up and eventually the boost pressure came up to it's normal 5 psi max. Got to where I was going, parked a while, unloaded, and headed home. No boost, even on a warm engine. I was also getting black smoke going up a steep hill, where I would definitely have expected to see good boost pressure.

Oh, I should mention that each time the boost has come on it has been when I was giving it pretty hard up a hill, then after that it seems to react normally, giving me boost when I'm just normally accelerating. Also, no check engine light. I'll get carcode down when I go get the manuals from the storage locker tonight and double check that no codes are being thrown.

Coincidentally, I have just received a TD max boost controller from Kennedy, but it is still in it's box and I'm not going to mess with that until I'm convinced that the stock system is working right.

I'm going to read the turbo chapter in the helms manual tonight, but please let me know what you think about the following lines of investigation:

1) waste gate - check vacuum pressure and free movement, but I don't think the wastegate would have led to the initial roaring and I can't see how it could be temperature related. Still, this sounds like the part that fails most frequently.
2) turbo fan free play - not sure quite how to check this, but I've heard it mentioned and the manual will tell me
3) turbo oil line - I mean, I know it's attached! But that's the one that seems most likely to be heat related - gets hotter, the oil gets thinner, eventually the turbo starts spinning freely. Or, like today, it doesn't.

Oh joy, another learning experience. Thoughts are welcome.

Thanks.

[More Power]

The turbocharger is likely OK. Since the boost pressures you're seeing are intermittent, I'd suspect the wastegate solenoid. This is an electric solenoid that is controlled by the computer, which regulates vacuum to the turbo vacuum wastegate actuator, which controls boost pressure. It's about $30-35 and is a 5 minute replacement.

Jim

[derekja]

Well rats, still on the hunt.

New wastegate solenoid, no change in behavior.

I also verified with carcode that no codes are being set.

How warm should the engine be in order to give some boost? When the oil pressure drops down to normal levels the engine is pretty well warmed up, right?

Also, wastegate is firmly open at idle. Push it closed and it snaps right open. This is expected behavior and at least a seat of the pants idea that vacuum is OK, right? I'll track down a vacuum gauge and do that test for real soon.

Just an update... thanks.

[DmaxMaverick]

At idle, the wastegate should be tightly CLOSED (not open). It is allowed to open (exhaust gasses bypass the turbine) as you approach the PCM's boost threshold. If you have enough vacuum, you should not be able to move it by hand. Not without significant force, anyway (most people can't). Sounds like you have weak vacuum, and/or a leak somewhere. With a vacuum gage, you should have 20"+ vacuum at the pump (25" is optimum), and 15" at the wastegate actuator, at idle. The WG vacuum is modulated via a pulse from the PCM.

[derekja]

Cool, thanks for the clarification on the waste gate. I couldn't tell which I was doing when I was pushing on it. It's quite stiff, but I can open it and then it snaps back when I release it.

I guess it's off to get a vacuum gauge.

Other investigations from today:

-- air filter is pretty clean
-- ground at wastegate solenoid is good
-- not sure how to test control side of solenoid electrical connection...
-- turbo fan spins freely while engine not running (ie. engine off, stick a screwdriver in there and spin it and it keeps spinning freely)

[JohnC]

The wastegate solenoid should not be grounded. One side has 12 volts and the other side goes to the PCM, which pulses to ground rapidly to modulate the vacuum.

One common mistake is reversing the vacuum connections. The pump connects to the port which has a restrictor in it.

[derekja]

A vacuum gauge at the wastegate actuator shows approx 19 in. Hg. I suppose to be complete I should T in a longer line that I can see from the driver seat and go for a drive. But it doesn't tell me off the bat that I need to do anything with the vacuum pump.

I guess since I've just had electrical problems that's what I'm going to carry on looking at next...

--Derek

[JohnC]

If it's really 19 then it's too high. There's a filter on the base of the solenoid. Make sure it's not plugged. Otherwise, the solenoid is probably sticking. Make sure the pump is connected to the correct side of the solenoid. You could try spraying some WD-40 or silicone lube into the suction side of the solenoid, but I doubt if that's a long term fix.

[derekja]

Actually, wait a second. I won't go to electronic stuff yet.

It occurred to me that I need to know if I'm EVER getting boost. So I wired the wastegate (just to be sure I got it the right direction.. I wired it down, right? So that it is never able to pull up into the actuator like it normally does at idle.)

Then I drove around the block, up a hill, lots of black smoke and no boost pressure. This was fairly cold, but even from a cold engine, when I hit the gas going up a hill with the wastegate wired I'd expect to at least see the boost gauge move a bit, right?

In this configuration, that means it's either the turbo or a connection somewhere between the turbo and the intercooler or the intercooler and the intake that is leaking away ALL my boost. If it were a leak, or exhaust restriction or something I would have first expected to see lowered boost rather than the all or nothing behavior I was describing, right?

Another thing I noticed is that the connection between the intercooler and the turbo is quite literally dripping oil. Some is normal. Does an excessive amount indicate something I should be concerned about?

[Bnave95]

Clean the intercooler,check that nothing from air cleaner got to the intercooler.
Sound pluged

[JohnC]

Backwards.

Vacuum pulls the rod in to close the wastegate. As pressure builds beyond the desired pressure the PCM modulates the vaccum lower and exhaust backpressure pushes the wastgate open, bypassing the turbine.

[DmaxMaverick]

You wired the WG OPEN. That means NO BOOST, and lots of black smoke with no power, as all exhaust backpressure is bypassing the turbine. Wire it the other direction and retest. I suspect it won't tell you anything. With 19" at the actuator, it will be held closed more than sufficiently. As John said, too much modulated vacuum. It should be ~15". No more than about 16, no less than about 14. This is at idle. As you approach the PCM max boost, the vacuum will be modulated to a lower level, as load, RPM and fueling increases.

[derekja]

D'oh! I had a suspicion I might have done that backward. Thanks.

Yup, next time around the block no black smoke. Still no boost registering on the gauge either, but the lack of black smoke means at least something is running through there.

The intercooler was clear, but there was a lot of oil in there. Out of the section running back up to the intake manifold from the intercooler there was at least a cup or a cup and a half of oil. Which is enough in a nearly straight up section to have me wondering how much restriction just the liquid was causing.

This is the first time I'd had that off since doing an engine swap, so all the oil down there could have been from the first little while on the new engine while things were seating as well.

OK, so the next test is to get a better idea of what vacuum is doing. After a couple runs around the block it settled in to about 16 and a half or 17 at idle.

[DmaxMaverick]

With that much vacuum, and the lack of smoke (when controlled by vacuum), I'd suspect a bad gage, a poor gage tubing connection (blocked), or a pinched tube. It should register some boost, or you'd be making black smoke, like you did with the WG wired open.

Some oil in the IC is normal. How much depends on many things, including time. There isn't much restriction from it, though. The oil is an insulator, and will effect the heat exchange process, making it less efficient (warmer IAT). I suggest cleaning it up and checking on how much oil gets trapped over a shorter, more specific time/mileage period.