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940 90 940 Turbo problem - Wastegate?

malloy1

Active member
Joined
Nov 9, 2003
Location
Denver CO
93 940 Turbo problem - Wastegate?

The other day I was driving my wife's 940 and the exhaust started to smoke, so I pulled over and checked it out. It turned out that the oil return pipe from the turbo to block seal was leaking (bad). I had the car towed home, removed the pipe and replaced the seal and gasket. That fixed that problem-stopped the leak.

Now the turbo won't pressurize according to the turbo gauge in the instrument cluster. It shows vacuum, but when I floor the car, the needle doesn't pass the mid-point to the pressure side. The car seems to drive fine otherwise, just not turbo'd.

The turbo is a Mitsubishi TD04 with the integral CBV mounted vertically:



So this is what I did when I replaced the seal:

-Disconnected the wastegate actuator rod at the wastegate shaft to get to the two bolts of the drain pipe on/off of the turbo.
-Removed and replaced the wastegate actuator to get the wastegate actuator rod back on the wastegate shaft. I didn't adjust anything with the turbo.
-Added some new vacuum hose from the intake to the turbo gauge. I didn't replace all the hose, but spliced in about two feet of it. It holds pressure/vacuum.

Not sure what I did? I'm sure I didn't put the wastegate actuator rod on the wastegate shaft wrong (the rod is on the engine side of the shaft arm).

Could it need to the wastegate actuator rod adjusted? I didn't move anything on it, but I couldn't get the rod to go back on shaft without unbolting the wastegate actuator from the housing - I would say the rod hole was off by 1/16" from the wastegate shaft arm with the actuator bolted up.

I owned the car for about 4 years, and I would say that the car really didn't have that much turbo power. The gauge never moved more than 1/4" above the mid-point.

Should I stop driving the car?

Paul
 
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Did you tighten the wastegate arm enough? Is it one of the wastegates that the end screws on? If so check and tighten as much as you feel like.
 
Did you tighten the wastegate arm enough? Is it one of the wastegates that the end screws on? If so check and tighten as much as you feel like.

I didn't adjust anything. it should be the same as before I removed/replaced it.

It does have an adjustable wastegate actuator rod.

Really don't want to adjust anything until I go through it a little bit and figure out what is causing the problem. If I adjust the wastegate, and it turns out to be a faulty gauge or something, I'm afraid it could damage the engine/turbo unnecessarily.

I did check the wastegate actuator by sucking/blowing into the hose connected the turbo housing to actuator. It held pressure/vacuum. I assume this means that the actuator diaphragm doesn't have a hole in it.

I also checked the turbo gauge by blowing into it. Not sure how much pressure the human lungs can produce, but I can push the needle about 1/4" above the mid-point.

Is there a test to check the actuator? Is it pressure or vacuum activated actuator? I assume it's pressure activated. Can I get the actuator to move the rod by blowing into the hose or does it need my pressure? I can pressurize my air compressor to 15psi and apply pressure to the actuator? How much pressure can it handle before I damage it?

I also replace the hose from the actuator to the turbo housing with some nice silicone hose I have (Gates DPFE).

Forgot to mention in the original post, when I was reattaching the actuator rod to the wastegate shaft, the shaft moved quite easily. I don't think it's the shaft binding up.

Paul
 
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You can probably tell whether or not it's a faulty gauge by seeing if you can get on the highway. If a turbo car builds no boost it will be verrrry slow. Is it slower than normal?
 
The car seems to be running fine. I never thought it had a lot of kick before, seems to be about the same before I touched the actuator. It's quicker than my '86 240 NA.

Maybe need to get a cheap boost gauge to see how much pressure I'm getting at the manifold.

It's weird because I'm assuming that the problem happened when I removed the actuator rod, so I'm trying to figure out what I did to change the reading at the gauge. Maybe it has to do with splicing in hose to the gauge, not anything to do with the waste gate actuator.

Paul
 
-unhook the vacuum to the wastegate,go for a careful ride(will boost fast/lots) if this work the turbo is fine.
--if no boost,take off the front hose and see if it spins.
---if it spins take off the bypass and block it off
 
-unhook the vacuum to the wastegate,go for a careful ride(will boost fast/lots) if this work the turbo is fine.
--if no boost,take off the front hose and see if it spins.
---if it spins take off the bypass and block it off

OK- So I took off the hose from the wastegate actuator to turbo housing. The car drove the same.

Next I took off the hose from the air filter housing to front of the turbo housing. The turbine spins freely, there is some play in the shaft.

If I take off the CBV, how do I block it off?

Paul
 
Not everything is caused by something else. Old cars break down, I had a slightly clogged cat and couldn't develop more than 4psi and I have heard of other cases where it's really clogged and no boost at all. I asked earlier in one of these threads how much actual play it has (just a hair or whoa damn it scrapes and touches) does the turbo spin easily by hand? Then I'd assume it's okay, the wastegate puck could possibly be cracked but it would still develop some boost expecially when your really looking for boost. The simplest check for making sure there's enough pretension on the wastegate arm is with it mounted up, try to by hand move the rod and open the wastegate. It should be kinda tough cause the spring and preload on the rod but that should tell you it's roughly adjusted right (I don't believe either of those could be your problem that's why I'm giving you test to dispel them)

If it were me and I was certain there's no obvious blown hose or hole/ crack in intercooler (should still build some boost I've seen a car with a half dollar sized hole in a coupler and still build 3psi without much issue) I think I would check the cat. I believe you can take it too a muffler shop and they can drill a little hole and put in a gauge or you can tap the cat with a hammer and listen for rattling crap inside. Or just take it out/get where you can see it and just visually check yourself.
 
If that rod is off but by just the slightest it will make much less boost. It needs to be very tight. If it's off a lot it won't make any boost.

When my cat clog or should I say turned into bbq dust my car would make about 3 psi.
 
Not everything is caused by something else. Old cars break down, I had a slightly clogged cat and couldn't develop more than 4psi and I have heard of other cases where it's really clogged and no boost at all. I asked earlier in one of these threads how much actual play it has (just a hair or whoa damn it scrapes and touches) does the turbo spin easily by hand? Then I'd assume it's okay, the wastegate puck could possibly be cracked but it would still develop some boost expecially when your really looking for boost. The simplest check for making sure there's enough pretension on the wastegate arm is with it mounted up, try to by hand move the rod and open the wastegate. It should be kinda tough cause the spring and preload on the rod but that should tell you it's roughly adjusted right (I don't believe either of those could be your problem that's why I'm giving you test to dispel them)

If it were me and I was certain there's no obvious blown hose or hole/ crack in intercooler (should still build some boost I've seen a car with a half dollar sized hole in a coupler and still build 3psi without much issue) I think I would check the cat. I believe you can take it too a muffler shop and they can drill a little hole and put in a gauge or you can tap the cat with a hammer and listen for rattling crap inside. Or just take it out/get where you can see it and just visually check yourself.

- The air side turbine has some play in it (a mm or two), but doesn't hit the housing, and spins freely.
- I've checked the WG rod again, it seems tight. I took the rod off the WG shaft arm, and I needed to pull the rod out to get it to go on the WG shaft arm.
- I'll need to check for leaks through the turbo by making a boost leak tester, but that needs to wait for another day.
- I would like to eliminate as much as I can before taking it to shop to work on it.
 
Sounds like you eliminated most everything there. Seems to me the cat is the next best place to look. try tapping it with a hammer like I said, if you hear crap in it that's probably what's going on. Idk if your state has emission laws but straight pipe or another cat.
 
You could also go for a nice 10 miles drive and look underneath the car to see if the cat is glowing red. It won't always glow red, but that can be an indication that it's clogged I think.
 
by what you wrote the turbo is not building any boost.
Maybe the WG is not or not fully closed.
i have noticed that on some TD04 turbo's it is possible to rotate the WG-arm 180 degrees. Maybe you have reconnected the WGA-rod on the WG-arm in the fully open position?
2nd possibility is that the actual WG-valve has broken off the WG-arm, leaving the WG wide open at all times...
3rd possibility is that the turbine housing is severely cracked around the WG-port. It is really common on older TD04 turbo's. The hot exhaust gasses pass through those cracks and act like a torch making those cracks wider and wider as time goes by. The WG will leak more and more over time resulting in slower spooling turbo.
4th possibility is that the exh. manifold has cracked on the block side, a common problem on 90+ exh manifolds which also results in boost building slower
5th possibility is that the turbine axel has snapped in half... i have seen that happen on a KKK.
 
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OK - I haven't done much further with figuring this out, but did get a turbo gauge with PSI on it, it shows 3psi max boost.

If it was the cat, wouldn't the car have a noticeable lack of power? To me, the car power is fine, but could have more power when floored.
 
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