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  #1  
Old 10-31-2014, 11:14 PM
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Boost gauge "jittering", low power up hills & lots of smoke

1984 300sd

Issues I've been having are:

Really low power up steep Pennsylvania hills, 35-40 mph tops, if that..
LOTS of acceleration smoke, grayish-blue? (Can't determine the difference between oil smoke and fuel)

Replaced the turbo and determined the new one was not leaking oil, also I made absolute sure the IP was drip timed correctly and even took off the ALDA w/ no change. Naturally I did a valve adjustment with clean filters all around w/ functioning kickdown switch w/ good oil and fluids.

So I put a boost gauge at the intake for some diagnosis help (I did find and seal intake leaks.. even switching to the non-egr manifold from a junkyard.)

When the car is on and at idle, the needle shakes back and forth approx 2 inches of Hg each way. ~ When I accelerate (with lots of smoke btw, idle has barely any smoke), the needle jitters in a 5 in-hg range with its center going up to around 12-13 psi. At no point is the needle steady. I DO recall a steady point, but something occurred that it started doing this?

For kicks and giggles.. I did seal up and blow air into the turbo for it to come out by the crankshaft.. I can feel the pressure from the blowoff tube.

I'm thinking my valve guides may be shot and my best option is to replace the head? Does anybody have any sound advice?

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  #2  
Old 11-01-2014, 11:44 AM
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Location: West of Ft. Worth. TX
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Where is your boost guage tapped into the system?

What makes me wonder is why is the boost guage fluctuating at idle when there shouldn't be any boost developed.
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84 300SD 350K+ miles ( Blue Belle )
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  #3  
Old 11-01-2014, 07:02 PM
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Quote:
Originally Posted by SD Blue View Post
Where is your boost guage tapped into the system?

What makes me wonder is why is the boost guage fluctuating at idle when there shouldn't be any boost developed.
Banjo bolt at the rear of the intake, where the ALDA used to tap.
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Old 11-02-2014, 04:16 PM
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"used to tap"?? If you have disconnected the alda, then that would explain all of the smoke. From what I've read, here on the forum, the smoke is limited by your right foot when you disconnect the alda. I still don't understand how disconnecting it will enhance your performance. When mine leaked, due to a tubing failure, it performed pretty lame.

Have you removed the bolt and checked for any obstruction? This might explain the jitters. Another possibility is the waste-gate hose.
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84 300SD 350K+ miles ( Blue Belle )
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Old 11-02-2014, 04:23 PM
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Quote:
Originally Posted by SD Blue View Post
"used to tap"?? If you have disconnected the alda, then that would explain all of the smoke. From what I've read, here on the forum, the smoke is limited by your right foot when you disconnect the alda. I still don't understand how disconnecting it will enhance your performance. When mine leaked, due to a tubing failure, it performed pretty lame.

Have you removed the bolt and checked for any obstruction? This might explain the jitters. Another possibility is the waste-gate hose.
I removed the alda to observe if there would be any change in the blue/gray smoke. A good running sd w/o an alda should blow a lot of black smoke, not gray.

Yes, I definitely checked for obstruction and even switched the tubing. ~ I also checked the wastegate and wastegate hose (replaced the hose for good measure) and added a manual boost controller just to make triple sure the wastegate diaphragm wasn't leaking. Zero change in any of this.
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Old 11-02-2014, 07:56 PM
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When you replaced the turbo, did you transplant the wastegate actuator from the old one?
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  #7  
Old 11-02-2014, 08:01 PM
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Quote:
Originally Posted by KarTek View Post
When you replaced the turbo, did you transplant the wastegate actuator from the old one?
no.
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  #8  
Old 11-03-2014, 03:41 AM
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Start by putting the alda back on, been there done that. Just made a **** ton of unnecessary smoke. Drip time the IP.
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Old 11-03-2014, 10:01 AM
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1987 w124 300D
 
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Check that one or more of your intake valves are not following the cam too closely. (Too tight).
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  #10  
Old 11-27-2014, 03:11 AM
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Quote:
Originally Posted by scottmcphee View Post
Check that one or more of your intake valves are not following the cam too closely. (Too tight).
Came back here to say; you called it right on. I apparently botched the valve adjustment (didn't tighten the nuts hard enough) and they must have gotten loose and went out of alignment. 6 out of 10 had been far too tight. Great call.

(since it was night when I tested it, I couldn't judge the smoke well enough, but power is more than enough to go up a steep hill at a good speed & vacuum gauge is very steady. Massive difference)

Also, I'd like to add to any who had this happen: if the top nut actually slips out while you're trying to adjust the valves.. compress the spring (and lower the valve) with a large and long hex wrench or something and try to side it in to screw back on. Might be obvious to some but others may need to know at some point in the future.

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