GMC28

Cdi won’t rev past 3000rpm

7 posts in this topic

I’ll do the usual digging/searching, but haven’t seen this before and thought I’d post the question:

On my short drive yesterday to/from town, In lower gears things seem fine, but I first noticed in 5th it wouldn’t rev past 3000 rpm.  Pulls/accelerates normal at lower rpm.  Happened when on the highway when I ofter let it rev into the low 3000’s before shifting to 6th.


later it rev’d normally, as I let it rev to 3500 in a lower gear just to troubleshoot.  Hmm…. Figured I must Must have been imagining things.  But then a few mins later the same thing in 4th and 5th where it just stops accelerating at around 3000-3100rpm.  
no other obvious issues or symptoms.

throttle position sensor going whonky?

 

 

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turbo waste gate stuck ?    happened to one of mine.   easy fix.   wd-40 and a pair of pliers and wiggle it back and forth till it looses up.

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57 minutes ago, Sydney said:

turbo waste gate stuck ?    happened to one of mine.   easy fix.   wd-40 and a pair of pliers and wiggle it back and forth till it looses up.

As Sydney has said, This happens to mine almost on a regular basis now after allowing it to sit after a heavy rain. Somehow the waste gate quickly gets rust around rod where it travels through the exhaust manifold body and it sticks. Easy fix, I use never seize after penetrating fluid and wiggle it to the full travel of the waste gate. The hardest thing is removing the rear bumper but if you have done this a few times it's a non-issue. 5 bolts and two wires a couple of screw and it slides off.  Make sure you put never seize on all bolts for next time...

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Many thanks-

I’ll dig into that next weekend, and do some other annual maintenance.  My father loves driving it so I don’t drive it nearly as much these days.  Don’t think he even noticed any issue.  
cheers

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Hoping to get out to shop this weekend to  get it lubed/freed up.

interestingly the little computer plugged into OBD2 shows higher avg fuel economy than usual. Makes sense I suppose with little or no turbo boost happening. But I’ve generally always driven it “gently”, and even now up until around 2700+ on the rpm it hasn’t felt much different without the boost, so I wouldn’t have guessed the fuel economy would jump like that.  

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I get rediculous fuel economy with my CDI, but I also baby it for the most part. I shift up around 2500 and let it drop to 1800 RPMs cruising around. Now, I live at lake level and it's basically flat lands here, slight rolling hills.  I average 3.5 litres per hundred kilimeters driven some days if I don't try and watch the gauge it drops to 3 for some reason...maybe I'm fluctuating too much when trying to get it to drop further?  I also drive 5 over the speed limit all the time on the back roads and 10 over on the highways. It also has  had a what I would call a hardish life before me, some younger person beat it well from the way he took me for a test drive...lol.  So, maybe it's a very well loosened up engine that doesn't burn a drop of oil between changes. Who knows.
BUT, getting back to the no-boost issue....you will definately notice it when you want to move forward when the waste gate is seized.....it won't excelerate worth a damn! But if you get used to it and baby it it shouldn't bother you that much. You just need to leave even more than a 5 ton gap in traffic when you want to merge with traffic...lol.

It's definately worth fixing it....imho.

 

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