Low RPM Engine Shutter/Shake

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Aug 15, 2008
Greenville, SC
I need some diagnostic help regarding a low RPM engine shutter/shake.

This is a 1996, 80 series, with about 155K on it. I bought it last August and it has run flawless to date. Recently, I have been doing a lot of highway driving out of town about 2.5 hours and then back home again on the weekend. It has a Slee 4", with 315 BFG KM2's with stock gearing.

I changed my oil, oil filter, and air filter on Saturday. After which, I noticed the truck shaking at idle. I was able to make it stop by shutting down the A/C. Then I discovered that upon accelerating from a stop, the engine does the same thing in the very low RPM's upon receiving throttle but would quit when the RPM's increased just slightly. So, the issue is in the low RPM's just above idle whether it is cause by throttle input, or increased RPM's from having the A/C compressor on. It also does not matter if the truck is in gear or not.

What do you think is causing this suddenly? I am racking my brain thinking of something or anything that could have got bumped when removing the oil filter, all the way down to if the oil level was over filled by accident since I was using gallon containers and filling and checking as I went. I am more inclined to think that this occuring after the oil change is a quencidence. Any help would be appreciated.

This shake does not seem to be causing any ill effects, it is just annoying.

Edit: Something else that I did not mention is the fact that the truck seemed down on power. However, I installed heavy Metal Tech sliders this weekend so I attributed it to that. I noticed this mostly on the highway this morning when cruising at 70-75 mph, the transmission would down shift A LOT more than it normally does to climb hills on the highway. Again, I attributed the extra weight of the sliders.

Could the mass air flow sensor be causing this or an O2 sensor? It seems that the check engine light would come on a throw a code if this was the case.

Sorry for the rambling, but I tend to get paranoid and look to find connections that may or may not be related.
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I did a bit more searching and may have found something.

When I replaced the air filter, I took loose the wing nut and the clamps that hold down the lid of the air box and opened it up to swap filters and moved it out of the way. I just found these two threads with the similar symptoms and in both cases, it was recommended to check for cracks in the intake tube.



I am going to check this when I can. Does anyone know why this could cause this problem? Would it be from unregistered air getting into the intake behind what the MAF sensor is picking up?
...Would it be from unregistered air getting into the intake behind what the MAF sensor is picking up?


That 13 year old tube is likely the culprit.
My truck has been doing the same thing after I cleaned my throttle and EGR. I'm thinking it might be the intake too. I did somehow manage to lose the wing nut holding the intake filter.
This is interesting.
I have nearly the same exact problem with the new '93 I bought.

The PO said he had to replace a cracked intake. The new one looks to be a crappy aftermarket piece.
Did that fix your problem? That will be the first place I look now!
I'm having the same issue and I think with all the miles the EGR is clogged up; have to take apart the throttle body in order to get in there and clean it.
Intake tube it's my guess I learned the hard way on a 94 I had years back nearly broke it in half changing the air filter.used a universal flex duct from AutoZone and electrical tape and fixed rough idle gone

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