Yukon Shaking

brownk01 · November 18, 2004

I have a 1999 Yukon with the 5.7L engine and auto. trans. After long accelerations (5-10 seconds) you begin to feel a vibration like a bad U-joint. It gets worse to the point of shaking the vehicle violently (like a bent rim) if I continue on the throtle. The shaking continues until I slow to below 35mph and the shaking appears to be tied to the speed of the vehicle rather than engine rpms (slows as the vehicle slows down). The shaking continues whether the tranny is in 3rd or 4th gear and putting the brakes on makes no difference. I have checked the rear differential and U-joints and both appear fine. Occasionally, if the shaking continues for more than 10 seconds, the engine puts off the #4 cyl. misfire code but the engine appears to be running perfectly. I replaced the plugs and wires the first time this happened but it did not help. This began at about 90,000 miles but is progressively getting more often at 114k. Any ideas on what could cause this?

phillyturbosix · November 18, 2004

Hi brownk01... I was just looking thru the post's here and saw your post. I have a 98 1500 and don't have this issue but a friend of mine has a 99 Yukon same as yours and it has been in the GM dealer for over a month now with this same problem! As I was reading your post I could not believe how you described his problem to a T! Your post was almost word for word what he told me. It is still at the dealer and they don't even know what it is. So far they have replaced his injectors and inspected his valve springs and nothing. I think he gets a #5 cyl misfire code. His truck has under 70K on it doing this. As soon as he gets it back and finds out what it is I'll post back for you. From what they tell him 2 of GMC's finest mechs are working on it all the time and come up clueless so who knows what they will find! Maybe we'll get lucky and someone had this issue before and will post! I'll let you know as soon as he gets his Yukon back!

Shawn T · November 18, 2004

Do bumps in the road tend to trigger this problem? I am no mechanic but I can do most of my own mods. This problem sounds very close to a worn out idler arm. I owned an 88 k1500 and the description you give sounds exactly like a bad idler arm. A small roll in the road or acceration would trigger it and the truck would thrash around violently. Of course, you could feel this through the steering wheel also. The only way you could stop the wabbling is to slow below 35 mph. It got progressivly worse. At first I thought it was a drivetrain problem too. I may be way off. It was like "Murphy's Law" though. It only did it when I drove it. The only reason I figured it out was to actually stick my head out of the window when it happened and see some wabble in the front tire. I hope you find out it is not something real serious. Good luck!

phillyturbosix · November 19, 2004

Good input but would a bad idler also trigger a engine code of a misfire? I alsmot think it's in the valves or something. Really weird that is for sure!

99Sierra_Z71_5.3 · November 19, 2004

Good input but would a bad idler also trigger a engine code of a misfire? I alsmot think it's in the valves or something. Really weird that is for sure!

<{POST_SNAPBACK}>

I am new to the forum so I would like to say hi first, but I also wanted to see if I could help with this problem because I had a similar problem with my truck and it was carbon deposits on my valves as well as dirty injectors. Have a mechanic run a compression test on the engine to see if the compression is low if it is then you probably have the same problem I had and it cost me about $600 to fix, but was worth the money because the problem is gone and the truck is running stronger than ever. I would also suggest running some seafoam through a vaccum line to see if this would help, might do it if the carbon is not built up that bad. I hope this helps.

davefinn · November 19, 2004

This is my 99 Yukon that PhillyTurboSix is talking about.

Like he said, it's going on almost a month in the shop. I just purchased it a couple months back and luckly it is covered by a used car warranty. I will post a reply if I ever get my truck back... Oh well...

brownk01 · November 19, 2004

Road conditions make no difference. It only happens after long accelerations. I haven't tried this yet but I am thinking of shifting to neutral and shutting off the engine while it is shaking. This will determine if it is the engine or drivetrain. Other than loss of power steering and brakes, do you think this will cause any damage to the vehicle?

Thanks for the response.

brownk01 · November 19, 2004

This is my 99 Yukon that PhillyTurboSix is talking about.
Like he said, it's going on almost a month in the shop. I just purchased it a couple months back and luckly it is covered by a used car warranty. I will post a reply if I ever get my truck back... Oh well...

<{POST_SNAPBACK}>

Sorry to hear you are having the same problem. I will let you know if I find out what it is. At least you are not alone.

phillyturbosix · November 19, 2004

For some reason I think it's what 99Sierra_Z71_5.3 is talking about. Dave they did injectors and made it "better" or go away somewhat but now with people talking about this carbon on the valves I'm thinking that's what it is. You hear about it to much on these engines and it seems to cause all kinda problems. I think I'm going to take my 98 1500 and have the top engine cleaning done on it just because it seems to be such an issue with these trucks. Maybe you should call them Dave and ask them if they would preform a compression check and see where that leads.. my bet now is that its carbon build up like 99Sierra_Z71_5.3 says! Thanks for the input guys! This is how you fix a problem that the dealer pretends to know nothing about!

davefinn · November 19, 2004

I spoke with the service manager today. They claim that the compression is good on all 8 cylinders and do not believe it to be a carbon issue. The valve springs were also inspected.

They also claim that it is not throwing the cylinder #5 missfire now. Because of that, they say they have no where else to go with the problem. Basicly, they admit to verifing my complaint but can find no problem!

Thanks Brownk01!

brownk01 · November 19, 2004

I spoke with the service manager today. They claim that the compression is good on all 8 cylinders and do not believe it to be a carbon issue. The valve springs were also inspected.
They also claim that it is not throwing the cylinder #5 missfire now. Because of that, they say they have no where else to go with the problem. Basicly, they admit to verifing my complaint but can find no problem!

Thanks Brownk01!

<{POST_SNAPBACK}>

Thanks for the update. I will continue to troubleshoot on mine. I will keep you posted on any findings. Thanks again davefinn

mcreyaufmiller · November 21, 2004

In the old days when we wanted to clean the carbon from the engine, we took off the air cleaner and got a spray bottle full of water (distilled) and sprayed the water into the carb. When the water turned to steam, the carbon would fly off and come out of the tailpipe. I would imagine you could do this with FI, but I have never tried it and will not suggest that you try this at home (unless you just want to).

Back to the problem here, does your truck do this every time you drive it or is it intermitent? If it does it everytime, check your tires, the belts could be coming apart inside the tires themselves. Also, and just a thought here. Has anyone thought about checking the torque converter? Should one of the fins break off inside the converter, it could cause this type of problem as well.

Let me know if this helps!

Mike

phillyturbosix · November 21, 2004

Hey Mike, Well I can speak for my friend's truck here.. His has brand new tires on it. Torque converter could be an issue but you think it's possible 2 truck had that happen to them? I guess anything is!

gixxer · November 21, 2004

I had a similar situation on mine years ago but that was just a fuel filter that needed replacing in combination with a bad universal joint. Made you think it needed a converter.

mcreyaufmiller · November 22, 2004

Phillyturbosix,

It is possible that there is a problem with the torque converters, but that is just an idea I had. I was brain storming the problem and this was one idea. I had an older truck with a broken blade in the converter and it was a similiar problem to what was described.

I will keep thinking.......

Mike