2001 shuddering while driving and sitting

[azrielstear]

First off, I was unable to find this in the forums so if it is somewhere please point me in the right direction.

I bought a 2001 qx4 2wd 3.5V6 a while back. I got it for my wife so she had something other than a 2 door coupe to carry our child in. She complained that it would ride rough with her and she has had previous bad experience with a car doing the same thing so it really scared her. I would drive and nothing would happen to me. Eventually it did happen to me and has happened occasionally. The problem seems to be just a rough idle. However, it continues to ride rough at cruising speed. Not matter what speed I am going, when the RPM's are in the 2100 range the whole vehicle shakes. Not a wheel alignment shake at speed, but an odd rumble. During this there also seems to be a loss in power. The last time it happened, I floored the gas pedal and nothing happened. Similar to trying to take off in 5th gear around 20 MPH. One other time, I was driving and it was rumbling and then it felt like something hit the axle with a sledgehammer and the shuddering stopped. I thought it may be a fuel thing or some electrical thing (which it may be), but the fact that it only happens occasionally is what confuses me. I do apologize for the poor construction of this explanation, but I was trying to get all the information together that I could remember. I am at a loss for what to do. If anyone knows what is going on or can give me some direction, that would be really helpful.

Thanks,

[Buzzman]

The symptoms you describe sound exactly like what happens when it goes into limp mode.
Are you getting any codes?
Check the temp gauge as well. If it senses an overheat condition, it will do what you describe.

[azrielstear]

I will have to get the codes re-checked. I did this a while back but nothing really came up. Or at least I dont remember it being bad. I really like the vehicle and want it to work. Let me get the codes checked, probably this weekend, and I will reply.

[asnorton44]

Does it drive worse when the engine is warmed up?

[barnaclebob]

Is the shaking at speed related to the engine or suspension? I know the resonance of the car and the wheel rotation is somewhere around 70mph. Your lack of power could be the MAF but that should also show surging problems when trying to accelerate at from idle speeds.

How many miles are on it? Sounds like you could use a full suspension inspection at the least.

[azrielstear]

I am very sorry for the late reply. I did not get the codes re-checked as I said. I was reading around and some of the other posts about spark plugs and issues there had me wondering. So, I changed that plugs. Huge shout-out to the post on here with pictures, because that was amazing and helped tremendously. This did alleviate the problem that I was having. So, for now, it has been solved and this topic can be closed. In reply to Asnorton44, it was pretty steady of a shudder warm or cold. Barnaclebob, it shuddered at all mph and would do it as the vehicle settled into its set speed. So in overdrive and at a constant speed. Anywhere around 2k rpm. The ride and suspension seem a little loose to me. Lots of body roll on small bumps. It almost feels like I am driving on a trampoline. I did clean the MAF and Throttle Body while changing the plugs. It had just about 170k. The plugs were WAY overdue for a change. There was no peak on the plugs and the gap was around a quarter inch between the electrodes. I do thank everyone for the input and if I have more trouble later, I will be back.

[azrielstear]

I am back...the vehicle is still doing it, but it was much much longer since it did. Now it does it almost every single afternoon. I read around and saw that vacuum hoses might be a cause. I have two hoses that are either loose or off all together and I haven't been able to find out what they are. Both are located near the airbox. One actually connects to the air intake tube. Right after the MAF and the other goes into the top of a canister looking thing just next to the air intake resonator (i think that is what that is). I am trying to upload pictures, but I am not very versed in that on forums. https://goo.gl/photos/1YiyF3sBybZYvDwJ6 That should be the canister thing. https://goo.gl/photos/Fm5K5ifNp3LHU4M19 That should be the other hose. The second hose will not stay in what so ever. Even with the clamps. If these happen to be very important, please let me know. Also, please let me know what the canister thing is. The hose is completely broken off...not sure how that happened.

To my OP, I still have no idea why it keeps shuddering and if these fixes don't help...I really dont know where to go from here.