Vibration issue out of nowhere....

[nuQ]

As some know, I am in the process of bringing my 1990 Q45 back to great condition. In the past month I have fixed an exhaust leak, fuel filter change, and just got my tires balanced.

Last weekend I noticed that an odd vibration began as soon as I started the car. The idle speed is fine (600rpms) and there doesn't seem to be a noticable loss of power. The vibration/shudder is more pronounced from 600 to 2000rpm's and seems the worst under 40-50 mph's. It is also harder to notice under full throttle (highway speeds), but very noticable from a complete stop up to the 40mph mark. I've also noticed a belt sqeal or idler pulley sound that seems to be getting louder.

I'm not sure if the cause will be very apparent to one of our experts here just by hearing the symptoms, but from what I've been looking up, could it be bad motor/transmission mounts, out of balance driveshaft, or fuel injector issues. I have not noticed any fuel smells inside the engine compartment or in the cabin.

Any advice is very much appreciated!

[Q451990]

Any chance your power steering fluid is low? That will cause a shudder and noise in the steering wheel... An injector will feel more like a bounce at idle than a vibration - and will be less noticeable when crusing vs. accelerating from a stop up to speed.

Heath

[nuQ]

Thanks Heath, I will check that today. Before it sat for the past 5 years, I completely changed the power steering fluid to full synthetic, but that's not to say it could have leaked, or just got low.

PS---I also wanted to let all know that I also did a full MAF and full intake cleaning into the plenum last week. Ever since I bought the Q in 03, the intake has been almost brand new in appearance, so a dirty intake is definitely not the problem.

[nuQ]

I'm not sure......the power steering fluid is fine, and tires balanced (which, of course, would be a non-issue at idle), but the problem still persists. My plan is to get it on a lift this week, and check below and work up. I want to see if the motor/trans mounts are ok, check to see if there are no further exhaust leaks (it does sound a little loud), or any other issues from the front end.

Another question I would ask is; can a seized up pulley bearing cause a noticable shudder at idle and speed? Before I parked the Q years ago I was thinking about replacing the pulleys because they would squeal under excelleration. There is a noticable squeal when I start the car and when turning the wheel at low speeds. Just a thought....

And I guess to elaborate on what you wrote Heath, it is more of a "shudder" at idle and when excellerating,,,not so much at a cruising speed. I suppose a vibration would be more of a very quick sequence, where a "shudder" (like what is happening now) is almost like feeling the engine "rumbling" with the car "shacking".....can be felt all over while sitting in the seat,,not just the steering wheel...If that helps describe things a little better. Thanks

[Q451990]

A seized pully will just break the belt. I really don't think that's your problem - although they should be repalced.

I'm still going to guess that it's an injector issue. I describe it as a "bounce" at idle...

Heath

[nuQ]

Thanks Heath,,,I think you are correct with the injector being the issue. You are right about the Q feeling like it is 'bouncing' at idle, and a steady shudder under gradual excelleration---under wide open excelleration it is hardly noticable...

I think this will prompt me to finally do the under plenum job, and along with the injector, replace the hoses and knock sensors (which I have two new ones), and the pulleys. I will now have to begin searching on what options I have with finding and replacing the one, or all, of the injectors, as I have never been down that road before. Any help on that would also be appreciated.

[Q451990]

Tons of threads on the injectors lately - especially since the move to add ethanol a couple of years ago.

There is a lot of good information here. http://www.q45.org/techhelp.html My first step would be ohm testing your injectors.


Heath

[Buckshot]

Also better think about injector connectors also they get brittle and brake

[BELGERM]

was the injector the issue ?

I am haveing the same problem, just started this past week.