Will a cracked fan blade cause a vibration

[Drake57]

that changes with engine speed? I get what feels like a relatively low frequency vibration or trembling feeling which changes frequency with engine speed as the car accelerates and changes gears, and my fan blade is cracked (1992 Q45).

I suppose I could remove the fan blade and see if the vibration disappears. I've done normal maintenance: new plugs, new fuel pump, new filters, fixed oil leaks, replaced vacuum tubing and smog hoses.

***And*** ocasionally I get what looks like an odd flicker of backlighting on the instrument panel, a very brief flash. Is this normal?

I just really started driving the car over the weekend, and I definitely like it.

Sadly, the reason that I can now insure and drive my Q is that some careless clown rear ended my son's 1990 Q. It's off the road, so I no longer need to insure it, and can insure my own.

[maxnix]

Timing chain guides?

Underplenum hoses? Cleaning?

Yes it can cause vibration, but the far greater danger is a fracture will complete and part of the fan will damage your radiator.

[Q451990]

If the cracks in your fan blade are fairly small, I wouldn't be too suspicious of them as the cause of your vibrations - but it does need to be replaced. As Brian mentioned, it can eventually come apart and cause major damage to the radiator and hood. You might as well replace it to eliminate it as a potential cause for the vibrations.

My guess about your vibration would be more related to a fuel injector issue. A bad or clogged injector can cause a dead miss that I typically describe as the "injector death bounce" - you can almost see the hood bouncing up and down. I would ohm test them and have a power balance test completed and post the results here. Check out http://www.Q45.org for an excellent Q&A on the timing chain guide issue Brian mentioned as well as how to ohm test your injectors. You should also replace your transmission mount (third motor mount) and exhaust hangers to help reduce or eliminate vibrations if this hasn't been done recently. The bad transmission mount is typically most evident starting out from a stop facing up a hill, and usually seems to be coming from the seat bottom...

The flickering backlighting you mentioned is actually part of the instrument cluster working as it should on occasion. The early Q45 has a pad made of a material that I can best describe as the "indiglo" part of a Timex watch sandwiched behind the trim around the gauges. It was supposed to recreated the gentle light passed through those paper Japanese screens that they use as room dividers.

In the "lemonaide out of lemons" department, most of the parts off of your son's '90 will fit on your '92 if you have a place to store it and use it as a parts car.

Good luck!

Heath

[AlabamaDan]

Could be lots of stuff, but I'd go with a miss in the engine. Could be a plug, coil pack, injector. etc.

[Drake57]

but it seems unusual: It's not a dead solid miss like one plug not firing. Idle is really smooth, hard acceleration is smooth in a forceful way, but this tremble is definite under moderate throttle conditions. IIRC I did ohm the injectors, but it's been a while.

I've actually owned the car a year, had the timing cover and valve cover off, replaced a metal TC guide that had shed part of it's plastic, inspected and replaced some of the smog hoses under plenum, replaced the starter, actually had the oil pan off, added transmission cooler, but only started driving it over the weekend, due the aforementioned insurance circumstances.

Power balance test and xmission mount replacement sounds like a good idea.

I do have other fixup to do: It leaks refrigerant from a plug that is on the very bottom of the AC compressor - I can see a drop of oil and some of the dye there. Said plug is retained by a snap ring - I suppose it is sealed by an O ring. Last summer it would pump out 40 degree air, sitting still at idle. I already have a couple of leather hides the right color to re upholster the front seats - I can even practice on my son's seats.

My son's engine is low mileage, has metal TC guides. I'm tempted to install it in my 1985 XJ6. I think that would be a great combination.

Thanks for helping, Drake.

[maxnix]

Sure wouldn't hurt the XJ. That 6 is a slug.

[silkysmoothyjud]

It's your belt!!! loosen/tighten your alternator belt!!!! Easy attempt, my vibration felt like it was coming from the rear almost, but it went away after driving for a while..... One of my blades went, massive vibration on the highway, but Niqole showed it to my like a kid with a cut (fan would put the broken blade on top) lucky, Im going to the CASINO!

[Skibane]

Immediately after a cold engine start, the fan clutch is disengaged - which means that the fan only spins slowly, regardless of engine speed.

So, if you notice the vibration immediately after a cold start (i.e., before the engine has warmed up enough to engage the fan clutch), it's quite likely that your vibration isn't coming from the fan.

[maxnix]

Immediately after a cold engine start, the fan clutch is disengaged - which means that the fan only spins slowly, regardless of engine speed.

So, if you notice the vibration immediately after a cold start (i.e., before the engine has warmed up enough to engage the fan clutch), it's quite likely that your vibration isn't coming from the fan.

Or the fan clutch has failed!

[silkysmoothyjud]

or injector, or belt and/or pulley failure or, a freakin monkey with a hand grenade, under the hood, shootin dice with the gremilins...

[maxnix]

True, multiple failures are almost impossible to diagnose.

[silkysmoothyjud]

Just drove Niqole through a flash flood in Missouri yesterday!!! Gunned it, bumper high water, she made it, but that vibration came back worse than ever for a while. That belt is making a noise now. My belt pulley is so ghetto rigged. I've got a hose clamp, yes a hose clamp on the threaded adjuster that is supposed to keep it from vibrating. I am about to put another clamp on it just to be sure. I'm so hood!! (wanna see a pic?)

Please be advised that all of my injector failures ohm out beautifully (phase 2). I even had some rebuilt ones ohm like brand new, but misfired when warm. I never would have found them, had I not put them in there myself THREE FREAKIN TIMES before I figured it out....

Modified by silkysmoothyjud at 9:32 PM 6/16/2009
Modified by silkysmoothyjud at 9:41 PM 6/16/2009

[Q451990]

had the timing cover and valve cover off, replaced a metal TC guide that had shed part of it's plastic

That's interesting... I have only heard of this once. I assume you replaced all of the guides? On the 90-92 (and most 93s) the straight guides (I think they're the tension-side guides) are all plastic and are the typical failures.

Heath

[maxnix]

Yeah, I think someone posted one had cracked, but not broken free.

[Q451990]

I remember Dennis mentioning a 94 or 95 at T3 with this issue...

Heath

[kevinpaigeking]

how can i trouble shoot a coil pack

[silkysmoothyjud]

94? ya don't check coil packs, those things are solid as a rock. Its an injector and/or fouled plug unless your coil packs are unplugged. sooooooo....pull the coil pack covers and push the plugs on the packs to make sure they are connected. then....get your self a pair of long handled pliers, ya know, the big ones. Wait for the car to misfire and start unplugging injector connectors one by one until you find the one that does not change the miss or idle.Please be advised that your corresponding spark plug may be foul with gas as well. sooooooooOnce you find the missing suspect(s) pull the plug and see if its dripping with gas too...oh yeah, almost forgotyou cant get to injector # 7's plug, so you pull the plug from the coil pack.