Q45 vibrations at low speeds.

[wgreene63]

I recently bought a low mileage (86K) 1990 Q45. It runs pretty well but at low speeds it has what feels like a vibration. Felt when accelerating from a stop in about the 2000 rpm range. Car doesn't pull too well under hard acceleration until around 4000 rpm and I suspect from reading earlier posts that I might need to replace the fuel pump. Will be doing that shortly. Is the fuel pump possibly the cause of the vibration I feel when accelerating from low speeds. I also have a problem with the shifting under hard acceleration at redline. It hessitates for a while before it shifts. Any advice would be appreciated.

[maxnix]

Go to NICO and read extensively. Beware of failing chain guides!

[skoobdawg]

My car does the EXACT same thing and I have no idea why. I've searched all over NICO trying to figure out what it is, but so far I've been unsuccessful. Let me know if you find anything out and good luck!

[project-man]

Originally Posted by wgreene63

I recently bought a low mileage (86K) 1990 Q45. It runs pretty well but at low speeds it has what feels like a vibration. Felt when accelerating from a stop in about the 2000 rpm range. Car doesn't pull too well under hard acceleration until around 4000 rpm and I suspect from reading earlier posts that I might need to replace the fuel pump. Will be doing that shortly. Is the fuel pump possibly the cause of the vibration I feel when accelerating from low speeds. I also have a problem with the shifting under hard acceleration at redline. It hessitates for a while before it shifts. Any advice would be appreciated.

I'm new to this forum so please be patient, anyway, check your driveline to see if your carrier bearing is bad. The easiest way to to do this is to raise the front of your vehicle high enough to reach your driveline. The driveline is two-piece so if you have any play at all REPLACE YOUR DRIVELINE. If not the driveline could break at the bearing and potentially fall off of your vehicle. These items cost about $800-$1000 to replace new because of the dampener on the front of the driveline. However, you can have a custom driveline made for about half that price without the dampener, the only draw-back is you will notice your shifts are a little stiffer.

[riversphoenix]

well it is definitly a problem in common w/ 90% of 91-94 q45 owners that i have run across in the past 5 years since i inharited mine from my grandparents.. i have been trouble shooting a what feels like one or more cyldrs have been shut down and making it stutter when accel and idle..also seems to not like 58-64 mph either..it has been bout 2 years that i have been driving it reguardless...i had dealership 4000$ tuneups to adding 99c injector cleaner to fuel. I even got ahold of an complete intake manefold w/ injectors from another q45 of same year..and my theory is the injectors themselves get a buildup of bad fuel deposits around the micro screen like filter that surounds each inj that is supposed to be completly submerged in the pump pressureized fuel dist chambers of the intake man....after inspecting inj my self after removing them one by one from the spare manif that stood alone..and if you have ever seen a carb that has been sitting for a while not being used with unused gas that transformed to a nasty carmel like substasnce that causes most people to replace carb instead of attempting to clean this crap out of micro jets and anywhere else the fuel had been sitting. well the injectors of a 14yr old 160.000 mile car have build up of everything main filter let past and or any residual fuel sedament in between main and injectors own secondary filterscreen. i soaked, sprayed. brushed tring to clean out the screens wile the injector was removed and able to be inspected like a small light bulb out of its socett. needless to say i destroyed 2 just trying to remove them and still the screens arnt clear

[maxnix]

Why a regualr use of BG44K before each oil change will do wonders for injectors. Too much ethanol will crap them out anyway, eventually.

[bradyb]

if there is a half a quart too much oil in it....it will hit the crank under low RPMs and cause vibration.....once the RPM's come up it will go away

try that

[Texasoil]

Many such low speed vibrations are due to tires--uneven rolling resistance. Others are due to bent rims or bent axle flanges. Other, lower cost causes are hardened/failed exhause system hangers. The Q45 (all G-50's) have a tendency toward exhaust system 'shudder' that is quite easily felt. Other cause is sagged rear engine(transmission) mount which allows tranny to just touch the cross member--exciting a resonant vibration. If the vibration is felt with the car stopped, in Neutral, just slowly increasing engine speed--it is either exhaust hangers or tranny mount (or engine mounts). If it happens ONLY when rolling, its tires, wheels, drive shaft, or bent axle flange--however, it is does not vibrate when 'coasting' in neutral at the offending road speed, its tranny mount and/or exhaust hangers.