What maintenance should I do on a new Q45?

[pageerror404]

I bought a 1994 Q45 have been driving it for about a week. It drives great and is really smooth. But it's high mileage (235,000) and I want to take good care of it to ensure it lasts. I'm gonna keep a log of everything I do to it. So far I have had the oil and transmission fluid changed (they were black and brown), and the spark plugs and air filter appear very new (previous owner did them). What else should I do to help it run smoothly?

Also there are a couple issues I want to fix but I'm not sure what to do.

1. It idles rough. It's not horrible, but there is definitely some moderate vibration and "jiggling" when it's sitting in park or drive.

2. Also when idling I hear this metallic rattle underneath the car. Sometimes it doesn't do it at all, other times it's mild, and occasionally it's loud and high frequency. I believe this is the heat shield on the catalytic converter because when I push against it, it stops rattling. It may be the car is vibrating too much from the rough idle. Is there a way to tighten this so it stops?

Thanks.

[Lokim]

Check your MAF connections.

As far as the rattle goes, I have the same year and same problem. I'm at 201,500 miles. I found after much trial and error that it was not in fact my heat shields, but the catalyst material inside. Mine only does it when hot at idle. Over time, the catalyst honeycomb cracks, and as it heats up, the skin expands and allows "rattle room" for the catalyst. I'll be replacing mine soon...

[pageerror404]

I don't think that's the same problem because mine rattles even when cool.

[qship96]

most likely it is the heat shields- rip them off and throw in trashcan- just dont park hot car on tall dry grass to prevent possible fires.

transmission fluid being brown is a major concern- be sure you change it enough times so it looks like BRAND NEW FLUID on the dipstick.Often, it takes multiple changes to get it looking like new- even if one pays for the over-hyped "mechanical flush" method.

Shake at idle could be many things- have engine control unit{ECU} scanned for possible trouble codes- hopefully it is not a bad fuel injector.

[jrthurm]

I would agree with qship96.... The transmission is your first concern... Do everything you can do to get this back to clear fluid... Definitely is a point of concern....

[BadQ45t]

The best way to deal with old transmission fluid is to find a shop that can flush the entire contents of your tramission and refill with nearly 100% fresh fluid. Since you really have no idea when any of this was done previously i would find a shop that can do all your fluids, transmission, power steering, brakes, rear end and radiator. Flush all of these and replace with high quality synthetics at least Mobile 1 or Redline/Amsoil if you can find and afford the better stuff. This will go along way to getting that transmission and other parts to run another 100-200k before they die on you.

I would also look up any records that the previous owner had with what is already been fixed. If for example they haven't done athe value cover gasgets, knock sensors, coil packs, those are all probably coming and can be done at the same time you put in fresh spark plugs. Those are usually done at 60k but also should be done every 5 years too.

This can be a sweet ride but with that high of mileage don't be surprised if you have to drop 2-4k into in over the next year or two.

[maxnix]

Simply replace all filters and fluids of unknown provenance. Add an auxiliary ATF cooler when the mechanical exchange of the ATF is performed. Remember the AT has an internal screen filter and and external filter also.

Be sure to read the writing on your trunk!

[pageerror404]

Any idea how to stop the idling issue? I checked the MAF sensor and the thing looks pristine, practically brand new.

[maxnix]

If the MAF connection is secure, and the IAC valve is clean, check the throttle body for cleanliness. Are you sure MAF is OEM and under 160K miles? How often has aier filter been replaced?