AWD or FWD? . . . . . . .
 

As some of you know, I've had difficulty in diagnosing an engine (and possibly a drivetrain) problem my car has developed in the past few months. It has intermittent rough idle for a few minutes after startup and a shuddering that can be pretty severe from 40 up to 80+ mph.

Since several of you (and a mechanic who drove the SVX while at the alignment shop last Monday) believe the shuddering to be a drivetrain problem (including possibly the driveshaft [U-joint?]), I thought of trying something that might be diagnostic.

I switched from AWD to FWD to see if there would be any difference. It's too early to tell yet, but it sure shudders LESS!

1. Is this switch going to be diagnostic of ANYTHING?

2. What's the deal? Am I normally supposed to drive in AWD (and switch to FWD only for dyno smog tests etc.) or is FWD good for normal driving in certain circumstances or conditions?

THANKS for your input, Jim :confused:

Close to the facts
 

Jim,

You may be very close to the truth here. It is likely you have two problems; a fuelling or misfire one, and a driveline judder that is not related to the rough idling
[BTW, did you see my post on fault-finding on the Sensor School thread?]

If you have run the car in FWD, and the shudder is still there, but less than it was, then this possibly indicates a problem with the rear drive, maybe the u-Joint you mention. It would still be rotating, but causing less judder because it is not under power.

The FWD fuse is only meant to be used for short periods, as in testing. Randy ran his for a long time with no ill effects, but the short answer here is you are only masking a problem by taking it out, not fixing it. You still need to identify and fix this shudder.

Joe:)

The drive shaft joints have been a problem on other SVX's. If you can get your hand on the shaft near the joint and move the shaft it is bad. A twisting sideways motion works best.

FWD ing! ONLY???
 

So, do you think it's alright to drive for extended periods, maybe hundreds to even a couple of thousand miles without any mechanical damage to my SVX? [Switching back and forth between FWD and AWD for diagnostic aid]

{I'm not trying to postpone fixing the driveshaft if needed, It just helps in determining the poor idle problem too.}

THANKS FOR YOUR COMMENTS, Jim :)