Cadillac Owners Forum banner

1 - 8 of 8 Posts

Registered
Joined
14 Posts
Discussion Starter #1
Hi All,

New member (former Lincoln) and (hopeful) future Caddy owner here.

The car I'm talking about is an Eldorado but I figure the Powertrain is identical to any other fwd Cadillac of this vintage so ...

Got my eye on a pretty clean 1991 Touring Coupe. 182000 kms (113000 miles).
I'm pretty much sold on the style / cool factor of the car. Impressed by the ride and road manners as well.
My Concerns (hoping the community can chime in with some insight here).

Once the car is fired up and running - and in gear - there is a (rhythmic) shudder you can feel at idle.
You don't feel it once you're on the gas but once you're off the gas and coasting to a stop - you feel it.
I'm aware of the fuel injector issue with these cars and I'm inclined to think (hope) this is the problem. Feels a lot like a misfire to me.
Is there any case of a the transmission causing this condition?
TCC shouldn't be a factor at idle - am I right?
Recent new battery so no relevant codes stored (I checked). Love how you can do this without a scanner https://www.*****************/forum/images/smilies/wink.gif

Did I mention that I'm SMITTEN with this car? 馃殫馃ぉ
 

Registered
Joined
629 Posts
There are stories out there about Cadillac 4.9 bearing thump. I never had it on my car. You could google it and see if it sounds familiar. I would be bummed if I had such a car. Hopefully it is just a misfire from sitting around. I would run some Techron in the gas and hope for the best. A lot of guys changed injectors to a newer style. I never needed too. I always wanted a 4.9 Eldorado too. My buddy has one and I am keeping an eye on it in case he gets tired of it.
 

Registered
Joined
516 Posts
The bearing thump wouldn't cause the vibration. It is felt more under a load, and not really felt but heard. It sounds to me like a bearing, maybe in the tensioner or the harmonic balancer. If you have the car, remove the belt and let the motor run, if you dont hear the thump, then its not that bad, the thump is caused by the accessories pulling on the crank as it turns up....there is just a little to much clearance. It wont hurt anything, its just annoying.

As far as the injectors, before you get into those take the breather off and look down in the throttle body, the holes may be clogged up, which will cause a rough idle they may just need to be cleaned out, you an rod the holes out with a metal coat hanger or a nice long wire brush and use some barb cleaner. It sounds to me like air flow instead of injectors.
There are tons of possibilities, you could have a little moister in the fuel system. Some Techron some other water dissipater will work. Look for the easy stuff first. And only some will disagree, but use premium fuel, the 4.9L's just dont run well on lower octane fuel. My Deville runs terrible on 87 octane. And if its been sitting, the fuel is old and that will cause it to run rough.
 

Registered
Joined
382 Posts
The engine bearing issue is real, but has never caused me any issues. My car never even had its spark plugs replaced but did have its transmission rebuilt if you can believe it. The transmission are a weak point of the 4.9 but have never had an issue with mine since I've owned it except for the pan bolts needing tightening after the car sat for a while. The 4.9 is a very hardy engine and I'm glad to have owned it. I've driven the car completely through more than a dozen States with no issues.
 

Registered
Joined
14 Posts
Discussion Starter #5
There are stories out there about Cadillac 4.9 bearing thump. I never had it on my car. You could google it and see if it sounds familiar. I would be bummed if I had such a car.
I've done quite a bit of reading about that in my travels. From what I can gather I don't think that's what this is but who knows ... I'm not at all familiar with these machines. But I'm getting there ;)
 

Registered
Joined
14 Posts
Discussion Starter #6
The bearing thump wouldn't cause the vibration. It is felt more under a load, and not really felt but heard. It sounds to me like a bearing, maybe in the tensioner or the harmonic balancer.
I did think of that. Is that at all common on this engine?

There are tons of possibilities, you could have a little moister in the fuel system. Look for the easy stuff first.
I hear that. I can't really mess with much since I don't own the car (yet). Trying to decide if I should go for it. My thought is if I can determine it is something big (trans - worst case scenario), then I will walk away.

It really is a slick car.
 
1 - 8 of 8 Posts
About this Discussion
7 Replies
4 Participants
91FleetwoodCoupe
Top