1994 Cadillac Sedan DeVille

[hgoodwiniii]

Can anyone help with a 1993 Sedan Deville. The car has 90K miles on it and has been very well maintained. However, we are getting a code 38. MAT sensor is low. I changed the MAT sensor and plug but the code remains. Does anyone have any suggetions on this? Thanks.

[urbanski]

i have a suggestion. make a new thread in the proper forum for your car.

[lyonsheart5000]

Hello There,
I own a 1994 Cadillac Sedan Deville and I have a problem with it.
I just google'd '1994 Cadillac Sedan Deville Problems' and your very informative post about them came up.
I noticed that the last post on it was 1995 though, so I was messaging you to see if you still exist

[lyonsheart5000]

Problem, please help
I own a 1994 Cadillac Sedan Deville with a 4.9 motor
Shortly after I purchased the vehicle used I noticed a small knock/tap in the motor during minimum acceleration, but the knock/tap would vanish as the acceleration continued until I would come to a stop and start back when I would accelerate again until I picked speed up once again.
Well, a friend of mine suggested that I use some Lucas Oil Treatment.
I did so, and the knock/tap seemed to disapear.

Now since it is cold outdoors when I first start my Cadillac in the morning I am am hearing a terrible knock I assume from the motor. I am far from a mechanic.

I took this Cadillac to the Chevrolet dealer here in town and had the service manager listen to the small tap/knock before I put the Lucas Oil Treatment in it and his opinion was that the cam was making the noise and that it would only get worse with time.

Please give me some valuable information on this problem?
I have always wanted to own a good Cadillac, and I don't want to get rid of this car if it is not a serious problem

[behind-bars]

First off welcome to the forums. but you may have better luck starting a new thread in the 4.9 sub-forum, But the consensus you will probably get is that lucas treatment and other "additives" really dont solve many problems, they can cover them up a bit but dont last.

Few things I would look at, If they dont solve it start a new thread and you will probably get more help from everyone else.

Do you have any codes? Press off+warmer and see if any show up, their is a sticky thread in the 4.9 forum with more details.
Knock on acceleration can often be caused by egr and timing settings. If you aren't already try running a higher octance fuel and see if it improves.

I would also hit the basics like making sure your not low on oil or antifreeze.

[Stoneage_Caddy]

Knocks in the 4.9 are normally becuse of the undersize stock #1 main bearing.

2 things you can do

1 switch over to mobil 1 DELVAC 15w40 diesel truck oil. This works pretty well but wont get rid of the knock completly, normally this is recomended for the 4100 engines becuse of the distributor gear. But it works well for all the pushrod 4.x liter engines. Mine had nothing but devlac 15w40 since i got it in 2003 till the last oil change. No job so i put in chevron , i regret it but moneys tight. now i have oil leaks again....

the other thing you can do once your 100% sure it is the main bearing is to replace them. took me a week on the garage floor to change out all 5 , 4 of them replaced with stock and the number 1 replaced with the upsized GM service unit.

I would go with the oil first , esp if the lucas helped. Be sure to use a GM filter also.

[lyonsheart5000]

Thank you very much Stoney
I will try that oil and the GM filter
How wil I know 100% weather it is the bearing though?

Does this motor have known cam issues?

[Stoneage_Caddy]

Originally Posted by lyonsheart5000

Thank you very much Stoney
I will try that oil and the GM filter
How wil I know 100% weather it is the bearing though?

Does this motor have known cam issues?

ive never heard of cam issues , ive got some lifter noise in the front bank , one never really pumped back up after the main bearing job. but cam bearings and such ive never heard of issues with.
if it knocks under a light load and is hot , say driving in a parkinglot after being on the highway its most likely the mains...and really it will run like that a long time ...mine did it forever , it trashed mains (#1 chunked, 2-4 scored badly, 5 chunked) but otherwise survived ok ...

[lyonsheart5000]

I am nowhere near a mechanic, but before I put this Lucas oil treatment in the car it sounded like a lifter maybe.
It would be a faint tap, some people might not hear it.
It would happen between the speeds of 5-15mph then it would fade away, I noticed that it would get worse on big hills or inclines though.
So far, the Lucas has gotten rid of that noise, but what concerns me is that it is a real problem that is just being disquised for now.

I wish I knew for sure what this awful noise was when I first start the car up in the morning. I noticed it is worse when it is very cold outdoors and especially when I have not started the car in a couple of days.

I considered taking it to the Cadillac service center in a neighboring city, but I was afraid they would just find any and everything wrong with it just to make some $$$ you know

[papermaker19]

I need some help here. I believe the instrument cluster panel has shorted out on our 94 Deville Concours. I think I've found a place to repair it but I don't know how to get the panel out. Can anybody help here? I have some mechanical skills. Has anybody else experienced this problem. The Deville just hit 100k a month ago...what a great car. I would appreciate any help.

[rick davenport]

im guessing everything applies to 95 devlle with 4.9 also? ive used prem since day1 and now it knocking , what should i do to stop it?