1994 Cadillac Seville STS EGR valve problem?

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CaddyMaster

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My 94 Cadillac Seville STS started running sluggish and rough idle after using three tanks of 87 Octane gasoline. I changed back to Premium and it's a little better but still idles a little fast and rough when stopped and in gear (at red light etc).

I figured maybe a tuneup would solve the problem so had the plugs, plug wires, fuel filter, air filter, and pcv valve replaced which cost me $560.00. Wow !! That was a shocker..

I think my EGR valve might be bad... Does that make sense???

After all that the car doesn't seem to run any better. Last night I was coming to a stop on an upgrade and thought I was stalling out but it came right back. Any suggestions ? I am going to try some dry-gas and Shell V gas. Maybe that will help.
 
There's a number of things that "could" be causing your problem. It IS possible that your EGR valve is not closing completely. This "could" be caused by a bit of carbon blocking it's movement. You can verify this by removing the valve and inspecting it. Who did the "Tune-up"? Didn't they notice it was still running poorly? Any mechanic worth his salt would never just throw some parts in a car and give it back without at least asking about the poor idle or near stalling.
 
Could a bad EGR valve cause the gas milliage to go way down? I recently had a complete tuneup like CaddyMaster on my 91 Seville, which did improve the rough idle some, but it's still not idling correctly. At a stop signs/lights the rpm's constantly go down to 650 and up to 800 like a yo yo. I have improved the gas millage from 6.9 when I got it in September, but I still only get 11 mpg. Unfortunately my car was not running right when I got it, so I'm not sure what to compare it too yet. I would think that the rpm's would be a little more consistant, and the mpg's would be at least close to those estimated by GM.
 
gas mileage

I have almost the same problems.
But your gas mileage? That's Scary!!

I get 19 city 23 highway with my 91 seville,
I ONLY, and I emphasize ONLY use Shell, Or Cheveron HIGHEST octane.
BP is one of the worst for my car.


The EGR, Is allways, a common problem, with stalling , rough idle etc.
One question to ask,
does it stall when its dry and warm, or cold and wet, Or all the time?

Reason I ask, Is on a different auto I had, The problem was a coil pac.

Do a search on Google, about seville codes.
There is a way to bring up your codes using your dash panel.
 
kycaddie said:
I have almost the same problems.
But your gas mileage? That's Scary!!

I get 19 city 23 highway with my 91 seville,
I ONLY, and I emphasize ONLY use Shell, Or Cheveron HIGHEST octane.
BP is one of the worst for my car.


The EGR, Is allways, a common problem, with stalling , rough idle etc.
One question to ask,
does it stall when its dry and warm, or cold and wet, Or all the time?

Reason I ask, Is on a different auto I had, The problem was a coil pac.

Do a search on Google, about seville codes.
There is a way to bring up your codes using your dash panel.
Click to expand...

It does not stall at all. There are NO error codes. I haven't had it on the highway since I got it home after putting a new transmission in. It had 8 new fuel injectors put in right before I bought it. Since then I have had a lots of things fixed on it like the brakes, starter, water pump, complete tune up, 8 new fuel injectors, and a new coil pac. I was assuming that if the EGR was bad I would have an error code message, but none found. Kinda of grasping at straws here?

As for the gas, well the only two around home with premium octane is BP, and Murphy USA @ Wal-mart. Not sure about the Citgo 10 miles up the road. No Shell, Cheveron or Standard within at least 35 or 40 miles.

Any other suggestions would be helpful. The gas milliage is hurting me.
 
I was looking at my guages today.
I have 178493 miles on it, and am getting 19.4 on average.

I bought this car last april, so I don't know the history. anyway,
BP gas to my car, is like putting sugar in the gas tank.
Within 2 miles, the car sometimes dies, at low rpm.
To correct this, I use Chevron techtron (Spelling?)

With your car, I am thinking of the following.
Fuel filter-- VERY difficult to do
pcv valve,-- CHEAP and Easy to do.
check plug wires--
Best to do in total darkness, to see if you see any sparks.

The BIGGEST HELP, I ever did to help my car, was to use Valvoline MAX life oil.
the first oil change, I gained 4-6 mpg on it.
even if your not a valvoline fan, Penzoil, makes a high mileage oil, I would recommend something of the nature.

Check inflation of tires, inflate to highest psi allowed by your tire.
avoid speeds of 65-70, This is a killer to do, but helps.

I will check with my mechanic, to see what he says.
Also, check for any burnt valves, any type of smoke from exhaust, this is hard to do in the winter time, but could be a factor if it is doing so.

If Your unable to get the higher quality gas, Check to see if there is any kind of ocatane booster that is available.
alot of people say use the lower octane, but they don't drive a caddie either.


hope this helps!
 
Thanks for the hints!

Even though they are new, I will check the spark plug wires tomorrow night to make sure they are all getting sparks. They are less than a month old, but sometimes even the new stuff is bad. 2 of the tires are new and the other are decent, all with the max 35psi. Wheel alignment was also just done when I had the new Monre shocks and struts put on a couple of weeks ago.

I'll need to check into the gas filter, as this was not done with the tune-up. Theres no smoke from the exhaust, except when its cold. At least I didn't notice any somke today, and it got up to 63 degrees. Unbeliveable for Illinois this time of year.

I can get the 93 Octain, just not happy with the quality of gas. I used Amaco gas in my cars in the past, as it was the best around my small town, but they were bought out my BP last year. Now I'm using the one at Walmart, since neiter of my choice seem to be a good ones.

I'm not sure of the exact history of this car either, but with all of the stuff I've done to it in the last couple of months it wasn't a very good history. The engine oil was complete black and gritty when I got it. Had been a long time since it had been changed. It was changed with the Transmission since they had to take the oil filter off anyway. After running it about 800 miles I had the oil changed again with penzoil, and it was pretty dirty even with the low miles. I didn't think of using high millage penzsoil. I'll consider the Vallvoline MAX on the next go around. I'll be changing it more often until I get it cleaned out.

I have not done any work on my own cars in many many years. Now that I have the older Cadillac I wanted, it's time to re-learn. Lets see - the fuel filter and check for burnt valves. I wouldn't want to start with anything easy.

So what's up with avoiding the 65 - 70 range. Are you telling me to not go so fast or the going 75 or 80 is better than the 65 -70 range for some reason?

Keep the ideas coming. By the way. I am missing the front spoiler that goes below the bumper. Do you thing this would make much of a differnce in town? I know it will make some difference on the highway.

Thanks again.
 
Gas Milage

from what you've said your doing-and done. You should be on your way to improving you mileage.

TRY not to Drive over 70.
It increases your rpm more, going from 65 to 70.
more RPM= more engine usage, = more gas used.


My mileage hit 180000 today, Thought it was less the other day, but I was wrong.

I don't think the spoiler will cause much difference, If there's more wind resisistance, It will not improve nothing, other than looks.

Definatly, use the highmilage oil.
And if your near a chevron sometime, Even if you have a half tank, Fill it up with the higher grade. Small dosages, work better then None!

I will check back later this weekend.
I will see what else I can come up with.
Thanks!
T.F
 
Getting spark from all eight cylinders.

If I can trust the instant mpg on the drivers display, gas milage is getting worse with the colder outside temp. The other day it was 63 degrees outside, today it is 7. I noticed that the engine temp is only getting up to 159 degress, I think I read somewhere that it should be between 190 and 220 degrees. That's the next project.
 
genechaz said:
Getting spark from all eight cylinders.

If I can trust the instant mpg on the drivers display, gas milage is getting worse with the colder outside temp. The other day it was 63 degrees outside, today it is 7. I noticed that the engine temp is only getting up to 159 degress, I think I read somewhere that it should be between 190 and 220 degrees. That's the next project.
Click to expand...


That is correct.
I get concerned with mine if it goes over 224 degrees.

It usually runs around 210-214 on normal operations.
you should consider getting the higher rated thermostat.
Also.
I was informed that some caddies, fuel problems are not fuel problems. of course this makes sense, but if you have a catylatic converter, it may be clogging. I don't know the symptoms on a caddie, but on my S-10. it sounded like it was running out of gas, so this may not be a problem for you.

keep me informed.
thanks
 
also,

your instrument panel, states the mpg and another version of mpg.

you have one that stays the same, or close to it all the time.
and the other, will change as you push the gas pedal.
I assume that you know this, but just crossed my mind.
Goodluck !
 
The instant millage was what I have been watching the most since I bought the car in 09/04. Occationally I would look at the average MPG, RPN, and Cooling temp.

When I got the car the cooling temp ranged between about 192 and 204. The instant millage was not what I thought it should be as compared to my wife's Explorer Limited, which has Fords version of the same thing. The average milage was around 7.8. After the waterpump and tune up, the gas milliage went up to an 8.9 average. I've been so busy looking at the instant mpg, that I didn't realize the the cooling temp was no longer in the correct range.

Not sure when the thermostat went bad but it did. Maybe it was bad all along but was overheating due to the bad water pump and extra work on the engin until I had the tune up. Who knows. Any way, I had it fixed today. I only drove a few miles home, but I noticed the cooling temp got up to 200 degree, and I also noticed that the instant millage is giving me some higher numbers.

I put 9.051 gals of gas in the tank to fill it up. Figured out that on the last half a tank I got 8.4 mpg (76 Miles), which was slightly lower than the 8.7 showing on the average mpg on the drivers information center. Not sure what I'm going to get out of this next tank, but I already know it will be much better.

In another 2 days I will have owned my new toy for 4 whole months. The mechanics and I have put almost 1000 miles on it. As of today, I have spent $6003.03 in mechanical repairs. Now, I new it need the interior redone when I bought it, and I expected a few repairs. But I think it's time for a break. Not to mention the fact that I want to drive it! Keep your fingers crossed for me and cross your toes while your at it too. I need all the help and luck I can get.
 
Sounds like

Your on the right track.
HOWEVER,
If you intend on spending another couple grand on it, I will sell you mine !

I was looking over our threads, and saw that you replaced the waterpump,
I don't know why, but I missed that, But it's a good thing you got your thermostat taken care of too.
Mine is due for an oil change, 180,149 miles.
I noticed that since I am getting near the end of the "oil Index" life
the milage has dropped to 18.7
That's just down a half mile per gallon,
But that indicates to me that the oil change, does Make a difference.


I am looking into a 4x4 Blazer, and am really thinking My caddie. I hate to. but im in Ky, And work alot out of town, and hate to wear it down.


The interior, is not that bad, not great, but not bad.
I am looking for a console cover cap to replace the one I have, it was ripped when I got the car a year ago.

I have a guy looking into it, but Who knows? I may never hear from him.

anyway. Here's us hoping for the best! :invasion:
 
I didn't intend on spending more than $3000.00 on mine, but there wasn't much point in getting it started and giving up half way there to end up with nothing more than an expensive yard ornament. This is somthing I've wanted for a long time, and will also be kind of a hobby as well. I do need to go out of town, using back county roads every now and then so I also need it to be dependable.

Funny you should mention a couple grand to buy yours. $2020.00 is what the estimate was to totally redo my interior. Headliner, trim between the doors, door panels, seats, put in the new carpet I bought on ebay and the door panels. They werent sure what they were going to do with the door panels, but said they would figure out something to make it better. KY isn't that far from IL.
 
Yeah,
Somewhere I found your post that you were from ILL,
Btw, Great team this year,
anyway, I paid 1500 for mine, and knock on wood.. I haven't done any "major" work to it.
I intend to do so, since the blazer deal fell through, This spring.
Going to hit the junkyards sometime this week.
T.
 
I only Paid $700.00 for mine on Ebay. But as you can see I have spent a lot to get it in good mechanical shape. It has 124,112 miles on it as of today. If I can get the gas millage up to where it should be, put a front spoiler on it, and get the interior fixed, it will be like new. I intend to keep it for a long, long time.

Hope you have better luck with the junk yards around you. The ones me do not have any 86-91 Sevilles, much less one with the right parts.
 
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