Rare 89' Coupe Deville - Problems

SilkyBrown · #1 (**permalink**) 07-06-09, 08:21 PM

My 1989 Coupe Deville (4.5L V8) has been acting up. I tried to start the car a couple days ago and all of a sudden i heard the RPM's go very high while ideling.. Its a continuous sound that does not go down until i put it into drive. The sound is still there in drive but it sounds a little less noisy.

Also as soon as i shift it into drive the car automatically takes off whithout me pressing on the gas. And not just a little, it takes off up to a top speeds of 80 km/h. I didn't press the gas the whole way home (About 10 km's , had to get home).

I immediately knew from this point that the car had a serious problem and i should not drive it anymore. I then proceeded to pull the DTC Codes. Here they are:

E26
E27
E48

I checked the definitions and it says it has something to do with the Throttle Body. I let the car sit for the night. The next morning i started her up just to see how she would react. I immediately heard the same high RPM Sounds... But then all of a sudden i hear liquid spilling, I check under the car and all i see is a huge puddle of Coolant and its continuously pouring out of the car. From what it looks like all of it poured out. At this point i dont under
stand whats going on with my car.

Can anyone tell me what the most likely cause of this problem? I am towing her to the shop this weekend. I just want to know what it could potentially be.

Could this be a blown headgasket? I didnt think so because it was pouring from under the bottom of the engine and not the top.

Any help is appreciated. Thanks in advance!

**Ranger** · #2 (**permalink**) 07-06-09, 09:29 PM

If it was leaking from the coolant reservoir overflow, it could be a head gasket, but without knowing exactly where it was coming from, it's hard to say.

SilkyBrown · #3 (**permalink**) 07-07-09, 09:29 AM

Ok i'm assuming the resevoir overflow is somewhere at the bottom of the engine? Do u think the coolant leak is related to the HIGH RPM issue? And the fact that the car takes off in Drive without me touching the gas pedal

**Ranger** · #4 (**permalink**) 07-07-09, 11:04 AM

No, the coolant reservoir is up top near one of the fenders. It is where you add coolant. It is not related to RPM.

SilkyBrown · #5 (**permalink**) 07-07-09, 11:53 AM

Ok Great so now i have more than one issue.. Now that we got that out of the way.. What could be causing this Throttle Body issue... High RPM's at Idle... And the fact that my car drives itself? lol

**Playdrv4me** · #6 (**permalink**) 07-07-09, 06:23 PM

Your car is "driving itself" because the throttle is behaving as if it is mashed down. Obviously as soon as you put the car in "D" it's going to take off like a banshee. The car will crawl along with the engine running even at normal idle once it is put into Drive. I assume that it is also alot more difficult than normal to put the car in "D"? It is really NOT good for your transmission to have that kind of load as it slams into gear.

I don't know anything about that car you have, but I had this exact same issue on a 1990 LS400 Lexus and a rubber piece of intake hose had actually got sucked into and stuck in the throttle plate causing the RPMs to skyrocket as soon as the car was started. Had my mom been driving it when that happened it could have been disastrous. If the car has one, I suppose a Throttle Position Sensor could also cause similar behavior.

ehall · #7 (**permalink**) 07-07-09, 09:12 PM

Are you sure it was coolant spilling out? Maybe it has been overflowing for a bit and some of it sprayed onto the throttle body causing it to get sticky.

There is a handy OBDI reference on the site here http://www.cadillacforums.com/forums...x-engines.html (OBD I codes for 4.x Engines). E26 and E27 both point to the throttle switch, which is an ON-OFF sensor inside the Idle Speed Controller assembly. E48 points to EGR valve. Either the top of the engine got coated with coolant or it's been let go.

codewize · #8 (**permalink**) 07-08-09, 12:13 AM

I think without even playing around your idle problem would be resolved by replacing the ISC motor and the TPS. Had the same types of things on my 89 STS with the 4.5

It's also possible that the gasket under the throttle body is leaking. I had to replace mine as well but I'm willing to bet it's one or both of those sensors.

The good thing is these cars are extremely easy to work on. You could probably do all the work yourself in an hour or two with some basic hand tools.

Coolant loss is another issue.