Cadillac Owners Forum banner

1 - 20 of 28 Posts

·
Registered
Joined
·
28 Posts
Discussion Starter #1
Hey everyone, I have browsed through here many times before i registered. I hope to get alot of info regarding my eldo.

Of course i have a question,thanks for asking...


I have a 1993 Cadillac Eldorado Touring Coupe. I purchased this car about a year ago. The engine that was originally in this is now gone. Prior to my purchase. The car has ran wonderfully until recently. It will not idle for nothing. When started, it will race high then low, all day long. I know this sounds like a ISC problem. I took it to a dealer to have them look at it. They were unable to positively tell me what was wrong with it. They did suggest that i replace the ISC unit. Well i did that yesterday. the problem is still there.

Can anyone shed some light on this for me.

Thanks
 

·
Registered
Joined
·
28 Posts
Discussion Starter #3
delzy said:
I'm assuming this is a Northstar. Is the car throwing any codes? This was my similar experience: http://www.cadillacforums.com/forums/showthread.php?t=45939
When you figure it out be sure to post your findings. Good luck.
I'm sorry, Yes this is a Northstar motor, I was told it came out of a STS with 40k. I put about 20k on it since i've had it.

Yes there are some codes.. Nothing current except for P105 ( Brake Booster Vacuum too low)

Other codes that are not current.

P020 Open fuel pump circuit
P052 PCM Memory Reset
P071 Intermittent Map Signal ( already replaced)
P074 Intermittent MAT Signal ( i am assuming this is the one under the intake cover)
P095 Engine Stall Detected
P109 Keep Alive memory
I052 Keep Alive memory error
A048 Low Refridgerant pressure
T072 Serial Data Link Fault
 

·
Cadillac Owners Connoisseur
Joined
·
1,164 Posts
anothereldoowner said:
I'm sorry, Yes this is a Northstar motor, I was told it came out of a STS with 40k. I put about 20k on it since i've had it.

Yes there are some codes.. Nothing current except for P105 ( Brake Booster Vacuum too low)

Other codes that are not current.

P020 Open fuel pump circuit
P052 PCM Memory Reset
P071 Intermittent Map Signal ( already replaced)
P074 Intermittent MAT Signal ( i am assuming this is the one under the intake cover)
P095 Engine Stall Detected
P109 Keep Alive memory
I052 Keep Alive memory error
A048 Low Refridgerant pressure
T072 Serial Data Link Fault
Well, I think that code is telling you exactly what the problem is. If the brake booster vacuum is too low, it's because the vacuum line going to it is broken or disconnected, or the booster itself is leaking because the diaphragm is breached or shattered. That's what's causing your idle problems, most likely. If the dealership couldn't tell you that, I suggest you never go back to those idiots again.

If other codes become current as the car is running, there may be other sensors going bad or a wiring issue or a vacuum leak. Check the codes while it's running and let us know.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #5
mcowden said:
Well, I think that code is telling you exactly what the problem is. If the brake booster vacuum is too low, it's because the vacuum line going to it is broken or disconnected, or the booster itself is leaking because the diaphragm is breached or shattered. That's what's causing your idle problems, most likely. If the dealership couldn't tell you that, I suggest you never go back to those idiots again.

If other codes become current as the car is running, there may be other sensors going bad or a wiring issue or a vacuum leak. Check the codes while it's running and let us know.
I went ahead and cleared the codes, and rechecked. The only code that is now current is P095 Engine Stall Detected. I looked over the brake line. and it appears to be fine.All connected and in good shape.
 

·
Cadillac Owners Connoisseur
Joined
·
1,164 Posts
anothereldoowner said:
I went ahead and cleared the codes, and rechecked. The only code that is now current is P095 Engine Stall Detected. I looked over the brake line. and it appears to be fine.All connected and in good shape.
If the brake booster vacuum line is in good condition and you're absolutely positive that the booster itself is internally OK, then you probably have a vacuum leak somewhere else. There are lots of possibilities here. Do you hear any hissing or rushing air sounds anywhere under the hood while it's running? What if you hold a piece of rubber hose up to your ear and move it around the intake and vacuum hoses?

Did you disconnect and reconnect the battery after installing the new ISC? Has the throttle body been cleaned any time in the recent past?
 

·
Registered
Joined
·
28 Posts
Discussion Starter #7
mcowden said:
If the brake booster vacuum line is in good condition and you're absolutely positive that the booster itself is internally OK, then you probably have a vacuum leak somewhere else. There are lots of possibilities here. Do you hear any hissing or rushing air sounds anywhere under the hood while it's running? What if you hold a piece of rubber hose up to your ear and move it around the intake and vacuum hoses?

Did you disconnect and reconnect the battery after installing the new ISC? Has the throttle body been cleaned any time in the recent past?
I installed the ISC with the battery out of the car. I can almost be positive that the booster is ok. And as far as checking for vacuum leaks, I can't keep the car running on it's own without dying. I will go over all the vacuum lines when i get some more time. I will let everyone know how it turns out. What vacuum lines should i be concerned with at this point? I realize there are plenty in the car, but would like to cut it down to as little possibilities as possible..
 

·
Registered
Joined
·
131 Posts
The brake vacuum line is a BIG HONKER! You better make sure the booster HOLDS vacuum by putting a vacuum pump on it (like a MightyVac) and suck it down... or use the Mark 1 Facial Orifice unit.

Also check your EGR system and your PCV system, each also vacuum-related.
 

·
Registered
Joined
·
3,887 Posts
Wait... Are you running the engine with the beauty cover off? On the 93 and 94, the beauty cover is the top of a huge vacuum chamber. Inside it is the FPR with no vacuum hose attached to it. When there is no vaccum to the FPR, it will screw with your idle speed.

I wouldn't be surprised if this whole problem is due to a misaligned beauty cover.

I would worry about that open fuel pump circut though. Just because it's in history doesn't mean that the problem fixed itself. Remember that the fuel pump is not in use while the engine is off, so there is no way for the PCM to test that circut with the engine off. SO of course it will be history.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #10
Krashed989 said:
Wait... Are you running the engine with the beauty cover off? On the 93 and 94, the beauty cover is the top of a huge vacuum chamber. Inside it is the FPR with no vacuum hose attached to it. When there is no vaccum to the FPR, it will screw with your idle speed.

I wouldn't be surprised if this whole problem is due to a misaligned beauty cover.

I would worry about that open fuel pump circut though. Just because it's in history doesn't mean that the problem fixed itself. Remember that the fuel pump is not in use while the engine is off, so there is no way for the PCM to test that circut with the engine off. SO of course it will be history.
No Sir, everything is in place when i try to start the motor. I think that the fuel pump circuit is due in part becuase i pulled that fuse, and tried to start the engine. It was an oversight on my part.

I did notice however, the problem is neither worse or better with the ISC unplugged. I am completely stumped to this problem. I went over the vacuum lines, all appear to be ok. Just like the map sensor, there is a vacuum line running to the MAT sensor under the intake cover. that is not connected. I tried to find a hose of some sort, and cannot find any that might go to that.
 

·
Registered
Joined
·
3,887 Posts
The MAT (Manifold Air Temperature) sensor doesn't have a vacuum hose going into it, it has wires. I think what you were looking at was the FPR (Fuel Pressure Regulator). The FPR doesn't need a vacuum hose on your car because the whole chamber that it's in is under a vacuum.

Check for irregularities in the gasket on the beauty cover. From the codes, there is definatly a vacuum leak somewhere. The only problem now is finding it.

On all gasoline engines, the vacuum source is the intake manifold. Just follow any tubes or hoses that spiderweb from that.

Hope this helps.
 

·
Registered
Joined
·
44 Posts
check all your engine and ecm grounds . sometimes they can be rusty or broken causing your ecm to get bad signals and make the engine idle go nuts. i had this problem on my old 86 seville. the broken ground was at the psgr side rear of motor. i am not sure where the grounds are for the northstar. good luck
 

·
Registered
Joined
·
28 Posts
Discussion Starter #14
I just wanted to add one more symptom, but before that let me tell you what i did. I thought perhaps i didn't have the ISC adjusted properly, so i went ahead and screwed it in just until it started to lose contact with the throttle. Now i can get it to stay running. It does not jump in RPM's as fast or as high/low as before. Now it will stay between 1000 and 1500, with the occasional 2k spike. When i apply the throttle it will rise in rev's but sounds like the rev limiter is kicking in( at 3-4k). If anyone knows what that is like. then you know what i am talking about.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #15
I went out this morning and looked over the car. I could not find one single problem with a vacuum line. I went ahead and took the intake cover off( beauty cover) and poked around inside. pulled this, tugged on that. I put it all back together. Cleared all codes. restarted. this time it started right up.reved high at first, then it wanted to settle down. Idle quality still sucked. Checked codes, it is throwing the ISC rpm out of range. I am going to poke around here and see how to adjust this properly, as i am sure the aforementioned way i did it was wrong. We shall see what happens this time.

Krashed989,
"I wouldn't be surprised if this whole problem is due to a misaligned beauty cover."
Perhaps this was the issue. Not so much as it being misaligned, but loose.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #16
Ok, i have tried just about everything i can think of. As i said previously, The idle is the same way with the isc connected or not connected. It seems as if the rev limiter is kicking in. I am about to give up on this.
 

·
Cadillac Owners Connoisseur
Joined
·
1,164 Posts
anothereldoowner said:
Ok, i have tried just about everything i can think of. As i said previously, The idle is the same way with the isc connected or not connected. It seems as if the rev limiter is kicking in. I am about to give up on this.
If it does the same thing with the ISC disconnected, then there is a huge vacuum leak somewhere. I don't know anything about how it's set up on a pre-96, so I can't be of much help with the intake, but if there's enough of a leak that the engine gets up to 4k RPMs with the throttle blade closed, it's a huge hole somewhere.
 

·
Registered
Joined
·
28 Posts
Discussion Starter #20
Ok, I unplugged the TPS, and of course it throws a code. So i am assuming that it is working properly when plugged in. Secondly. I unplugged the ISC, and there is NO CODE... What gives? Possible shorting out somewhere?

When unplugged, it does the same thing. I can't even control idle with throttle. When unplugged it dies if i take my foot of the throttle. I am assuming that is what it is suppose to do. Also, i tried to put it into drive( yes it is on jackstands) and see if it would calm down and atleast idle somewhat. No luck. I tried to apply the throttle, and it acts as if it is missing, or some plugs aren't firing. I am assuming that if that was the case, it would toss me some sort of code.

I am at my wits end.. I am almost thinking of paying the 3200.00 to the dealer to put in another engine. Better yet, i might even get a Chrfab motor.
 
1 - 20 of 28 Posts
About this Discussion
27 Replies
9 Participants
anothereldoowner
Top