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2002 STS, 2005 STS, 2007 DTS
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Discussion Starter #1
Hi,
I have a 2002 STS with 99k miles.
If the car has been sitting for more than 30 mins or so and I start the engine, it will idle a bit rough and misses like it's running on 7 or less cylinders. This goes on for about 5-8 seconds then it runs perfectly for the entire trip until next time it sits with the engine off. For example, when I go to a store, shut it off, do my business and come back to restart the engine, as long as it's been less than 30 mins it runs fine, if it's been sitting longer, it will do what I've described above.
When it acts up, I get a random engine missfire code, but after driving for a short while, the CEL goes away.

My initial thought is the head gasket (s) is starting to bleed some coolant into the cylinder(s) when the car is off and the cooling system is still pressurized.

Any other ideas?
 

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2002 STS, 2005 STS, 2007 DTS
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Discussion Starter #3
No I have not had to add any and I just checked this morning, but this symptom just started within the last week or so. I was planning on flushing the fluid anyway, it's time. What is the procedure for properly bleeding a closed pressurized system? I've drained, flushed and refilled other cars, but all had a cap on the radiator.

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I was going to add bars leak head gasket repair to the new coolant after I complete the flush, as a last resort effort to try and save from tearing down the engine or at least to get me through the rest of winter, since the leak is still so minor, if I even have a coolant leak. Has anyone had any success with that product?
 

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2010 DTS
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87,448 Posts
:tisk: DO NOT put any snake oil in the engine, trans or fuel tank! If you are not overheating or adding coolant, the HG's are probably fine. HG repair in a bottle will not work anyway.

How does it start when cold? If you are only having hard hot start problems, it's probably a leaky FPR.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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20,124 Posts

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Registered
2002 STS, 2005 STS, 2007 DTS
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8 Posts
Discussion Starter #6
What is a FPR.

The rough idle is the same with a cold or hot engine. It has to do only with how long the car sits.

I remember using "head gasket in a can" about 4 years ago on my Ford Taurus that was leaking coolant out the side and onto the rear exhaust pipe at about a rate of 1 gallon per 10 miles. I bought the Bars product as a last resort and it immediately stopped the leak and the car still runs great even after 4 years. That's why I wanted to try it on this one.

Also, in the cavity under the intake manifold, there is a large amount of oil. I siphoned about 1/2 quart of oil about a month ago when I replaced the intake plenum; I also noticed that the side of the block in the "V" cavity was wet right below the head gasket; today I checked under there with a flashlight and there is about a cup full of dirty oil under there. Is that from a leaky head gasket too?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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20,124 Posts
What is a FPR.

The rough idle is the same with a cold or hot engine. It has to do only with how long the car sits.

I remember using "head gasket in a can" about 4 years ago on my Ford Taurus that was leaking coolant out the side and onto the rear exhaust pipe at about a rate of 1 gallon per 10 miles. I bought the Bars product as a last resort and it immediately stopped the leak and the car still runs great even after 4 years. That's why I wanted to try it on this one.

Also, in the cavity under the intake manifold, there is a large amount of oil. I siphoned about 1/2 quart of oil about a month ago when I replaced the intake plenum; I also noticed that the side of the block in the "V" cavity was wet right below the head gasket; today I checked under there with a flashlight and there is about a cup full of dirty oil under there. Is that from a leaky head gasket too?
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What is a FPR
Fuel Pressure Regulator -

here is a "translator" page -
http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/205754-acronyms.html


I remember using "head gasket in a can"
about 4 years ago on my Ford Taurus

that crap won't work on a Northstar motor -
DON'T DO IT -

Northstar head gasket failures RARELY - if ever -
involve external leaks of either oil or coolant -

they also don't transfer oil into the coolant -
or coolant into the oil -

the normal symptom of head gasket failure in a Northstar motor is -
exhaust gasses in the cooling system -

-----------------
your head gaskets are just fine -

-------------------------

now - getting back to your problem -

check for codes -

check for a leaking FPR -

check for a leaking fuel injector -
 

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Discussion Starter #8
Ok thanks for the suggestions.

IS the FPR vacuum regulated as in the older cars or is it electronic? If so, how do I check it for leaks?
I should've checked the injectors while I had a fuel rail out. Anyway, I do not recall seeing any fuel injector bleeding fuel while I had the rail suspended above the manifold.

When I first start the car every time, cold or warm, I hear a loud noise like a jet turbine from the engine compartment, after about 10 seconds it turns off. Is that an external vacuum pump or something like that? Could this be related to the misfire issue at start up?

The only code that comes up is random engine misfire (p0300).

What about my other issue. Lots of oil in the V cavity. The valve cover gaskets are new so it can't be that, that's why I thought it was the head gasket.

Now I have a new issue. I have no heat. The heater hoses that go in/out of the firewall do get very hot when engine is at normal operating temperature, but I get only cold air from the heater vents. When I rev the engine 2500-3k rpm's I get a little bit of warm air from the heater vents. The coolant reservoir is full. I thought it could be a plugged up heater core. Any thoughts?

I just bought the car a month ago so I don't know much about it's history. It has relatively low miles 98k.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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nojodas67 said:
IS the FPR vacuum regulated as in the older cars
Yes.

how do I check it for leaks?
Disconnect the vacuum line from it with the engine idling. Any sign of fuel at the nipple indicates a ruptured diaphragm - bad FPR.

When I first start the car every time, cold or warm, I hear a loud noise like a jet turbine from the engine compartment, after about 10 seconds it turns off. Is that an external vacuum pump or something like that? Could this be related to the misfire issue at start up?
That's the A.I.R. pump. It pumps fresh air into the exhaust upon cold start, to allow the cat to reach an efficient temperature more quickly.

What about my other issue. Lots of oil in the V cavity. The valve cover gaskets are new so it can't be that, that's why I thought it was the head gasket.
Failed head gaskets don't leak oil. The valve cover gaskets are the only possibility. It's probably just left over from before they were replaced.

Now I have a new issue. I have no heat. The heater hoses that go in/out of the firewall do get very hot when engine is at normal operating temperature, but I get only cold air from the heater vents. When I rev the engine 2500-3k rpm's I get a little bit of warm air from the heater vents. The coolant reservoir is full. I thought it could be a plugged up heater core. Any thoughts?
If both hoses are hot, the core isn't plugged.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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20,124 Posts
Ok thanks for the suggestions.

IS the FPR vacuum regulated as in the older cars or is it electronic? If so, how do I check it for leaks?
I should've checked the injectors while I had a fuel rail out. Anyway, I do not recall seeing any fuel injector bleeding fuel while I had the rail suspended above the manifold.

When I first start the car every time, cold or warm, I hear a loud noise like a jet turbine from the engine compartment, after about 10 seconds it turns off. Is that an external vacuum pump or something like that? Could this be related to the misfire issue at start up?

The only code that comes up is random engine misfire (p0300).

What about my other issue. Lots of oil in the V cavity. The valve cover gaskets are new so it can't be that, that's why I thought it was the head gasket.

Now I have a new issue. I have no heat. The heater hoses that go in/out of the firewall do get very hot when engine is at normal operating temperature, but I get only cold air from the heater vents. When I rev the engine 2500-3k rpm's I get a little bit of warm air from the heater vents. The coolant reservoir is full. I thought it could be a plugged up heater core. Any thoughts?

I just bought the car a month ago so I don't know much about it's history. It has relatively low miles 98k.
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IS the FPR vacuum regulated
YES -

how do I check it for leaks
pull the vacuum supply hose off the FPR -
if there is ANY HINT of gas in the vacuum hose -
the diaphragm inside the FPR has ruptured -
and engine vacuum is sucking in gas -

I first start the car every time, cold or warm,
I hear a loud noise like a jet turbine

that's the air injection pump -
it pumps air into the catalytic converter - to help "light it off" -

The only code that comes up is
random engine misfire (p0300).

our cars will not display WHICH cylinder is misfiring -
it takes a hand-held scanner to do that -
go to AutoZone - Oreillys - NAPA - whatever -
and have them scan for codes - they will do it for free -
P0301 is cylinder #1 - P0302 is cylinder #2 - P0303 is for #3 - etc -

find out which cylinder is causing trouble and report back with the findings -

Lots of oil in the V cavity
I thought it was the head gasket

without an inspection - I can't tell you what it COULD be -

but I CAN tell you - it is NOT a head gasket problem -

failed head gaskets on a Northstar motor DO NOT leak oil -
they also DO NOT mix oil in the coolant - or coolant in the oil -
as are the symptoms of almost every other motor -

I have no heat
IF the heater hoses at the firewall are both hot -
the heater core is just fine -
you have a MIX DOOR or MIX DOOR ACTUATOR problem -
try this -
run the temperature control from 60 to 90 and back several times -
if the MIX DOOR is stuck - this might free it up -
if it doesn't help - the actuator probably needs replacing -

check for Diagnostic Trouble Codes -

if you don't know how - go here and read the ENTIRE post -

http://www.cadillacforums.com/forum...ncluding-1985/138257-how-pull-codes-dtcs.html

if you have any codes - post them here -
ALONG WITH THEIR DEFINITIONS -

I would expect a MIX DOOR fault of some sort -

DAMN - MC beat me - AGAIN
 

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Discussion Starter #11
First of all...thanks for the detailed responses. I have responded in red this time.

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IS the FPR vacuum regulated
YES -

how do I check it for leaks
pull the vacuum supply hose off the FPR -
if there is ANY HINT of gas in the vacuum hose -
the diaphragm inside the FPR has ruptured -
and engine vacuum is sucking in gas -
Ok, I will look for that soon.

I first start the car every time, cold or warm,
I hear a loud noise like a jet turbine

that's the air injection pump -
it pumps air into the catalytic converter - to help "light it off" -
IS it normal for the air pump to go on every time the engine is started?

The only code that comes up is
random engine misfire (p0300).

our cars will not display WHICH cylinder is misfiring -
it takes a hand-held scanner to do that -
go to AutoZone - Oreillys - NAPA - whatever -
and have them scan for codes - they will do it for free -
P0301 is cylinder #1 - P0302 is cylinder #2 - P0303 is for #3 - etc -

find out which cylinder is causing trouble and report back with the findings -
I do have a handheld code reader...CEL is off now, but the one time it went on I checked the code and it was p0300. Next time I drove the light went off.
The CEL goes on once in a while, but as the car idles for a few minutes, it stops misfiring so then the CEL goes off after a few miles of driving.


Lots of oil in the V cavity
I thought it was the head gasket

without an inspection - I can't tell you what it COULD be -

but I CAN tell you - it is NOT a head gasket problem -

failed head gaskets on a Northstar motor DO NOT leak oil -
they also DO NOT mix oil in the coolant - or coolant in the oil -
as are the symptoms of almost every other motor -
I had the plastic intake manifold off where I could clearly see the starter motor (bad place for it BTW). And there was a lot of oil (at least 1/2 quart) in the cavity. The only source nearby that would accumulate there would be the head gasket. So I scooped it up, cleaned the whole area really well. 2-3 days later, I checked under there with a flashlight and there was a lot of oil there again. The side of the V that is towards the firewall, below the rear cyl. head was wet with oil, so I thought that the oil must be running out of the head gasket right below the rear head, and down the side of the V cavity and pooling at the bottom.
I have no heat
IF the heater hoses at the firewall are both hot -
the heater core is just fine -
you have a MIX DOOR or MIX DOOR ACTUATOR problem -
try this -
run the temperature control from 60 to 90 and back several times -
if the MIX DOOR is stuck - this might free it up -
if it doesn't help - the actuator probably needs replacing -

check for Diagnostic Trouble Codes -

if you don't know how - go here and read the ENTIRE post -
I'm thinking the Mix door is ok, because when I change temps from 90-60, I hear a difference in the air sound and the incoming air goes from lukewarm to ice cold (outside air) and vice versa at the panel vents, so the Mix door is moving. There are no other codes stored in the ECM or PCM.

http://www.cadillacforums.com/forum...ncluding-1985/138257-how-pull-codes-dtcs.html

if you have any codes - post them here -
ALONG WITH THEIR DEFINITIONS -

I would expect a MIX DOOR fault of some sort -

DAMN - MC beat me - AGAIN


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Again, Thanks for your help. My comments are in red.
Yes.

Disconnect the vacuum line from it with the engine idling. Any sign of fuel at the nipple indicates a ruptured diaphragm - bad FPR.

That's the A.I.R. pump. It pumps fresh air into the exhaust upon cold start, to allow the cat to reach an efficient temperature more quickly.

Failed head gaskets don't leak oil. The valve cover gaskets are the only possibility. It's probably just left over from before they were replaced.
I siphoned all the oil that was there and I got a bit over half quart; 2-3 days later, I looked under the manifold and there was a lot of oil there again. I checked the dipstick and it was 1 quart low.

If both hoses are hot, the core isn't plugged.
I'm thinking it may be partially plugged, because I get a little bit of heat (just warm air, not hot), but only when the engine is revved up to 2.5-3k rpms. So if some coolant is flowing through the core, the return hose will still be hot, right?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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20,124 Posts
First of all...thanks for the detailed responses. I have responded in red this time.



----------

Again, Thanks for your help. My comments are in red. I'm thinking it may be partially plugged, because I get a little bit of heat (just warm air, not hot), but only when the engine is revved up to 2.5-3k rpms. So if some coolant is flowing through the core, the return hose will still be hot, right?
-----------------------------
I'm thinking it may be partially plugged,
well - flushing it certainly won't hurt anything -
but - if the inlet hose was hot - and the outlet was substantially cooler -
THEN you have the symptom of a plugged heater core -

with the reduced circulation of hot coolant
through the partially plugged heater core -
the coolant spends more time in the heater core - and looses more heat -
so the outlet hose is usually much cooler than the inlet -

another possibility is that the RECIRCULATION door is stuck open -
allowing cold - outside air in -
the RECIRCULATION DOOR is automatically fully closed
in both the 09* and 60* settings -

try manually selecting the RECIRCULATE position -
do you hear the door move -
 

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Discussion Starter #13
Ok I will try flushing the system.
How do I bleed the cooling system when I refill it?

If I remove the glove box, can I gain access and be able to see the recirculate door?
I will check the recirculate position and report back.
 
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