: runaway eng Speed -Glowing exhaust -4.6L N*



C170B
08-26-06, 10:38 PM
I just replaced FPR on 1994 Concours 4.6L .

Cranked it up and Engine is runaway will not idle down. 2500 + RPM. Loud
throaty sound on start up.

I let it run about 3 minutes and shut it off. It is dark outside and I was really shocked when I noticed Bright orange glow between rear of engine on firewall cowling. Cherry red to orange...

This was to be a simple driveway replacementof FPR on 94 N* Concours.

Unless some one can help me w advice quickly I may have to purchase another vehicle or find a commercial repair shop.

What did I do wrong ? THe FPR replacement was straight forward, installed the "O" ring supplied w part.

Why won't it idle normally as before the FPR was replaced?

regards,

codewize
08-27-06, 12:03 AM
I've never done the job before but my first guess would be a bad or mis-adjusted regulator allowing to high of pressure.

I'm only guessing because you're asking for immediate help.

dkozloski
08-27-06, 12:21 AM
You've got a huge intake leak. Calm down and wait 'til daylight. You'll be okay.

Ranger
08-27-06, 11:20 AM
'94 had the FPR inside the intake as I recall. Either you installed it wrong and are leaking raw gas into the manifold (which would explain the glowing cat) and/or you installed the manifold cover wrong and as Koz said, you have a bad vacuum leak (which would explain the high RPM's).

dkozloski
08-27-06, 11:43 AM
'94 had the FPR inside the intake as I recall. Either you installed it wrong and are leaking raw gas into the manifold (which would explain the glowing cat) and/or you installed the manifold cover wrong and as Koz said, you have a bad vacuum leak (which would explain the high RPM's).

Lean mixtures give a glowing exhaust because the mixture is burning so slowly that it is still burning in the exhaust manifolds and even back through the intake port. This is how fuel dragsters can launch the blower. This is also why an intake leak burns up exhaust valves if given a little time. A rich mixture gives cool combustion which is why aircraft engines are richened up at high power settings to help cooling. If you use an exhaust gas temperature gauge to plot exhaust temp Vs. mixture and power you will find that peak exhaust temp comes just a little on the lean side and a little down on power. As you richen the mixture the exhaust temp drops until you get max power about 100deg.F down from the peak exhaust temp. Best economy comes about 25deg.F on the rich side of the EGT peak. Some aircraft engines cruise way over in the lean region but the exhaust can be very erosive in this mode. Lean mixtures destroy a turbocharger and burn up exhaust systems in short order.

eldorado1
08-27-06, 02:35 PM
Lean mixtures give a glowing exhaust because the mixture is burning so slowly that it is still burning in the exhaust manifolds and even back through the intake port. This is how fuel dragsters can launch the blower. This is also why an intake leak burns up exhaust valves if given a little time. A rich mixture gives cool combustion which is why aircraft engines are richened up at high power settings to help cooling. If you use an exhaust gas temperature gauge to plot exhaust temp Vs. mixture and power you will find that peak exhaust temp comes just a little on the lean side and a little down on power. As you richen the mixture the exhaust temp drops until you get max power about 100deg.F down from the peak exhaust temp. Best economy comes about 25deg.F on the rich side of the EGT peak. Some aircraft engines cruise way over in the lean region but the exhaust can be very erosive in this mode. Lean mixtures destroy a turbocharger and burn up exhaust systems in short order.

Agreed w/lean condition and likely vacuum leak somewhere. Check manifold cover gasket... Maybe remove and retorque.

C170B
08-27-06, 02:41 PM
Thanks to all of you for your input and support.

I actually got a little excited, thought it was fire truck time.


It seems like a simple job and I even had a small tool made to press the "0" ring in bottom of FPR. But I don't have even the haziest idea of what the FSM stated about replacement procedure.

I am determined to buy the right manual on EBAY or go to big library .

Massive manifold leak as suggested does sound plausible as I did have to install it twice.

Let me describe replacement as I saw it.

The FPR is inside the top of an engine cover [ beauty cover? ] Could this be termed a manifold cover? I bled the fuel pressure from a schrader valve then removed the engine cover. The FPR is setting in full view and held in place by the plastic spacer/gasket. Carefully lifting this spacer allows R&R of the FPR.

Lifting this full perimeter spacer /gasket also lifts what I think are the actual injector bodies. They are snapped in like fish on a stringer! there appeared to be a greeen silicone rubber seal at base of injector/cyl head? TWO came loose and I tried to put them back in location w a long screw driver. I did not want to distrub them but apparently did so.

There are twelve cover (12) bolts w rubber cushioned washers to evenly distribute the pressure and prevent leakage. The bolts all look like they are same length, NOT so. Carefull examination of cover reveals that the two on R Side facing eng are shorter. I methodically place removed parts on a shop cloth so I reinstall same bolt in same hole. Fooled me once.

The post about Fuel Dragster Blower/ exhaust is about to sink in that something is wrong inside my engine , like an injector not seated. Blow torch down iside the CAT?

Thank you for helping maybe I can save this job. Embrassing to create problems while trying to install such a simple part.

dkozloski
08-27-06, 02:45 PM
It's a simple problem with a simple solution. Hang in there!

Ranger
08-27-06, 05:26 PM
Well I'll be dipped. I had it bassackwards. I could have sworn that a rich mixture was blamed for glowing exhaust manifold in a not too distant thread. Oh well, live and learn. Thanks for the correcting me Koz.

C170B,
On your car that is the manifold cover. On the 95+ engines if is strictly a beauty cover/sound deadener, and unlike your engine, the 95+ can be run without the cover as it is nonfunctional.

C170B
08-27-06, 07:06 PM
FOUND IT!

Caddy is purrring like a kitten out in driveway as I write.

LONG LIVE the Northstar


After reading the post esp Kosloski and Ranger it was a huge vacuum leak.

Upon removing the manifold cover I saw the problem.

The sheet metal northstar signage that proudly proclaims 32 valve NORTHSTAR had been pushed under the securing bolts and gasket.

My son would say, Well DUH!

It must have been an opening approx 10 inches by .020 , that is a massive
vacuum leak ! Expertly called on this forum. You guys must wear White hats that say Cadillac.

Thank you Thank You.

Ranger
08-27-06, 07:32 PM
:thumbsup:

dkozloski
08-27-06, 07:38 PM
Well I'll be dipped. I had it bassackwards. I could have sworn that a rich mixture was blamed for glowing exhaust manifold in a not too distant thread. Oh well, live and learn. Thanks for the correcting me Koz.

C170B,
On your car that is the manifold cover. On the 95+ engines if is strictly a beauty cover/sound deadener, and unlike your engine, the 95+ can be run without the cover as it is nonfunctional.
When you lean out your old British twin motorcycle the first thing that happens is the chrome exhaust pipes turn blue, never to be shiny chrome again. If you have a rich mixture it slobbers and struggles to keep running, all the time smoking black and stinking. I learned my lessons the hard way.

dkozloski
08-27-06, 07:41 PM
FOUND IT!

Caddy is purrring like a kitten out in driveway as I write.

LONG LIVE the Northstar


After reading the post esp Kosloski and Ranger it was a huge vacuum leak.

Upon removing the manifold cover I saw the problem.

The sheet metal northstar signage that proudly proclaims 32 valve NORTHSTAR had been pushed under the securing bolts and gasket.

My son would say, Well DUH!

It must have been an opening approx 10 inches by .020 , that is a massive
vacuum leak ! Expertly called on this forum. You guys must wear White hats that say Cadillac.

Thank you Thank You.
I got as a freebie with my CTS a black hat with a Cadillac badge on it. It's pretty chintzy. I used to wear it in the shop to keep grease out of my hair.

Ranger
08-27-06, 07:50 PM
"I learned my lessons the hard way."

Those are the ones you never forget.

dkozloski
08-27-06, 08:02 PM
"I learned my lessons the hard way."

Those are the ones you never forget.


Experience is what you have left after you've ruined everything you own is my motto.

Ranger
08-27-06, 08:07 PM
:histeric::rofl:

FrankT
09-04-06, 11:20 AM
[QUOTE=Ranger;788867]Well I'll be dipped. I had it bassackwards. I could have sworn that a rich mixture was blamed for glowing exhaust manifold in a not too distant thread. Oh well, live and learn. Thanks for the correcting me Koz.

Ranger,
You are also correct, remember the catalytic converter stores oxygen, so when the engine starts to dump extra fuel into it the catalyst it will start to burn off all the extra fuel in that process it will glow red-hot.

Now A misfire is the catalyst worse enemy it will over heat and melt the substrate in a matter of seconds. You didn't have it bassackwards. Both conditions extremely lean causing a misfire or excessively rich causing extreme heat (burn off) will cause the converter to glow red.
Take care,
FrankT