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New cat still glowing and rough idle


I am just about stumped. Please read below and let me know if you have anything to offer.

The subject is a 2003 Ford Escape with a 3.0L V6.

Symptoms in order of notice:
Leaking oil pan
Leaking front cover
Leaking crankshaft seal
Leaking transfer case (possibly unrelated)
Leaking valve cover
Slight rough idle

Replaced / Results:
all intake manifold gaskets / no changes
Front cover / stopped leaking
crankshaft seal / stopped leaking
oil pan gasket / stopped leaking
valve cover gaskets / stopped leaking

After the above repairs were complete the car was started and there is a loud squeak, knock, then a rough Idle.
The rough Idle appears to go away at about 3000 RPM. There is no smoke from the tailpipe.

Symptoms in order of notice:
Rougher idle than before
Glowing red catalytic converter after a few minutes (referred to as ‘glow’)
melted baffling spewing out of exhaust (caused by hammering to remove manifold)
much louder exhaust
slight smell of gasoline
Check engine light (code for O2 sensor)

Tests / Results:
spark plug boots / strong regular spark
remove spark plug boot on cylinders 4 and 6 while car is running / no change in idle or ‘glow’
swapped spark plugs / no change in idle or ‘glow’
swapped boots / no change in idle or ‘glow’
Compression test / constant increase in pressure up to 182

Replaced / Results:
Exhaust manifold gasket / quieter exhaust (still slightly noisy) bolt sheared off.
Catalytic converter / began to glow on the upstream side of the converter. Immediately shut off.
Upstream bank 2 O2 sensor / no change in idle or glow
Fuel Injectors on 4 and 6 / no change in idle or glow
Replaced IAC / no change in idle or glow
Replaced air filter / no change in idle or glow

Took the car into two mechanics:
Mechanic 1: thought it was a misfire (still considering)
Mechanic 2: thought it was bad injectors (incorrect)

I will be happy to answer any questions to help clarify the situation.
Any direction is appreciated. Thank you.

The thing that I first notice is the combo of the exhaust noise and the sheared-off exhaust manifold bolt. My speculation is there’s an exhaust leak, which is bad news in modern cars. The reason is for the O2 sensor and other mixture controlling stuff to work, the engine has to be air tight from the air intake to the exhaust pipe. Any extra air getting in anywhere will confuse the heck out of the engine computer, and it won’t know how much gasoline to inject. This can cause all sorts of problems, a glowing cat one of them. So first off, make sure your exhaust path is 100% air tight.

A glowing catalytic converter means raw fuel is in the catalytic converter. So that converter is shot.

There’s too much fuel being introduced into the engine.



I agree with your opinion. I will drill out the old bolt and re thread the hole. I will have to remove some front-end components to get some room to drill and tap the hole so give me a few days.
I will post again when I take care of this problem.


I appreciate your opinion and agree that I think there is too much fuel being introduced into the engine. However, the current catalytic converter started glowing upon first ignition after installation. The old catalytic converter was also glowing. I find it hard to believe that the brand new catalytic converter is shot. I would also rather spend the time to drill and tap one hole than to spend the money for a new cat.

Thank you both for your timely responses.

Tester is correct about the converter. There really are only 3 reasons for a converter to glow red.

  1. Excess fuel as mentioend by Tester.
  2. The converter is clogged. Should not be an issue if new.
  3. The exhaust system is clogged a bit further downstream.

It may be hard to believe because it is so much money but once they start glowing, they are usually damaged. Normally, you would want to correct the reason the original one was glowing before installing a new one to prevent throwing away all that money.

Pulling off spark plug wires to check engine effect is also not a good practice. You can easily damage ignition coils and other electrical parts. They are not designed to withstand that kind of abuse anymore. Maybe OK with vintage iron but not on a modern car.

The engine control computer is very good at recognizing ignition miss. If it is not flashing the check engine light, likely there is no miss. It’s dumping excessive fuel. That could be from many sources ranging from a bad temperature reading causing it to stay in open loop, bad readings from the oxygen sensors, bad fuel pressure, bad injectors…a scanner will help to rule out some of those but this is not a problem I would be shooting at blindly…

It sounds like you have a misfire, on cylinders 4 and 6.

Check your wiring to the ignition coils on those 2 cylinders, as I assume you had them off to do the other repairs you listed. You may have the wires reversed. If the wiring to those coils looks properly routed, they aren’t. If they look awkward and stretched, they’re correct.

Thanks for your second on Tester.
I disconnected downstream the cat and the old one was still glowing.

Would it help if I re installed the old cat until I get the glowing resolved? I thought if I used the old cat it would throw off O2 sensor readings. I will check the O2 sensor reading with new cat while the car is running and return and report. Give me a few days for that one.

I will take heed to your words the next time I pull spark plug wires. Thank you for the advice.

Would you or another reader be able to direct me somewhere I can find more information on what may cause excess fuel to be dumped into the cylinders on fuel injected cars?

I did remove wiring to do other repairs. However, the wiring is not stretched. The length of the wires on these coils makes it difficult to mis-wire.

I still agree that I need to take care of the exhaust problem. I plan on carefully drilling using a 3 size step up process with a vacuum and then tap a new hole. I will leave the current exhaust manifold bolted on for a guide. Any objections or other opinions?

I will also try to get my hands on an O2 scanner to read the levels and return and report.

Thank you all for your input.

Here’s a brief tutorial on possible causes of a rich fuel mixture.

A rich exhaust gas can be caused by an ignition miss also. What would concern me would be the apparent speed with which the converter starts glowing as it’s stated this only takes a few minutes.

Given the red hot converter maybe a compression test is in order because:

  1. Low compression could cause a miss and little change in idle speed with plug boots removed.
  2. A glowing converter can cause problems upstream as it can cook piston rings and cylinder walls.

You say there is no change in idle or glow when pulling plug wire off 4 and 6. How many miles on your engine? I am wondering if you have bad valves on 4 and 6. I started writing this before I saw ok but I agree with him. Bad valves are one of the things that can cause low compression.

Humor me. Swap the wiring for cylinders 4 and 6 and see what happens. What have you got to lose?

Thank you.

A compression test was preformed and dry results returned 182 PSI on each cylinder.
The very top of the brand new converter starts to glow a few minutes after the car has reached normal operating temperature.

If there is a change when I pull the plugs it is so minute I cannot tell.

There are 180000 miles on the engine.

Thanks for your second on ok4450.

Did the compression test verify that compression was normal?

I currently have the front end of the car removed ready to extract the sheared off exhaust bolt from the cylinder head. I hope I can get to this tonight but I will let everyone know when I do it.

Thanks again for your comments.


I took heed to your words and investigated the wiring. I noticed that there was an old sticker on one of the spark plug wires that had a number 6 on it which was plugged into the number 4 cylinder.
I have yet to start the car as I am still working on extracting the exhaust bolt.

Thank you for your suggestion asemaster, I think that may be it. I will return tonight with an update on my progress.


The sheared exhaust bolt was recessed into the head approximately 1/8 of an inch. the bolt came out nicely with a drill bit and an extractor set (2 hrs of work). I would have preferred to use a left handed bit for this job though. The exhaust manifold was then tightened properly and re assembled.

I swapped the spark plug wires fired the car up and she purred like a kitten.

Thank you all for your help and advice, I will remember you in prayer.

Hats off to asemaster for steering you in the right direction. :slight_smile:

Glad you got it up and running again. I think you did better than I would have. I hate drilling broken bolts.