how do you know when to replace Cat
New User
Joined: Apr 2001
Posts: 2
Likes: 0
how do you know when to replace Cat
How do you know when your Catalydic Convertor is bad. I know the ole when you start smelling rotten eggs. I have a 93 F150 4.9L
with 180,000 and it has never been replaced, I have recently started getting a slight miss when I take off. I have changed Plugs, wires and am still getting it. It isnt that bad and truck runs good just really anoying.
Thanks
with 180,000 and it has never been replaced, I have recently started getting a slight miss when I take off. I have changed Plugs, wires and am still getting it. It isnt that bad and truck runs good just really anoying.
Thanks
Senior User
Joined: Feb 2001
Posts: 230
Likes: 0
how do you know when to replace Cat
Your problem is probably not being caused by the cat. A bad cat will effect all cylinders, not just one.
Test for a bad cat with a vacuum gauge. Take a manifold vacuum reading at idle. Take another reading at a steady 2000 RPM. The reading at 2000 RPM should be HIGHER than the reading at idle. If it's not, suspect a clogged cat. A good shop can confirm it for you with an exhaust backpressure test.
The older 4.9s were good for clogged/leaky injectors. A static fuel pressure test will show if an injector is leaking. A good cleaning will cure a clogged injector.
One question...have you done a cranking compression test?
Test for a bad cat with a vacuum gauge. Take a manifold vacuum reading at idle. Take another reading at a steady 2000 RPM. The reading at 2000 RPM should be HIGHER than the reading at idle. If it's not, suspect a clogged cat. A good shop can confirm it for you with an exhaust backpressure test.
The older 4.9s were good for clogged/leaky injectors. A static fuel pressure test will show if an injector is leaking. A good cleaning will cure a clogged injector.
One question...have you done a cranking compression test?
Lead Driver
Joined: May 2000
Posts: 9,236
Likes: 12
From: Senoia, GA
how do you know when to replace Cat
man with 180,000 on them i would go ahead and replace them and while ur at it put an exhaust system on it. Try true duals with 18" glasspack coming out the back of the rear tires. NO TIPS, they look good but sound fake. I've had much experience.
-jason-
-jason-
Fleet Mechanic
Joined: Aug 2000
Posts: 1,504
Likes: 1
From: Texas
how do you know when to replace Cat
You should hear my exhaust. Fake? I think not! It may have a single inlet dual outlet muffler, but I guarantee you this. There isn't a six that I know of that can begin to sound like this!
1988 F-150, SWB, 5.0 EFI (formerly 4.9 EFI), M5OD 5 speed, 3.08 gears, Summit shorty truck headers, Custom built Flowmaster exhaust system. Force 4 LP6000 lightbar, Federal signal PA-300 100 watt siren, Icom IC-V100 50 watt mobile radio.
=======================================
1965 F-100 (just purchased 1/18/01), SWB, 390, C-6 auto. Dual exhaust, Not much else to do to it.
Can see both below.
[link:www.geocities.com/hotrodford_88/|Hotrodford_88's Webpage]
1988 F-150, SWB, 5.0 EFI (formerly 4.9 EFI), M5OD 5 speed, 3.08 gears, Summit shorty truck headers, Custom built Flowmaster exhaust system. Force 4 LP6000 lightbar, Federal signal PA-300 100 watt siren, Icom IC-V100 50 watt mobile radio.
=======================================
1965 F-100 (just purchased 1/18/01), SWB, 390, C-6 auto. Dual exhaust, Not much else to do to it.
Can see both below.
[link:www.geocities.com/hotrodford_88/|Hotrodford_88's Webpage]
