2001 5.4 Expy.... low power issue
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Joined: Jul 2020
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2001 5.4 Expy.... low power issue
Hi folks, looking for some help on how to diagnose my issue, quick breakdown:
I bought a 2001 Expedition with over 200,000 miles, its a California car with full emissions. The owner said the head gasket was bad. When I checked the oil and water no signs of mixing but the coolant was getting pressurized. The truck started and ran and idled fine but seemed to be misfiring bad. Cylinder #1 was dead per the codes it was throwing. After some searching around I figured it more than likely was the intake manifold.
I changed the Intake manifold, spark plugs, new coil on #1 and replaced all the boots on the rest of the coils. Did the passenger side valve cover gasket cause it was leaking, new air filter, new fuel filter, new PCV valve and tube, and cleaned the filthy throttle body.
Fired her up and no more missing in the motor but it felt like I wasn't getting close to full power, lag in acceleration like I was hauling a heavy load.
Based on the dead cylinder and unsure of how long the previous owner ran it like that with unburnt fuel dumping into the exhaust I'm dreading the CARB cats.
The truck sat for over 2 years... so I put fresh gas in and when it was less than a 1/4 tank I ran some CATACLEAN through it and it did help smooth it out on throttle response, but still much to be desired.
I took it up to Tahoe and the mountain climbs were painfully slow but with some time I could get it to do highway speeds on the flats.
No check engine light and no pending codes
No sulfur smell
SO MY QUESTION IS:
I got under the truck when it was cold started and could smell exhaust on the passenger side, same bank as the dead cylinder. Could a small exhaust leak on the manifold be enough to cause this?
I purchased new exhaust manifolds when I bought it cause I saw its a known issue and the truck has plenty of miles.
If not, what's the best way to test my Cats to be sure they are either good or bad?
Thanks!
I bought a 2001 Expedition with over 200,000 miles, its a California car with full emissions. The owner said the head gasket was bad. When I checked the oil and water no signs of mixing but the coolant was getting pressurized. The truck started and ran and idled fine but seemed to be misfiring bad. Cylinder #1 was dead per the codes it was throwing. After some searching around I figured it more than likely was the intake manifold.
I changed the Intake manifold, spark plugs, new coil on #1 and replaced all the boots on the rest of the coils. Did the passenger side valve cover gasket cause it was leaking, new air filter, new fuel filter, new PCV valve and tube, and cleaned the filthy throttle body.
Fired her up and no more missing in the motor but it felt like I wasn't getting close to full power, lag in acceleration like I was hauling a heavy load.
Based on the dead cylinder and unsure of how long the previous owner ran it like that with unburnt fuel dumping into the exhaust I'm dreading the CARB cats.
The truck sat for over 2 years... so I put fresh gas in and when it was less than a 1/4 tank I ran some CATACLEAN through it and it did help smooth it out on throttle response, but still much to be desired.
I took it up to Tahoe and the mountain climbs were painfully slow but with some time I could get it to do highway speeds on the flats.
No check engine light and no pending codes
No sulfur smell
SO MY QUESTION IS:
I got under the truck when it was cold started and could smell exhaust on the passenger side, same bank as the dead cylinder. Could a small exhaust leak on the manifold be enough to cause this?
I purchased new exhaust manifolds when I bought it cause I saw its a known issue and the truck has plenty of miles.
If not, what's the best way to test my Cats to be sure they are either good or bad?
Thanks!
Laughing Gas
Joined: Feb 2003
Posts: 877
Likes: 27
From: South Florida
Call around to some of the exhaust shops in your area. They have a backpressure test gauge that they put in the front O2 sensor hole and measure exhaust backpressure per side. They can tell you if your Cats are bad or clogged up. Or other people run SeaFoam through an intake vacuum line and it also helps clean out the cats. But yours may be damaged beyond repair and need to be replaced anyway.
Fleet Owner
Joined: Apr 2008
Posts: 24,318
Likes: 5,128
From: 0,0,1
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New User
Joined: Jul 2020
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thanks for the input guys... I’m assuming the upstream O2 sensor is the one closest to the motor?
Fleet Owner
Joined: Apr 2008
Posts: 24,318
Likes: 5,128
From: 0,0,1
Yes it is. The one before the cat is upstream and the one after is downstream...just like the flow of a river.
Laughing Gas
Joined: Mar 2019
Posts: 947
Likes: 144
From: Columbus Ohio
Hey Hamfisted... we are on the Expedition Forum together...lol
that's a tell tale sign of a clogged cat. Mine did that a few years ago, and was so slow it couldn't get out of it's own way! Replaced that cat and all was good again.
that's a tell tale sign of a clogged cat. Mine did that a few years ago, and was so slow it couldn't get out of it's own way! Replaced that cat and all was good again.
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