Hits a wall accelerating

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Jun 20, 2023 | 08:29 PM

Ba Mustang

Thread Starter

Trailering

Joined: May 2023

Posts: 18

Likes: 13

Hits a wall accelerating

I have an issue where my 98 4.6 will hit a wall when trying to accelerate. It happens around 2500-3500 rpm no matter what gear I’m in. It idles fine and cruises down the road just fine. When it hits the wall I can let off the gas, give it throttle again and I may gain 500 rpms before it hits the wall again. I previously had issues with misfires and lean codes but those have since gone away. I tried cleaning the egr valve with carb cleaner but that hasn’t changed anything. The engine also revs freely in park so only happens when under a load.

These are the parts I’ve replaced so far to deal with the misfire and lean codes I had previously. I’ve put 30+ miles in it since replacing these and no codes have shown back up. One known issue is the speedometer is off due to larger tires, I’m currently waiting on the replacement speedo gear.

Spark plugs
Fuel filter
Fuel pump
Fuel pressure regulator
Upstream O2 sensors

is a video I recorded of it going through first and second. About half way through I have my foot to the floor and hold it the rest of the time.

Jun 21, 2023 | 04:16 AM

Jon Freeman

More Turbo

Joined: Sep 2017

Posts: 574

Likes: 146

Maybe transmission problems ?

Jun 21, 2023 | 05:43 AM

Ba Mustang

Thread Starter

Trailering

Joined: May 2023

Posts: 18

Likes: 13

Quote:

Originally Posted by Jon Freeman

Maybe transmission problems ?

I’m starting to think that is the problem. Fluid looked good though, may have been slightly overfilled. I forgot to try it but I need to go back and manually shift the transmission to see if it still does it.

Jun 21, 2023 | 12:04 PM

70f100longbed

Fleet Mechanic

Joined: Aug 2002

Posts: 1,900

Likes: 29

From: Raleigh USA

Cats are probably restricted. You could try loosening the pipes at the manifold and see if it still hits the wall. Highly doubt its a trans problem. I've also seen the plastic cone come off the air filter and block the flow when it was under a load.

Jun 21, 2023 | 12:21 PM

Ba Mustang

Thread Starter

Trailering

Joined: May 2023

Posts: 18

Likes: 13

Quote:

Originally Posted by 70f100longbed

My coworker and I were talking about a good way to test out the cats, I'll have to give that a try. I may go ahead and remove the filter during a test drive to also eliminate that possibility.

Jun 21, 2023 | 07:21 PM

97F250guy

4th Gear

Joined: Jun 2023

Posts: 4

Likes: 1

From: St. Louis

Quote:

Originally Posted by 70f100longbed

I am thinking the same thing, if the transmission was slipping that badly it should stink of burned clutch material.

Jun 22, 2023 | 10:17 AM

Hit Man X

Lead Driver

Joined: Sep 2002

Posts: 9,568

Likes: 2,036

From: North Texas

Cats or fuel delivery.

Fuel filter installed correctly? I have pulled them off backwards before. May want to get a gauge and run it to the cabin to check pressure under heavy load.

Maybe with a scan tool you could see O2 data under load too.

For cats, I would just remove the front O2s and go for quick spin. Truck been sitting? Maybe some critter built a nest in the tailpipe. Happened on my 4.9 truck I pulled from junkyard...big cloud of acorns came out of it.