5.0 efi motor knocking

[ekalley]

I bought a 1990 f-150 with the 5.0 efi motor. Ran fine when i got it three days ago. Going down the road i lost power and it started knocking. I checked the vacuum it is steady at 18inches. Compression is 100 - 115psi in all cylinders. When cold the motor doesn't knock until given gas. After it warms up the knocking gets louder. I'm lost please help

Thanks, Eric

[dfordski]

Scan for error codes.

[ekalley]

I tried that and not pulling up any error codes engine light never comes on either. I am in the process of getting the motor out i'm going to tear it apart hopefully I can see whats going on. Thanks for the reply

Eric

[dfordski]

If your CEL light doesn't come on temporaraly at start up, the bulb is out or PCM prob.

[ekalley]

It does come on at start up i took it to ford dealer they ran the test said no errors were found.

[ekalley]

I think i'm going to just put all new cam bearings and rods it the motor and what ever else it needs when i tear it apart. Any ideas on what else i need to change while i have the motor apart.

[rhandwor]

Looking at the compression and knocking I would get it bored and install new pistons and rings while it is apart. Also do a valve job while apart. Sometimes lifters make noise but not a knock. For the amount of work to install new bearings I would do a rebuild.

[dfordski]

Originally Posted by rhandwor

Looking at the compression and knocking I would get it bored and install new pistons and rings while it is apart. Also do a valve job while apart. Sometimes lifters make noise but not a knock. For the amount of work to install new bearings I would do a rebuild.

Ditto An engine is only as strong as it's weakest link. My 87' 5L tests +- 2 psi of 180/ cylinder. Only 78k, the last 25k running synthetic w/ a stablizer added to insure upper end lube filming for start ups. Switching to Synth. after break-in will insure the most return on your investment!