OK, so I am having problems pinpointing a vacuum leak or leaks. These are my symptoms: when starting to move, engine under load I have low power. Also, at the same time, under load, the vacuum activated hubs start chattering. The chattering goes away as soon as the motor is not under load. The fuel mileage seems to be low, but I'm not sure how low. And, I have a P0020 code check engine light. Not sure if the vacuum & 0020 are related, trying to fix the problems one by one.

I've done the work and vacuum checked everything on the vacuum lines going to and from the hubs, the iwe appears to have been replaced (it has the water shield on it). I've also done the starting fluid test all around the top of the motor, nothing... I have no problem with the idle or stalling at a stoplight.

The Truck: 08 F150 Lariat 4x4 that I bought from Craigslist with 240,000 miles on it. The motor was replaced with a reman motor just under 30,000 miles ago (I have the documentation). I know that the P0020 Code could mean a bad VCT solenoid but I would have thought these would have been new with the reman engine, just under 30,000 miles.

Anyone have any thoughts on this??

 

Have you checked the check valves? Make sure that they are holding pressure.

 

You know, I was just reading about that. No, I have not yet.

As a matter of fact I went ahead and ordered the complete vacuum line set up and 2 check valves because they are cheap. The whole thing cost me 70-80 bucks online.

Thanks for the reply Roadblock.

 

Don't forget the third check valve near the brake booster.