My son's 2003 Ford Ranger 4.0 4X4 with 164,000 miles lost oil pressure while driving. He pulled over and shut down the engine. He checked oil and it was fine. After talking to him we decided to start the engine. The oil pressure gauge came back and there was no noise from the engine. He then drove it a bit but said it would not go over 2k RPM and there was some noise from the drive train. He pulled over and shut it down. We towed it home.

In the driveway there is a slight clatter from the back of the engine when we we rev the engine a bit. There is no check engine light and my code reader does not pick up any codes pending or otherwise.

Does this sound like the oil pump? How would we diagnose it? Do these have a limp mode to protect the engine with such a failure?

I thought it might be a plugged Cat but the exhaust pressure changes when you rev the engine. I checked the throttle body operation and it appeared to be functioning correctly. I am unsure of the condition of the fuel filter. If that was clogged would it cause a code and CEL?

Any help would be appriciated.

Thanks
Chris

 

what transmission does it have?

 

Change oil filter just because its cheap and can cause what you describe

The 3.0l should not start if the Cam sensor/oil pump drive is not spinning, i.e. sheared off cam synchro gears roll pin

High or low Oil pressure can not cause reduced RPMs as described, computer has no oil pressure "monitor"
But spun main bearing could if oil pump did stop working for a bit, but usually doesn't start working again, lol

If you have an OBD2 reader then unplug the CAM sensors 2 wire connector and see if engine starts, if it does fine, if not fine, but then read the codes, should have Cam sensor code, this is a "sanity" test for computer, just to make sure it can "see" errors and set codes

Look it up here: https://www.therangerstation.com/tec...trouble_codes/

 

@docm Automatic Transmission

Ive read watched a few youtube videos and possibly it is a clogged cat which could be causing enough back pressure to cause the loss of power. rattling could be a loose heat shield or exhaust hanger that starts rattling as the back pressure builds up.

We could also be dealing with a broken timing chain cassette. will have to pull the pan to look for plastic bits. not sure this would cause the loss of power and not being able to rev over 2k rpm.@RonD Good call on the oil filter change. This is a 4.0 engine so would it not start if the Cam sensor/oil pump drive is not spinning? I think Ill pick up an oil pressure testing gauge that I can "T" into the existing sending unit and see what it tells us. oil condition would tell us a lot as well. I will also see if I can get the computer to throw a code.

Plan of attack is to get it to Grandpa's garage and start testing to find out more.

 

Pull out the 2 upstream O2 sensors
Start engine, it will be LOUD, but if it REVs OK then blocked exhaust is the issue

Or use a Vacuum gauge($30) on the intake
Start engine 18-21" vacuum expected
REV engine to 1,500rpms and hold, vacuum will drop and then come back up to 18" and hold steady if it doesn't or is slowly dropping then clogged exhaust

 

Update: I am pretty sure its one of the Cats. Once we got it in the shop and could get under it I was able to identify the rattle coming from one of the Catalytic converters. Vacuum tests appeared to show blockage but it was not that bad. The Rattle/Clatter went away. Changed the oil and filter while under there. Talked to the local muffler shop this morning. He is pretty sure one of the cats is clogged. Can't get it in till next week. I will update when I learn more.

 

Update

New catalytic converters installed. Truck is running like a champ. Shop said pressure test immediately showed blockage.