OK - you guys seem to know how to resolve problems with these fantastic trucks; perhaps one of you can help me with a recent problem I have noticed on my 1997 F150 4.2L Auto Longbed (with 106.5K miles). It is used gently as a daily driver (for very short commutes, 1-3 miles) and once a week to the mountains (100-150 miles away) to ride my dirt bike.
At 105.5K I had the oil (and auto trannie oil) changed at a local, reputable, Ford dealership. Soon afterwards I noticed that after longer drives (15 miles or so) the oil pressure guage would drop to near zero when one came to a standstill and, a few seconds after that, the red oil light would come on. If I engaged neutral or park the oil pressure would shoot back up to its regular 3/4 mark and the idiot light would extinguish. The situation would arise in any of the forward gears or reverse but only at a standstill. This problem does not occur when the engine is cold or even if it is warm but only a few miles have been travelled. Oil level is perfect although oil seems very thin(?). No weird noises and the engine doesn't seem to have lost any of its power. Truck does not have a tach but when engaging neutral or park one can hear the revs rise a little. This made me think that the idle is merely set too low and then one wouldn't notice this when cold as the auto choke is presumably kicking in. Still, it seems odd that the pressure would drop so low merely because the revs were down. And then the fact that this doesn't happen in neutral/park implies the transmission is dragging the revs down.
Perhaps one of you have noticed this problem and have a remedy for me (just please don't tell me my engine is going to expire - all those anti-V6 warnings in the forums have got me panicky!!). And, if this is indeed the problem, some info on how best to set the idle would be appreciated.
Thanks in anticipation.

Greg
Atlanta GA
saintgreg at mindspring.com

 

Hey Greg. When you had the oil changed last time, did you by chance go to a synthetic type oil?

Dave Powell

 

Hello Dave

Thanks for your reply. The answer to your question is no! I didn't ask for synthetic and my invoice merely states "030 5W30Spec Oil 5B $1.40ea" - too cheap for synthetic I'm sure! The service was the 105K "mini" service. I have heard of some people having problems with synthetics. This truck is relatively new to me - I have had it about 3 months and 3.5K miles or so. This is the first oil change I had performed and the previous owner stated that he had just done an oil change before the sale (and the window sticker oil-change alert echoed that fact).

Cheers,
Greg

 

Hey Greg. You might try putting a regular direct read oil pressure guage in, and drive your truck to see just what the story is. A direct read guage will tell a lot that the electronic ones in the dash don't. You might have to change to a heavy weight oil. Good luck, and let us know what is going on. We have some high mileage engines in our trucks, and all seams well.

Dave Powell

 

Welcome to FTE Greg.

It seems the problem surfaced right after your first oil change as a new owner of a high mileage truck. My guess is the previous owner had a heavy weight oil in the engine, which will mask low oil pressure at idle. Low pressure at idle when hot usually indicates some wear in the main bearings, but is not necessarily a death sentence.

Try changing to a heavier oil, such as 20/50, and see if the condition improves.
Also, don't overlook the possibility of a brand new but defective oil filter.

Good luck.
Bru

2002 F150 Super Crew
Black 4X4 Lariat
5.4 Engine Ford Chrome Bars
Ford Bedliner

1979 Bronco 351M 75K orig.

 

I have the exact same problem with my 97 4.2...if you find out the cause let me know...

 

Hello Superbru

Thanks for the advice re the heavier weight oil and possibly defective oil filter. That change of oil viscocity idea had passed through my mind - the previous owner seemed a touch dubious! - but I (perhaps incorrectly) dismissed that notion as the truck doesn't burn any oil or give off any smoke - under start-up or acceleration. Plus, there seems to be no difference in performance after the oil change. But then perhaps it is too subtle a difference to pick up? I have experimented with the idle and a very slightly higher idle seems to clear the pressure problem up (in that at she then sits at the perfect pressure level).

Nonetheless, I think it would be wise for me to take the truck back to the dealership and get them to give it a once-over... perhaps that "new" filter is clogging at low revs??

Thanks again!

Cheers,
Greg