farmertx

1990 f150 302 5.0 ext cab
Greetings everyone

I've lurked around here for about 1.5 years but never posted anything. Today changes that, and I'm hoping to get some information/advice as well as share the project I have. Thanks to everyone in advance. Forums are awesome.

Backstory: In 2020 My wife and I moved back to the family ranch. I saw a 1990 5.0 ext cab sitting beside a shed in an old RV park, and I struck up a work/trade deal with the owner and received the truck and title. All I know of the truck is the previous owner was an old man who bought it new and kept receipts on services. He left it to his granddaughter who abandoned the vehicle at the rv park for several months before I got it. This truck has been generally taken care of. No real rust, interior is clean and the body is straight.

Knowing next to nothing about these trucks, I was able to start it, and drive it the 10 miles to our place on dirt roads. The owner of the rv park was going to make it his truck, but on a trip to town, couldn't get the truck to go above 45-50mph, so he parked it.

I tried as well to get the truck up to highway speeds and it just loses power arounf 45-50. I'm far from expert level but I just don't feel like its a tranny issue, because it's not like the tranny is wound up and not shifting, it's more like I just push on the gas and nothing happens beyond that point. Power felt good up to 45 though, shifted nicely etc.

Initial things I noticed when I checked 'er out.... There is oil in the air filter, and the pre-filter or whatever is non existent that goes to the valve cover neck.

When running, I could rev it up and I could literally see oil and air escaping out of the valve cover gaskets. Further inspection showed me that the bolts around the valve covers were barely hand-tight. I didn't check the codes yet on the obd1.


Anyway it has been sitting here for over a year, and my main ranch truck is about dead so I've been digging back into this one again. So here is what I noticed tearing into it yesterday. I can add photos if needed or helpful to anyone else.

1. There are some red and yellow vacuum lines behind the manifold in a loom. one yellow one that looks like it goes to the ACV (according to under-hood sticker) and one red that I think goes to the vacuum can on the passenger side are broken or have been chewed through.

2. The pcv valve rattles when I shake it, but is it possible for it to be ''too loose/rattly?'' I initially suspected the pcv as the issue pertaining to the blowby ending up in the air filter, but I'm not sure. I read on here somewhere that a bad pcv can cause cylinder 7 or 8 to have issues, and would be evident in the spark plugs.

3. So next to the plugs - I pulled them and while they show eveidence of running rich, they are not caked in gunk. Furthermore, these were not very tight in the sockets either.

4. The best part is when I removed the valve covers, I was pleasantly surprised to see that the gaskets were new and it appears someone has done the piston heads. The hardware and bolts under there look brand new, have no play etc. I can still see all the writing on the bolts, it looks very fresh.


Now on to my questions...

What is the part I need to look for to replace those vaccum lines, and could someone tell me what they do? They are connected to the vacuum tree on one end with some rubber nipples. Do I have to replace the whole thing with the nipples or can I just run a tube from one broken end to another?

Seeing as someone has already done the piston heads (or whatever they are) - Is it possible that the lack of power could come from the valve covers not being tightened up enough? That would be incredible.

I'm going to replace the pcv anyway since it's 2 bucks but how likely is it that the blowby issue is caused by that?

... I don't know but I wonder if the person who had it before, had the blowby issue with oil in the filter - then had the piston heads (i think) done and they didn't replace the air filter OR tighten the bolts on the valve covers? Could I be so fortunate? I sure hope so...

Anyway I'm hoping for suggestions and tips because I'd really love to get this thing running well enough to work on the ranches out here.
Thanks for reading.

Steve83

You should put ALL the truck's details & history into your signature as this page explains:

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Phone apps don't always show signatures, so you may need to switch to a real browser in desktop mode on your phone, or just use a desktop/laptop computer. Put your location in your profile & upload an avatar of the truck. Yes, more pics are always better. Not only to make sure we understand what you're saying, but also because we may see things you don't know to look for. My recent post in a thread in this forum about a fluctuating idle will give you an idea of what can be gleaned from enough good pics.That's the PCV intake "breather" filter.

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The software that these trucks use is EEC-IV; OBD1 was a short-lived GM system that has become slang for all systems before the international OBD2 standard. This page (which is VERY long) explains everything you never wanted to know, but it includes the full code list specific to these early trucks:

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That's a bad sign, since rodents can do a LOT of damage. And they can ride hundreds of miles in the truck while it's being driven, so you should park it out in the wide-open (away from bushes, holes, trees, tall grass, water, food...) and put poison in & on it. I have to keep all 6 of my trucks, both mowers, and my golf cart poisoned because I live in the woods. This shows the type I prefer, because it's hard enough to jam into gaps and stay while driving:

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This is one of several rodent-damaged trucks I've had to fix:

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No. The rattle is the valve that blocks backfires from overpressurizing the crankcase, so it should always be very loose. If it gets too gummy to hear, it needs replacement; or if it's due on the maintenance schedule (which is virtually the same for all '85-96 Ford EFI trucks).

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The PCV breather hose is the PATH for that oil, but the PCV valve & system are not the CAUSE. The blow-by is the cause, which overloads the PCV system's capacity. Read the 2nd link above.Again: the PCV valve & hoses are the PATH, but not the CAUSE. The blow-by is overwhelming the oil separator (built into the valve cover) which results in oil being lifted into the plenum. Since the early PCV nipple was at the rear, that oil was concentrated at the #8 (& #7) intake runner(s). Later trucks have a revised routing that deposits the oil in the center of the plenum (near the vacuum tree).

If you still have the valve covers off, do your best to wash/scrub out the oil separators, which are the baffles welded inside the tops of the covers. Use pipe cleaners, bottle brushes, carb cleaner, or a plastic storage container with a few inches of kerosene/naphtha/mineral spirits to remove as much residue as possible.Pics.

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That was contributing to the lack of power, but it doesn't explain the blow-by."Cylinder heads".

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...and that's a bad sign, given the blow-by & lack of highway-speed power. It suggests that someone assumed the problem was in the heads, and then found that it wasn't, and gave up on the truck. Before spending ANY MORE MONEY on it, I'd run a compression test at the very least; if not also leakdown, vacuum, oil pressure, & timing chain slack tests.

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The function is indicated by the color, but most of them are for emissions controls. The VECI label's vacuum map shows most of their functions.

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But the ones for the HVAC system are not shown there. Only the reservoir, check valve, & recirculate motor are under the hood (forward of the firewall, indicated by the dotted line on this diagram).

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My preference for replacement is 3mmIDx8~9mmOD factory-colored silicone from eBay because it's far more-durable, while retaining the identifying colors.

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Patching saves a few pennies on the length of hose you have to buy, but it's not worth it to me because you'll just be wasting more time & money when those last few scraps of original tubing fail. I always remove the ENTIRE run and replace it with a single run of new hose.No. The valve covers do not affect the engine's power output - they merely keep the crankcase oil in & dirt out.

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That's a BAD habit to develop. Cost does NOT indicate the likelihood of something needing to be replaced, OR the likelihood that it will solve any problem. The lug nuts are cheap, too, but they're no more likely to solve any of your truck's problems than the PCV valve. Do not diagnose things with your wallet. Diagnose them logically, and then make a rational decision on what's worth fixing AFTER you know what's actually going to fix the problem(s).It's not EITHER; not likely, and not caused by the PCV.Follow the links on this page, and READ before you spend...

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