I just sold my bigblock F250 and bought an 88 F150 with the I6 that is in better shape with less problems. The truck has 134,000 miles on it (verified on carfax) and seems to have been very well maintained from top to bottom. The plugs looked old and it seemed a little doggish when I got it, so I put new plugs, wires, cap and rotor in it when i got it. I was happy to see that the plugs had no black burnt oil residue on them. I've put about 400 miles on it since then(drove 70 miles yesterday at 65mph) and it still seems doggish especially going up hills but it doesn't knock, tap, burn oil, or leak oil. The thing that has me concerned is that the oil pressure gauge gives me odd readings. Sometimes when I start it cold it reads to the N in Normal, other times its about halfway between N and Low. It seems like as I drive it very slowly creeps towards Low but never gets quite there. On a few short drives its crept down and then crept back up. Not really sure what this means, but like I said it seems a little doggish especially on the highway in 5th gear. The temp gauge also always is pegged at cold, leading me to believe i either have a bad gauge or sending unit. I replaced the 2 wire sending unit that is just above the alternator and a little to the right, but still reads cold. Also, the electric engine fan always runs for a while after I turn off the engine...like maybe 10 to 15 minutes. Could this be a thermostat problem or something?

 

my 88 with 4.9 does the same thing with the oil.. Its somthing to do with the bearings is what my dad told me before he died.. the warmer the engine gets the more it expands and the oil pressure drops.. but once you start driving it picks back up.. I just put a quart of lucas oil stabalizer in with my last oil change and it helped get higher pressure a little

As far as the temp Ill pass on some advice from Good Old Bill.. Get the truck to running temp then check the coolant with a meat or candy themometer.. it should be high like 190F or more.. if not then you have a problem with you T-stat or fan if it is reading 190 then you have a problem with the sensor or gauge itself..

And I dont know about the electric fan.. mines a clutch fan

 

Thanks for the advice! The oil looks pretty good on the dipstick but maybe if its nice out on Tuesday I'll try to drain a little bit off and put some Lucas in there. Candy thermometer is a great idea and I happen to have one thats been sitting in the drawer waiting to be sacrificed for a greater cause like this. As for the fan, its not the main engine fan, its like some alternate fan at the front passenger side of the engine. Not really sure what it does. I'll post when I try these things.

Also wanted to add the the engine light blinks when its cold when I've got my foot on the gas, then goes out after a minute of driving. Probably completely unrelated, but cant hurt to throw it out there.

 

the temp sensor for the gauge is a 1-wire sensor on the head above the starter...you can get under the vehicle and look up under the exhaust manifold and see it...

 

Thanks for the tip about the temp sensor. Some previous posts made it seem as though there was only one, and others made it seem like there were two. I'll look for it tomorrow when its light out.

As for the engine light flashing, I read a little bit more and learned how to check for error codes. I'm not 100% sure that I read them properly, but any of the codes it came up with look like they could be related to the exhaust leak in my manifold.

 

So I drove about 15 miles to work this morning and did my best to check the coolant temp. I wasnt quite sure how to get the thermometer in the coolant, so I stuck the thermometer on the big hose that goes across the top behind the radiator and it got up to 159. I'm not certain this was really an accurate reading, since the coolant sounded like it was boiling away in there. I failed to find the one wire temp sensor, but later when its cooled off Ill feel around for it with my hands.

 

jack up the truck and put the front on Jack Stands...crawl under the truck on the passenger side...follow the exhaust up to the engine...the rear towards the cab is where it is at...right under the number 6 exhaust port...

I think it is actually in the block...it is hard to see unless you look up there and can see everything...use alot of light..I saw mine pretty easy but then again I have been working on cars over 20 years...

 

Sweet, I found the sensor and bought another one at NAPA. The guy there said I could probably change it without having to drain any coolant so we'll see how that goes tonight.

Also, I drove home from work today with the heat on full blast because I still have no temp gauge and thought maybe I'm running hot. I sorta tried this before, but today I just left it on from when I left and finally saw some sort of pattern in the oil pressure gauge readings. The pressure started off low, between N and Low, and then as I started driving it rose up to N and even to O! It seemed to stay there until I got to NAPA, when I started it again it had to slowly rise back up from between N and Low. Interestingly, when I turn off the heat (like instantly) the oil pressure starts to fall, and when I turn it back on it slowly rises back up. Can anybody decipher this?

 

bad ground...simple as that...it's back feeding thru the heater circuit...

 

Ok...thats what I was starting to think, but I guess I'm kind of hung up on this temp sensor. Maybe they both have bad grounds or I have a crimped section of wire somewhere. Where should I start looking for this bad ground? I'm not sure if thats like asking where I can find the needle in my haystack, but I'm a little new at this. I'm guessing that I start by pulling the instrument cluster and simply following the wires as far as I can looking for breaks? or is there a main ground on the frame that might be rusty? Also we have a good Fluke at work, that I'm mildly experienced with that I can put to work if you can tell me what to look for. And thanks, I really appreciate the advice.