Hello All,

I am starting to use my 1989 E-250 van as a daily workhorse, used for installing satellite dishes. It's got an injected, stock, 302. She runs fine, starts well hot or cold, gives good heat, radiator is freshly redone, all is well, except, I am getting 8.6mpg in town, and 9.5mpg on the highway. I am a very lightfooted driver, and am really surprised at this low figure. The van weighs around 5200lbs.

Is there a temp sensor that may be faulty and telling the engine that it's cold and to run in full rich? What's the best way to find and test it?

My check engine light is frequently on.

Any advice is appreciated,

Steve S.
Seattle, WA
41F and rainy

 

If your check engine light is on, have your computer scanned for codes and fix those first, then go from there.

 

I hate to ask, but you do know what they call those dash warning lights?

The Check Engine Light came along with computer controlled fuel injection/ignitions & the required onboard diagnostics. When the CEL comes on its telling you that faults have been detected & can store most codes. In my area it can be hard to find a parts store that will still read OBD 1 codes used on '81-'95 FORD, but if they can, its free. Some mechanics will also scan for free. IMO buying a fault code reader was the best money I spent on this Club Wagon.

Depending on how its been run & loaded you shouldn't expect more than 12-14 mpg. If its running rich there could be black inside tailpipe & black spark plugs. Common things like: vacuum leaks, dirty air filters, soft tires, restrictive cats or dragging brakes can rob efficiency.

 

Thank you for the input. I shall get the codes checked out asap. I guess I just didn't have much faith in the OBDI codes.

I'm fearing accessing the coolant temp switch, I can't even see it in the van. Is it best accessed with the engine cover off, or from the front of the van?

I'd love to get 12-14mpg! That's over 50% improvement. I got 8.8mpg last fillup, which is what I am consistently getting, 8-9mpg, and I really am a lightfoot.

On another note, my wiper switch came apart, and while fixing that, I lost all my dash lights. All my fuses appear to be intact, so I must have knocked something loose while taking off that side dash panel to fix the wiper switch. Where's a good place to look to fix the dash light problem?

Thank you in advance,

Steve S.

 

I wouldn't be "fearing accessing" anything specific until after I'd discovered what the problem was. My '92 302 has fairly easy access to the coolant sensor from up front, under the hood, after removing the air filter-it also has an 'air charge' temperature sensor hidden on the driver side, top, middle. This is hard to see once the dog house is off, but is still easy to R&R.

An '89 is mighty easy to get into the dash compared to '92 & up.

 

True enough, but I still have to access the coolant temp sensor to test the resistance across its 2 contacts.

Any idea where to start looking to get my dash lights back? I'm assuming it's by the headlight switch, as that's where I was messing around while I was fixing the windshield wiper assembly.

Oh yes, for testing purposes I removed my catalytic converter a few months back, as we found it was partially clogged. Mpg remained the same, and it just passed WA state emissions yesterday. The muffler is new, and the radiator was just cleaned and flushed.

Many thanks,

Steve S.

 

Just a hunch, are you familiar w/the rheostat at 'front' of headlight switch, that dims the panel lights? Its on the 'rear' of the large wheel, just behind the dash & at the 'front' of the switch box itself. They have a reputation for being fragile & easily disturbed. Sometimes just turning the **** L&R a bunch of times will either make the lights come back on or reveal failure in it's action.

 

Well don't focus on the coolant temp sender alone.
Fuel pressure regulator, oxygen sensor, throttle position sensor, air charge temp sensor, manifold air pressure sensor, stuck thermostat, plugged cat, gummed up air filter, all this could mess with your mpg too. LOTS of people have the fuel pressure reg go bad, it's easy to test- pull the vac hose off it. If fuel comes out, then the pressure diaphragm has a hole in it and it's bad. The stock "cocktail straw" hard plastic vac lines are prone to crack with age (esp if you've have an exhaust manifold leak the heat will harden them right up). Also intake manifold leak (there's a test with an unlit propane torch or some carb cleaner).

I had a stretched timing chain make my vehicle run weak and get poor mpg for quite awhile.

BTW, there are 2 coolant temp sensors- one goes to the dash gauge and does nothing else, one goes to the computer to switch it from "cold" to "warm" mode.

You mention being a dish installer. Do you have a roof rack, like for the ladders? Those do cut badly into mpg on the highway. LOTS of aero drag.

 

I don't have a roof rack, and at in-town speeds, I don't think it'd lower mpg that much.

What surprises me, is how well the van runs, that's why I'm perplexed at the low mpg. The idle is high, which is what made me think it's running in 'cold' mode. She starts great, hot or cold, no driveability issues, just a bit down on power in my opinion, again, as if it were running too rich.

I'm trying to run the self-diagnostics, but the diagrams show a self test input, and how i'm supposed to run a jumper to the signal return on the obd1 diagnostic connector. Fine, but I simply do not see the self test input they show on the diagram. All I have is my diagnostic connector, nothing else. Where is the self-test input?

Any leads are greatly appreciated. Time to change the oil and filter now. First day off in quite a while, where it's not raining!

Steve S.
Seattle, WA

 

High idle may be caused by an intake manifold leak, upper (plenum) to lower. This lets in unmetered air. Check by starting it and spraying some carb cleaner or an unlit propane torch (make sure no ignition sources are present) around the gasket. If it speeds up then it's sucking air (and, during this test, extra fuel) into the engine. It mainly affects idle though, I doubt it would make for a drastic mpg drop.

 

How could you have any "faith" w/o checking the OBD1 codes & considering the onboard self diagnosis?

You passed w/o cat? Have you done a compression check? How old is the O2 sensor? What's the general condition of this 19 YO?

Mechanics usually test for vacuum leaks using a gauge & known values. Once its determined a vacuum leak exists, the 1st thing to do is search for obvious defects, often broken/split/pulled off hoses & connectors. There are dozens of places for vacuum leaks to occur, if only it was as easy as checking "the gasket". That's where the "Check by starting it and spraying some carb cleaner or an unlit propane torch" tip is so useful-prospecting for the hidden source of vacuum leak. Sometimes it seems as if there are miles of vacuum lines!

 

Yes, i did pass without a cat. I guess Seattle area emissions testing for this type of vehicle aren't so stringent.

I have not done a compression check. I dread getting into a few of those spark plug holes. Took me quite a while to change the plugs when I bought it 3 years ago. The engine is a transplant. It was born with a 351, which is why I bought it, to tow my race car. I didn't realize that when they put a remanufactured motor in it they put in a 302. Damn.

I've not changed the O2 sensor. Overall condition is fine, like I said, she starts and runs fine. I figured with various vacuum leaks she would not idle or run so well. Odometer reads 05500, so I'm assuming 205,500 miles on the chassis, 50k or so on the engine. If it's been running rich all this time, then the cylinder walls are probably pretty well washed out and more worn than they should be. With early Bosch K-Jetronic, not having an O2 sensor is not the end of the world, it doesn't go 'full-rich' without it. It's all about the engine map, the O2 sensor just fine tunes it, but the engine just uses the fuel map in the ECU. I have an 02 sensor, but no cat. I suppose I could test the output of the O2 sensor at various temperatures.

I hope to find time to access the coolant temp sensor so that I can test it. I'll be looking for brittle vacuum hoses while I'm there.

Thank you!!

Steve S.
Seattle, WA

 

OH. Yeah, you could have mentioned that!
Sound like you've got the wrong computer alfasteve. How's a computer with constants calibrated for a 5.8L gonna work right with a 5.0L?

Is the wiring harness the same on a 302 computer? Can he just drop one in?

 

Hmm, one would have thought they put in the right ecm/ecu when they replaced it, but that might be assuming too much. I'll start researching part numbers. Is the ecm/ecu located by the passenger's feet? Wonder what other computers would need replacing?

Many thanks, and happy new year,

Steve S.
Seattle, WA

 

It is located by the passenger's feet.
There are numbers on a big black-on-white label on the side.
There are several webpages that list what computer model number went into each make, model, and engine type for the Fords.