Hi guys I have a 1989 f150 300/6 5spd that experiencing very bad gas mileage.
Its had dist cap leads and plus replaced as well as o2,tpi,and map sensor replaced. cat removed to.
Has a stumble just off idle and lazy till about 1500-2000 revs and smells really rich at idle I'm wondering it its all connected maybe injectors?
I am also thinking of removing the smog and deleting the egr valve because here in nz we can.
Also fuel filter and intake pump module have been replaced.

 

If it's smelling really rich I'd suspect your new O2 sensor is defective, or the engine is not warming up.

 

Possible temp sensor, or Tps.

 

Thanks guys, TPS been replaced, temp has always been a issue to get it running hot enough, when I got the truck it didn't have a t/stat in it and temp guage never moved now have a 180 and it comes to about 1/4? I'm gonna try putting old O2 sensor back in it as I still have iit.

 

The truck is actually recommended to run at 192. Ford's recommendation for optimum operating temp. 180 would probably cost you some mileage - motor doesn't get hot enough.
Only time I'd use a 180 is the real heat of the summer hauling a trailer or camper through the mountains.
I run a 192 year round with no issues.
When you replaced the TPS, did you adjust it to spec or just install it ? The signal wire should be reading .9 volts at closed throttle - if it's reading more, the ecu will think you have your foot into it and feed more fuel.
Also most people will recommend MOTORCRAFT ONLY for the TPS (also for the VSS and PCV valve).
A couple of possibilities for you to look at.

 

Like I said, the engine is not warming up...........

180 is not approved for that engine, hasn't been since they first started putting computers in vehicles. If it's too cool to go into closed loop, it will run rich as hell.

 

I put a 190 in it today and its running marginally hotter about 1/3 up the scale even without a fan scroud and in our summer.Huge radiator in these trucks huh.
I also put the original O2 sensor back in and doesn't seem 1/2 as smelly I can walk past the exhaust without it trying to kill me! lol havnt taken it on a big run yet tho?
I been buying standard T-series parts off rockauto they seem middle of the road price wise?
Annoying thing now is the stumble just off idle and roll at idle which to me being old school seems like a vacuum leak but its got 19-20in and steady depending on the idle roll?
Ive heard these 300/6 are not very good on gas mileage 15-16mph at best but I dought its doin that? and id be happy with 15-16 as I only use the truck for towing my car recovery trailer.
There doesnt seem to be a slot to adjust the TPS where do you adjust it?
thanks for your help cheers Barry.




cheer Barry

 

It's usually done at install when the throttle body is already off. With most of the earlier ones, the mounting holes are slotted so you can "dial it in". The later ones weren't adjustable, self adjusting, maybe through the ECM, I think.

 

To test the signal from the TPS.
Done with key on, engine off (KOEO)

Multimeter set to 20 volts dc. Black lead to battery negative. red lead to TPS signal wire (usually black). It should read .9 volts at closed throttle. As you open the throttle steadily, the signal should climb steadily and smoothly with no interruption all the way up to 4.5 (or5) volts at wide open throttle (WOT). It should fall just as steadily as you slowly close the throttle. Any wierd 'bumps' or dead spots indicate a problem.

A TPS which reads higher than .9 vdc at closed throttle will be telling the ecm that the throttle is open partway (when it isn't), so the ecm will supply more gas to match what it's being told by the tps.
If the TPS is providing a good signal there is no need to test any of the other 2 wires.

You can also do a 'bump test' whereby somebody gently taps the tps with a screwdriver handle as you do the signal test. This is to simulate a rough road.

The other wires are the feed wire (usually red) which should show 4.5 to 5 volts when the key is on - tested the same way as the signal wire.
The last wire (usually green) is the ground, which is tested the opposite way (red lead to battery positive, black lead to tps ground wire. Some people disagree with testing the ground this way as it feeds 12v to the ecm ground, but it's generally accepted.

The only reason to test the feed or ground is if you are getting no signal or if WOT is below 4.5v

 

ok we have a black wire white tracer-12vdc-11.98
green .9closed -4.2 -4.49 wot
white/orange 4.5-4.9vdc
slight vary between scale multimeter and digital but bugger all.
2nd reading is digital.

 

OK, so that's set right. Next you could check the ECT, usually above the thermostat housing. The ECT tells the computer if the engine is warmed up yet or not.
You can look up the proper ohms of resistance it should have, but I think it's in the neighbourhood of 50,000 to 60,000 ohms cold, and only a few thousand ohms when hot.
For what they cost, some people will just replace them, but I like to test things. It saves replacing perfectly good parts but also helps you know what was wrong, in case you run into a similar problem again.

 

Thanks will do. BTW where is the temp gauge sender mounted I cant for the life of me see it? I want to check out its reading correctly.

 

Should be passenger side, very back just below the last tube of the intake.

 

Thanks which is best chilton or hanes manual?
Apart from rock auto is there any other parts supplier you would suggest?
Limited market her in nz.

 

I can't think of any other reputable supplier that would ship to NZ, perhaps one of the discount online Ford dealers such as Tasca might. I'd get a real Ford manual:

http://www.ebay.com/itm/FORD-1989-Br...-/290841858410