Hopefully someone can help.
1986 Ford Ranger, 2.9L.
Used to get 20mph but now gets 14.
All sensors have been changed except the oxygen sensor after the cat converter. The one before the cat converter has been changed.
The air valve on the side of the motor that controls engine idol has not been changed.
The EGR valve has been changed but keeps sending a code telling that it has not been recognized.
Ford did a tune up with cleaned injectors, distributor, new spark plug wires, etc.
Any Ideas?
Thanks in advance.

 

Since it's a 1986, it has anEEC-IV computer, thus only one O2 sensor just before the catalytic converter. What is the actual code that you are getting and in which test condition (Key Off Engine Off (KOEO),Key Off Engine Running (KOER) or Continuous Memory (CM))?

Which actual sensors have been changed up to this point so that they can be eliminated?

 

Thanks for your reply.
This is what I found out. The sensor before the cat converter was changed out.
The test condition was Key On Engine Off ( Hopefully that sequence was right. I'll check to make sure. ) that produced code 33.
So far they replaced the following:
the ERG valve and sensor.
the throttle positioning sensor.
the map sensor.
the fuel filter.
the distributor, rotor, plugs and wires.
temp probe changed.

There are no cracks in the exhaust manifold.
Engine has strong 15 lbs of vacuum.

Ford cleaned the injectors and replaced the fuel regulator and set timing.

Hopes this helps.
Thanks again.

 

Still having the mileage problem. Any ideas anyone?

 

There are 2 coolant temperature sensors. One is for the temperature gauge/idiot light and the other is for the emissions system. Do you know which was changed? If the emission coolant sensor was bad, it would normally cause the engine to run rich as the computer would think that the engine is cold all the time.

The only thing that I can thing of which would set a code of 33 is a clogged or bad EGR, bad EVP/PFE sensor or a bad/sluggish O2 sensor. Which you have already replaced these items.

Still scratching my head...

 

Both coolant sensors have been switched as well as the other sensors we've discussed so far.
Here's more info.
Truck runs good at low speeds but engine starts cutting out at 65mph.
It has 35 lbs fuel pressure.
Vacuum is strong 15 lbs.
Timing is set at 10° BTC.
Already mentioned, fuel economy went from 20 to 15mpg.
Fuel and temp gauges cycle to highest point at same time and after some time they drop back to normal...maybe a short in wiring.

Regarding the mileage do you think the problem could be from the distributor even though it's been replaced?

 

I have seen new distributor caps with a hair line crach that causes the loss of MPG due to spark leakage. Also causes the engine to run like crap at higher RPMs. Could be thaty somebody dropped the cap and fractured it. If you still have the old one, give it a try.

 

We found out the engine runs the same with the old or new cap. Are there any kind of electrical components in the distributor besides the rotor and cap that could cause these problems?

 

Are you having mis-fires? If so hairline fractures in the plugs can also cause this problem. No way to see them, just try another set..............

 

check your trans fluid to see if its up to full mark.you could be low? also check to see if your intake plantum has a vaccumn leak.