I have a 1986 Ranger, I got it a couple of years ago and have put the following parts on it. Injectors, spark plugs, calipers, bearings, clutch, and rotors. I started to drive it and noticed that when I would put the throttle peddle down to the floor it would not rev up but die down. I drove it 25 miles before one of the intank fuel pumps went out. I switched tanks and got another 25 miles before the other fuel pump went out. Trailered it home and changed the fuel pumps. Also changed the high pressure pump. Ever since then though it has not run well. When first starting the idle jumps all around. And to keep it from dying I have to put the throttle on a little bit then let it off very quickly. After a bit and the engine has warmed up some I can rev it up by pumping the peddle. But if I just put the peddle most of the way to the floor it will die.
I've noticed that there is a lot of moisture in the exhaust.
Things I've checked so far are these: good consistent spark to each spark plug, fuel pressure regulator is working correctly, map sensor. I found the egr wasn't working so replaced that and it still runs just has bad.
If I rev the engine up and then let the clutch out with the rpms high it will move forward. But if I let the clutch out even slipping it with the rpms down a little above a high idle it will instantly die.
Any ideas? I'm so stomped over this one.

 

Welcome to the forum

Assume 2.9l from the section?

Could be a few things from a vacuum leak to spark system

Any changes after engine warms up, does it run better?

It reads like your base Spark timing might be off, have you tried to time the spark with SPOUT Connector unplugged?
Base spark timing should be 10deg BTDC

On the 2.9l the SPOUT Connector is usually near the distributor on its wiring harness, grey or black plastic "pill/tab" that can be pulled out of its connector, this disconnects the computers spark/load advance so base timing can be set

You should only set spark timing after engine is warmed up

SPOUT looks like this: https://www.fordforumsonline.com/att...spout-jpg.866/
Pull out that top part, and don't lose it



The Computer needs to "choke" the engine until it warms up, this means computer needs an accurate temperature reading from the engine
So an ECT(engine coolant temp) sensor was added for fuel injection, its a 5volt sensor located near the thermostat housing AND near the 12volt Temp SENDER used for the dash board temp gauge

They are not interchangeable and not the same type of temp detectors

You can test the ECT sensor with an ohm/volt meter, but most just replace them, it is a TWO wire sensor, the SENDER is usually 1 wire

 

Yes it's a 2.9l.
I've checked for a consistent spark with a timing light and didn't see it skipping when the engine would surge.
How do I check for vacuum leaks?
Once the engine has warmed up it runs better but not anywhere close to good.
Yes I've checked the timing with the SPOUT connector unplugged. It was 10 degrees.
I have not checked the ECT sensor, what should the ohms be on it?

 

ECT info here: https://www.thedieselstop.com/faq/94...es/a12842b.gif


After engine is warmed up, and idling, unplug the IAC Valve, RPMs should drop to 500, engine may stall, either is good it means no vacuum leaks
If RPMs stay high then IAC Valve is bad/stuck or you have a leak

You can remove an IAC Valve and plug it back in, turn key on, it should now be open all the way
Unplug it and watch the valve inside move, it only move 3/8" but should move, plug it back in and it should open all the way again, repeat as you see fit to confirm it works or doesn't work

 

I went to pull the ECT last night and got it pulled. But had to bring the truck up the hill out of the shop I'm using. So I just lightly screwed it in and didn't plug it in. The ranger runs perfect now.

 

Could be the ECT has failed in the "warmed up" resistance, so computer always thinks you are just restarting a warmed up engine, so never applies Choke mode

 

That's what I'm guessing. I'm going to order a new one. And hopefully it'll be good.

 

I put the ECT in and it still runs rough. If I unplug the air charge temperature sensor it will run a lot smoother when I run the rpms up.
The fuel pressure is just a little over 30 psi until I put the throttle on and it'll go up to 40 psi when the rpms are up higher.
I'm not sure what to do now.

 

Fuel pressure is OK, it has vacuum assist to lower pressure when throttle is closed, high vacuum, then when accelerating, vacuum goes down and fuel pressure goes up to meet the higher fuel demand
So what you observed is correct operation

I didn't think the IAT sensor could effect engine that much but may be, I guess change it

Good read here on the old EFI systems: Fuel Injection Technical Library » Sensors

You would have a speed density system so you use a MAP sensor not a MAF sensor

Read thru Strategies , link on the above page

 

Thanks.
How do I know if it is the Air Charge temp sensor or something else throwing it off?
I don't have much to spend and don't want to figure the problem out shotgun style.

 

Some forums I've read suggest something about a ground issue but I can't find much info on it.

 

You don't know, you can test it with a volt or ohm meter

OHMs are easiest to test, remove sensor and have some hot water on the stove, boiling water is about 200degF, and you should know what outside temp is, so test IAT for that temp
Then submerge tip in the hot water for a minute then test it, then submerge it longer and test

OHMs you should see listed here: https://www.freeautomechanic.com/ima...ting-chart.gif

OHMs should go down as temp goes up

Also at the above site look at this page: Fuel Injection Technical Library » How To Run a Self-Test

See if there are any codes, your year would use 2 digit codes, also listed on that site

 

Thanks for the chart. I will test that when I have a break from school.
I checked the codes before I reset the computer to reset the senor readings. Here's what I got.

51 - Ect (I changed that)
54 - IAT or ACT (I had that unplugged while running)
63 - Throttle position sensor (I also unplugged while running)
33 - Egr (I changed the egr)
I need to run it more to get the codes back if there are codes then check them.

 

So I switched the IAT with one from my dads 86 ranger and it still runs like before. However the IAT I pulled out of mine had a smell of fuel on it. I hadn't ran the truck in a couple weeks too. So my question is that there isn't supposed to be gas in the intake manifold is there? And how would that fuel be getting in there.

 

The problem is worse the colder the engine is when it starts.

 

No, to fuel in the intake, with fuel injection the injectors are turned off with key off but engine RPMs are still at say 700, so as engine spools down any residual fuel(which there shouldn't be) would be sucked out

Leaking Fuel Pressure Regulator, check its vacuum line

Leaking injector, cycle key on and off several times, to build up fuel pressure, then check intake for fuel smell, pull off the tube from air cleaner and open throttle to smell intake air

 

Ok thanks. I've checked the pressure regulator and even put a manual vacuum gauge and pump on it, still ran terrible.
I will check for a leaky injector as soon as I get a chance.

 

Why would the ranger run rough unless I unplug the ECT or IAT sensor? Seems like that wouldn't change a leaky injector.

 

Does anyone have any suggestions?