Trying to find issues and solutions

[Ranger86]

Hello,
Here is what I have going on. First let's start with what I have. I have a 1986 Ford Ranger XLT 2.3 EFI 2WD Automatic. Bought the truck about a year ago knowing the original owners and the mechanics that have worked on it. I purchased the truck and got it home. I knew it had a few issues, but to me that would be minor, so I thought. The mechanics said that they have tried all that I'm going to mention but all have failed. New fuel pump, new fuel filter, new maf sensor, new o2 sensor, new throttle position sensor, new computer, new temp sensors. So I asked myself what is going on? Where to start? They all said the same thing. It would run fine for five to six miles then all of a sudden it would load up and start to shake. The one mechanic said you would have to start feathering the throttle and then it would smooth out. I got it home. Started to mess with it and sure enough it would do exacting what they said. So my son and I went through all the wiring and fixed anything that looked bad. Then I pulled the upper intake, throttle body and did a good cleaning on it. Got the truck back up and running and the engine would run smooth as a sewing machine at idle and run for however long you want it to, 30 minutes or and hour.. But give it a few throttle pops and she would start to load up shake and within 30 second or so smooth back out. So now the time it takes to smooth out has reduced but is still there. Whats next? What am I missing? I believe the cat has been removed as well. So being clogged is out of question. In advance thanks for any help with this.

 

[Mark_88]

Welcome to TRS~!

Another strange sounding one but it is displaying what appears to be fuel starvation. Two things I would suggest, even with the new pump, is to attach a fuel pressure tester on it so you can see what is happening to that while under load.

The other thing to try as a test is to bypass the Inertia Switch. That can be found under the dash on the passenger side near the transmission hump. Just pop it off and jump the wires and see if that clears it up.

I had very similar issues with my 89 Ford Tempo and had to replace the fuel pump 5 times and the Inertia Switch once.

hope that helps...can't hurt considering what you've replaced so far.

 

[tomw]

Rusted out muffler that is partially blocking the exhaust would explain the ability to run at idle for 30 minutes plus, but fall on its face whenever you give it some throttle.
I believe you have a MAP sensor rather than a MAF sensor in a 1986 model.

Which fuel pump was replaced? There may be 2. The low-pressure lift pump in the tank and the high pressure injector pump on the frame rail. The lift pump fills the filter housing reservoir as a 'ready source' for the injector pump. The injector pump may pull more fuel quickly on acceleration than the lift pump will want to provide, so the reservoir/filter housing acts as a buffer.
If the lift pump in the tank has not been replaced, you could have a failing pump (30+ years old), or a semi-plugged sock on the end of the pump intake. That would limit fuel delivery.
Have you checked delivery volume over time to know if the pump(s) are providing adequate fuel? You must know how much it can pump, not just the developed pressure.
tom

 

[Ranger86]

Thanks for the information gentlemen. You're right about it being a MAP sensor Tom. I am not sure which fuel pump the mechanic replaced. Won't be hard to figure that out being I know the one that mentioned it. Thanks about checking the inertia switch as well didn't know they had this, I knew the tempos and such had them but will look into this as well. Anything else that might come to mind with anyone; all help is appreciated very much.
Thanks,
Michael

 

[RonD]

Well fuel injected engines don't have a "gas" pedal, they have an "air" pedal

There is no "squirt of gas" from accelerator pump like a carb had when you pressed on the "gas" pedal, when it was a gas pedal, lol.

So your symptom is when you add more AIR it stalls out.

I would do a twist on 50/50 test
Put some gasoline in a spray bottle
Remove air tube from intake
With engine idling manually open throttle plate and spray some gasoline in when you do

See if it REVs up like it should when given enough fuel

If it does then you have narrowed down the problem to fuel delivery, period, no doubt.

If it doesn't then I would look at spark advance/retard which is TFI module and computer.
Get old time timing light and check spark timing with SPOUT disconnected and then connected, disconnected should show about 10-12deg BTDC base spark timing
SPOUT connected should show 20+ deg BTDC, the computer does this via the SPOUT wire.

Vacuum gauge is one of the best tools to use on gasoline engines, $25, and can tell you alot about what is happening while engine is running.
From sticking valves to plugged exhaust
An engine is basically a self power air pump, so what better tool to use than an air gauge
Fuel injection, distributor, or distributorless, throttle sensor, O2 sensors, air temp sensor, MAP sensor, ect...........engine is still just an air pump

Good read here on that: http://www.gregsengine.com/using-a-vacuum-gauge.html

 

[Ranger86]

It revs up fine when you pop the throttle open for a few second bursts of two to three times. Then it starts to load up like running rich when you let up off the throttle for it to go back to idle. Then it starts to shake and a little bluish black smoke comes from exhaust when you start to feather throttle open & closed in small movements. I will try the 50/50 and see what I get from that as well. Heck anything I can try is a blessing. And thanks for the info on the vacuum gauge. To be honest, I completely forgot about doing the vac test. It has been a while since I have done any restro or mechanicing on anything. Thanks again for all the help. Maybe we are onto something.