87 2.9 issues....

[DZG400]

Hey guys, new here.

I got an 87 Ranger 2wd with a 2.9/5sp, and been having some issues....

1- It floods out if you "engine brake" (downshift and coast)

2- It acts really odd sometimes randomly driving down the road. Itll be running fine then itll buck/chug a couple times, then the whole tune of the motor changes. It gets quieter, and will only rev to about half throttle then go to missfireing and not gain any more RPMs (this is while driving, not just a neutral free rev) then after a couple miles, it clears up and all is well till next time.

It exhibts none of these symptoms untill it warms up.

The engine seems to be healthy, it doesnt use any oil (3/4 qt over 3000mi, and im sure most of that is leakage). It pulls 18/19 on a vaccuum gauge with a rock solid needle. And doesnt make any bad noises.

Fuel pressure is in spec, 40PSI KOEO and 35 while running.

Ive been fighting various issues with it the whole 6 months ive been driving it, but got them all figured out but this one.

Its throwing a code 41 "O2 sensor lean" during KOER code tests. And a memory code 87 (fuel pump circuit intermittent). Passes KOEO test.

I have replaced...
Plugs/wires/cap/rotor.
Distributor.
TFI.
Coil.
O2.
Coolant temp sensor AND sender.
MAP sensor.
EGR valve/Egr pressure sensor.
Fuel pump (on frame rail)
Fuel filter....

The only thing i havent replaced besides the IAC is the TPS. I tried testing it but i used a digital meter and im not great with wireing.

Also, yesterday i tried the "floor it to kill injectors while cranking" and it fired right up like normal. Which leads me to this question...

Does this sound like its TPS related?

 

[410Fortune]

I suspect the boost pump in the fuel tank due to the lean code
I suspect a lean condition
I suspect the slow start and missing is due to a weak in tank boost pump.

When my BII had dual fuel pumps (1988 setup, boost pump in tank, high pressure pump on frame rail) it would run fantastic until the boost pump would get warm, then it would only skip and lean out once in a great while. It seems the high pressure pump has enough pump pressure to run the 2.9L most of the time.
I would change out my fuel pump relay and consider changing the in tank boost pump. It would be nice to see fuel rail pressure while this is happening, I bet it drops below that 35 psi

 

[DZG400]

I forgot to list that i did the relay already.

Heres a question....does the inertia switch kill the high pressure pump, the in tank pump, or both?

My inertia switch isnt bolted down. Im wondering if thats causing it???

Just remembered that.

But i was wondering about that lift pump....but was really hopeing that wasnt it

 

[410Fortune]

if the inertia switch was tripped neither pump would run. Both pumps run on the same power circuit.
Dont be scared, lift pump no big deal, on a Ranger you can even lift the bed if you dont want to drop the tank.
In my 88 BII I cut a big square hole in the cargo area floor so I can access my fuel pump easily, even on the trail. 4ea sheet metal screws and a simple silicon gasket I am looking right at the top of the fuel tank.
I also converted my 88 to a 89 style = one in tank fuel pump, no more boost pump/rail pump. I simply added a second filter where the old high pressure pump used to be and installed a Walbro aftermarket pump in the tank

 

[DZG400]

I figured lifting the box would be the easy button over dealing with 31 yr old tank straps.

The box floor is about the only rust free/nice thing on the truck so i dont really wanna cut it up lol.

But lemme ask ya.....what would cause it to rich out on decleration?

 

[410Fortune]

The computer is seeing a lean condition from the 02 sensor, this means that it is already opening up the injectors as much as possible, dumping as much fuel as it can and it is still reading lean.
Possibly a leak in the exhaust upstream of injector?

This:
" It acts really odd sometimes randomly driving down the road. Itll be running fine then itll buck/chug a couple times, then the whole tune of the motor changes. It gets quieter, and will only rev to about half throttle then go to missfireing and not gain any more RPMs (this is while driving, not just a neutral free rev) then after a couple miles, it clears up and all is well till next time."

sounds like lean condition

This:
"It floods out if you "engine brake" (downshift and coast)"

Please explain, under engine braking what makes you think it is getting flooded?

It could be a fuel pressure regulator issue? boost pump issue, or other.. I would love to see fuel psi numbers during the "lean" and "rich" conditions
How many 02 sensors does a 87 Ranger have? I forget? Just one?

 

[DZG400]

Just 1 O2.

I know its riching out, cause if you mash the clutch after decleration, itll stumble around, wanna stall, blow black smoke and stink to high hell. If you feather the throttle itll either come back or stall. If it stalls itll immediatly fire back up like nothing happend

 

[roscoe 0202]

my 86 bronco II had that problem fought it until I replaced boost pump in tank then next week had to replace high pressure pump code kept coming up egr reading lower than expected so I figure no gas no egr pressure
roscoe

 

[DZG400]

my 86 bronco II had that problem fought it until I replaced boost pump in tank then next week had to replace high pressure pump code kept coming up egr reading lower than expected so I figure no gas no egr pressure
roscoe

I Had EGR issues as well. Changed the valve and sensor then realized there was a rock hard mound of carbon blocking the port. It made it run better but im still having these issues....

Guess ill try a TPS off my parts truck for poops and giggles and if that dont fix it ill sideline it till i get time to do the in tank pump.