Fuel issues

[1986RangerXL]

Okay I have read Ron's post about it being the anti-diesel screw and that it should NOT be adjusted. BUT I used 'idle screw' for clarity since a lot of people dont know yet. I was only messing with it last night because I adjusted it before I knew not to lol so was just trying to find where it should be

I will try to find Ron's post, my TPS, IAC, and anti-diesel just needs to be complety reset at this point

 

[RonD]

As to why wiring could matter for surging idle

IAC Valve gets system voltage on the RED wire and the computer then Pulses the ground on the other wire to adjust this solenoid to set stable idle
So IAC uses alternator voltage when engine is running
I would test system voltage after startup, should be high, above 14volts and STEADY, if voltage is jumping around then IAC Valve would as well

Also check for AC Volts, you shouldn't see more than .1vAC at any time in a vehicle system, alternators generate AC volts, which is converted to DC, but a failing diode can cause AC volts to leak into the system, causing issues

Sensors all get 5vDC from computer, so wouldn't be effected by this
Most control solenoids, i.e. EGR, EVAP, that use system volts, aren't used cold or don't need precise control, IAC Valve(solenoid) does need stable voltage

 

[1986RangerXL]

Thanks @RonD, I will head down to Autozone to pick up a multimeter so I can test this

 

[wildbill23c]

Interesting perspective there WildBill. How do you hook it up to perform that type of test?

Hook the fuel pressure tester up just like you normally would. I just didn't close the hood all the way so it wouldn't pinch off the hose and secured the gauge to the lower corner of the windshield so I could read it while driving.

I need to find a mechanical voltage gauge and install so I can monitor that while driving too, a volt meter won't work at least I haven't been able to get the leads to stay connected securely enough to work LOL...so a mechanical gauge is a must for these things. I have a volt/water/oil gauge set I just have yet to install it in my Bronco 2, maybe temporarily hook it up in my Ranger to see what voltages I'm getting.

 

[RonD]

Volt/OHM meter is a good tool to have, I also still use a Vacuum gauge all the time, another cheap tool that can tell you alot about any gasoline engine

 

[wildbill23c]

Volt/OHM meter is a good tool to have, I also still use a Vacuum gauge all the time, another cheap tool that can tell you alot about any gasoline engine

I don't have a vacuum gauge yet, but yes they're extremely helpful for sure and they're pretty cheap. A multimeter is indispensable for any automotive work related to wiring, sensors, etc. I found one last week with the tachometer leads, don't see those very often anymore either, granted its a cheapy ($50) Harbor Freight model but it does seem to work good.

 

[RonD]

I still have tach/dwell meters and timing lights, thats how OLD I am, lol

 

[alwaysFlOoReD]

I still have tach/dwell meters and timing lights, thats how OLD I am, lol

Yep, me too. And an analog tachometer that you hold against a spinning crankshaft to get rpm's. I'm probably not quite as old as you but really like old tools so collect them when I can afford to.

 

[1986RangerXL]

Update for tonight. I got the voltmeter and did a system test and voltage is steady, and in the correct range. Another one of Ron's post in a different thread described how to test the IAC plug and it checked out.

We got the idle set to a normal speed, and got it to idle down without dying by putting another coil in. (It died while idling down because of misfire, I think.)

Still a consistent misfire at higher RPMs, so going to check if any of the plugs are fouled from the previous injectors and high idle, then check the plug wires

 

[PetroleumJunkie412]

Hey, just out of curiosity... When it idles, and you pull the spout connector, does it hold at perfect 10 deg, or does it wander around a bit?

 

[1986RangerXL]

Truck still has bad misfire, the oil smells like gas, and apparently the distributor loosened itself.

I know the PO dogs on his vehicles, maybe a rebuild is in order..

 

[1986RangerXL]

Fixed a couple electric wires that could be problematic, wired the O2 sensor back in, and retimed the motor. Idle seems back to normal, still battling misfire issues. Oil pressure, compression test, and vacuum test to determine if the motor is junk coming soon. Drove it a bit and front differential started leaking, looks like owner used caulk instead of a gasket..

 

[1986RangerXL]

Would someone like to educate me on how an EGR works and how to test it?

Also, why do 87-88 have MAP sensors and pre '87 don't?

 

[Dirtman]

EGR valves dump hot exhaust gas into the intake which through SCIENCE actually cools the combustion chamber temps which lower NOX emissions. They do not work all the time however, only when cruising with little load on the engine. They are either computer controlled or in the case of older vehicles vacuum controlled. The diaphragm that opens the valve to allow exhaust gas in is balanced between exhaust pressure and engine vacuum. High vacuum and low exhaust pressure would be closed (idle) no vacuum and high exhaust pressure also closed (heavy load).

As for the MAP, there are two ways of measuring incoming air on a fuel injected engine a MAP sensor or MAF sensor. Map sensor measures air pressure inside the intake manifold and a MAF sensor measures air flowing past it. Two ways of accomplishing the same thing. Sometimes there are both. Most modern cars use maf sensors since they are more accurate but in the 80s it was a crapshoot... you could have one, the other or both.

 

[1986RangerXL]

@Dirtman Thanks. Sounds like the EGR isn't the problem here