I recently bought a 96 2.3 Manual trans ranger. It has a new tp sensor and iacv. No vacuum leaks that I have seen. However when warmed up it idles at about 1000-1100 rpm. With the a/c on it's around 750-800. Shouldn't it idle normally at 750 or so? I do get a p1506 idle speed code and a p1443. I would suspect the idle speed code has something to do with my issue but I cannot find any faults. The p1443 is the purge valve I believe. Would that cause any of this? I'm a little confused. It idling slightly high isn't a huge deal but if I can correct it I'd like to. Thanks everyone for any input you provide!

 

Welcome to the forum

Engine should idle COLD at 1,000rpm, that's normal
After warm up, 5 to 8 min, manual trans idle should be 700-750rpm

After warm up, and engine is idling, at 1,000rpm
Unplug the 2 wire connector on IAC valve, valve will close
Idle should drop down, engine may even stall, thats GOOD, it means no air leaks

If idle doesn't drop down then you have an air leak/vacuum leak

Air flow into the engine controls RPMs, not fuel flow, that's how the Throttle works, let in more air and RPMs go up, so at idle, throttle closed, there should be a known/limited amount of air allowed to flow into the engine
When more air can flow in then idle goes up higher, same as opening throttle a bit more

P1443 Evaporative Emission System Control Valve (low/no flow)
EVAP system uses vacuum from the engine to suck out gas fumes from the gas tank, so that code could indicate a broke or unplugged vacuum hose, and THAT is allowing in the extra air
So these two things could be related

Check vacuum hoses on drivers side of engine, pull and prod them, lol, try to find one that is unhooked or broken
There are some that are hard to get to and see under the upper intake on the 2.3l, so look closely

 

I did not see any vacuum leaks. I sprayed around with carb cleaner as well and got nothing. 🤷

 

What happen with the test?
i.e. unplug IAC Valve with idling warm engine

 

Unplugging the idle air control valve make no difference at all I have sprayed everything with brake clean I've visually inspected all of the lines as well and smoke tested the system and found zero leaks. I did replace the canister to purge valve vacuum lines since they were being sucked closed. Those line are now all new and still I have the same issue.

 

Once the engine is very warm unplugging the iacv didn't make it shudder and the idle drop and then it adjusted for it and ran pretty ok. Didn't die or anything.

 

The IAC valve is the computers only means to adjust idle RPMs, when it is unplugged the computer has no way to adjust the idle, and the CEL(check engine light) should have come on, and a code was set for IAC Valve being unplugged, code clears itself when IAC Valve is plugged back in

So I am not following your test results
It can only be done on a warmed up engine
Either the RPMs dropped or they didn't, which was it?

Its better to spray soapy water around an engine looking for air leaks, its way cheaper and won't catch on FIRE, lol, and you just end up with a cleaner engine if no air leaks are found
Engine will stumble if soapy water is sucked in

After engine is warmed up shut it off
Leave IAC Valve plugged in
Remove power brake booster hose from booster, and plug the hose, tape, large bolt or ??
Re-start engine
See if idle is lower
If so booster is leaking
If not replace hose

Now do same test but disconnect PCV Valve hose and plug it
Restart and see if idle is lower
If so replace PCV Valve


Its all fairly strait forward, engine RPMs are control by AIR, the throttle plate allows some air in when closed
The IAC Valve is on an air passage that bypasses the throttle plate, the computer opens and closes this valve to set idle RPMs based on engine temp, and its accurate +/-4rpm so very accurate system

If idle is high then either the Computer is doing it, or air is coming in from an unknown place

Unplugging the IAC Valve takes the computer out of the system, so if idle drops when you unplug the IAC Valve that means The Computer was setting the higher idle, for some reason
If unplugging the IAC Valve does not change the idle then either IAC Valve is bad/stuck, or there is air leaking in

Ford uses a true Solenoid IAC Valve, 3rd party(non-Ford) IAC Valves are stepper type valves not true solenoid valves, so they can work but often cause odd issues
A used Ford IAC Valve is a better replacement than any new 3rd party IAC Valve, just FYI
Hitachi also makes true solenoid IAC Valves, so they can also be use

 

When I first did the iac unplug test the gauge was pretty much in the middle when I plugged the scan tool in to see the actual temp it was a 165° once I let it idle until it was in the 190° range and pulled the iac plug it did stumble and make a difference. The iacv is a part store aftermarket one. Maybe that's causing the slightly high idle? Brake clean evaporates so fast I wasn't worried about it catching fire, people have tested vacuum lines with starting fluid and stuff like it for years. Besides the slightly high idle the truck runs great. I'm oddly amazed at the torque it has for such a small mill. I owned a 2.2 Sonoma years ago it was a good truck to but gutless by comparison.

 

Any temp above 160degF is fully warmed up a far as computer and idle is concerned, i.e. no choke and closed loop operation

If idle RPMs dropped at all when IAC was unplugged then computer was holding idle high

 

When it was fully warmed up and I unplugged it it stumbled and the idle dropped and then it leveled out.

 

So no air leak
Computer is setting the higher idle

Turn off WARMED UP engine
Unplug IAC Valve
Key on
Test the 2 IAC Valve wires, should see about 10-11volts, thats start up volts, Computer opens IAC Valve all the way for starting
Start engine, IAC Valve still unplugged
Test wires, should see varying volts 5v to 10volts as computer tries to change idle RPMs

 

I've figured out the idle the idle set screw had been messed with previous to my ownership. It now idles right about 750rpms. Another issues I've been having is at idle it runs rough. Almost fees like a misfire. Plugs are new wires are new coils aren't original either. I don't get any codes and it runs great overall just at idle it feels rough.

 

Fuel injected engines can't have an "idle screw", they have an "Anti-diesel screw", just FYI, but they do the samething, lol, adjust the Closed Throttle position

Unplug the 3 wire connector on either coil pack
Start engine
Go for as drive
Should run smoothly no misfires but slightly less power

Then do same test but unplug the other coil pack
You are testing if all 4 spark plugs on the "working" coil pack are OK

2.3l uses Dual spark plugs to get a little extra power, but that engine ran fine from 1974 thru 1988 on just 4 spark plugs, and still will
You should do this test once a year because you would never know if a single spark plug wasn't working

So a spark issue would not be first choice on a Dual Spark plug engine, when there is a rough idle, as BOTH spark plugs would have to misfire

Could be dirty fuel injector tips, run some Seafoam, or similar fuel system cleaner, in the gas tank, see if idle smooths out after a few days of driving
Dirty tips cause fuel to drip at idle, so poor fuel mix and misfire, at higher RPMs they will spray so no misfires

Start of a compression issue
Metal on metal is not a good seal to be air tight, so compression is time related
The faster the piston is moving the less time there is for compression air to leak out
Compression is fine above 1,000rpms but too low in some cylinders under 1,000rpm, causing misfire
Leaking exhaust valves are the most common cause of lower compression
You can do a compression test to take this off the table or to find out it is the start of a bigger problem, as it will get worse over time

 

I will do a compression test tomorrow afternoon. Right before I bought it the previous owner said he changed the plugs they look new but they are Bosch platinums I'll put motorcraft plugs back in it. I'll also try that test with the coil tomorrow as well. I hope it's not low compression I have read about leaky valves on the web for this engine so probably a possibility. I hope not though.

 

here are the four plugs on the passenger side of the engine. I haven't removed the other 4 yet. I did however do a compression test. The first cylinder (closest to front of truck) is the white plug that looks like it hasn't been firing. the compression for that cylinder was 116 dry the rest were 140-150. Wet cyl 1 went to 200. Possibly that cylinders rings are more worn. Either way at 116 it should still fire and that plug doesn't look like it has been. The gap is also way off. They are all gapped at .55 possibly a bad coil?

 

116 is very low if others were 140-150, thats 20% less

Misfire in this case is a bit misleading, the rough idle can be a partial fire, with an actual misfire(no fire) mixed in now and then
4 cylinder engine only fires every 180deg of crank rotation, its why even a perfectly running 4cylinder engine vibrates at low RPMs

Compression is also power, like winding a rubber band up and then releasing it, the more you wind it, the more energy is released
Its why high compression engines have more power
If 3 cylinders are 145psi and one is 115psi you will feel that reduced power at idle, less so at higher RPMs, a rough idle because power is not balanced