2.3L ('83-'97) CA Emissions Failed — Troubleshooting Before Retest

[turner]

Ok, opening this back up. After that last fail I gave up and just drove illegally for a while. Going to try another test here soon.

First thing I did today was another round of EEC IV tests. Got TPS out of range, and it was indeed too high at throttle closed. This TPS is <2 years old but it's pretty unstable. When I installed it, I'm 100% sure I set it correctly just below 1V. This time, I couldn't get it below 1.2V turned all the way, so I removed some material from the mounting arms to rotate it more. It sits right around 0.9V, although it hunts without anyone touching the throttle, 0.9 - 1.1V, which makes the idle RPM hunt. It stopped doing that long enough for me to move on. Ordered a new one just in case.

I also remembered that the smog tech had tried to "adjust idle" which made me think he fooled with the stall screw. Sure enough, it wasn't touching the throttle. So I got that reset so the truck idles at 650rpm with the IAC unplugged.

Went ahead and checked the timing. I didn't have the same problem as the smog tech. When I remove the SPOUT plug, RPMs drop, and a timing light reads a hair above 10°.

Ran the engine off test again, and passed that.

Ran engine ON test, and it gives me a code 13: RPM too low at idle. This is definitely not true, it settles nicely to 875 (when the TPS isn't glitching). During the test, the throttle push causes the engine to stumble momentarily after release, but otherwise the RPM actually seems high. During the test it sat above 1100rpm. Turn off the tester, back to 875.

I ran the test 6 times today in all, and got 13 every time. The last one also threw code 21: cooling temp sensor (or ECT) out of range. This is frustrating because I just replaced that, like less than 50 miles ago. I'm pretending that test didn't happen.

Part of me thinks I should do another smog test, since the fault that failed me is now gone. On the other hand, these tests are $80, and I've got active codes. By the time I get this truck passed, I'll be less than a year away from my next one

Any ideas what would be causing the 13 code?

 

[RonD]

I have code 13 as "(R) Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)"

ECT (code 21) out of range is also interesting in that computer uses ECT temp to set idle higher or lower
Computer sets idle at 1,100rpms when ECT reports coolant temp under 80degF
About 1,000rpms at 80-100degF
Then 900rpms or so up to 140degF
Over 140degF choke is off and regular warm idle should happen, on a 4cyl manual 750rpms, with automatic 800rpms
ECT output voltage should be 4volts at 40degF, 3volts at 70degF, then 2volts at 110degF
And under 1volt at 160degF
Operating temp, 190degF 0.6-0.7volts


The TPS thing is weird, TPS is a variable resistor so same as a light dimmer or volume control, voltage should be stable unless throttle shaft moves
Also test the input 5volts, to make sure its steady, all sensor share that 5volts so there would be several more codes if it was changing, but could be local, just on the TPS connector

 

[turner]

The book that came with my code reader (granted, not produced by Ford) lists:

12=RPM at idle out of range/high
13=RPM at idle out of range/low

The IAC has not been replaced by me, so could be original for all I know. Worth replacing?

It idles at 850-875 fully warmed up, which is within the acceptable range on my emissions sticker... barely. If it's supposed to be 750, that could be a hint. I'll try probing the cooling sensor and see what those voltages are.

TPS... to check input voltage would I just probe the 3rd wire? I'm currently probing what I assume is signal out and ground.

 

[RonD]

Yes, there is a 5v wire, center wire is usually OUT to computer and a ground wire
ETC has same 5volt wire, shared by all the sensors
4.8v to 5.2volt is OK as long as its stable

I used this code list in the Tech section: https://www.therangerstation.com/tech/obd-i-diagnostic-trouble-code-dtc-applications-2-digit-ford-codes/

If the IAC Valve is able to do high idle when cold and then dropping the idle RPMs as engine warms up I would say its OK
And if its 650rpms when unplugged then its closing all the way, so capable of 750rpms plugged in
Might try taking it off and spraying some cleaner/lube might have some build up in the area where it spends most of its open time, 750-800rpm area
If you have it off and have the key on engine off and plug it in it will open all the way(does that for start up) then unplug it and plug it back in a few times, it only moves maybe 3/8" from closed to fully open

 

[turner]

Ok, first thing I did today was remove the IAC and disassemble the two halves, and realized that I have replaced the motor side, just forgot. The diaphragm side looks original, but it moves freely.

I noticed that I left an open fastener bore in the side of the airbox, Maybe it was for a different shape of IAC. Went ahead and plugged it, thinking maybe that's introducing extra air AFTER the computer has made it's adjustments.



I no longer got code 13. I did have to back off the anti-stall screw (to compensate for the loss of air?). For some reason now it hunts from 650—850 in a gasping loop during the IAC-removed test. I screwed it back in until it was hunting 750—800. Too high, but it seemed happier so I left it there.

I probed the temp sensor this whole time, and I think there's a problem there. It started at 3.3V (55F outside) and the volts/RPM descended in unison like RonD said they would. But it never dropped below 1.9V. The truck was idling for an hour by the time I was done tinkering, still 1.9V. Could be the reason that my idle is 875-900rpm? Could be the reason for the 21 code?

There's a (possibly) related issue where the temp gauge in the cabin never reaches "Normal". It moves around the "C" area as shown below. One time I got it up to the "L" in "NORMAL" in traffic during a heat wave. The heater also never works in the first 30 minutes of a trip. It seems to take around 20 minutes of idling for the idle to settle down (to 875rpm).



This temp sensor is very new. Is it possible my engine is never getting up to operating temp? Wrong thermostat?

 

[RonD]

If idle wanders with IAC Valve unplugged block PCV Valve hose port and see if that stops it
If it does clean or replace PCV Valve
With IAC Valve unplugged idle should be lower but stable, so either a variable air leak or spark timing is changing

You should have cab heat after 5 to 8 minutes, 180+ degF
Temp gauge on the 2.3l can be low because the Temp Sender is not at the top front of the engine, its at the rear drivers side of engine, but should be at least 1/3 on the gauge, would be close to 1/2 on V6 with temp sender at the top front of engine, not because it runs warmer

But a very simple test for thermostat is to start cold engine
Feel the heater hoses at firewall and then upper rad hose, should be same temp of course
Wait 2 min and feel them again
Heater hoses should be getting hot, upper rad hose still COLD
If upper rad hose is warming up same as heater hoses then thermostat is not closed all the way and it should be, replace it

A radiator is only there for extra heat generated by an engine, in colder climates radiator might never be used in the winter

I would check this before replacing ECT sensor

 

[turner]

Removed the PCV hose at the intake, capped off the intake nipple and plugged the loose hose. This DID fix hunting idle with IAC unplugged. Actually, the first run, it made the hunting even worse. Second and third it was gone. These computers seem to need time to settle into changes.

This would be the third time I've replaced the PCV in 2 years, most recently did it before my first (failed) test in October. If they didn't check for this in the smog test I'd be tempted to vent to atmosphere.

Waiting for cold engine to do the rest. It's odd that my thermostat might be stuck open, but also my heating is ineffective. You'd think the heater box would get hot coolant right away if the thermostat was always open.

 

[turner]

Thermostat seems to be working fine. The upper radiator hose didn't start warming until 8 minutes in. The morning dew on the hose even stuck around until then.

The driver's side heater hose got warm pretty quickly. The other (return?) heater hose never got very warm at all. I assume normal for a heater box.

Looks like I need to replace the ECT sensor again... might go looking for OEM this time, the one I used in August is Standard Motor.

 

[turner]

I'm also a bit confused about these sensors. The one I installed (Standard Motor TX6T) is pointed. Looks like this:



The Motorcraft part (DY-1145) is flared, looks like this:


Rock Auto shows both styles as compatible. Gonna order the Motorcraft since I know that will work, just thought it was odd.

 

[RonD]

It used to be the cone shaped tip was a 5volt ECT sensor, and a cylinder shape was a 12volt temp sender(for the dash gauge)
Not interchangeable

All piston engines have "Blow-by"
When a cylinder fires some of the high pressure HOT gases(exhaust) blows by the piston and rings and into the crank case
This vaporizes some of the oil coating the cylinder walls and piston
Only place HOT enough in an engine to vaporize oil
As an engine gets older blow-by increases, and so does the amount of oil vapor

In the bad ol' days there was just a vent in lower block or upper oil pan so the Blow-by could just exit the engine, and that vent did drip oil, lol
But blow-by is exhaust and pollution is pollution
So PVC system was added
PCV valve uses engine vacuum to suck in the Blow-by, so it can be re-burned in the engine
But............then there is the oil vapor this clogs up the PCV Valve, so it needs to be cleaned or replaced every 4 or 5 oil changes with newer engine or 3 oil changes as engine gets older

People do install Catch Cans when oil vapor gets to be too much


Reverse the hoses at the heater core, it reads like your core is clogged up
Both hoses should get hot, if you have the fan on HIGH one hose might be a little less hot, but should still be hot
Reversing the hoses might get some flow back but I would look at changing the core, easy to do on a pre-1995 Ranger, and they are not expensive, thinking $25-$30

You should reverse heater hoses every time you change coolant or every 2 years, it will help heater core last longer

 

[turner]

Dang, ford.oempartsonline.com has that part listed as a "sensor", then in the fine print also says "sender". I need to get a proper factory parts book so I'm not searching in the dark.



All my wrenching experience is 60's/70's sports cars, so I'm used to venting to a catch can. This is the newest vehicle I've ever owned. I seem to remember my Corvair just venting to the road. Unfortunately our smog test checks visually for PCV. I'll just replace it before every smog test.

Good to know the reversed hoses trick, makes sense. Might as well replace the core too next time I do coolant.

Edit: if anyone has a parts catalog, would love to know what the motorcraft part# is for 1987 2.3L N/A. This part is hopelessly tangled online, the cross references show both the pointed style and flared style, use sensor/sender interchangeably, etc. Just want to get the correct OEM motorcraft part.

 

[Shran]

I hate tracking down parts for my ‘88 2.3 for the same reason you are struggling. TPS for example, nobody carries the correct one, the 2.9 version doesn’t fit and several others don’t turn the right direction… I eventually found that a Merkur XR4Ti had the right part?

Anyway a coolant temp sensor from any other Ranger, ‘86 up to the early 90s should all be the same. Try looking up the part for a 2.9 powered truck. I bet you will have better luck.

 

[turner]

Unfortunately this confusion extends to all Rangers. I've seen three styles show up as "sensor" so far. All of them can also be found listed as "sender", so that distinction can't be trusted.

#1: Cone: I've only seen this from the aftermarket... I can't find a Motorcraft part that looks like this. Two wires.


#2: Flare: This is what the "official" ford database-linked sites show as the "sensor". I have one in my hand now, and the package says "sender", lol. It also has two wires. Perhaps the original part is NLA and this is continuation?


#3: Rod: One wire, also listed as "sensor". I'm guessing this is the dash sender, even though I've never seen mine.

 

[RonD]

Yes, one wire/contact is for sure a sender

2 wire can be either but connectors are not interchangeable

Also you can test OHMS
ECT sensor should be 4,000-5,000ohms at 70degF, room temp
Temp sender about 110-130ohms at room temp

 

[turner]

4520ohms, looks like this is a sensor... after this pineapple express passes I'll install it and see how the voltage reads.

My truck passed smog yesterday, so now I'm just chasing gremlins for fun.

Edit: should note that the connector on this doesn't match the ECT connector on my truck, but they included a pigtail. I'll probably test it non-destructively first