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

[turner]

1987 2.3L 4x4 - I bought this in 2021 for cheap because the PO couldn't get it to pass smog. It was a "gross polluter", which in CA just means abnormally high HC/CO readings. This forum was a great resource then, I got it to pass without starting a thread. This time I'm a little more stumped, since I've so recently (2 years ago) addressed all the usual suspects.

Let's start with the test numbers. I passed very comfortably 2 years ago. And I failed miserably this past week. I was very surprised that in 2 years, and less than 3,000 miles, the emissions regressed so far.

2021

	HC (Max is 150/180)	CO (Max is 1.20/1.20)
Idle	11	0.00
2500 RPM	11	0.00

2023

	HC (Max is 150/180)	CO (Max is 1.20/1.20)
Idle	3295	8.60
2500 RPM	303	5.32

Functional checks at smog station 2023:

• PCV pass
• Cat pass
• EGR pass
• Fuel cap pass
• Spark controls pass
• Thermo air cleaner pass
• Vacuum lines pass
• Ignition timing pass
• Sensor wiring pass
• Evap controls pass
• Oxygen sensor pass

What I've tried to date:

• New TPS - 2021 (confirmed good/adjusted with voltmeter 2023)
• New MAP - 2021 & (again) 2023
• New PCV - 2021
• New dizzy rotor and cap - 2021
• New ignition wires - 2021
• Retimed ignition - 2021
• New cat - 2021
• New 02 sensor - 2021
• Seafoam treatment in fuel + top end - 2021 & 2023
• 10W-30 changed - 2021 & 2023
• Oil filter - 2021
• Air filter - 2021 & 2023
• Replaced coolant temp sensor - 2023
• New plugs - 2021 & 2023 (properly gapped)
• New air charge sensor - 2023 (old one was oily and bent, but bench tested good)
• Engine on/off EEC4 tests - no codes - 2023

The smog checker is an experienced local mechanic. He told me to check the coolant temp sensor, that perhaps I was never leaving open loop mode. He was concerned that my dashboard temp gauge barely moved, but that's always been the case, and it passed with that condition. He also said it's running rich, and what I've read online suggests the same... rich running would fail both HC/CO. However, the plugs are chalky white, so it's not running rich. It's lean. I'm not sure what to make of that, or why he thought it was rich.

I absolutely flogged it up and down a mountain road before testing, but no idea how quickly the tech started my test. I've heard it only takes 10min for the cat to fall out of ideal heat range.

There are no vaccum leaks. I have not tested compression. I have not tested fuel pressure in 2023, but it was good in 2021. I have not tested the 02 sensor or cat, but they're both so new. The truck runs perfectly. No starting issues, no hesitation or stumbling or idle issues.

This is my daily driver, except I only drive once a week, and usually <2 miles. It might be in need of an italian tune-up, but surely that doesn't explain the huge increase in readings.

What else would you address before retesting?

 

[turner]

I did smell gas in the vacuum line running to the fuel pressure regulator. Is that a sign that the bellows (or whatever) inside has failed?

 

[RonD]

Yes, replace the FPR if you smelled gas in its vacuum line, and that would cause the high readings for sure

It means its leaking internally and unmetered gas is being sucked into the intake, via that vacuum hose

Yes, do the "Italian tuneup", highway 60+MPH for 15-20min. drive, after changing FPR

Starting and running an engine for under 10min at a time is very bad for the engine and its systems, just FYI
Remove oil fill cap look for white residue on under side, same for PCV valve pull it out and check
White stuff is oil mixed with water(condensation), that hasn't been able to be evaporated because engine is not being warmed up long enough, i.e. under 10min drives repeatedly
The oil also stays dirty because if never gets hot enough to burn off the blow-by gases, and condensation

If you have a compression gauge I would test at least 2 cylinders, all 4 would be best
Could be timing belt has stretched a bit, and lower compression causes incomplete burns and high emissions
1987 2.3l is 9.0:1 ratio so 145-155psi is expected

You can do this simple test to see if valve guide seals are leaking
Drive up a hill then get up some speed to go down the other side but keep trans in gear and use the engine as the brakes to slow vehicle down while going down the hill, don't touch the gas pedal
At the bottom of the hill give it some gas pedal and watch the tail pipe emissions, puff of smoke means valve guide seals are leaking

Using the engine for braking causes very high vacuum in the intake, this will suck in oil from the valve train(intake valve stems) IF valve guide seals are leaking
Burning even a little oil causes high emissions

 

[turner]

Copy that, will replace FPR. PCV has already been replaced, didn't notice white residue. No residue under filler cap. I can check compression too, thanks for the values.

One more bit of confusion, if unmetered fuel was being dumped into the chamber, wouldn't the plugs read rich? I've attached a photo in case you disagree on them. They all look identical.

I live in the mountains and drive the Ranger like a sports car (on longer trips), engine braking down through the gears while on the brakes, then full throttle out of the corner. Even raised the throttle pedal so I could heel toe . Never any smoke. Over the past year/3000 miles it hasn't consumed enough oil to drop below the min line on the dipstick. The shorter trips to town aren't ideal, but not sure what to do about that.

I usually work on pre-EPA carb'd cars, so this black box stuff is frustrating. I'll shotgun a bunch of fixes, pass smog, and learn nothing about what worked. Wish there was a home-sniffer.

 

[rusty ol ranger]

Generally if the FPR blows it runs pig rich.

So yes the plugs would be black

However with your short tiny trips im wondering if its not really "rich" untill it gets good and warm...since they use more fuel anyways when cold.

I would also toss a t stat in it...if its not getting to temp (assuming its not a gauge issue) the coolant sensor is going to feed it more fuel anyways thinking its still cold

I cant believe cali makes you emission test an 87. Thats slightly ridiculious IMO

 

[rubydist]

Did you look at all the plugs or just one? Because another possibility is a fuel injector that is not closing, and that would only affect the plug associated with that bad injector.

 

[turner]

The mixture should be richer on those short trips, right? And richer again if the t-stat is keeping the engine too cool. Richer if the FPR is leaking... the smog tech was sure it was running rich. That's what's weird about the lean plugs. They were all identical, combustion conditions/wear are likely even between the cylinders.

This t-stat was in the truck when it passed with flying colors, and the gauge behavior is consistent. I bet PO put in a colder stat, so I should probably change it anyways since that works against me passing emissions. Although... my plugs are lean so maybe it's currently helping, lol.

CA is weird. On the one hand, they smog-test everything after 1974. On the other, they make it incredibly easy to drive earlier cars, likely because the classic car industry is centered here. It creates funny situations, like a 1974 BMW 2002 is desirable but a 1975 is worthless. Or me, struggling to get this little truck road legal while Jay Leno drags a Duesenberg all over Burbank with cops waving to him.

 

[RonD]

On the 2.3l Lima the temp sender is at the side back of the head by the oil pressure sender so it will read lower that a sender up by top front of engine(where ECT sensor is)

If the HC and CO levels were high then not much of a guess as to why, rich running or burning oil
Could be the new Cat has completely failed but extreme longshot

Could also be spark timing

And it could have been a problem with the test equipment, they do fail

 

[turner]

I can check timing again. I've so far ignored it because timing got a passing grade on the test (whatever that means), and the tech made a note of saying "timing is fine".

Can we assume I'm not running rich based on the plugs? They've been in the car for 2 years/3000 miles. On my carbureted cars I would be 100% sure that I'm lean (I use an AFR gauge anyways). Might be a dumb question but I try not to assume anything with computerized/sensor-heavy engines, since I have no experience with them.

 

[rubydist]

No, the test results clearly show its running rich. So either the testing equipment took a dump, or its rich. You cannot get HC and CO numbers like you have from it running lean, if its lean the NOx will be too high.

That is why I asked - did you look at all the plugs or just one?

 

[RonD]

Yes, the spark plug tips show no rich running or oil burning, so based on that alone I would discount rich running or leaking valve guide seals

But..................the emissions test shows otherwise

 

[turner]

No, the test results clearly show its running rich. So either the testing equipment took a dump, or its rich. You cannot get HC and CO numbers like you have from it running lean, if its lean the NOx will be too high.

That is why I asked - did you look at all the plugs or just one?

Copy that. I answered in my last reply, and it's in the original post too. All plugs are identical, they're so uniform that I didn't even bother photographing the others. I already replaced them. I don't even see NOx on my test printout, or at least I dont know where it is.

So that's very confusing. It sounds like you're saying the results cannot be accurate given my plugs. Even if my cat has completely failed, a lean condition wouldn't lead to high HC/CO, correct?

That means the sniffer rig has to be bad, which seems unlikely too! I'll be taking it to the same station for a free re-sniff... if the rig is reading high (or whatever), they'd have noticed by now, they test cars every day.

 

[turner]

Yes, the spark plug tips show no rich running or oil burning, so based on that alone I would discount rich running or leaking valve guide seals

But..................the emissions test shows otherwise

Any ideas on how that discrepancy could happen, besides faulty test equipment?

 

[RonD]

Long shot
Catalytic converters use heat and chemical reactions to change CO into CO2
And to change HC into CO2 and Water(H2O)

Also NOx into N2<<< did you get an NOx reading?
If your NOx reading was higher but still passed I would think Cat Converter issue, newer or not
The 2.3l Lima doesn't run hot enough to produce a lot of NOx
EGR systems are used to reduce NOx more than Cat converters

 

[turner]

Also NOx into N2<<< did you get an NOx reading?

I'm not seeing NOx on either the 2021 or 2023 test (attached). Unless I'm missing it...