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

[rubydist]

It says "oxides of nitrogen... are not measured during the idle test" so they don't measure or report NOx numbers.

I don't think that just a cat problem will result in those numbers, but you could always replace the cat and see what happens.

 

[turner]

Ah missed that fine print.

The cat (at least here in CA) is $500 for the Walker generic, so that's my last resort. Especially since the one on the truck is only 2 years/3k miles old. It does have a 5 year/50k mile warranty, but I imagine they don't make that easy to claim. If I have to buy another one it's going to be reserved for smog tests only

Thanks for the help everyone. I'm going to test the O2 sensor, replace the FPR, and try another sniff. I'll show the tech my chalky plugs and see if he has any ideas.

 

[turner]

After reading up on CA and universal cats, it might not be so crazy to think the cat failed within 2 years. An exhaust shop tech claims that Magnaflows consistently fail inside of a year. They seem to like Walker more, but say all universals have less material inside than OEM, so they die quicker. Lots of people call them "smog-passers".

It also seems that my short trips have a specific contributing factor... if the cat never gets hot enough to burn off hydrocarbons, it gets bogged down (whatever that means).

That doesn't really explain (or I don't understand) why my lean condition is showing as rich on the sniffer test, but we'll see if that's consistent on the next visit.

 

[RonD]

Lean causes pinging/knocking, rich causes smoke out the tail pipe

If you don't hear any pinging/knocking when accelerating, so under load, then for sure not running Lean
If there is no smoke out the tail pipe then it's not that Rich

Warmed up engines
Smell the exhaust on a newer vehicle, that passes smog, lol
Then smell your exhaust, you can smell Rich

 

[turner]

Honestly the truck runs great, no knocking, no smoke. The plugs do look lean, but not severely. I'm "warming up" to the idea that it's just a bad cat.

Wish I had a newer vehicle to sniff, lol. This is the most modern I've ever owned, hence my lack of knowledge. I'm used to tuning carbs to 13:1 at WOT and calling it good enough.

 

[RonD]

Warm up the engine and see how hot exhaust pipe is before and after Cat, should be much hotter after Cat

"As a “rule of thumb” the temperature immediately after a cat should be 150–300 degrees (F) more than the temperature immediately before a converter. This means the converter is doing its job. "

IR Temp guns are not too expensive and cool to have, but make sure it can do high temps

 

[turner]

I'll add that to the list. I've got a kitchen IR gun that claims to go to 1000F. I've read somewhere else that I need to pull a plug wire and ground it to do that test, couldn't figure out why.

 

[alwaysFlOoReD]

I'll add that to the list. I've got a kitchen IR gun that claims to go to 1000F. I've read somewhere else that I need to pull a plug wire and ground it to do that test, couldn't figure out why.

If you pull a plug wire and ground it the unburnt fuel will go thru the cat. The cat will burn it...or not. I'm not sure that's necesary but maybeit's a sure way of checking.

 

[RonD]

I would do the temp test as is

If its not a lot hotter after the Cat then you can feed it some extra fuel by unhooking a spark plug
If it gets a lot hotter then you could actually be running too lean and Cat might be OK

A 1986-1994 Computer should squirt in extra fuel now and then to keep Cats hot its just part of the software
And its why the O2's after the Cats was added in 1995 and up with the newer computers
The computer could then add extra fuel just when its needed instead of just on a schedule, so better MPG

 

[scotts90ranger]

Not to correct Ron as that seems unnatural

"Modern" 3 way catalysts operate on oxygen storage where they constantly switch between rich and lean to keep the chemical reaction alive in the catalyst so the fuel system is constantly being switched between just rich and just lean of stoicheometric air/fuel ratio (14.7:1 on gasoline, "lamda" is more better for alternative fuels but whatever, not important...) and switch between the two idealy several times a second. The post catalyst oxygen sensor is normally checking that it is NOT switching like the pre cat sensor to make sure the cat is still working, sometimes systems will add in an intrusive fueling at random times (usually steady state operation within a steady rpm and load window) to make sure the post O2 is responding to see if someone just put in an antifouler... they also check for the voltage to be within a certain range, Stoich is .45V so normally they'll look for like .2-.8V...

That said, I'm very familiar with what we have at work obviously, but what GM does and what Ford does might be way different...

That said, like said I'd change the fuel pressure regulator if you smell fuel in that line then retest, looking at that plug unless there's another cylinder that's dead from a stuck injector or something it'll likely be different than the last time

 

[turner]

Closing the loop on my previous issue (and starting a new one)... replacing the fuel regulator got the truck to pass the sniff test with the existing cat, so thanks for encouraging that. I shotgunned some other stuff at the same time: new PCV, new air temp sensor, new coolant temp sensor, new MAP.

Unfortunately, it now fails for timing. Which is annoying, because it passed timing at the first test. Apparently to test timing they pull something called a "spout connector" to "disconnect the computer" (again, I'm a carbs guy, this is greek to me). When they did this, the truck hunted between lugging and surging and wouldn't settle into an idle. This didn't happen during the first test (different shop).

I did notice after replacing the FPR, the idle is now 100-200 RPM higher, probably 900-950, and a little less stable than before.

 

[turner]

Ran the code reader and got some fresh codes. It came back clean before my first (failed) test, strangely. KOEO (key on engine off) gave:

23 -- TPS out of range. I've previously replaced & set this with a multimeter, had to do it to pass two years ago. Confirmed it was still correct before my test last month, and it passed. So curious to see what it will read now.

31 -- EGR valve control sensor fault (first smog passed the EGR function). I replaced this 2 years ago.
-- OR EVAP control system below min voltage. Don't know what EVAP is, but will look into it

 

[RonD]

SPOUT is SPark OUT

You must have a distributor on your 1987 2.3l
The ignition module and the distributor don't have Spark Vacuum Advance, which is required for engine operation when its under load

The fuel injection computer does have "engine load" data from TPS, MAP sensor and RPMs
So the SPOUT signal comes from the computer and goes to the ignition control module to advance or retard spark timing as needed
Replaced Vacuum advance
Unplugging the SPOUT removes computer control for spark, so Base Spark timing can be seen, 10-12deg BTDC, with warmed up engine is expected
(Same as unhooking vacuum advance hose when setting base timing on old distributors)

SPOUT on the 2.3l is on passenger side engine bay about midway on a wiring harness, usually 2 yellow wires on a connector, the end of the connector unplugs and that disconnects the 2 yellow wires, the SPOUT wires

You will need a timing light to test Base Spark timing

 

[RonD]

Forgot to mention, the 2.3l Lima engines could wear out distributor gears
First thing I would check is distributor shaft for wobble
Remove the cap and push the rotor around to see if there is play in the shaft, should be tight, no play
If possible have someone crank the engine over while you watch the rotor/shaft for any wobbling, needs to spin true

 

[turner]

Forgot to mention, the 2.3l Lima engines could wear out distributor gears
First thing I would check is distributor shaft for wobble
Remove the cap and push the rotor around to see if there is play in the shaft, should be tight, no play
If possible have someone crank the engine over while you watch the rotor/shaft for any wobbling, needs to spin true

I'll give it a look... I did replace the rotor/cap/plugs as a group a couple years ago and didn't notice any play. I also set the base timing, so I must've known where that SPOUT plug was at some point! Your description helped, yellow wires with green trace that end in a plastic plug.