Failing Smog - Suggestions?

[Keto]

Failing Smog - Suggestions? - FIXED!

I have a '96 3.0, 107K miles, failing CA smog, just barely. Passes 25mph test with flying colors, fails the 15mph in only 1 category. Everything is good except HC is just a pinch over max. So close its stupid. Tried the CRC stuff (didnt work), tried ISO Heet trick too, cant get it down.

Full tune-up not too long again, plugs, wires, coolant flush/replace, oil change, air cleaner, etc. Throws no codes at all.

I've done the following things:

* New EGR valve, cleaned out the pipes/tube too.

* Replaced all the o2 sensors with new Bosch units, reset the ECM too

* Checked all the vacuum lines, replaced a couple ratty ones.

* Looked for misc vacuum leaks

I have new exhaust manifolds on the way, I *think* one has a small leak and they look like hell (rusted, etc). Gonna pull off the exhaust and reseat/seal everything on the y-pipe, etc. That may be what the problem is.

Putting that aside for the moment....

Anyone have any suggestions on other things to look at specifically?


Thanks

 

[RonD]

Pull a spark plug and see what it looks like.

Are you using oil between changes?
The miles are very low for a '96, so vehicle probably sat for long periods, and that means the valve guide seals probably dried out and cracked, so oil is getting into cylinders.
The intake valve stem pass from the valve cover area down thru the intake, because of the vacuum in the intake, oil on the tip of the valve stem can be sucked passed a worn valve guide seal and into the intake.
PCV valve creates negative pressure in the valve cover area this can help lessen oil leaks and oil passing the guide seals, so make sure yours is working.
Lucas makes an oil treatment that swells rubber seals, like main seals and guide seals, might be worth a shot if you think it could be burning oil.

When you drive it at 15mph, say up a hill, can you feel it misfiring occasionally, the misfires cause the higher HC.

You could widen the gap on the spark plugs a bit, stock gap shows .044, try .048
Spark gap is set for average not best spark, wider gap gives better firing at lower RPMs but has less recovery time at high RPMs.
Narrower gap is better for high RPM driving, but makes for harder cold starts and low RPM driving.

An O2 sensor only sees Oxygen content in the exhaust stream, it can't see fuel.
Too much oxygen in exhaust means lean
Too little oxygen in the exhaust means rich
Exhaust manifold leak will suck in air, the O2 sensor sees this extra air as a Lean burn so computer adds more fuel than is really needed

 

[Keto]

Pull a spark plug and see what it looks like.

Are you using oil between changes?
The miles are very low for a '96, so vehicle probably sat for long periods, and that means the valve guide seals probably dried out and cracked, so oil is getting into cylinders.
The intake valve stem pass from the valve cover area down thru the intake, because of the vacuum in the intake, oil on the tip of the valve stem can be sucked passed a worn valve guide seal and into the intake.
PCV valve creates negative pressure in the valve cover area this can help lessen oil leaks and oil passing the guide seals, so make sure yours is working.
Lucas makes an oil treatment that swells rubber seals, like main seals and guide seals, might be worth a shot if you think it could be burning oil.

When you drive it at 15mph, say up a hill, can you feel it misfiring occasionally, the misfires cause the higher HC.

You could widen the gap on the spark plugs a bit, stock gap shows .044, try .048
Spark gap is set for average not best spark, wider gap gives better firing at lower RPMs but has less recovery time at high RPMs.
Narrower gap is better for high RPM driving, but makes for harder cold starts and low RPM driving.

An O2 sensor only sees Oxygen content in the exhaust stream, it can't see fuel.
Too much oxygen in exhaust means lean
Too little oxygen in the exhaust means rich
Exhaust manifold leak will suck in air, the O2 sensor sees this extra air as a Lean burn so computer adds more fuel than is really needed

Good info, thanks Ron

Doesnt use any oil between changes, I think its ok there. Changed the PCV valve about 6 months ago, checked it last week, still good/clean.

I was going to pull the plugs to check them this weekend to see if any of them are mis-colored (etc). If theyre 'clean' I'll re-gap them per your suggestion.

It doesnt misfire under load, but its always had a rough idle. Almost seems like a misfire, but its not throwing any codes. I've been told the vulcan in the Rangers do idle a little rough, so I dont know.

Manifolds will show up tomorrow, so I'll have lots of fun this weekend, lol

 

[RonD]

First, I am not made of money, and my wife and kids wouldn't defend me very hard if someone called me "cheap", lol, but I have been wrenching for quite a few years.

When I know I will be dealing with exhaust manifolds or pipes on a DIY project, I drop off the vehicle at my local muffler shop, tell them what I will be doing and they remove all the exhaust bolts/nuts I will have to deal with and then snug them back up, replacing any that break or get stripped heads.
Most I have ever paid is $60 including parts, they have all the custom tools and torches needed to get it done in well under an hour, and they do it daily so......they are fast, and any parts needed are on-hand.

I have spent hours on 1 or 2 bolts, and it is just a pain to have to run to parts store to get replacement parts or the right size reverse drill bit or...........??

 

[adsm08]

I have a '96 3.0, 107K miles, failing CA smog, just barely.

You could always move. In my research I have found this is often the most effective and reasonable way to deal with California emissions.

 

[Rearanger]

It doesnt misfire under load, but its always had a rough idle. Almost seems like a misfire, but its not throwing any codes. I've been told the vulcan in the Rangers do idle a little rough, so I dont know.

I can attest to slightly rough idle with an immaculately cared for engine. I can't explain it or improve it, but even my 4 cyl'd Camry has a better idle. It does feel like a "miss" but I've had no codes. I've put it down to an old design pushrod engine pushed past it's outdated technology.

At present I'm investigating dirty injectors as cause for slightly rich fuel trims.

No tailpipe emissions here so smog a lesser issue than CA.

 

[Keto]

Thanks guys

Pulled off the exhaust Y-pipe, cats, and passenger-side manifold today, I'll get to the drivers-side manifold tomorrow...

Thank gawd for PB Blaster, even with the right tools these exhaust bolts (et all) can be a real Bear.

Much to my surprise, the passenger-side manifold did not have a gasket... or gasket material of any kind on it, or left on the engine side. Clean as a whistle... and definitely explains my exhaust leak.

 

[RonD]

Manifold exhaust leak causes computer to run engine rich.
Exhaust leaks suck in air, on 3 cylinder bank it would suck in air 2/3 of the time
O2 sensor only reads air(oxygen) content in exhaust, not fuel, so it sees this extra air and reports it to the computer.
Too much air in exhaust = Lean burn
Computer adds more fuel, engine is now running richer than it needs to because of false Lean.

 

[Keto]

Another update...

New manifolds, new gaskets, buttoned everything else, and it failed far, far worse than before, lol.

Ran some temp checks on the cats, and they arent really lighting up. Exhaust fume smell very evident.

Now, the truck has new cats. Exhaust fume smell gone, and the exhaust is putting out water as it should.

Re-test later this week....

 

[alwaysFlOoReD]

So you believe it needed new cats originally? Or was new cats just part of the solution?

 

[Keto]

So you believe it needed new cats originally?

More than likely.

I think the cats were probably shot before, and someone removed the manifold gaskets as a way to help get around smog. With an exhaust leak, pulling in outside air was probably helping it pass the sniffer test. When I sealed it all up proper, no outside air and a horrible fail.

Testing the cat temps was the last thing... 107K miles took their toll apparently.

 

[Keto]

Just thought I'd make the final update on this...

SO, Walker Exhaust makes a nice bolt-in cat' set specific to the Rangers, CARB approved, $330 on Amazon.

Bolted up with new gaskets, and smog'd it again. Passed brilliantly, super clean out the tail-pipe, the BAR tech commented its passing better than when it was new.

Old cats were without doubt BBQ'd, lol.

 

[Rearanger]

Old cats were without doubt BBQ'd,

Nice to know why, could save you another set soon. If you still have the old ones maybe cut them open for look-see.

 

[Keto]

Nice to know why, could save you another set soon. If you still have the old ones maybe cut them open for look-see.

When I pulled the old cats to begin with, they were remarkably clean. Didnt see any of the usual signs of severe poisoning by coolant/oil/particulate.

I suspect they were spent, partially by the engine running so rich for quite some time (due to exhaust leaks, etc, and 107K miles). Cats do burn out eventually, lowering their efficiency drastically.

 

[hoosier1104]

I burned up a Warner cat in 3 months on my 8. There is a reason why the OEM cat costs $1500 new.