First off California sucks!!! high nox on my 86 4runner. so the guy at the shop said its timing, egr, or the small round valve next to the egr with the 3 ports. He said he replaces a lot of those valves. I checked timing and it was 5 btdc shorted so timing was good, checked egr and it checked good with vacuum so has to be the little black valve next to the egr or maybe the cat but I changed that 2 years ago so it shouldn't have gone bad so soon. I don't want to spend $60 at the dealer does anyone have a good one (the valve next to the egr) laying around for cheap or hopefully free.

Thanks in advance. Chuck

edit: sorry Im in Lancaster so cal area 93534

 

That small valve is the egr vacuum modulator. It's easy to change out yourself. I replaced it on my 95 4Runner. Autozone had the part for about 35 bucks. Did they check that all of your vacuum lines were routed properly? Two of my hoses were crossed which were part of the problem with my high NO problem.

 

If the egr had vacuum at the right time then the modulator is fine, and it's probably either a stuck egr valve or clogged tubes.

Lean mixture can cause higher nox, too, and that's most likely from clogged injectors, though bad tps or vafm readings can do it too. Bad O2 sensors usually result in rich mixture. Red Line's SI-1 Complete Fuel System Cleaner has the most polyether amine, which is by far the most effective injector cleaner. CRC's "Guaranteed to Pass Emissions Test Formula" also has a good amount. Those are the only two with PEA that I know of - Techron, BG-44 and Gumout Regane apparently no longer have PEA.

Other measures you can take for the test include running 91 octane and setting your timing (with jumper attached) back to 4 deg btdc.

When was the last time your cat was replaced? If you had a new one, it would probably convert those noxes (word?)

 

What were the test results?
Please include HC, CO, CO2, O2 and NOx for both idle and 25 miles per hour tests.
Otherwise, add a vote for the converter.

 

what good is running 91 going to do? seems to me like that will actually make it pollute more with the gas not burning as fast as the 87 does.

 

The issue mentioned by the OP was high Nox, which is primarily caused by high combustion temps. This comes from faulty EGR, lean mixture, timing too advanced, but can also come from detonation or preignition. Higher octane will reduce chance of Nox due to detonation/preignition.

I've also seen a couple studies that indicate that ethanol, while it lowers hydrocarbon emissions, actually causes higher Nox. Hard to get away from the stuff these days, especially in CA.

 

the readings

-----hc-(ppm)----------------co (%)----------------no (ppm)
max--ave---meas--------max---ave---meas-----max--ave---meas
124---41-----29---------0.78---0.13---0.03-----1089--399---1580--at-15mph
99----29-----28----------0.58---0.11---0.02------919--332---1547--at-25 mph

I replaced the cat about 4 years ago. I can check the timing again and drop it a little that might help.

 

I checked and autozone doesn't carry the modulator here in Lancaster and all the vacuum lines are in the right place.