81 pickup, 22r, engine is a fairly fresh rebuild (~30k), new stock carb, new plugs/cap/wires, new cooling system (not that that matters). 1500 miles on oil change.

my hydrocarbons are 2x and 4x what they should be. i ran it through last week on a faulty thermostat (it was running really cold) and it failed. i figured the cat wasn't getting up to temp so i got the stat switched out to a 195, now it runs perfectly in the middle of the gauge. but still no real change in hydrocarbons.

the numbers are last weeks test running cold, first number is first idle test, second number is the idle after revving to 2k rpm for 30 seconds. the second numbers are todays numbers, same test but it was running at normal temp.

first: 572, second: 752

first: 474, second: 836

hydrocarbon limit is 220 in both tests.

every other test (CO and CO2) are within limits.


the test page suggests a misfiring engine (unburnt fuel or oil), causes:
plugs/wires/coil/cap.
vacuum leak
EGR malfunction
timing
catalytic converter failure
worn valves, seals or piston rings
carb malfunction.


because the ignition and carb are new on a rebuilt motor (that nix's most of the list), so i'm thinking about the EGR, if not that then the catalytic converter.

any way to test the EGR to know for sure?


Al

 

Valves Adjusted?

Other than that, i'd look to cat and EGR as well.

 

FSM has proceedures for checking the EGR. I can scan & post if you want..

 

Have you considered o2 sensors.. they can be making it run rich or leaning it out depending on how they are reading. Might be a cheaper option than going with EGR and CAT. O2 are around 40 vs 70-90 on universal Cat thats cost on parts maybe alittle higher depending on where you go. On testing the EGR you can apply vaccum to it to see if it holds.. thats how we test them.

 

Our trucks don't have 02 sensors.

 

I would rule out the EGR as a cause for high amounts of hydrocarbon. EGR is designed to control Nox and not carbon. Sounds like you have a jetting issue or a non functioning cat or both. Has the carb had any modifications? Many of these trucks ran really lean at idle from the factory (especially Canadian or Cali spec) and people rejetted them to make them run smoother. Pull the carb and clean it. Make sure your choke linkage is working properly as this will cause a rich mixture for sure. Check the jet sizes and low speed air screw settings.

My 84 22r past the emission every year I needed it to. Somtimes I retard the timming a couple of degrees from stock before the test just for some extra insurance as well. This helps mostly with the NOX reading though.

 

Fair enough lol, Ive only been a yota owner for about 2 weeks.. wasnt sure when they started puttin o2s on vehicles prolli atleast has to be fuel injected otherwise the o2 wouldnt do much anyway.

 

the carb is new from what i understand. one of the PO's had a problem with bad carbs (kept letting the same idiot rebuild it) and when he sold it to the next guy he put a new carb on it (or maybe remanned) and everything ran great since.

but IF the knuckle heads rebuilds were running horribly rich, i suppose it could have burned up the cat.

Al

 

update:

finally got a new cat installed this morning. ran it for 40 miles on the highway per the exhaust guy's recommendations before running it through DEQ again. in fact, the exhaust guy was a 1st gen nut, and even tried to solve my 'brake' dash light issue while it was in the shop. he gave me some other tips (most i'd already known) and even told me him or one of his buddies would buy it in a heartbeat.

anyhow.... 40 miles and a DEQ test later... it barely squeaked by in the hydrocarbons department, but it PASSED!! a little bit of celebration on my part, but i'm still concerned why i'm shooting so high on HC's. maybe an EGR change in the not too distant future?

Al