Cm1lls

Hello I have a 1988 Toyota pick-up, its a 4 banger with 4wd (manual). I recently took it in to get it smogged in California and it passed everything (visual and functional) except the emission test because of the NO and CO. The truck had been sitting for a while besides the occasional start up and let it sit for a little bit and used to pass no problem, but now it wont. Below are the emission results. The person who tested it said that the reason the first CO was high was probably because the NO or it wasn't hot enough. Before we got the test we ran it for a while and made sure to have barely any gas in it and then filled it. Once we got there and sat for a while and probably cooled down. I was wondering if anyone has any ideas on what is wrong and/or what I should check out. ANY HELP WOULD BE GREATLY APPRECIATED.

TEST (15mph)

RPM: 1612

%CO2: 14.1

%O2: 0.8

HC (PPM)- MAX:135 MEAS:106

CO (%)- MAX:0.87 MEAS:0.91

NO (PPM)- MAX:1058 MEAS:2410

TEST (25mph)

RPM:2537

%C02: 14.1

%O2: 0.8

HC (PPM)- MAX:115 MEAS: 42

CO (%)- MAX:1.08 MEAS:0.31

NO (PPM)- MAX:918 MEAS:1738

*MAX=Maximum Allowable Emissions MEAS=Amount measured

P.S. Sorry If this isn't the right place to post couldn't really find a better place. If so let me know! Thanks A LOT!

kennyboy019

Well, I think NO comes into play when your burning too hot, but I may be wrong.
Could mean too lean a mixture, or your EGR is bad.

How many miles and which engine. And did you change the oil and run some fuel cleaner?

Robert m

iTrader: (2)

make sure the timing is set at 5*. mine was at 9* and it caused the NO to shoot way up the first time i smogged it. how old is the cat?

fireman1559

i would check the EGR and clean it or replace it more than likely replace it. it may also be running to hot and if its been sitting for a long time antifreeze does something weird it turns into like a mud looking substance and it will clog up everything so maybe a good flush and replace the hoses and thermostat and that should help with that problem. times like this im glad to live in a state where we dont have to do emmsions testing. good luck on passing it again

abecedarian

I'm with Robert_m on this. Excessive advance can cause high NOx readings due to higher combustion temps and can also elevate CO levels so check the timing.
That both CO and NOx drop at the 25mph test suggests that EGR is working properly, lowering temps. But since NOx is remaining high and continues to fail implies the converter isn't operating properly.

4Crawler

iTrader: (3)

Make sure everything is good and hot before the test, the cat won't work well cold nor will an unheated O2 sensor. Try driving 10-20 miles at highway speed before the test and leave the engine running until you get to the test machine. And yes, check the timing, try retarding it a bit if you can, I usually try to run my '85 as close to 0 BTDC as I can for the test to reduce NOx readings. And yes, check that the EGR valve is working properly and that it is very CLEAN.

Cm1lls

Thanks for all the suggestions I'll start doing some of that stuff and let you know. To answer some of your questions.. The engine is the 2.4 liter 4 banger. It has about 189,000 on it but recently (3-4 years) put in a rebuilt engine...from then it sat for a couple years. We didn't change the oil or ran fuel cleaner but we did have a new tank of gas. THANKS

Cm1lls

Let me clarify the truck has 189,000 but the engine only has like a years worth of normal use...not sure how many miles