'93 7AFE 1.8L Failed HC's, HELP!

[92GTA]

I've got a CA 1993 Corolla with the 1.8L 7AFE, 100% bone stock.

I failed my HC's (Hydro Carbons) on the sniffer. Those of you familiar know that you are allowed a PPM of 92 @15mph and 57 @25mph. Well I hit 100 @15mph and 78 @25mph.

So as you can see I'm just a little over.

Is this a common problem on Corollas this old? I'm broke and out of work but I know cars and can work on them. 2 years ago I replaced the cat and that barely got me by, I don't wanna have to do it again. I tested it twice and the second I added Xylene to the tank thinking that would help. I couldn't get a good comparison against my 1st test for the HC's and the Xylene because on the first test I failed for a broken and bypassed thermo valve in the head between the canister and the throttle body, now that is fixed but I still got the above readings.

So, any ideas?

Thanks!

Alex

[RedAE102]

I have a few questions for you... I also have a stock CA 7A-FE 5-speed. Tell me a bit about when you took the car in... did you drive straight there in the morning or what? You can usually just barely sneak by on a borderline car by driving it at least 10 miles prior to smogging, and driving it REALLY hard for those last few miles to get everything good and heated up. It can also help if the car is kept in a lower gear during the test (shifter kept in 2 or possibly even L). Anyway, my first thought is the O2 sensor (the one on the manifold... the computer could care less about the back one). Also, being a CA model, your car has two cats, not one. My car (November reg.) is going to be due for smog again this year as well.

[92GTA]

I have the auto so it's simply in drive when on the smog dyno. I should mention I tune cars so I know about sensors and heat range so yes I drove it hard right before taking it in.

I tried locating an o2 sensor and all the parts places says dealer only and Toyo wants like $400!!!! So yeah, ummm NO. I could always tap into the ECM's data stream and check to see if that sensor is bad though I guess.

Any other thoughts? I'm not familiar enough with emissions to know specifically what directly effects HC levels like o2, egr, evap system, etc. The car has 140K and they are hard miles, I drive the piss outta the thing. I did a very basic tune-up on it, oil, filters, plugs, wires, but no sensors cause I'm broke, lol.

[Flashmn]

I tried locating an o2 sensor and all the parts places says dealer only and Toyo wants like $400!!!!

Considering an o2 sensor is standardized equipment, there shouldnt really be any problems in putting in a no-name brand one.

[RedAE102]

Bosch O2 sensor no. 12031, universal type, available at both AutoZone and Checker/Schuck's/Kragen/Advance Auto Parts for $33 (also at Napa for $1 more), and is a normally stocked part at all of them. OE type is $130. The difference between the universal and OE type is that you have to splice the existing connector onto the new sensor's wire... nothing else.

[REN69]

main reasons to fail a smog test/emissions test:
O2 sensor
Catalytic converter

Its cheaper to replace the O2 sensor.. if the car still fails, try the cat.

[94_Rolla_Guy]

The high HC's are caused by excess fuel or incomplete burn... if by chance the engines burning oil thats most likely the cause. If it hasn't had plugs in a while thats not a bad thing to do also clean the throttle body and tune-up stuff, now ive never heard of xylene, but i have heard of the methyl hydrate or gas line antifreeze aproach, also if its high on HC and you don't care about whats causing it try advancing the timming like 2 deg, that will lean out the engine, just be careful in doing so...not to lean it out too much keep an ear out for pinging...also to much lean out and it will fail on NoX

[foodaa]

1st Test
-No Data-
-Xylene in fuel??-

2nd Test
-With Xylene-
50/15 = 100 PPM HC
25/25 = 78 PPM HC

Why did you add Xylene? Maybe the reason you failed the test was because of the Xylene you added. I know Xylene is flammable, but I'm not sure how it mixes with fuel or how it affects how the fuel vaporizes/burns.