HELP! Failed SMOG!

I guess its running rich at 2500 rpm or so. I noticed after a while back when my CPS shook off and I reinstalled it (with better bolts and nuts this time) it hasn't been running all that great at that RPM, but would that cause a RICH condition? Its not running rich at idle at all.

CLICK FOR SPECS

Gotta get it fixed ASAP and I don't have the $$$ to buy all kinds of parts tryin' to fix it.

Sixteen dollars for a smog check and you're complaining? Around here, I'm doing good if I can get done for $57!

Seriously, from what I'm seeing you're starting to have catalyst failure. If you were running truly rich, you'd have failed both HC and CO. Catalytic converters seem to fail on one or the other first, then you lose on both.

If the catalytic converter is original, it probably needs replacing by now anyhow. You can use a "universal fit" for Chevvy and have the bolt flange welded on, and just clamp the lot together. I did that, and it passes the Smog Nazis out here, so you should have no trouble with that setup. Besides, if you use a BBChevvy converter, you'll breathe better. Might as well toss in a Walker Turbo muffler (for $20) while you're about it - if that's the original muffler, it's probably close to shot as well.

Be glad it's not your EGR valve - that thing is OEMR only and about $150. I can say that because your HC and CO are still fairly elevated - if they both drop to nothing, your EGR just crapped out! I've been thru all this before, in case you are wondering...

Expect to pay about $80 for the converter, $20 for a Walker Turbo, and probably $15-$20 in parts, pipes, and sundries. I say keep the bolt flange simply because that makes it FAR easier to do heavy transmission work (especially if you have the 5-speed!)

5-90

You can get a high flow cat on ebay for around $40....


And little alcohol in the tank can work wonders...

Alcohol in the tank, eh?

5-90, I believe you are steering me in the wrong direction, but I may not have provided all the info I should have.

This thing passed CA smog earlier this year, and the CAT is not very old. IT DOES run choppy between 2k and 3k.

Carbon monoxide (CO) is a product of incompleat combustion, which is fully combusted in the catalytic converter by a catalyst of rare earths and high heat (just like HC - same situation, different stuff.) But, if you just replaced the catalytic converter (you didn't tell me, which is why I brought it out first - it's under there and gets knackered about pretty good...) we'll go ahead and cross it off.

The other component that tends to drive HC/CO emissions one way or the other is the EGR valve - but when it fails it drives both of those DOWN. So, we'll leave that aside for the moment as well (yes, everyone, I read the report. It's an 88, so it has an EGR valve. Just wanted to get that out before anyone said it...)

Since the cat and EGR are no longer candidates, the other components which effect fuel metering come into play - the Intake Air Temperature (IAT) sensor, the Manifold Absolute Pressure (MAP) sensor, and the Heated Exhaust Gas Oxygen (HEGO) sensor. Of the three, the HEGO is most prone to failure (heat and crud) followed by the IAT (just crud.) Sometimes a good cleaning will do the job.

If you have an FSM handy, you should be able to find resistance values for various pressures/temperatures, and you can check with a multimeter, using a hand vacuum pump for the MAP and a pot of hot water and a thermometer for the IAT. The only real test of the O2 sensor is of the heating element within, if that's shot you replace the sensor entire. The good thing is that (as I recall) all of those parts are available in the aftermarket, and are significantly cheaper than the EGR valve.

Which one is it? Break out your tools & toys to find out, 'cos I can't tell you from here. I'm going to go out on a limb and say the EGR vacuum circuit is fine, tho, from what I'm seeing of your results.

5-90

Sometimes it helps to adjust the throttle position sensor. If it is a Renix unit, the overlooked sensor is the air charge temp sensor. Like the man said, there is no way to say from a distance. Each and every one of these sensors can cause the problem.

My gut reaction is the O2 sensor or the MAP. O2 sensors tend to last about 80k miles or so before acting up. You can also have a failure because the sensor wire gets melted on the exhaust manifold. Do you have a friend with a Renix system? See if you can do some sensor swapping to diagnose the problem.

Some GOOD advice, guys!

I cleaned up my CPS and it runs a lot better but not perfect. I'll continue to check and figure it out.

I don't have a friend w/ a RENIX here ... I just sold a '90 with a RENIX too!

I just moved here from out of state less than a month ago so I haven't made too many friends yet.

Thanks for the help guys!