Catalytic converter and smell

[micbrody]

I have fixed most of the "smell" issues in car. I changed all the fuel lines;checked interior metal fuel lines (no leaks ); repainted gas tank ; checked csi ; adjusted throttle screws; car starts great; runs great.
However, even with top down, i still smell something; my car is an 81 Fi . Previous owner removed catalytic converter; believe most of smell is just exhaust. So my next steps (based on reading board posts):
1) extend and point down exhaust pipe (mine is straight)
2) add catalytic converter back
3) check exhaust manifold gasket(and other spots)....though not sure how to


P.s: I think my present exhaust tip is 1.5 inch diameter ; not sure of test pipe(I need to measure)

My questions:
1) any suggestions of aftermarket exhaust tips that will look nice (chrome) and point down
2) seems like magnaflow catalytic converter is highly regarded. Is there a specific model? Also, I don't have welder. Can I put some sort of connector that bolts/glues/clamps the converter to cut portion of test pipe; and how do I attach/stabilize converter so it does not rattle; and I am not sure, but I don't think heat shield present....what can I put (and how) in its place?

Lastly, what were the original diameters of exhaust system for 1981 FI . Any advantages of increasing diameter(s)?

[TimpanogosSlim]

non-catalyzed exhaust does have a distinctive odor.

I'm unsure personally of the best way to search for exhaust leaks. Might be a quick youtube search away.

Magnaflow actually has both california and federal emissions mufflers for old spiders. And what it'll take to install it depends on how the old one was removed.

It might be a bolt-in affair, which you can do yourself with some exhaust system joint sealer, though you will probably need or at least want new hardware. and you might have to use a die grinder to get the old hardware off.

Or you might need someone to weld it.

Take a look under the car and see what the situation is.

bolt-in is 23503 - $185 from Amazon, weld-in is 94004 - $78 from Amazon. Federal emissions.

I don't really know if there's a clamp joint sort of method you can use - maybe there is? The temperature extremes and vibration are both a concern.

I paid a shop $100 to weld a magnaflow catalyst into a catless downpipe on one of my cars, for reference.

[bradartigue]

If it is just a stock FI system then buy the stock parts. Then go to a muffler shop if you need the chrome tip; but really with the semi-bent tip you hardly see the thing. The stock stuff works fine, won't leak, and everything fits, except sometimes the catalytic converter fit is wonky and you have to return it.

[micbrody]

Why are stock converters so much money compared to magna flow?
Also, do you know diameter specs on exhaust pipe for stock?

[micbrody]

I just measured circumference of test pipe.... about 5.5 inches which translates to 1.75 inch diameter

[So Cal Mark]

if you have exhaust smell without a catalyst, more than likely your fuel mixture is too rich

[micbrody]

If mixture too rich, how would I proceed? Change oxygen sensor? I tested csi and thermo time switch; both work and shut off.
Curious: shouldn't exhaust smell if catalytic converter absent?

[So Cal Mark]

a rich mixture with a working cat will result in a sulfur smell, a rich mixture without a cat will result in a burned fuel smell and hurt your eyes if it's really rich. With the proper mixture you shouldn't smell much of anything. Swapping parts isn't a very good diagnostic technique. If you don't have access to a gas analyzer, connect a voltmeter to your oxygen sensor. A proper fuel mixture will result in a .450 reading on your voltmeter

[bradartigue]

If mixture too rich, how would I proceed? Change oxygen sensor? I tested csi and thermo time switch; both work and shut off.
Curious: shouldn't exhaust smell if catalytic converter absent?

The O2 sensor has a very limited influence on the fuel mixture, you could say it optimizes the mix; if you are running very rich then you'll just ruin the new sensor. If slightly rich - dark brown plugs vs. the brownish white common with L-Jetronic, then it may be the sensor. Go drive the car, then pull out the spark plugs. If they are black, sooty, you're running rich. A potential cause of rich running in L-Jetronic is the temperature sensor located near the radiator in the "T" coming from cylinder head. If it is telling the ECU that your engine is cooler than it really is then you'll get too much fuel.

But check the plugs first.

I also find exhaust has a smell to it w/o a catalyst, but we all have different noses.

You can also put a voltmeter on the O2 sensor lead and test the range. This will tell you if the O2 sensor is working or not. If not, if ruined, then fix the problem of rich running first, then replace the sensor. Remember to have a nice warm engine when testing an O2 sensor, they don't work cold.

[micbrody]

so I checked temperature probe resistance when getting car to 190 deg on gauge. I disconnected connector, car stalled (I think that is suppose to happen), and measured about 275 ohms on probe .

I also traced connector from oxygen sensor to an electrical union that had a weird crumbling connector around it. Within connector was an electrical spade connector. I checked voltage relative to ground on connection side that goes to sensor, and it read 0.46 volts.

Question:
1) is that correct ohms for temperature probe at 190 deg
2) the wire that connected to the lead from the oxygen probe had a single blade connector, but the wire coming from car side seemed to be an insulated wire with a stranded wire shielding under the insulation. Why does this wire need this shielding? or is it connected to a wrong wire?

[TimpanogosSlim]

Why are stock converters so much money compared to magna flow?
Also, do you know diameter specs on exhaust pipe for stock?

The "stock" converter may be a California emissions converter.

Or maybe it's just arbitrarily expensive due to supply and demand (low production numbers, or long storage, etc), where the Magnaflow unit is just the universal magnaflow converter that is roughly appropriate for the engine in the spider.

I can tell you that the magnaflow spun converter that some tuners recommend for the 3" aftermarket downpipe on my 2.0T volkswagen doesn't really fool the catalyst efficiency o2 sensor for more than a few days. It is not near as dense as the factory converter, which i've never owned. It's also about 1/7th the cost of the factory converter.

[TimpanogosSlim]

so I checked temperature probe resistance when getting car to 190 deg on gauge. I disconnected connector, car stalled (I think that is suppose to happen), and measured about 275 ohms on probe .

I also traced connector from oxygen sensor to an electrical union that had a weird crumbling connector around it. Within connector was an electrical spade connector. I checked voltage relative to ground on connection side that goes to sensor, and it read 0.46 volts.

Question:
1) is that correct ohms for temperature probe at 190 deg
2) the wire that connected to the lead from the oxygen probe had a single blade connector, but the wire coming from car side seemed to be an insulated wire with a stranded wire shielding under the insulation. Why does this wire need this shielding? or is it connected to a wrong wire?

Check the crimps where the contacts are connected to the wires. These connections may be shot - look for powdery corrosion. I am adept with a soldering iron so i prefer to apply generous flux and solder in some of these situations, but it may be a better idea to trim back an inch or so of wire, apply a good contact cleaner to the wire, and re-crimp. Follow the crimp by treating the connectors with a heavy silicone grease and cover whatever metal would be exposed in operation with heatshrink tubing, tape, whatever.

If the only the connectors themselves look corroded, clean them with a good contact cleaner. I prefer Deoxit, but that's not widely available in retail stores (I buy it online). If you can, gently tighten the female socket with pliers. I mean, assuming it's a style that can be tightened. Packing with silicone should keep the weather out in the future.

The shielding does need to be there. Take care to not short that shield to ground or signal wires.

Brad is the L-Jet expert, so i defer to his expertise, but my general belief is that a control system is only as good as it's sensors. It sounds like the temperature sensor is a more likely culprit than the o2 sensor, but in my experience, o2 sensors have a limited lifespan.

So i suggest follow brad's advice wrt temperature sensor, clean up sensor contacts, then look at replacing the o2 if things are still a little rich.

If you are friendly with a shop owner, they might be amenable to shoving a smog sniffer up the tailpipe and telling you if it's running rich?

I keep meaning to buy my own wideband o2 system.

[micbrody]

I need to correct a previous reading on oxygen sensor:
The 0.46 volts was about 2 minutes after I shut off car. Probably not a great test as to its precision; just that it creates voltage.

I restarted car and got it up to temperature. While running, I checked voltage at connector, while connected (relative to ground). Voltage continuously fluctuated up and down at least twice a second; ranges from 0.1 to 0.7 volts. I then disconnected the connector and immediately checked voltage: 0.85.

Not really sure what to make of it. I know ECU will change fuel mixtures based on sensor, so maybe thats why it fluctuated so much while connected.

[micbrody]

i think I agree that car is running rich, ( though my eyes do not burn).

Some other hints that might help:
I usually can start car by cranking for a second or two. When it turns over, it barely starts (very low RPMS); and then over next 3-5 seconds comes to 1100 ish RPMs. Eventually when warm RPMs read 900-1000.
Sometimes, car does not turn over after a few seconds. I stop. Wait 3-5 seconds and try again; usually it does not immediately turn over second time unless I press gas pedal down (I know I should not have to)

[TimpanogosSlim]

I need to correct a previous reading on oxygen sensor:
The 0.46 volts was about 2 minutes after I shut off car. Probably not a great test as to its precision; just that it creates voltage.

I restarted car and got it up to temperature. While running, I checked voltage at connector, while connected (relative to ground). Voltage continuously fluctuated up and down at least twice a second; ranges from 0.1 to 0.7 volts. I then disconnected the connector and immediately checked voltage: 0.85.

Not really sure what to make of it. I know ECU will change fuel mixtures based on sensor, so maybe thats why it fluctuated so much while connected.

It may help if you understood what you were looking at.

The oxygen sensors we use on combustion exhaust systems are quite literally a fuel cell that converts oxygen into a weak electrical potential.

They only work when they are hot, so in many systems power is applied to a heating element that heats the cell.

The reading is only valid when the engine is running and the sensor is good & hot.

What we're most interested in is the voltage from the o2 sensor when the engine is at normal operating temperature and running.