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Discussion Starter #1
I'm still pretty new to Alfas and this incredible community, but you all have been a fantastic help already. I'm hoping you can help me problem solve another issue with my 84 Spider.

The car runs great, but I've always known it runs rich. I took it in for an emissions test (I don't need it - exempt in Utah), and I was really surprised at the results. All CO numbers were great (.74 idle, .72 loaded) and the loaded hydrocarbon (HC) number was good (104); but the idle HC was 1508 (220 standard)! So, I need some advice problem solving.

What I know or what I've already done:
-Engine compression is good - 125 across the board (dry).
-I had already suspected a vacuum leak so I replaced all the vacuum lines - however, I'm not sure about the injectors leaking (air).
-Plugs are new - I'm not sure about the age of the wires, but they look good.
-CAT temps are good on the in and out sides. Not sure about O2 sensor.
-I replaced all filters - air, oil, fuel - and fluids.
-No noticeable misfires.

The car really runs really well, but that HC at idle is far too high. Ideas?

Thanks a ton for your help.

Ty
 

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1973 Spider; the daily
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I'm not familiar with that generation car. Do they have spica direct injection? The spica are known for getting out of alignment. Even out of alignment they can run pretty well but to get good emission numbers you might need to get it tuned up. Just my personal opinion. I could be totally wrong.
 

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Incomplete combustion at low rpm. Maybe a leaking injector but first try a new set of correctly gapped spark plugs.
 

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he's just put in new plugs (that would've been my first suggestion too)

I'd be looking at the O² sensor and the jetronic temperature sensor (or sensors, depending)
some data to check here for the temp sensor(s)
What is this L-jetronic sensor?
 

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Replace the single word o2 sensor with a 3 wire sensor, the black wire goes to o2 reading, the 2 grey wires one to 12 volt one to ground, this will give you better readings
 

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Discussion Starter #6
I appreciate all the feedback so far! The 84 is EFI - so nothing to adjust from that standpoint.

I did just replace the plugs, but they already don't look great, which makes me wonder about my gap. My assumption when I ordered the plugs was that they were set to correct gap (which was stated to be correct from the parts vendor). They are set at .9mm. Is this correct, or is a bad assumption on my part?

I have had a new O2 sensor on my list, but my hesitation is that it is just throwing high HCs at idle. Would that be consistent with a faulty O2 sensor?

I'll take a look at the sensor info. That's getting outside my experience, but I love to learn! Thanks again for all the help!

Ty
 

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Do the plugs look alike or is the coloring different?
 

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But Mad North-Northwest
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The gap spec for a stock '84 injection system should be 0.6-0.7mm (0.025"). But even if your gap is 0.9mm (0.035") I can't see that causing rich idle.

I would go through the L-Jetronic guide and see what you can figure out. As Dom said, most likely culprits are the coolant temperature sensor (CTS) or the oxygen sensor. There are instructions for testing the CTS in the guide, and if you dunno how old the oxygen sensor is I'd just replace it.

 

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But Mad North-Northwest
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And as I'm thinking about it, could also be the fuel pressure regulator, although when that goes usually the engine runs like crap. Pull the vacuum hose to the FPR and make sure it's completely dry (one common failure mode is to leak fuel into the vacuum hose.)
 

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Discussion Starter #10
Thanks again everyone!

The plugs do all look very similar - a little scorched at the very bottom.

I will check the CTS and order a new O2 sensor. I've also been working may way through the FI tune up.
 

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The heated O2 sensor is a good idea. The original O2 sensor in your '84 Spider would be a single wire. An O2 sensor needs to be fully warmed up for it to function and send valid signals to the computer. At idle the single wire O2 sensor will not stay hot enough to work and then the computer ignores it and follows its pre-programed fuel map which is slightly rich. Another reason to consider replacing the O2 sensor is that as they get old they don't work as well - again causing the computer to ignore it.

You can use a digital voltmeter to test the O2 sensor. Leave it connected to the wire harness but push the rubber cover back so you can attach the red lead of your voltmeter to it. Ground the black lead. With the engine warmed up & running, the readings should jump around but average ~ 0.45V. You'll need to rev the engine to ~ 2500 for a minute or two and then take the readings during the next minute. After that the O2 sensor will have cooled down so rev the engine again to heat it up. If it does not jump around every few seconds the O2 sensor is likely old and not functioning.

If it jumps around but averages high or low you can try adjusting the idle air mixture. The adjustment screw is in the Air Flow Meter (AFM). It may be covered by a aluminum plug - use a sheet metal screw to pull the plug out. Underneath the plug is an allen head screw for the idle air adjustment.

1618784
 

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Discussion Starter #12
Follow-up question: I can hear a lot of air moving through the vacuum hose between the plenum and the AAV. It's audible over the engine noise. Is this normal - just air movement with the AAV open in a cold start condition? Just something I'm not familiar with. Thanks again!
 

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If your motor mounts are toast,and the engine moves around alot, it can make the large plastic hose to come loose. Also take it off, look for cracks.
 

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What altitude are you at? 125 psi is not great compression but if you're at altitude might be OK.
Andrew
 

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Discussion Starter #15
What altitude are you at? 125 psi is not great compression but if you're at altitude might be OK.
Andrew
I'm at 4500'. Plus, the compression as tested cold. I need to do it again, but many say 125 is pretty good for this engine with L-jet (118-132). Is this incorrect?
 

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But Mad North-Northwest
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Well you should really test it hot, but 4500' will cost you about 15%. So your 125 is probably more like 145 at sea level and you're probably fine.
 

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Another possibility is that your exhaust cam timing is retarded, This can make the motor feel stronger as the power stroke is lengthened but the later closing can allow some fresh charge to be ejected through the exhaust valve just before it closes. This is more likely to occur at idle and low rpm.
 

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Discussion Starter #18
Another possibility is that your exhaust cam timing is retarded, This can make the motor feel stronger as the power stroke is lengthened but the later closing can allow some fresh charge to be ejected through the exhaust valve just before it closes. This is more likely to occur at idle and low rpm.
Thanks for the idea. Is there a way to diagnose an exhaust cam timing issue?
 

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Do you have 4 into 2 headers? If so the 3 wire O2 sensor is a good upgrade. My '85 has the 4-2 headers and I had sooty exhaust at idle before I upgraded to a 3 wire. I had to start with cardboard under tile pipe to keep from staining the garage floor (I still do occasionally, my upgrade is only a few hundred miles ago). Great idea to check your plastic intake for leaks, if you search the BB you'll see posts about using smoke to find leaks and Shoo Goo to seal 'em up. Especially the ears where the unit mounts to the intake manifold. I thought mine was in great shape, tried the smoke test and the ears were leaking as was the main connection. Shoo goo worked perfectly.

Best of luck to you. Best advice, drive her, Alfa's don't like to be parked for long. Even if I just have to move my Spider to access the garage, I take her for a drive and get her to temp.

Gubi's link to the L-Jet doc is gold.
 

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Thanks for the idea. Is there a way to diagnose an exhaust cam timing issue?
Remove the cam cover, turn the engine so the #1 piston is at TDC (pointer aimed at 'P') and check that the mark on the camshafts align with the mark on the cam cap.

1618913
 
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