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1979 450 SLC R107
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41 Posts
Discussion Starter · #1 ·
Good morning All,
Thank you for reading this post.
I bought this 1979 450 slc last year at good deal, but as you can imagine I ended up spending more money on parts than I what paid for it 馃槈; finally I got to run late last summer and I have been driving it one day a week to short distance errands; everything time I would get home from driving it, my wife would tell that I had a very strong gas smell. During a long drive I even smell, so started to tinkering with air/meter to make lean, but I if made it to lean it would die in idle. This summer is very hot in Texas so I needed it to make richer by again adjusting the air/gas meter to be able to run the AC with this the carbon monoxide level was to high that I bothered my throat. I read in this some threads and manuals that the carbon monoxide levels can be adjusted by adjusting the CO screw in the ECU ; all information stated that the ECU in under glove box and after spending a few minutes trying to find it; it turns out that my ECU never came with the car 馃槒. See the picture below.
The two questions that I need assistance with are:
1. Can I the CO levels down without the ECU? Other than adjusting the air/gas meter.
2. Where I buy a used or new ECU for my car other place other than eBay?
Thank you for stopping by!
Oscar.
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1980 450 SL
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671 Posts
The 1980 450 only has a Lambda control module under the floor board directly under the glove box that controls the frequency valve. This is also called an ECU by some. The 79,80 and prior years have an ICU ignition control unit in the engine compartment. No Lambda control, oxygen sensor or frequency valve on 450's prior to 1980
I think you are looking for something that doesn't exist on the 79 . I apologize if I am wrong and maybe someone will correct me.
 

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1979 450 SLC R107
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41 Posts
Discussion Starter · #3 ·
Thank you JR.
It is nice to hear from you again.
it is very helpful, because the car has been running great other the strong CO smell. so based on the information you provided, I can adjust the CO level by tinkering with the ICU ignition control unit. where is this located in the engine compartment? do you think that this is the main contributor to the strong CO smell?
again thanks for your guidance.
 

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1978 450SL
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22 Posts
I can adjust the CO level by tinkering with the ICU ignition control unit. where is this located in the engine compartment? do you think that this is the main contributor to the strong CO smell?
again thanks for your guidance.
I don't think that's what he's saying, just that the ICU is as close to a computer as you're gonna get on a '79. As for the CO smell, I think you need to be looking for exhaust leaks in the engine compartment or under the floorboards. They don't need to be heard to be small pinholes in and around the joints. I wonder what the "7" stands for?
 

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1979 450 SLC R107
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41 Posts
Discussion Starter · #6 ·
CO has no smell; that's why it's so dangerous. I suppose the OP is talking about rich exhaust i.e. unburnt hydrocarbons?

you could be correct here. it is more like unburnt gas. any ideas as how tackle this one other than the adjustment of the air/gas metering unit.

Thank you for your assistance.
 

Premium Member
1980 450 SL
Joined
671 Posts
Thank you JR.
It is nice to hear from you again.
it is very helpful, because the car has been running great other the strong CO smell. so based on the information you provided, I can adjust the CO level by tinkering with the ICU ignition control unit. where is this located in the engine compartment? do you think that this is the main contributor to the strong CO smell?
again thanks for your guidance.
No the reference to the ICU was just that was about it as far a computer goes on a 79. It probably would not run great if there was something wrong with the ICU. Your wife said she smelled gas. Look for a leak or maybe an issue with fuel vapor that should be going to the charcoal canister.
The 79 has a rather complex EGR setup that could be an issue.
 

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1979 450 SLC R107
Joined
41 Posts
Discussion Starter · #8 ·
I don't think that's what he's saying, just that the ICU is as close to a computer as you're gonna get on a '79. As for the CO smell, I think you need to be looking for exhaust leaks in the engine compartment or under the floorboards. They don't need to be heard to be small pinholes in and around the joints. I wonder what the "7" stands for?
I am sorry, I misunderstood his comment about the ICU. The unburnt has is stronger if I am standing outside; also when I am in red lights I can smell it a little bit; I think as "Dugald" pointed out it could be unburnt gas. Any ideas or recommendations.
The "7" was already there when I bought, but it can represent how many times I wake up at night thinking about this issue! ;)
Thank you for your assistance.
 

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1979 450 SLC R107
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41 Posts
Discussion Starter · #9 ·
No the reference to the ICU was just that was about it as far a computer goes on a 79. It probably would not run great if there was something wrong with the ICU. Your wife said she smelled gas. Look for a leak or maybe an issue with fuel vapor that should be going to the charcoal canister.
The 79 has a rather complex EGR setup that could be an issue.
Thank you JHTx,
I checked for fuel leaks already and no minor/major leaks found. The smell is more like a unburnt gas "like the unburnt gas you smell from a leaf blower" the hoses going to the charcoal canister and the canister looked pretty dried; like they have not being used in a while; I am not sure if this they way how it should look.
 

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1979 450 SLC R107
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41 Posts
Discussion Starter · #15 ·
Thank you cousinMB, I installed new spark plugs last year and the old ones were ok, but I will check them again. Thank you 馃檹馃従
 

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1987 300SL
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2,036 Posts
Thank you cousinMB, I installed new spark plugs last year and the old ones were ok, but I will check them again. Thank you 馃檹馃従
They'll probably be ok, but check anyway
I had a similar problem to yours, car stank! It was going through some oil too, and did get a bit smokey
We changed to a heavier weight synthetic oil and I had to apologise every time I stopped at the traffic lights, the exhaust smell was foul!!!
Rebuilt the head due to shot valve guides. Oil consumption stopped, plugs are clean, car idles and goes far better, and the exhaust smell is mostly gone
 

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1979 450 SLC R107
Joined
41 Posts
Discussion Starter · #17 ·
Thank you CousinMB for this information. based on the smell, it it's more like unburnt carbohydrates; not much like burnt oil, but I will double check the spark plugs this weekend. the exhaust is much stronger now because I had to adjust the air/fuel metering unit to be able to run the AC in the summer therefore I am not driving it that much because of the bothering smell.
 

Premium Member
1979 450 SLC R107
Joined
41 Posts
Discussion Starter · #18 ·
Thank you CousinMB for this information. based on the smell, it it's more like unburnt carbohydrates; not much like burnt oil, but I will double check the spark plugs this weekend. the exhaust is much stronger now because I had to adjust the air/fuel metering unit to be able to run the AC in the summer therefore I am not driving it that much because of the bothering smell.
 

Premium Member
1979 450 SLC R107
Joined
41 Posts
Discussion Starter · #19 ·
CousinMB,
I just checked all the spark plugs and the rear driver side one was the only one that looked like it was having some issues. See the pictures below; I saw that the rear fuel injector was sticking out a bit. This could have caused the bottom part of the injector was spraying onto injector boot; causing the fuel just to drip into the combustion chamber. Maybe this could haven the issue, I test drive it this weekend.
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1987 300SL
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2,036 Posts
CousinMB,
I just checked all the spark plugs and the rear driver side one was the only one that looked like it was having some issues. See the pictures below; I saw that the rear fuel injector was sticking out a bit. This could have caused the bottom part of the injector was spraying onto injector boot; causing the fuel just to drip into the combustion chamber. Maybe this could haven the issue, I test drive it this weekend. View attachment 2765642
Most of my plugs looked like your bottom one. Wouldn't hurt to get a compression test done
 
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