Recently, I was having problems with my 84 380SL having a rough idle after restarting the engine during a partial cool down along with piss poor MPG. @cwmoser recommended to me in a different thread that I check the ignition timing.
After doing a bit of research, checking the FSM, and watching youtube videos I decided to tackle the job. It's astoundingly easy to do, however without the pictures and knowing where to look it can be a royal pain in the rear. I'm going to outline the steps so you don't have to go hunting!
What is ignition timing?
This video outlines the purpose of what we're doing in more detail:
Why mess with my ignition timing?
Generally, you won't need to play with this at all because the factory will have set it for you correctly. However, it seems a lot of clueless automotive professionals and people out there play with timing in an effort to pass emissions testings or make up for failing parts. In the case of my vehicle, the previous owner in an attempt to mask a leaky vacuum system, advanced the timing by what I think to be -5* BTDC. This caused all sorts of problems ranging from poor fuel economy, poor performance, and exasperated issues with other downstream components.
This guide may be useful for you if you find yourself in crunch time and need to quickly change your timing to allow for your emissions to "pass". Do a search on the forum for tips on how to achieve this. For the purposes of this guide, we will be setting the timing to factory spec on a 1984 380SL. Your timing specs will be different. Check the FSM using the link below to confirm what is most appropriate for you!
So without further ado, I present to you the "How to Set R107 Ignition Timing" guide for all of you raving roadster hooligans.
Ingredients
1. A 7/32in Hex Key or small sized hex bit (Note: Make sure to check that your hex key can fit and turn in this tight location.)
2. An Ignition Timing light
3. Your specific vehicle's timing specs per either your emissions sticker or from the FSM https://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883
Optional: 12ft jumper cables (unless your ignition timing light is self powered or if you have a spare car battery lying around).
Let's familiarize ourselves with where we will be working
Meet Mr. Ignition Distributor. There are many like Mr. Ignition Distributor, but this one is mine. He lives directly in front of the engine and has a bunch of plugs coming off of the top.
The vacuum elbow that connects to the side of it is the vacuum advance. Depending on your vehicle you may have to disconnect and plug this with a golf tee.
There are two screws that can be used to remove the cap on the distributor so you can view the inside. This is unnecessary for the purposes of our exercise but good to know.
The next area on our tour will be to find the tiny timing degree marks on the flywheel.
Someone had previously mucked around on mine. Thankfully, he marked the 0* BTDC (before top dead center) mark and either the -5* or -10* locations above it with white paint.
Here's a better angle where you can more clearly see the timing pointer and timing marks.
To find these marks, stand on the driver's side of the engine bay (for the Bonnet/Japanese folks ie LHD vehicles, this will be your passenger side) to ease in finding this.
Comfortable yet? Alright, let's get started.
0. Fully warm up your car and turn the climate control off.
1. Standing directly in front of the distributor look to the lower left corner of it almost underneath. You will see a hex bolt and a clip.
Slide the clip off and put your 7/32inch Hex key into it. Loosen the nut until the distributor can turn freely. Don't go crazy turning it! Just make sure it's easy to turn, but tight enough that the engine vibrations won't lose your settings.
Special note:This nut is in a complete pain in the arsch to loosen. All of my hex sockets were too big, so I had to use a hex key. My first key was too big and would ding against the fan belts. Thankfully, I had another set that were smaller and allowed me to loosen the nut. If you're not as lucky as me, make sure to go out and either buy a set or hack one smaller to fit.
2. Depending on what your FSM specs say, you may or may not need to disconnect the vacuum advance. On my 84 380SL this was mentioned as being required for accurately setting the timing so I disconnected it and plugged off the rubber end with a golf tee.
3. Next, get your ignition timing gun. Here's a picture of mine:
I bought him at Harbor Freight for $30. He has a advance knob on the back as well which I set to 0*.
4. On your timing gun, there will be a wire to a clip that slides back. This is used to "inductively" sense when electricity is traveling through the wire to the spark plug. This cable needs to be connected to cylinder 1's spark plug wire. If you're directly standing in front of the engine, cylinder 1's spark plug wire is the first wire that appears on the left side of the engine closest to you.
5. If your timing gun is self powered, skip to step 6. If it's not and you don't have a spare 12 volt battery lying around, get your jumper cables and attach them to the battery in the trunk.
Next, run the jumper cables from the trunk to the engine bay. My cables were 12ft in length and just barely made it safely in.
Clip the red clips to the red end, clip the black ones to the black.
I lazily decided to hold my jumper cables in place by using the windshield fluid pipes that run to the hood. This isn't ideal in the slightest nor is it safe (sparks galore if they fall), but I did it anyway because YOLO that's why.
In a perfect world, you should rest these cables on a non conductive surface like a rubber mat Be smart and don't do what I did.
Carefully drape the wiring for the guns towards the rear of the engine bay to avoid getting anything tangled in the fans and belts.
6. Next, start the car.
7. For bonnet cars (LHD) vehicles stand on the passenger side. For the rest of the world (RHD) stand on the driver's side with your ignition gun.
Aim the light directly down where I previously showed you in the "getting to know your car" section and pull the trigger.
Unzt unzt unzt: Club 116's sick strobe beat
Use a timed strobe light to the spark on cylinder 1, we're able to ascertain where the cylinder is in relation to the spark.
See the red circle in the middle and the white blobs in the middle? This shot was taken when the engine was running. Without the timing gun, we would just see a blur of light. With the timing gun we can see that the car now has the timing set to 0* BTDC.
If you want to advance, turn the distributor clockwise. To retard, counterclockwise. As you do this, the numbers on the flywheel will either go up or down depending on the direction you turn the distributor.
Having trouble seeing the timing marks?
My numbers were somewhat hard to read. They were covered in gunk. Thankfully someone else had marked where 0* BTDC was for me so I didn't have to hunt to hard for them. If you're having trouble, turn your car off, illuminate the engine bay, put the car into neutral, choke your wheels, and rotate the engine clockwise only ( no really, only rotate the engine clockwise) using the power steering belt pully bolt. Once you see the numbers you need, use a shot of paint to mark the location and go back up above to finish your adjustments.
8. Once you've set your timing in idle, you now have the option of finding a friend to help you check the timing at various levels of engine load and making further adjustments.
These instructions and timing specs are outlined in the FSM. Generally, they include running the engine at 3500 rpm and checking the timing while also adding in the vacuum advance.
Edit: If you disconnect the idle air controller module (do this with the engine off) the car will automatically set its idle to 1500 RPM. This will allow you to set the timing spec to this amount. I recommend you at least do this, because just setting the idle timing will not get you the "peak" performance the FSM wants.
9. Once you're satisfied with your adjustments, tighten the hex bolt from step 2. Be very careful as it is incredibly easy to bump the distributor and mess up all of that work we just did.
10. Once the distributor has been tightened, restart the car and do one last check of your idle timing with your ignition timing gun to make sure it is set to where you want.
Congrats! You've successfully set the timing on your car. Crack a beer and take her for a spin. Bonus points if you do both and not get pulled over for a DUI.
Special thanks to @cwmoser for suggesting I look into this. This solved my rough idle problem and here's hoping it solves my poor MPG issues!
After doing a bit of research, checking the FSM, and watching youtube videos I decided to tackle the job. It's astoundingly easy to do, however without the pictures and knowing where to look it can be a royal pain in the rear. I'm going to outline the steps so you don't have to go hunting!
What is ignition timing?
This video outlines the purpose of what we're doing in more detail:
Why mess with my ignition timing?
Generally, you won't need to play with this at all because the factory will have set it for you correctly. However, it seems a lot of clueless automotive professionals and people out there play with timing in an effort to pass emissions testings or make up for failing parts. In the case of my vehicle, the previous owner in an attempt to mask a leaky vacuum system, advanced the timing by what I think to be -5* BTDC. This caused all sorts of problems ranging from poor fuel economy, poor performance, and exasperated issues with other downstream components.
This guide may be useful for you if you find yourself in crunch time and need to quickly change your timing to allow for your emissions to "pass". Do a search on the forum for tips on how to achieve this. For the purposes of this guide, we will be setting the timing to factory spec on a 1984 380SL. Your timing specs will be different. Check the FSM using the link below to confirm what is most appropriate for you!
So without further ado, I present to you the "How to Set R107 Ignition Timing" guide for all of you raving roadster hooligans.
Ingredients
1. A 7/32in Hex Key or small sized hex bit (Note: Make sure to check that your hex key can fit and turn in this tight location.)
2. An Ignition Timing light
3. Your specific vehicle's timing specs per either your emissions sticker or from the FSM https://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883
Optional: 12ft jumper cables (unless your ignition timing light is self powered or if you have a spare car battery lying around).
Let's familiarize ourselves with where we will be working
Meet Mr. Ignition Distributor. There are many like Mr. Ignition Distributor, but this one is mine. He lives directly in front of the engine and has a bunch of plugs coming off of the top.
The vacuum elbow that connects to the side of it is the vacuum advance. Depending on your vehicle you may have to disconnect and plug this with a golf tee.
There are two screws that can be used to remove the cap on the distributor so you can view the inside. This is unnecessary for the purposes of our exercise but good to know.
The next area on our tour will be to find the tiny timing degree marks on the flywheel.
Someone had previously mucked around on mine. Thankfully, he marked the 0* BTDC (before top dead center) mark and either the -5* or -10* locations above it with white paint.
Here's a better angle where you can more clearly see the timing pointer and timing marks.
To find these marks, stand on the driver's side of the engine bay (for the Bonnet/Japanese folks ie LHD vehicles, this will be your passenger side) to ease in finding this.
Comfortable yet? Alright, let's get started.
0. Fully warm up your car and turn the climate control off.
1. Standing directly in front of the distributor look to the lower left corner of it almost underneath. You will see a hex bolt and a clip.
Slide the clip off and put your 7/32inch Hex key into it. Loosen the nut until the distributor can turn freely. Don't go crazy turning it! Just make sure it's easy to turn, but tight enough that the engine vibrations won't lose your settings.
Special note:This nut is in a complete pain in the arsch to loosen. All of my hex sockets were too big, so I had to use a hex key. My first key was too big and would ding against the fan belts. Thankfully, I had another set that were smaller and allowed me to loosen the nut. If you're not as lucky as me, make sure to go out and either buy a set or hack one smaller to fit.
2. Depending on what your FSM specs say, you may or may not need to disconnect the vacuum advance. On my 84 380SL this was mentioned as being required for accurately setting the timing so I disconnected it and plugged off the rubber end with a golf tee.
3. Next, get your ignition timing gun. Here's a picture of mine:
I bought him at Harbor Freight for $30. He has a advance knob on the back as well which I set to 0*.
4. On your timing gun, there will be a wire to a clip that slides back. This is used to "inductively" sense when electricity is traveling through the wire to the spark plug. This cable needs to be connected to cylinder 1's spark plug wire. If you're directly standing in front of the engine, cylinder 1's spark plug wire is the first wire that appears on the left side of the engine closest to you.
5. If your timing gun is self powered, skip to step 6. If it's not and you don't have a spare 12 volt battery lying around, get your jumper cables and attach them to the battery in the trunk.
Next, run the jumper cables from the trunk to the engine bay. My cables were 12ft in length and just barely made it safely in.
Clip the red clips to the red end, clip the black ones to the black.
I lazily decided to hold my jumper cables in place by using the windshield fluid pipes that run to the hood. This isn't ideal in the slightest nor is it safe (sparks galore if they fall), but I did it anyway because YOLO that's why.
In a perfect world, you should rest these cables on a non conductive surface like a rubber mat Be smart and don't do what I did.
Carefully drape the wiring for the guns towards the rear of the engine bay to avoid getting anything tangled in the fans and belts.
6. Next, start the car.
7. For bonnet cars (LHD) vehicles stand on the passenger side. For the rest of the world (RHD) stand on the driver's side with your ignition gun.
Aim the light directly down where I previously showed you in the "getting to know your car" section and pull the trigger.
Unzt unzt unzt: Club 116's sick strobe beat
Use a timed strobe light to the spark on cylinder 1, we're able to ascertain where the cylinder is in relation to the spark.
See the red circle in the middle and the white blobs in the middle? This shot was taken when the engine was running. Without the timing gun, we would just see a blur of light. With the timing gun we can see that the car now has the timing set to 0* BTDC.
If you want to advance, turn the distributor clockwise. To retard, counterclockwise. As you do this, the numbers on the flywheel will either go up or down depending on the direction you turn the distributor.
Having trouble seeing the timing marks?
My numbers were somewhat hard to read. They were covered in gunk. Thankfully someone else had marked where 0* BTDC was for me so I didn't have to hunt to hard for them. If you're having trouble, turn your car off, illuminate the engine bay, put the car into neutral, choke your wheels, and rotate the engine clockwise only ( no really, only rotate the engine clockwise) using the power steering belt pully bolt. Once you see the numbers you need, use a shot of paint to mark the location and go back up above to finish your adjustments.
8. Once you've set your timing in idle, you now have the option of finding a friend to help you check the timing at various levels of engine load and making further adjustments.
These instructions and timing specs are outlined in the FSM. Generally, they include running the engine at 3500 rpm and checking the timing while also adding in the vacuum advance.
Edit: If you disconnect the idle air controller module (do this with the engine off) the car will automatically set its idle to 1500 RPM. This will allow you to set the timing spec to this amount. I recommend you at least do this, because just setting the idle timing will not get you the "peak" performance the FSM wants.
9. Once you're satisfied with your adjustments, tighten the hex bolt from step 2. Be very careful as it is incredibly easy to bump the distributor and mess up all of that work we just did.
10. Once the distributor has been tightened, restart the car and do one last check of your idle timing with your ignition timing gun to make sure it is set to where you want.
Congrats! You've successfully set the timing on your car. Crack a beer and take her for a spin. Bonus points if you do both and not get pulled over for a DUI.
Special thanks to @cwmoser for suggesting I look into this. This solved my rough idle problem and here's hoping it solves my poor MPG issues!