Can anyone help with timing and idle mixture

[jettfuel]

I have a '90 GW with the Motorcraft 2150 carb. I just completed the TFI upgrade and now the idle is really rough when warm. Could someone give me a step by step process to set timing and idle speed/ idle mixture. I read on a post that this could be accomplished using a vaccum gauge? Do I need a timing light? A tachometer? This is my first time doing timing and carb adjustment. TIA.

[JeepReeves79]

The first thing you want to do is adjust the timing. you want to get it up to operating temperature. then you disconect the vacum advance hose on the distributor and plug it. if you don't have a tach get a tach dwell meter and hook it up. hook your timing light up set your timing at 10 degree below top dead center at 600 rpm in drive. test drive it and if it pings or spark knoks uder a load then do the same thing only set it a 8 degrees below top dead center at 600 rpm in drive. that sould take care of your timing. you will want to set your spark plug gap to .045. before setting your timing sorry I didn't tell you that first.

[jettfuel]

Thanks,JeepReeves79.
Does anyone know how to properly adjust idle speed/ Idle mixture?

[Sgt. Dave]

Sure,
After you set the timing, leave the vac gauge connected to manifold vac. With the air cleaner on, set the idle speed to the specified rpm. Next, pick a idle mixture screw to start with (I always start on the left, no reason, just always do)adjust the mixture to show peak manifold vac.
If necesssary, reset the idle speed, and repeat the process on the other idle mixture screw. Reset the idle speed to the base setting. Check both idle mixture settings again, adjusting for max vac. Recheck the base idle speed. Now reset each idle mixture screw, leaning the mixture for a 50 rpm drop of idle speed. You now have the carb set for lean best idle. ;)

[Ralph]

jettfuel, I sent you an email with an excellent shade-tree guide attached. It was previously written and posted by another IFSJA member on the original forum. I've edited it a bit. If anyone else needs a copy, email me and I'll send it.

[jettfuel]

Thanks Ralph, That really helped.

[ColeTrickle]

Hey Ralph. You mind sending me a copy? I need all the help I can get.
I'm not sure if I need a rebuild carb or not.
TIA

[Ralph]

Okay, fellas, much as I love y'all I just don't have time for 50 emails with the same question. Yes, it's 1:35 AM here, and I just came in from work. Did the same thing yesterday, and I have to open the shop a few hours from now. So, here is the article in its entirety (if the Moderator will allow it):

To adjust the air/fuel ratio is pretty easy. You will need a low range tachometer and a screwdriver or special tool to turn the needles. I use a 1/4" drive screwdriver bit with a piece of large vacuum hose over it. The hose keeps the screwdriver bit from coming off while adjusting the needles.

To adjust the mixture:
1) Set your initial static timing.
2) Set your low idle speed. Make sure the engine is warmed up and that the choke is open, and that the fast idle cam is not engaged.
3) Adjust each screw by turning it CW until you see a drop off in rpm on the tachometer. This is known as lean roll. From lean roll turn the screw CCW about 1 turn or until you reach the highest idle speed you noticed when turning the screw CW to lean roll.
4) Repeat with the other screw.

NOTE: A good starting point for this procedure, if you've never done it, is to turn the screws to the full rich position. Then turn each screw CW three turns and then adjust each screw until you hit lean roll. Some people adjust the screws simultaneously, which is probably better but is more of a hassle.

When would you want to set the air/fuel ratio? Well whenever the engine is idling rough. A properly set air/fuel ratio can do a good job of smoothing out a rough idle (presuming the cause is a maladjusted carburetor.) Also, whenever you replace an old vacuum hose, which presumably leaks, with a new hose which presumably does not leak, the manifold vacuum signal to the carburetor will increase and tend to make the carburetor run rich, thus you must readjust the air/fuel ratio. If you replace a lot of old hoses you will notice just how rich the engine will run. Also if you are turning down your idle speed significantly, you will need to readjust the mixture. Various performance modifications, particularly improvements to the exhaust, will make the engine run lean, so there again you will need to adjust the mixture.

NOTE: with performance modifications the air/fuel ratio may change so much that you may have to re-jet the carburetor to get the right mixture.

[ColeTrickle]

Ralph, thanks a bunch. Its people like you that makes this such a great site that I'm proud to be apart of.
Hope I can pass the favor someday.
Again thanks.