Idle adjustment on an 84 CFI setup

[Quicksilver]

Matt / Jeff, this topic brings back a lot of memories and stories as I went through this on a BIG scale when my car ('84 CFI/AOD) was still under warranty. Almost went to arbitration with Ford over this but I didn't want to risk loosing the car.

But, for you, it sounds like you're almost there in solving any issues. I'm glad.

Long story short, my CFI intake and throttle body are long gone but I still have some of the original wiring, vacuum lines, connectors and sensors.

Items like the MAP sensor and the computer are sitting in a tupperware container in the garage.

If there is some CFI part that you need , just pm me. If I have it and you are willing to cover the shipping, it's yours. I'd rather the parts help someone than sit in a box forever.

[Matt J]

Thanks, Rob! I'm hoping at this point it's just a matter of a few more adjustments and maybe a leak here or there. It's funny, I've driven it a few times since, and it runs perfectly, but once in a while it drops off the charts and I have to two-foot it. Then the idle seems to find itself again, and it runs fine. Maybe the computer is figuring it out. I'm in the process of making a pretty major move to GA in the next few months, so I haven't had as much time to work on it as I'd like. I'm going to take it to my dad's shop in NH for a day or two of heavy duty work (my new place won't have access to a lift, for sure!), and I'll see if I can dial in a little better where the issue is.

[zak]

Anyone know if these VOTM/carb dashpot idle speed controllers are supposed to hold a vacuum? I am having the opposite problem - idle is too high when warmed up. In the past I've adjusted the "choke" on the passenger side of the throttlebody to lower cold idle speed (5.0L 1985 CFI).

When I use a pump to apply vacuum to the VOTM (after disconnecting it's supply hose), it kicks the throttle up briefly but bleeds down right away. Could this leak enough vacuum to raise idle speed?

[Matt J]

Anyone know if these VOTM/carb dashpot idle speed controllers are supposed to hold a vacuum? I am having the opposite problem - idle is too high when warmed up. In the past I've adjusted the "choke" on the passenger side of the throttlebody to lower cold idle speed (5.0L 1985 CFI).

When I use a pump to apply vacuum to the VOTM (after disconnecting it's supply hose), it kicks the throttle up briefly but bleeds down right away. Could this leak enough vacuum to raise idle speed?

Vacuum leaks are hell. No way around it. Fast idle, jagged idle, rough running, hell mine sounded like it had a burned valve, it was a vacuum leak. I think there's a reason they moved from vacuum operated everything to electronic/electric wires. So to answer your question, any vacuum leak in these cars will cause problems. That said, there's a very good chance that your "choke heater" isn't working correctly. If you don't know what that is, there's a wire running right off the top of your alternator back to the passenger side of the throttle body, it provides a small charge of about 7-8 volts something like that. It attaches to a bi-metal spring that when electrical is applied to it will expand and move the "choke position" back to a low idle. I needed to replace mine, it was pretty cheap and a 5 minute install. You can see if it's working by starting the car cold and seeing if the throttle position moves back within a few minutes. Also to look at is the idle kick-down which is right next to it, it's a small hook that pulls back on the cam to "kick down" the high idle during warm up. Mine was probably original to the car, and the rubber bladder inside of it was all disintegrated and not working (and probably also leaking vacuum). That kick-down is a big deal when driving down the road when the car is idling around 1800 RPM, you're using a lot of gas and a lot of brakes...they're easy to pull off and look at, that's where I'd look first.

[fgross2006]

Anyone know if these VOTM/carb dashpot idle speed controllers are supposed to hold a vacuum? I am having the opposite problem - idle is too high when warmed up. In the past I've adjusted the "choke" on the passenger side of the throttlebody to lower cold idle speed (5.0L 1985 CFI).

When I use a pump to apply vacuum to the VOTM (after disconnecting it's supply hose), it kicks the throttle up briefly but bleeds down right away. Could this leak enough vacuum to raise idle speed?

I know this is an old thread, but I wondered the same thing. My dashpot would pull vacuum but lost it quickly. On a hunch I ordered a new dashopt and the new one holds vacuum perfectly. I also found the choke kickdown housing has a runner diaphragm in it that also was not holding vacuum. I got a new one on ebay for $3.50 and now I have no vac leaks at all. sagging idle is gone. It purrs like a kitten now.

[zak]

Trying to recall whether I swapped the VOTM for a spare, or whether I adjusted the VOTM all the way out (definitely tried the later). At the same time I fixed a timing cover coolant leak which may have been allowing the car to slightly overheat producing a high/rolling idle.

To the OP, the canister in the fender is a vacuum reservour that IIRC serves more than just the cruise control.

[fgross2006]

The TPS doesn't affect your idle speed, but on a CFI engine, a bad TPS will often make the idle hunt.

If you adjust the idle speed on a CFI car by more than 50 RPM, the AOD Throttle Valve adjustment
should be redone.

The CFI idle adjustment is done by moving the throttle positioner. Loosen the lock screw, turn the
adjustment lead screw, tighten the lock screw. Pretty simple.

The actual -procedure- for a CFI 5.0 is a bit more complicated.

• Set the parking brake
• Bring the engine up to operating temperature
• A/C-Heat selector Off.
• Shut the engine off, then restart and immediately bring it to 2000 RPM and hold it there for 60
  seconds in Neutral, then let it idle for 15 seconds
• Without restarting the engine, bring it back to 2000 RPM for more than 10 seconds in Neutral
• Put the transmission in Reverse, then check/adjust the idle speed within 60 seconds

If the idle speed is too low to get through the procedure, shut down the engine and turn the adjustment
screw one full turn, then repeat the procedure.

question about this procedure,

I assume this procedure should be done after setting the cold choke when the car is fully warmed up,

When you say to turn the adjustment screw, do you refer to the screw on the VOTM or the hi idle screw on the other side?

[JACook]

The above procedure only refers to curb idle speed. It does not have anything to do with fast idle, other
than to say it is expected that since the engine is at operating temperature, the fast idle cam is no longer
engaged. It is also expected that the VOTM is not extended.

The fast idle and curb idle adjustments are independent of one another. One does not affect the other.

[fgross2006]

The above procedure only refers to curb idle speed. It does not have anything to do with fast idle, other
than to say it is expected that since the engine is at operating temperature, the fast idle cam is no longer
engaged. It is also expected that the VOTM is not extended.

The fast idle and curb idle adjustments are independent of one another. One does not affect the other.

I gotcha, what I need to know is where do I adjust the curb idle? Is it on the screws on the VOTM? There's two that I see. One on the dashpot and a small set screw on the throttle linkage.

Assuming I get the hi cam - low cam fast idle thing set and corrected, I still need to properly set my curb idle. Is it set on the dashpot?

What I've been experiencing is a very low curb idle after setting mi hi-cam fast idle. I got it hi idling at 2500 rpm as it says to on the under hood sticker, then after warm-up/kick down it droops the rpms to about 200. Should be 550 warmed up in drive.

[Matt J]

You know, I just saw this old post, and realized that I never updated the outcome of all my work on this, which might help out folks who are researching this same problem down the road. The dashpot was definitely bad, and replacing it ended up fixing the remaining idle problems with the car. Like most things, this was a bunch of different problems contributing different symptoms. Not unusual when working with 30 year old parts...

So, with a CFI car, fix all the vacuum leaks, and there are a ton of possible places they can come from; actually, just replace all the vacuum lines, they're old and probably brittle. Replace the dashpot (driver's side of the throttle body) and the choke heater and pull off on the passenger's side of the throttle body (the heater element has the wire running from the alternator, the pull off is vacuum actuated, but they work together). Both the dashpot and choke pull-off have rubber bladders in them to actuate, and over time the rubber breaks down and leaks making things inoperable. One works with the idle when it's cold, the other when you let off the throttle suddenly or when you turn on the air conditioning. They both contribute to weird idle problems...one makes it race, the other makes it stall, which is why it was racing sometimes and I couldn't get it to slow down from 1,800 RPM (choke heater wasn't working, and the choke pull-off wasn't either so it would race, but the dashpot on the other side of the throttle body also wasn't working so when I'd let off the gas it could quit or have the idle drop to almost quitting).

Also, the TPS is critical for smooth performance on the CFI. Actually, all of the sensors are. The CFI is computer controlled, those sensors are telling the computer what it needs to do. Most of them probably need to be replaced, but they're easy to tell if they're working right with a voltage meter. And Jeff Cook's information in this thread is solid gold, print and frame it on your garage wall!

Once you get the leaks fixed and the problems figured out, the CFI system really works well as a cruising car. Good mileage, easy starts and dependable performance. But at first they can be really tough to figure out. You're also dealing with mechanics "in the day" who didn't have any great love of those new-fangled computer things, and they'd often "fix" a problem by cranking up the idle screw or something like that. So you often have to un-do old fixes once you repair it correctly. In other words, you fix something correctly, and it doesn't run right because someone messed with the proper settings to overcome the original issue. A lot of folks just unplugged the "unneeded" stuff, and they didn't always really understand what they were doing. So sometimes there are things set in there that are just plain strange, you need to check that everything is the way it should be, don't assume it. If you're working on one, don't give up on it, it's worth the effort!

In the end, the car ran great up until it got wrecked, which is another old thread...