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1976 EFI Fast Idle Valve

Started by Joe Albanese, December 05, 2018, 03:46:32 PM

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Joe Albanese

Greetings!  Been awhile since visiting this forum.  I had the misfortune of having the tiny metal lever that triggers the fast idle solenoid to either energize the solenoid to heat or not (I guess) the valve, thus extending the piston to restrict the air into the throttle body, detach from valve.  I am capable of reattaching lever, yet it has bent and I am not sure of correct bend to facilitate proper actions.
A) does the fast idle valve always stay energized to force valve to restrict air flow the entire time the car runs?
B) Is total idle adjustment control achieved by first allowing idle valve to close air flow - then set remaining air flow by adjusting hex screw at base?
C) should idle valve contact point (that clicks) be depressed up or down on cold engine?
Thanking in advance for any recommendations.
Joe Albanese

79 Eldorado

#1
Joe,
I'm not an expert with these but I was reading some of the threads recently on them and there is basically a charged cylinder. I believe it has wax like a thermostat. So the plunger moves. Most people who were having issues found the plunger wasn't moving far enough over time so the solution was to place a dime size shim/spacer someplace... I know that doesn't answer all of your questions but I think it answers one of them at least.

Scott

bcroe

That valve is supposed to be fully closed when hot.  Once that is
achieved, you can adjust the throttle body idle screw.  If pushing
down on the valve slows the idle, it is not fully closed. 

That tiny switch initially increases current into the valve heater, to
close it faster.  That, by shorting out some resistance.  When the
valve moves to closed, the current decreases to a lower level to
hold it closed.  Bruce Roe

Joe Albanese

Scott, Thanks for your reply.  I have already shimmed out the inside of the plunger valve with a dime.  I'm thinking I may need to use a second dime.  The upper portion of the heater valve pivots inside the opening (has play) and therefore not securing the plunger valve securely inside bore.  I need to figure out that issue also.. 
Joe Albanese

Joe Albanese

Bruce, good to hear from you again!  You repaired my MAP sensor a few years ago if you remember.  You also checked out my spare ECU.  In trying to understand your comments concerning the heater valve and micro switch, it seems this valve gets constant current to energize the heater - just perhaps more prior to the plunger valve fully seating itself thus closing off the additional fast idle air.  The amount of movement is minimal, and the lever must be precise in its position to allow the micro switch to function.  so.. that being said - could I possibly eliminate the lever since it is out of spec and allow the micro switch to extend and use that current, or should I force the micro switch upward to top of heater valve to depend on that setting for current to the heater???  I'm not sure I can precisely bend lever to accommodate slight movement of piston valve to operate micro switch.  I hope you understand what I'm trying to accomplish here.  Or, in other terms, should lever hold micro switch up prior to heater closing plunger valve and then click down when plunger valve is seated, or does it work just the opposite??  Allow micro switch to be down with no contact until valve seats?  This is confusing at best. 
Joe Albanese

bcroe

Joe, hope the car is running OK.  That valve gets constant 12V from
the fuel pump circuit.  When the valve is open, the switch is supposed
to short a part of the heater resistance, so the current goes up, it
heats faster and closes.  When closed the switch stops shorting,
current drops, but still enough to hold it closed. 

My thinking is even if the arm comes off (low heat position), the valve
will still close, takes longer.  As for fixing it, nobody has presented a
complete cure yet.  Worst case, close off the valve and keep a foot on
the gas till warmed up enough.  Bruce Roe

Joe Albanese

Bruce,
I just drove my car 1100 miles from Ohio to mid Florida.  No problems with ECU since you repaired it.  Thanks again.  I noticed a engine miss and decided to replace three new injectors as well as new O rings.  Total of five injectors in last 3000 miles.  Problem is, till recently I never drive car much and last time O rings were replaced was 10 years ago.  So new O rings, a few more new injectors, and plan to button her down.  Just having problems with fast idle valve.  I'll take your suggestion and hold pedal down till warm up.   That is better than too fast idle banging into gear every forward to reverse shift. Take care.  Joe
Joe Albanese

79 Eldorado

Joe,
There's an excellent photo of a valve on the Cadillac King site:
http://cadillacking.org/index.php?main_page=product_info&cPath=32_34_122&products_id=121

I didn't want to post the photo here because it's not mine...

Knock-on-wood I haven't had this issue YET but I guess I will so of course I'm interested in the topic. If I look at that photo I assume the valve is at room temp because it's off the car. It looks like the lever touches a large diameter in that position. If the piston extends it looks as if the lever finger would likely end-up lining up with the smaller diameter. I guess that would either change the position of the lever arm, which interacts with the small switch, or the lever arm would stay in position and barely contact the piston in the smaller diameter area.

It seems like if it drops down into the smaller diameter area and changes the lever angle it would have a really hard time returning to the cold position without bending the lever arm finger.

I haven't had this part off the car so I'm asking a question based on your and Bruce's comments and the photo observations. The only show one view but the zoom once you find it is extreme.

I suspected they were rebuilding these because they were asking almost $100 for a core.

I also thought if you saw that photo it might help you sort-out the proper shape of your bent metal lever.

Scott

Joe Albanese

Scott, Your idea was excellent.  Great image of mechanism.  Believe I have valve positioned properly although the idle is still a little high.  Perhaps I have a vacuum leak.  And, to confuse matters even more, there was a spring clip that attaches to very bottom of plunger valve that probably held Spring assembly in place.  Mine has been missing for years.  I hope you never have problems with yours!  Thanks once again.  Joe A.
Joe Albanese

79 Eldorado

It would be good to check for vacuum leaks.

It seems like some of what you wrote goes back to the tip Bruce gave above "That valve is supposed to be fully closed when hot.  Once that is achieved, you can adjust the throttle body idle screw.  If pushing down on the valve slows the idle, it is not fully closed."

You're treading in an area where I have not had to walk yet but I would take Bruce's comment as once you think everything is up to temperature try pushing the valve down. If it slows the idle I guess he means either a) It's not really up to temp yet or b) The piston is no longer pushing as much as it once did. You already mentioned you were using one shim. In either case it sounds like it needs to be seated before the idle screw can be properly adjusted.

Reading the statement and not having personal experience with it other than seeing the part what is a little confusing to me is it looks like the "derby" hat at the far end looks like it establishes a base at one end and does not move. On the other end I assumed the electrical connector does not move. So what I thought moved was the large conical piece inside the large spring. I assume the brass colored piston pushes that conical section and in doing so probably closes a passage. So my point is where do you or where are you able to push because it seems like the moving part would not be exposed.

Scott

bcroe

Quote from: 79 Eldoradoit looks like the "derby" hat at the far end looks like it establishes a base at one end and does not move.

So my point is where do you or where are you able to push because it seems like the moving part would not be exposed.         Scott   

That black top fits somewhat loosely into the TB body.  The big spring
keeps it up at the top of its possible motion.  So you can push it down
(against the spring) a bit.  If the plunger is not already seated, it will
move down too and affect the idle.  Bruce Roe

Joe Albanese

Thanks everyone for your input.  I finished my project and I'm learning to live with the cold engine verses a hot engine that idles great. I must add. With the five new injectors, this car is almost like new in regards to power!  No hesitation, no vibration, even the exhaust odor has improved.  I'm a happy camper!  My best to you all..
Joe Albanese

79 Eldorado

Joe,
I'm still learning about these systems so the conversation here is good. I was wondering though if you checked your air temperature sensor. I know based on what I've read on this forum, with a strong influence from Bruce regarding FI and ECU related, that the coolant temp sensor has a strong influence on enrichment during starting. That same sensor PN is used to measure air charge temperature. I understand it seems like the coolant side has a more drastic impact on starting but I was wondering if the air temp sensor may help adjust the fuel after the car starts. So I was wondering if you checked the resistance of that sensor (probably good to check both). If it's good you will measure a reasonable resistance like 750 to 1500 Ohms but if it failed it acts like an open circuit so infinite resistance which the ECU would interpret as completely warmed up. I'm not saying that is the problem but if it was bad I would suspect it could make the situation worse (if it works the way I think it might). With a lot of input from Bruce I was trying to create a replacement for that sensor because it seems they are no longer available. The information I've read has been heavily weighted toward the impact of the coolant temp sensor and I haven't heard much about the air temp sensor.

If you decide to check yours I noticed they really take some side-to-side wiggling to get apart.

Scott

Joe Albanese

Scott.  Checking the two sensors was the first thing I checked.  Both related a resistance of 38.6.  When dipped into hot water they increased to 48.9 with just the hot water coming from the tap.  I'm not sure I had ohms set properly.  Was never certain how to gauge / set for resistance.  However since they both were exactly the same, they are either good or both equally bad. 
Joe Albanese

79 Eldorado

#14
Joe,
Based on those readings I'm not certain what you were measuring. I took a picture of my multimeter which I sometimes call old reliable :) I have a couple of newer ones but this one is still my favorite bought a looooong time ago from Radio Shack. I've seen others with the same one so maybe you have a similar one. Anyway none of them will be much different. The key thing is set the multimeter to a setting showing the Greek symbol Omega. You can see that's the lower dial on mine which shows k Ohms ( k is for kilo so to get Ohms multiple the reading times 1000). The bottom position is Ohms but my meter reads off-scale if the reading is over 300 Ohms in that position so it wouldn't work here.

The top dial I set to single digits because then the meter will show 3 decimal places and thus if you ignore the decimal you can read the kilo-Ohms as Ohms (just like multiplying by 1000). Sometimes if I don't know the level I will try first on k Ohms.

In this case it doesn't matter which side of the part you put the "com" common or ground black probe into. Some multimeters have 2 possible places to plug the red lead into (like this one does). If yours has 2 possible places you need to plug it into the position NOT labeled as AMPS. On mine it is the far right where the red lead is plugged into in the photo.

This photo was taken for you. I used the barrel connectors to slip the leads into so I could take a photo without needing 3 hands. The reading shown is the resistance at the temperature currently inside my house. So in fact if you go to the thread where I was working on these you could tell me the temperature in my house from the resistance :) 

I think you mentioned you are in Florida so possibly your car would start without ECU enrichment. Bruce also mentioned a trick which I was also using which was turn the key to on (do not crank) to energize the fuel pumps. Then pump a couple of times. That will add some fuel. Bruce pointed out the car will not add fuel during cranking however if you are pumping during cranking. Anyway where I was going with that is if your car starts in very cold temp the coolant sensor is probably ok. Mine would start with the pump twice in the summer but it didn't start on a cold day in November. Again I'm not certain if the ECU is using the air temp sensor for other functions.

Scott

bcroe

Quote from: Joe Albanese
Scott.  Checking the two sensors was the first thing I checked.  Both related a resistance of 38.6.  When dipped into hot water they increased to 48.9 with just the hot water coming from the tap.  I'm not sure I had ohms set properly.  Was never certain how to gauge / set for resistance.  However since they both were exactly the same, they are either good or both equally bad. 

Joe,
That reading is completely out of range, either those are the wrong
sensors, or the meter is read wrong.  There are other sensors on the
engine, the physical difference is they have one connection and return
through ground.  The 70s EFI sensor has 2 wires and no ground circuit. 

Bruce Roe

79 Eldorado

Joe,
So you have a visual the photo below is the one we are talking about. There should be two. I don't have a photo of the other side of the connector unfortunately.

Scott