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I have a question. Its regarding the "Fast idle adjusting screw" and the "cam adjusting screw", that's involved in Fast Idle Operation on the GSL-SE. Been reading all of the idle threads, and need some more details.
I was having an unusual 1300/1400 idle speed, (long story, just cleaned the injectors after a long hibernation) I serviced both injectors and the car came back to life.
It started and idled fine, but at 1300/1400, way high. ( been fiddling with it this week)
Yesterday I went adjusting the fast idle screw, thinking it was the idle stop screw ( kinda in the same area, big mistake). I must have went CCW ( dont recall, wished I wrote it down), and the idle did drop to about 1k, and after a while the car just died.
So I've been fiddling with it... and I guess I went to far, and can't get back to where I started. ( i did mess with idle richness screw, and the bleed screw too)
Well the car barely starts now, catches only, and I'm having a hard time putting the fast idle operation back to normal / standard operation. There seems to be multiple opportunities where the cam roller matches the 25C mark? on page 4B-46 in the FSM
1. Should I barely screw in the "cam adjusting screw" first , then adjust the "fast idle adjusting screw", so the cam roller matches the 25C mark?
Or is there another "standard operation procedure" to match the 25C mark to the cam roller, in order to set the fast idle?
there are two adjustments to the thermal wax, but you should make sure the hoses aren't plugged and there is actually coolant in there first
i would go in half turn increments too, and see what it does, they interact a little. at least that one is easy to get!
the bottom screw, i think decides the temperature the thermal wax does its thing. it should be "on" under about 65c, or the C mark on the gauge
the top circled one, i think does the engine speed. or how much the throttle gets opened. the factory setting is usually something like 1600-1800rpm, and every car is a little different.
i like to turn it down a bit, to more like 1200-1400, it in theory will warm the cat up slower, but save a little fuel
so the thermal wax on the FD's throttle body pushes the throttle open about 1mm or 0.040" so find a throttle stop on the primary and you should be in that ballpark
so the thermal wax on the FD's throttle body pushes the throttle open about 1mm or 0.040" so find a throttle stop on the primary and you should be in that ballpark
(Background) The car ran just fine on Saturday, although idled at 1300/1400 after the car was warmed up. Everything was fine, TPS, everything, coolant, fluids, etc. Revs to 7K.
The only adjustment I thought I was making...-> I messed up the top screw so much I don't know where I should be at. Hence why the car won't start and idle correctly.
( I thought that was the throttle stop screw, therefore by turning it, I would lower the idle rpms)
Which one of the two screws I circled above adjusts for the throttle opening ( Which is the top/primary throttle, when viewing from the passenger side)
I assume it's the top one, because tuning that will directly affect the TPS, and that would need to be readjusted immediately.
and I'm gonna ask a basic question. Primary throttle butterfly. Is it open (1.2mm) or closed, when the car is OFF.
In order to undo your changes to the Fast Idle Circuit, read through David Lanes instructions as linked above (* https://www.nellump.net/peri/tech/en...idle_problems/ ), and commit to memory what he's put together. It's a great resource, and the better your understanding of what he's written will remove the confusion around he SE Idle Control Circuits - there are several...
Take a look at these 2 pictures showing where your Fast Idle adjustment screws should be set. The top screw is nearly bottomed out, and the Lower screw needs to be somewhere near backed out fully so that it doesn't affect normal operating temperature idle speed;
If you can adjust these back to a starting position to remove their impact on normal running conditions (*warm engine, warm oil, normal operating temp), then we'll deal with these later. The top screw adjusts how far open the Throttle Plates are held, while the bottom screw controls at what point of Thermowax Pellet operation the Fast Idle Cam is committed. Set them as close as you can to my pics, as this gives a moderate ~2,500 RPM cold engine idle, and slides off the Cam easily once you start driving.
The purpose of the Fast Idle Cam and Thermowax Pellet are to allow more air into the system in cold weather conditions. The various Intake Air Temp and Coolant Temp sensors alert the ECU to a cold engine, which then adjusts fuel injector pulse duration to enrichen the mixture. The primary purpose is to accelerate the buildup of heat in the coolant by running the engine faster (to get cabin heat going quickly), and to get the Catalytic Converters (3) up to operating temp faster so they burn off emissions more efficiently.
Once you get the above taken care of, it should start and Idle acceptably well once warmed up. Note that the Fast Idle Cam engages during steady state throttle, like when you're sitting in your driveway on a cold day waiting for the heater, but once you start driving and the Throttle Plates are moving, the Cam is actuated by the Thermowax Pellet, and will eventually disengage, dropping to the standard idle speed of a warm engine. At this point, we can begin adjusting the ACTUAL idle speed.
To do this, you'll move to the forward facing section of the Throttle Body, specifically here;
These 2 highlighted screws adjust the Throttle Position Sensor (top) and Throttle Stop Screw (bottom). The TPS is adjusted using a 2-Light Rig, and is beyond the scope of this reply. Know that proper TPS adjustment is critical to avoid abrupt engine operation, stumbling at steady state cruising, and bumping on deceleration - so take your time adjusting it after setting it according to the FSM. I typically will set it to Factory spec, the go for a drive, making 1/8 turn adjustments back and forth until it's perfect for my driving style.
That 2nd screw lower down is the Throttle Stop Screw and is what controls how far closed the Throttle Plates will be when nothing else is keeping them open (*like the Fast Idle Cam...). Factory, this was a tiny, slotted head grub screw with a tiny lock nut facing out. You had to unlock the nut, rotate the threaded rod grub screw ever so slightly, and then lock down the nut without anything moving. It was annoying, so I replaced mine with a proper bolt with a spring under it to retain a tension. This allows for easier adjustment of idle. What you're looking for is approximately 800 RPM on a warm engine, with as smooth an idle as possible. Once set, it requires very rare adjustment.
Other Idle Circuit Adjustments and their net effects on idle quality and speed;
A) Idle Mixture Rheostat - located at the PS strut tower, this electrical adjustment was set at the factory and sealed with RTV to avoid people messing with it. It may provide a very slight idle quality improvement, but zero effect on idle speed. I don't recommend messing with it.
2) Air Bleed Screw - on the top of the Throttle Body, this silver screw in a recessed cut-out seems tempting as an idle speed adjustment. It's not. It only allows for a very slight change in air which bypasses the Throttle Plates at idle and provides little meaningful effect on idle speed or quality.
iii) Bypass Air Control Valve (BACV) - is actually 2 valves in one, electrically controlled by the solenoid bank immediately below it, and bumps up idle speed when your A/C compressor starts up to avoid bogging the engine down. It also compensates idle speed for high alternator draw and anything else which might slow the engine RPM temporarily. It is ineffective at setting idle speed - as it only increases it during certain situations.
That should get you started. My guess would be that once you put reconditioned Fuel Injectors in, the more efficient spray pattern resulted in better fuel atomization and combustion, as seen by higher idle speed. The incoming air was matched better for fuel efficiency, and an RPM increase was seen. This I'd as long as you didn't change anything else, just put it all back together and started it up. Possibly over time, as the Injectors were devolving in performance, your adjustments to keep the car running well added up. Dunno,...
The idle circuits on an SE are a bit complicated, especially for those coming from the Carbeurator world, but they have very logical and predictable performance to match the improvement due to Fuel Injection. Give that a go, and report back with findings,
Okay, starting at Step one. Getting a baseline. ( Right now the engine wont catch at all)
I took the throttle body off the car actually.
Lets start with the ( Top Screw ) Fast Idle Adjustment screw. ( I know this determines/sets the TOP Primary throttle plate).
Do I adjust the screw so that there's 1.2mm opening in the top butterfly. ( as shown in my picture)
Or am I wrong? I should adjust this screw so that the plate (circled in red) barely closes?
This screw seems to have a very wide range of "tightening"/ bottom out. I honestly don't know where to stop.
My throttle stop screw still has " goop" covering it right now, so I'm not messing with it.
I'm going to ignore the bottom screw ( cam adjusting screw) for now, because I can't even get it to turn/catch and idle right now.
Alright, man - since you've got the Throttle Body off of the car and in your hands, follow the FSM section 4B for setting the necessary clearances. Note that setting the Primary (*small) aperture is the single port at the top, and is what you're setting to spec. See the note about bending the tab to get proper clearance here, HOWEVER - if the car ran great before, I wouldn't go bending anything, just check to be sure you're within the FSM guidelines;
With that checked, NOW you can adjust the Fast Idle Cam to align the marks (*at 77degF), which should return your Fast Idle Adjustment screw to where it needs to be, as shown here;
This should be easier to see and set correctly with the Throttle Body out of the car. If everything looks right, I'd reinstall the Throttle Body to the intake and then go through my post above regarding how to set the Idle Speed.
Don't be afraid of the Throttle Stop Screw. The car is 40 years old, and you can't expect that what left the factory 40 years ago would still be perfect today. Lots of tolerances and sensor readings are likely off, and setting the proper idle speed will take some tinkering.
ohh man, super long morning.
So for some reason my current UIM and its throttle linkages will NOT let me adjust the primary butterfly to 1.2mm. (didnt want to disassemble the unit and get myself into more trouble right now)
I happen to have a spare UIM, but it was missing BOTH "fast idle screw" and "cam adjusting screw". Swapped them over, left 1.2mm clearance in the top butterfly, adjusted to where 25C cam should be. Installed. Cranked over, took 2/3 tries.
It caught and idled at 3K for 3-5mins. I didn't touch anything , when it got warmed up, revs came down to 1k, 800, then died... Well at least it's narrowed down to the UIM and the settings!
I tried a few more times to turn it over, but I assume the Thermo switch got warm, and the rod extended and (closed?) my primary throttle valve?
I didnt fiddle around with anything else, so I'm asking where do I go NEXT folks?
Remember, the Throttle Stop Screw (*threaded rod with lock nut) is what sets the minimum air passage at idle when no other Idle compensating circuit is in effect. This is how you set a baseline idle once all other systems are set.
Before you do that, though- it's worth making sure your TPS is set according to the FSM. It could be that the engine warmed up, the Fast Idle Cam slipped off of the lever and the Throttle Plates closed enough that the TPS said it wasn't idling. This is why the TPS is set with a warm engine and the Throttle Body at idle conditions.
I get you wanted to try something else by swapping to your spare intake, but doing so meàns you had to move over a number of parts and it has unknown Intake Air Temp Sensor and TPS positions. Good that you were able to set the Throttle Plates correctly, but now you're chasing more potential dragons. Give the above suggestions a try, and report back,
So I need to find a super small wrench first before I crack the nut that holds the Throttle Stop Screw. (looks like a 6 or 7mm?)
The car fired up again from cold ( took two tries) , but it did run up to 3000rpm and stayed there, until the Thermo Wax Rod warmed up and inched its way up ( I was observing it). After 3 mins of warm up, the engine bogs and died again.
Does the "cam roller" fall completely off the Fast Idle Cam once warmed up?
Just trying to understand the sequence of events, to better my understanding of the Fast Idle.
Thermo Wax rod warms and extends and enables the cam roller to rotate CCW, and the result is the Primary Throttle Valve ( Top) closes shut.
I've looked over page 4B-46 again, and it looks like I skipped over this step: below
Is it referring to the Primary Throttle Valve (I've set earlier to 1.1mm - 1.7mm) AGAIN? So now I have to adjust back down to 0.4mm-0.5mm (using the fast idle screw)? I'm a bit Confused
After the above is clarified, and if it's still running correctly..my next step is to unlock the "Throttle Stop Screw NUT" , and adjust the screw clockwise , maybe 1/4 or 1/2 turn at a time, in order to have the car idling. (but like I stated earlier, this screw has never been touched)
Does this sound reasonable?
Yes, that approach seems reasonable. Also, yes - when the Thermowax Pellet melts and extends, the Fast Idle Cam slips past the camming surface and moves freely. This is why the surface has a radius as shown below;
Once the Fast Idle Cam has slipped free of the actuator surface, it allows the Throttle to move freely - which is when your throttle drops clear, closes to the point that the Throttle Stop Screw allows for the standard (warm) engine idle speed, which on YOUR Throttle Body, closes completely, choking the engine off and it dies. I think the only way you can get it to idle will be to adjust the Throttle Stop screw so that when the Throttle Plates return to neutral, there's still a minimum flow of intake air to keep the engine running.
As it is now, you have zero Bypass Air coming in (*BACV closed off), likely the Air Bleed Screw cranked down, and not enough clearance on the Primary Throttle Plate to allow enough air into the engine to run.
ADDED: did you set your TPS? You really need to do that first, or any other adjustments will just throw it off if the TPS isn't reading correctly or isn't able to signal an idle condition for the ECU. DO THIS FIRST!
This Idle Adjust Screw (Red Above) is for the SECONDARY Throttle plates, correct?
(I've also consulted with some locals here over the weekend) There's also another Throttle Stop Screw just left of this area, that adjusts for the Primary Throttle Valve. (?)
Or does this info not matter? Just go ahead and adjust the above screw CLOCKWISE and get some gap in the secondary throttle plates, in order for the car to idle at least.
Your red-circled screw is the Throttle Stop Screw. It is the mechanical stopping point for the PRIMARY throttle plate. If you look at the back side of the Throttle Plate rod which it impinges, you'll see that both it and the TPS are activated off of that rod. It is a very fine thread pitch, so you can make very small changes to idle speed.
You set your TPS, yes? It's the most important thing you should do first before anything else right now.
USING THE SPARE - set up.
So yesterday, I was able to start the car using the Spare #2 throttle body, idled high for 3mins, then the car died as the rod extended. No other advances/adjustments yesterday. I didn't mess with the Throttle Stop Screws, as I'm thinking to myself the screws were still covered, and I was a bit uncomfortable to start messing with everything. (If everything is working correctly the throttle stop should be at the factory Throttle STOP setting.)
Today, I didn't start the car.
I put the TB's side by side, and noticed the above difference. The Spare #2 Throttle Body, Wax rod is extended at 6mm, when cold at room temp.
My original #1 Throttle body , the wax rod is only extended barely 3mm while at room temp, cold.
I have a hunch one of them is bad ( my original #1), since the #2 throttle body was able to start and at least warm up.
With #1 WaxRod only at 3mm, this led me to adjust the Fast Idle Operation incorrectly (OMG this really makes sense!) , and everything else downstream will be incorrect, even adjustment of the TPS.
Can I ask someone here with a GSLSE (LongDuck ) to help me find out how far the Wax Rod is extended when the car is cold? 6mm?
Then I'll know which one I have is working correctly, and then I'll go from there.
I can't test my original's Wax rod, because I can't get the car to start/ilde. Is there a way to check this parts correct operation (off the car)? I didn't seem to find any mention of this in the FSM.
Can I swap the #2 unit (*assuming its working properly) over to my original #1TB?
( I dont think this part is for sale anymore..#yikes)
Sorry it took me all day, I drove the SE today and I had to wait for it to cool down. This was taken at 70degF in my garage, cold engine, cold coolant, cold oil;
Caliper above the Dynamic Chamber reads 0.234", which in metric is; or about 6mm...
What this tells me is that you should use your #2 Throttle Body, HOWEVER - note that in your pictures, your Primary Throttle Rod is missing the Adjustment Screw and Spring for this setting. You'll need to swap that over from your original Throttle Body, and then set it according to the prior posts above from the FSM. Take your time and set the Fast Idle Cam position carefully, and you should be in business. Be especially mindful that the Primary Throttle Plate controls idle air volume, so you need to ensure you have the required tilt to the Primary Throttle Plate to get it to idle. Saving that, don't be afraid of the Throttle Stop Screw. It works wonderfully to set primary idle speed, with the Air Bleed Screw and Idle Mixture Rheostat being used for fine tuning of idle speed and idle quality.
At this point in the age of our cars and unavailability of replacement parts, I'm personally hesitant to swap brittle plastic parts in aluminum housings like the Thermowax Pellet. It's just too risky, and if you break something even as small as a plastic hose connection, you're using superglue and prayers that the repair will last.
Welps, I'm happy to say that the car is running this evening, and I'm embarrassed to report the cause of the issue here. First and foremost, THANKS to LongDuck with putting up with my questions and insistence that the Fast Idle screw and Spring was the root cause. IT WAS NOT.
Once it's set, that's it! ( But I do think that if the spring has been thoroughly crushed a few times, this would affect the primary butterfly gap/opening.) Shorter spring = smaller opening ( Turning screw CW compresses spring)
Let's cut to the chase, fuel gauge on the dash showed half tank. I went backwards to recheck the injectors this afternoon (they were clogged and serviced 3 weeks ago), performed bench test AGAIN. Wasn't squirting anything out. Clogged?! ( a 3rd time???). Tell me it aint so!... or geezz.. Maybe NO GAS? Pulled the supply line (which I am so familiar with) heading into the fuel rail, rigged the fuel pump from the test connector by the shock tower... viola... barely any juice. Looks like I found it!
Grabbed 5 gallons, primed the fuel pump, Started after 5 seconds of cranking. ( My fuel sender gauge will need to looked at since its still showing half tank) <-Problem
Last Tuesday when I was messing with the Fast Idle Screw, it just happened that the gas ran out MOST LIKELY, and I started blaming this action on the cause of the problem, leading to where I was chasing a ghost for 2 weeks. (remember my gas gauge showed half tank)
Things I learned.
Throttle Stop Set screw is 7mm, and its a B1tch to unlock. ( I managed to get one unlocked, but did not adjust the one used on the car)
Stock Thermo Wax Rod protrusion should be about 6mm.
Thermo Vacuum Valve is NLA - So please handle this part with care.
Make sure you have GAS!
It's idling at about 1k right now, I'm fine with it, but I think the cruise cable could be tugging it open.
Anyways, happy camper, it braps!
Thanks LongDuck, Thomas!
If you have your car idling 1K you should be able to "tweak" it down to 850 rpm by using the Air Adjust Screw (AAS) procedure on page 4B-64 in the FSM. This is the only adjustment I have ever had to make to my GSL-SE to maintain my idle at 850 rpm. As far as the idle mixture goes other than a failed resister, or engine change, it's best left alone.
I agree with SeniorChiefs comments above, and while it turned out to be a simple thing (*no gas!), it's better to be that than some of the more complicated things we'd have to dig into next.
Also, at this point, you've learned a TON about how the Fuel Injection, Air Induction, and ECU work to set idle speed on a Fuel injected SE! Most people won't know it to your level of depth, because you've actually had to tune the various adjustments to get it to run - the gas supply issue was just a red herring, and you figured it out quickly. Have you taken it on a short test drive to row it through the gears and ensure that everything is working right? That's the proof.
Get it out this weekend and report back if you have any bobbles. Setting the correct Idle Speed to 850 rpm at this point should be a few quarter-turns of a flat blade screwdriver and you'll have it where the FSM says it should be. Congratulations,... you won!
ive noticed on a car with the emissions equipment, that the mixture should be around the center if everything else is working correctly. if it runs the best with the thing maxed out, something else is wrong.
if you do not have the air pump/ACV then this doesn't apply and best idle mixture is with it maxed out. the "port air" is air pump air that is going to the exhaust ports, so when you remove that it changes the idle mixture
also if you messed with all the throttle stops and stuff, you should double check the TPS. i like to check it every 6 months or so anyways, they like to move around
As LongDuck mentioned in previous post the "importance" of a properly adjusted TPS on the GSL-SE and the fact that you didn't have what you needed to check the adjustment of your TPS. This hopefully will be an invaluable asset to have going forward now that you have gas and are on the road. Get two 12V LED bulbs (see amazon link below) and three male spade connectors and make yourself a TPS Test light and follow the adjustment steps on 4B-39, and happy motoring!
@Seniorchief Ohh I have one, its prolly 20yrs old. = )
Just a thought, see if you guys agree. If the car is cold, just flip the cam roller off the fast idle cam manually, and this should be "equivalent" to having the car warm, in order to get it in range of a warm engine?
02-21-24, 08:20 PM
) to help me find out how far the Wax Rod is extended when the car is cold? 6mm?
