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Here are the symptoms: When I touch the gas pedal gently - Engine speed drops.
When i remove foot from accelerator, engine speed grows.
When I push accelarator on low speed - 5mph - power drops, imidiately grows and engine little jerking
I already replaced : flowmeter and ISV
Could it be connectors of vacuum lines? One of them - on the throttle is loose.
There is link to YT clip of my idle:
I have the same characteristic operation on my 1990. I have always assumed it's just "the way it is" because of the way the ECU reacts to the switch indicating off-idle. I would be interested in hearing from any experts that can point out a way to "tune" this slight annoyance.
Also have the same behavior. Except my idle is a steady 1k rpm and drops to around 800 and comes back up much quicker. Can't figure out why it idles so high.
Thank all of You!
Today I replaced vacuum connectors and disconected batterie for few hours. I heard it hepls to addopting ecu ... but I ma not sure.
Next week i will have brand new ISV maybe it will help.
Your throttle butterfly is not open enough when in the fully-closed position, if that makes sense... Over years of use, the stop is worn away and the butterfly closes more and more till almost no air flows. The ISV shold supplement idle air, i.e. not provide all of it.
When you readjust make sure the throttle stop switch is sync'd to the new position.
I cannot find it... but there was an old service bulletin about the connector that plugs into the AFM. The wires were supposed to be folded back on themselves and tie wrapped. When I first bought my car, that wrap had been cut. I folded it back onto itself and have not had a problem since... other than, 1.) intake runner rubber sleeves were cracking and one had been torn /over tightened, especially the four large rubber sleeves holding the throttle body and resonance chamber 2.) previous owner had overfilled the oil and the intake had oil settling in the resonance chamber. 3. ) ISV valve was full of grunge. 4.) old/bad plugs. 5.) old/bad plug wires (they may look good, but on closer inspection, mine had been taped where they had been scraped. 6.) Caps and rotors looked good, but were old and worn... no hesitation now!
I think there is a little step forward ... maybe.
I still want to find reason why i have a hole in idle speed ... and ...
Look at the pictures.
Idle swich lost one screw! Was holding only by this one which is downstairs.
So, it ..... that idle swich was moved to the back. So i pushed it forward, and screw.
Now second thing.
On second picture is idle speed adjuster screw, some people calls this screw in that way.
Look, maybe this screw is not screw enough? So, it makes idle hole! Because when i push accelerator, idle swich turns of ISV, but throtle isnt open, and it makes idle drop?
It makes sense ...
So, the question is, how much of thread pitches is in yours engines?
Would You like to help me? So, i am looking forward for Your help
That is what I was saying about the butterfly being closed. Ideally you need to take off the butterfly housing (4 allen keys) to set the butterfly position. Then you can set the throttle closed switch accurately too. Fwiw, I set my butterfly to closed to a 0.7mm opening (I had some 0.7mm stainless lockwire...)
PhatPhlatSix
Great idea!
Nut i'm affraid abuot removing 4 bolts. Throttle removing, etc ...
I think about bolt adjustment. But i have to do it outside Wheater in Poland dosnt helps ... -5 deg of Celcius.
I will try to adjust with this small bolt. But i will only adjust on a free way of accelerator cable move.
Question about small nut. Is this 8 mm nut? Do You know?
today's news
After moving the idle switch, my engine lost a hole in power!!! And accelerates without jerking!!
During the weekend, I'll be setting adjust screw, because of reduce the time between the idle speed and throttle opening.
Of course engine still has idle drop and balanced to 880 after i push the accelerator and take my foot off ...
OK, so in order to get a good look at the throttle set screw and inside the intake I had to remove intake assemble from the engine. I was planning on doing this anyway to clean up an oil leak at the breather/temp/pressure gauge area so its two birds with one stone I guess!
After removing the intake tonight (and finding more oil than I expected in the plenums) I took a few photos:
-The first picture shows the throttle linkage with the two adjustment locations marked. #1 is the primary throttle stop set screw. #2 is the double set screw arrangement that determines how far the small butterfly opens before the large butterfly starts to move. Here you can see the part of the linkage that moves between the two opposing set screws.
-The second picture shows the position of the two butterfly valves when the throttle is is not being pressed. Both are closed tight.
-The third picture shows the position of the butterfly valves when the throttle has been pushed to the point where the small butterfly is opened to where where the mechanism starts to open the large butterfly. It looks the almost same a the previous photo but you can see a fine dark line at the edge of the small butterfly where it has opened a tiny amount.
- final picture shows Wide Open Throttle (WOT).
So the throttle assembly is designed to give a 3 step activation of the throttle which is adjustable via the set screws shown in the first pic:
1. As the gas pedal is pressed, the first tiny movement of the linkage deactivates the Idle microswitch. The butterfly control part of the linkage does not move away from the main throttle stop at this point.
2. Next the linkage simultaneously rotates away from the main throttle stop at adjustment #1 and the left side set screw of adjustment #2. The small butterfly begins to open.
3. The linkage contacts the right side set screw of adjustment #2 which starts to open the large butterfly. Pushing the gas pedal more continues to open both butterfly valves until WOT is reached.
This is a pretty complicated mechanism and I hope I have explained it clearly. If there is someone who can point to an adjustment procedure that covers the optimum setup for this it would be awesome!
12-05-2014, 05:10 PM
Idle speed drops when touch accelerator
Wheater in Poland dosnt helps ... -5 deg of Celcius.