When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Does the bottom of the air cleaner housing need to be removed to adjust the idle ---- or what ???
Please don't take this the wrong way...but if you don't know the answer to that...you shouldn't be messing with the throttle stop adjusting screw. Yes, you would need to remove the lower air cleaner housing, and then punch out a tin cap that is limiting access to the adjusting screw.
Idle speed should be controlled by the Idle Air Control valve & ECM. If the idle speed is beyond the ability of the ECM/IAC to control it, then you most likely have a sizable vacuum leak. Fix the vacuum leak.
Thanks I appreciate all the advice I can get. I saw images where adjustment can be made straight down after removing a plug. My shop manual has the adjustment from the back almost horizontal. I will take the bottom of the air cleaner off and get a good tach. I like the Carter AFB, I have about a half dozen, The Holleys remind me of flushing a toilet.
This C4 is the first gas injected, I have several diesel injected equipment.
I saw images where adjustment can be made straight down after removing a plug. My shop manual has the adjustment from the back almost horizontal.
If that's what your shop manual suggested, you need a new manual! What book do you have? If it's a Chilton or Haynes, please relegate those to the bottom of your bird cage.
The idle speed is controlled by the computer. The adjustments on your throttle bodies are used to balance the two throttle bodies. I have 240,000 miles on my '84, and those adjustments have never been touched! That's why they welded them at the factory!
Tom is correct. Find your vacuum leak. Think of it this way: If things are right, the computer will control both fuel and air to give you the correct idle speed. If you have a vacuum leak, the computer can't control the air flow, so the only thing it can do to maintain the proper air/fuel ratio, so the engine will run, is to provide more fuel, so the idle speed will therefore be too high! Way different than a dumb carburetor!
The manual I got was downloaded from Tradebit for $19 I would not recommend it as the images are poor and apparently some of the data is incorrect. Maybe the computer chip was reprogrammed.
I will check for vacuum leaks, WD 40 works good for that, although cheaper I don't like to use propane, especially in boats.
The reason I want to lower the rpm is it shifts hard into reverse and forward plus I don't like it idling that high.
Originally Posted by Hot Rod Roy
If that's what your shop manual suggested, you need a new manual! What book do you have? If it's a Chilton or Haynes, please relegate those to the bottom of your bird cage.
The idle speed is controlled by the computer. The adjustments on your throttle bodies are used to balance the two throttle bodies. I have 240,000 miles on my '84, and those adjustments have never been touched! That's why they welded them at the factory!
Tom is correct. Find your vacuum leak. Think of it this way: If things are right, the computer will control both fuel and air to give you the correct idle speed. If you have a vacuum leak, the computer can't control the air flow, so the only thing it can do to maintain the proper air/fuel ratio, so the engine will run, is to provide more fuel, so the idle speed will therefore be too high! Way different than a dumb carburetor!
800 + sometime. when i blip the throttle it will stay at 1200 to 1400 for a short time before dropping below 1000
the dash reading is inconsistent, I need a good tach.
I called a local AAmco about the shifting, he has worked on many Vettes, he will do an initial check at no charge.
Here is a link to some great pictures showing the procedure for balancing the throttle bodies. The article is for a 82 Crossfire but the same basic procedure. It will show where the plugs and adjustment screws are if you ever need that:
On my 84 I had vacuum leaks all over my engine including the top plate of the manifold. I got my idle back by fixing these leaks.
I did re-balance the throttle bodies after reaming out the throttle shaft bores on my throttle bodies and I installed bushings for the shaft to run in.
Thanks zachaeous I did a brief scan of your links, they should be very helpful.
It would be a wise idea to follow Tom's and Zachaeous' suggestions about vacuum leaks before you do any throttle body balancing procedures. If you have vacuum leaks, the balancing procedure will be a waste of time!
03-16-2018, 04:18 PM
How to lower idle rpm on a 1984 C4
