Hey guys my car idles at 1500 rpms use to idle at 2000 but I tightened throttle bolt to drop it to 1500 and that's as low as it goes now and the idle is also bouncing not much bounces from 1500-1700 but also I was looking at my car and tps sensor looks different from others can't figure out if previous owner swapped it or not but anyone got any ideas on how I could drop it to 850 rpms and stop the bouncing?

 

I have the same yr car, your gonna have to check all your sensors to make sure they are working properly, check all your vacuum ports for leaks. I have discovered that I am missing a bunch of stuff that the idiot I got the car from pulled off thinking it would run better.

 

Yea thanks I think my idler control valve is out and I found a vacuum line that's not connected to throttle body plates.

 

Have you verified the difference between the primary plate and the secondary plates yet?

 

It's the first plates you see after taking off the intake.

 

The primary plate is a single plate that has a small hole in it. The other plates are the secondary plates and there are two sets of these plates (these are not primary plates, period!).

If you pull off the intake w/the engine off and the primary throttle plate is opened by more than a minute amount it is not a function of the BAC as the BAC only supplies extra metered air to the engine while it is running. The BAC does not cause this plate to be opened too much whether the car was running or not. If you have the intake removed from the throttlebody and played w/the throttle linkage in front of the throttlebody you would see how the plate moves in conjunction w/movement in the linkage. If you press downward on the linkage then the plate opens up. If it is already opened too much then you would try pressing in the opposite direction which would be upwards. If the plate closes then that tells you what is causing the problem. You can either play games and get absolutely nowhere in solving your problem or you can actually do something constructive and move foward in rectifying your problem.

 

Sorry for the frustration I'm 19 and anew rotary user but so far I noticed secondary plates closest to intake is always open and doesn't seem to close or move when I pull on throttle linkage. And that's pretty much all I can tell you sorry. And if you want to stop giving me advice that's fine too I appreciate what you have told me.

 

Are you looking at the throttlebody on a cold engine or after it has been warmed up? On a warmed engine the outer set of secondary plates will be opened while on a cold engine they would be closed.

 

It's cold and the plates are wide open

 

Can you post a pic?

 

It's dark right now I can do it tomorrow tho forsure. But also I noticed the linkage to open and close throttle plates looks a but rusted.

 

Do you know where I can get a idle control valve for my car as well that isn't $500-$950?

 

^The parts for sale forum on this site.

 

Satch!
While we're on the subject of throttle plates, the FSM says the secondary plates should be horizontal with the pedal fully depressed.
Is cable the only part in play or are there vac operated parts involved, too.
Sorry to interrupt.
Joe

 

Just the associated throttle linkages.

 

So I checked bvac seems good checked tps it's good checked for vacuum leaks no leaks any suggestions?

 

You were supposed to post a pic. We like pics! And the previous owner might have modified the throttlebody thus causing the high idle.

 

Are you sure about the (No Vacuum leaks?) I found that 9 out of 10 times that's the reason for a high idle.

 

Yea me and my mechanic went through it all and didn't find anything and from what it looks like my throttle body is stock next to my friend 87 FC and same thing the plates are always open. Really frustrating I can't figure it out think I might just sell it I have no idea....

 

The other thing I was thinking is low fuel pressure. Remember that they -and most engines do- idle rich with respect to a stoichiometric ratio. That's why when you open the throttle -or have a vacuum leak- and let in more air (getting more stoichiometric) the engine speeds up. Don't despair. This sounds like a simple problem. Well figure it out. Check your fuel pressure for now.

 

Alright and another thing I looked up in the forum is something called fast idle cam and stop screw

 

If the Fast Idle Cam was not set properly it would cause the throttle linkage on the front of the throttlebody to be pushed down. This is why you were asked to press upwards on the throttle linkage while idling to see if the idle speed dropped or not. Upwards and not downwards.

 

What is the stop screw also? And from what I have done pushing upwards doesn't change anything another thing that I noticed only 2 injectors are working and the motor runs one really weird thing is that me mechanic unplugged them all and car still ran

 

There are 4 injectors. Two are buried under the Intake Manifold. You're mechanic probably just unplugged the secondaries which are only used at higher rpms

 

And there are oil injectors as well so if the car runs after 4 injectors were removed then in addition to the secondary injectors being unplugged, which only work w/the engine above 3800 rpm and under load, you must have unplugged some of the oil injectors in the process. If this is so then your mechanic is not much of a mechanic.

The set screw affects the primary plate (you have but one of them). Your problem is likely attributed by the secondary plates (you have two sets and each set has two plates). If you would post a few pics of how they are set up and the linkage connected to them it would probably be helpful and this is 'your" car.

Again, the primary plate must be almost completely closed w/the engine running for it to idle at the proper speed. W/the intake removed you are not necessarily seeing how the primary plate is positioned while the engine is idling. The Fast Idle Cam on the rear of the throttlebody has a piston which rests upon an updide down screw and the screw is part of the throttle linkage. If you placed a large rubber vacuum cap on top of the screw such that the cap rests upon the Fast Idle Cam piston that would prevent the fast idle warmup which occurs on a cold engine. So, when this is done the idle speed would be close to 800 rpm right after starting a cold engine outside of the temporary 3000 rpm rev for that last for 17 seconds.

And w/regards to the secondary throttle plates the set which is furthest from the intake are the most important as when they are closed it prevents additional air from passing through the throttlebody even if the other set of secondary plates are opened.