Hi to all . I have a 92 camaro rs 305 tbi that is having high rpms on start 3500 and stays between 1500 and 2500 on park an on drive between 1700 and 1500. This is fairly annoying because its burning my precise fuel that's expensive as it is . Now I have read a great tutorial on the site which is here https://www.thirdgen.org/tpimod2 but I ran into an issue. The idle speed torx screw section where you turn it clock wise to raise the rpm and counter clockwise to lower well the throttle doesn't go all the way back there's still a gap Any suggestions on my issue would be appreciated thank you .





in the picture you can clearly see the gap

 

Can you look down the TB to see the IAC cycle? I recall it cycles every time at key on.

Even if stuck wide open I doubt it will idle 3500 rpms. seems like a huge vac leak.

 

cant be a vac leak i replaced all the hoses or maybe it is. how dp i check for this vac leak?

 

Check the throttle body base gasket. You might find a chunk missing = vac leak common problem.

 

I just checked it last night I actually took the whole thing out and cleaned it was really junky and dirty but no difference . Here's a video .

 

Only way it can idle that high is with IAC setting incorrect or a vac leak

Did you inspect or replace all vac lines incl the brake booster. Could be a crack not detached which sometimes happens.

 

check your fuel pressure I think that can cause a high idle.

 

Your tach is reading wrong. The free rev shooting up over 7000 RPMs..... nah. Not in a million years could you get a stock TBI motor to rev anywhere near that high. Plus the ECM has a fuel shut-off that would kick in well below that point.

What is indicated on the tach as ~2000 sounds like about 800 or so to my ear.

 

typical shitty unreliable guages

 

What can I do about it ? Should I get an after marker one if so what kind thanks

 

There are known issues with the factory tach. In particular, there is one resistor that often goes out on the circuit board and usually causes the problem. Do a search- it's been addressed before.

 

Your car is idling fine buddy, its your tach. Its way off, you need to go to the wrecking yard and find one that works properly. FYI replace your battery instead cause your car is cranking slow and its building up a lot of resistance within the starter motor and will create a lot of heat within. That will ruin a good starter easily, and no need to rev this engine to moon especially when its not loaded. good luck

 

thank you all for your repliesssssssss

 

my 91 has the same issue
so its the tach that's bad? have been going nuts looking for vac leaks.... I shouldn't be able to rev that freely up to and beyond redline?

xavier_pr84
how does your car drive? have you noticed the tach reading higher while driving too.