Hesitation off idle and no idle when cold

[omegac11]

I have a new to me 120K miles 1991 with CTSC. I have fixed several issues already with new ignition switch and main relay that was causing a bunch of weird electrical issues. Now that I can actually drive it on the road I noticed some other issues. It is 50 degrees outside. When cold the car starts right up but it will not idle. When you take your foot off the gas, the rpms drop to zero. Its not a matter of the mixture not correct and rough idle, its more like a carburetor car where the throttle blades just completely shut. After a few minutes of holding the throttle at 1500 rpm then it starts to idle by itself but the water temp gauge is still at the bottom when it starts idling by itself. The idle however hunts around from 500 to 900. After letting it warm up to full operating temp, when driving the car there is a lot off hesitation off idle and when stopping at a light the idle drops really low and hunts. I have searched the forum and maybe I need to clean the throttle body and maybe something wrong with idle or fast idle components? How about the bypass valve?

Thanx Prime in advance.....:smile:

 

[DDozier]

When you have idle issues and the car is stalling you have to look at the Fast Idle Valve (16500-PR7-A00) and the IAC (Idle air control valve 36450-PR7-A01). The fast Idle Valve uses engine coolant temp to open and close a bypass air passage in the Throtle body to allow the extra air needed to hold a hi idle durring engine warm up. The IAC is an electronic valve controlled by the ECU to control the air needed to maintain a consistant idle. The service manual will lay out the steps to diag either problem. Both valves can be filled with carbon and need to be cleaned but they ussually have to be replaced to get them to operate properly again. Since you have had electrical issues you need to follow the steps in the manual to make sure it is either mechanical or electrical so you do not spend a bunch of money on shot-gunning parts.

If you have hi idle issues it is almost always a vacuum leak and on a CTSC it is ussually the bypass hose or pipe.

Dave

 

[Valhalla]

Dirty throttle body. Spray some carburetor cleaner in there and that might do the trick. Start with something easy and least expensive and work your way up.

 

[dynomike]

you might have a high boost kit that comptech offered it ran a different fuel regulator and higher flow injectors. check your fuel pressure it should be around 43psi at idle. If it is lower you have a regulator that is going bad or a high boost kit. I would have car checked on dyno to verify