Idle Problem

[Hallaian42]

Today...i noticed that my throttle body was really dirty so i removed it from the car...I cleaned it thoroughly in a solvant tank and with brake cleaner. I also put in new spark plugs. Now when i rev the motor...it takes a long time for the RPM's to go back down...Sometimes it doesnt go back down at all. Did i damage the throttle body some how. Did i damage maybe the idle control valve? The linkage is fine i already checked it. Its a 72 240z but it has a 77 L28 w/ n47 ...Any ideas? THanks

P.s. if i tap on the top of the throttle body with a hammer... the idle goes back down.

[Graeme Suckling]

It seems you were too thorough in your cleaning:finger:

I find that if you squirt some CRC/WD40 or similar on all the rotating bits the motion of the butterfly etc. loosens up.:classic:

Then for good measure, drop some very light oil on all linkages and shafts.:devious:

Rotate the butterfly by hand to ensure there is no binding.

Lets face it, you haven't broken anything, just cleaned it:D

[Hallaian42]

I know for sure there is nothing wrong with the linkage...because i watch it...I push on the linkage with my hand to rev the motor and then it goes back to the original position but the rpms STAY. they do not go back down. Am i going crazy or is this a problem of the idle control valve or maybe the throttle valve switch? I aslo notice a hisssing noise comming from the right side of the intake manifold. I took out the injectors right before that too. I cant visual see a vacuum leak but it sure sounds like one.

[2ManyZs]

I'm not sure if this may be your problem, but it might be worth checking. There is a switch of some type in the back of the speedometer which has something to do with the idle. I had a 75 280 that would not idle down between shifts or when pulling up to a stoplight. I put another speedo in and the problem was cured. I can't remember what it is called and since I no longer have an FSM I can't look it up. Might be worth a look see.

A vacuum leak on the throttle control valve is also a good possibility, been a long time since I messed with FI much so can't remember a lot. :cross-eye

[carguyinok]

I have used WD40 in the past ta find vac. leaks. Others use starting fluid but the chance of fire I dont like. Take and spray the WD40 around where you think the leak could be (with the car running). If it is A vac\intake leak. With the WD40 you will see blue\white smoke from the tail pipe. With starting fluid you will see A RPM jump.

Did you put A new gasket in ? If not I would just order one now.

The other thing is with the brake parts cleaner you should as Graeme Suckling oil the butterfly. Inside & out while moving it open & closed. The brake parts cleaner will eat any grease and oil that may have been there.

Have fun & good luck.

[Hallaian42]

That is interesting that you would suggest that because i do not have a speedometer installed right now. But here's the thing...The car is a 72 240z with the 280z motor...The 240z speedo only has the little lightbulb connecters and the speedocable connector...no switch. This is what i did. I took the throttle body, fuel rail, and injectors out of the car. I thoroughly cleaned the throttle body with brake cleaner and solvent. The fuel rail i sprayed an anti-rust aluminum color coat on it and then i re-installed everything. Then i have this problem. The butterfly is closed...somehow air is getting in, which leads me back to think it is the idle valve... Where can i get one of these?

[Hallaian42]

i will try and oil the butterfly tomorrow. What kind of oil should i use? Just WD40? THanks for the help guys