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C4 (89) red convertable greenwood pkg cant get idle right

  • Thread starter Thread starter Tedmag1
  • Start date Start date
T

Tedmag1

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I have to tap the peddle coming to a stop to idle down to 700 rpms or it will stay at 1100 rpms, just a light tap gets it down. This is what I did so far, first grounded out the alcl waited a min. unpluged IAC started the car adjusted idle to 400 RPMS in drive at an idle shut car off plugged IAC back in adjusted TPS to 0.54 volts STARTED CAR AND DROVE IT 40 MPH FOR 10 MINUTES no change!! Well after that I took off the IAC cleaned it real good inpsected the throttle body cleaned it ( at this time I took the time to ck the linkage for any hangups or play none ) re-installed the IAC well what a difference in fuel milage but still have the tap the peddle syndrome ( fuel mi went up 4-5 mi per gallon!!!) At this time I went back to the auto parts store bought a new IAC put it in re-set it the same way as before NO CHANGE STILL HAVE THE TAP THE PEDDLE SYNDROME Well the auto parts store let me return the NEW IAC (GOOD PEOPLE) SO I asked if they would do the same with a new TPS and they said yes so I put in the new one set the voltage drove it NO CHANGE what could it be the car runs really great other then that could it be a small vacum leak that I cant detect ? I also replaced the injectors I have perfect fuel pressure if that makes a diffence also everytime I took the throttle body off I would inspect it for any play or hangups there seem to be none the throttle snaps back real strong and hits the screww real hard . it has o be a small vacum leak !!! please if anyone has any insight abou this let me know ( I didnt have this problem before I changed my injectors I went with the bosch 111 flow mached no leaks perfect pressure thanks TED
 
YEAH every spare minute the dog and wife are getting jealous
 
Ted, first off, welcome to the Corvette Action Center!!

Since your post is more of a technical question, I'm going to move the thread to the C4 Technical and Performance Forum - HERE.

We want your post to receive the attention it deserves and the C4 T&P forum will give it better exposure.

Good luck with your issue... hope you can get it resolved soon.
:wJane Ann
 
I fought with that same problem for almost a yr off and on. It seemed to get worse right along. I installed a set of the Bosh injectors from FIC (which I needed because I had bad ones) it also seemed to make the problem worse. What I finally discovered is that my throttle shaft bore is worn. You will never be able to feel it with the engine running. I haven't taken care of the problem yet because winter is about here and it will sit till spring once the snow comes. For this reason I can't say absolutely that that is the problem.
BTW be sure to check all your grounds. Bad grounds can cause strange problems .

Glenn
:w
 
I had the same problem with my 89 and it went away when I changed the MAF burnoff relays. They are the two relays behind the battery on the firewall. Don't ask me why it worked???

Scott
 
What I finally discovered is that my throttle shaft bore is worn. You will never be able to feel it with the engine running.

:thumb
The fact that you can get the idle down by tapping the pedal indicates that something is binding up somewhere.
Engine vac pulls the blades to one side so they stick.
Try pulling over with the engine at the high idle revs , get out and see if you can knock the throttle closed further; you may find it is not fully back on the stop.
Also check for free momement of the cable. have been known to stick also
 
:thumb
The fact that you can get the idle down by tapping the pedal indicates that something is binding up somewhere.
Engine vac pulls the blades to one side so they stick.
Try pulling over with the engine at the high idle revs , get out and see if you can knock the throttle closed further; you may find it is not fully back on the stop.
Also check for free momement of the cable. have been known to stick also
yes the throttle has about a 16 th of an inch that i can tap back to the screw yes i have taken the throttle body off cleaned and examined it about five times (got it down to 7 minutes ) no damage no buildup snaps back to the stop screw real hard and fast re-set IAC according to the emanuel even replaced Iac no change put the old one back in and after cleaning it gained about 4 more miles per gallon but still have tap the peddle i even went so far as replacing the tps no change put the old one back re-set the Iac each time i dont think it is a vac leak I am leaning towards a throttle body hang up i saw no play in it when it was off need help
 

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