SES solved - IAC related
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Safety Car
Joined: Aug 2013
Posts: 4,430
Likes: 608
From: Minneapolis Mn
SES solved - IAC related
86 Convertible, L98 engine.
Passing this along in case it helps someone else. I had some issues a couple of years ago where when it was below freezing at times (not every time) I'd start the car and it would run fine for a few blocks then run like crap, didn't do it every time but enough to be a pain. Get it back in the garage, let it sit about 30 minutes and it was fine. No codes or indications of issues. I found by chance if I rapped the IAC with a plastic hammer it fixed it for a few months (found by accident).
Lately with the temp falling, every time I'd start the car I'd get a SES light, and it hunted for idle for a couple of minutes. Soon as the temp gauge went from 'LO' to actually showing a temp the SES light went off and idle evened out. Again no codes though rapping the IAC with the plastic hammer fixed it at times.
Without a code it was guessing but what I saw said it was IAC related. Finally got around to having the IAC replaced along with the O2 sensor and everything is back to what it should be. I've started the car 3 or 4 times from cold and no SES while running.
Only reason I'm putting this out here is because there was never a code or definite condition that pointed to the IAC till I started rapping it with that plastic hammer. Hope it helps someone out.
Passing this along in case it helps someone else. I had some issues a couple of years ago where when it was below freezing at times (not every time) I'd start the car and it would run fine for a few blocks then run like crap, didn't do it every time but enough to be a pain. Get it back in the garage, let it sit about 30 minutes and it was fine. No codes or indications of issues. I found by chance if I rapped the IAC with a plastic hammer it fixed it for a few months (found by accident).
Lately with the temp falling, every time I'd start the car I'd get a SES light, and it hunted for idle for a couple of minutes. Soon as the temp gauge went from 'LO' to actually showing a temp the SES light went off and idle evened out. Again no codes though rapping the IAC with the plastic hammer fixed it at times.
Without a code it was guessing but what I saw said it was IAC related. Finally got around to having the IAC replaced along with the O2 sensor and everything is back to what it should be. I've started the car 3 or 4 times from cold and no SES while running.
Only reason I'm putting this out here is because there was never a code or definite condition that pointed to the IAC till I started rapping it with that plastic hammer. Hope it helps someone out.
Safety Car
Joined: May 2001
Posts: 4,759
Likes: 1,647
From: Fairfax Virginia
Thanks for sharing that with us! Too often the little things get to haunt us if we ignore them for a while.
On the Idle Air Control the shape of the pintle is critical and if the wrong shaped Pintle (The tip that controls the air flow) is used then is used the IAC doesn't work very well. All to often people don't compare the new one with the existing one from the Corvette. When I bought mine from a NAPA store they had two or three variations on the pintle and none matched the one that came with my 1988 C4 Coupe. I finally after looking for a while found the right tip for my Corvette and it worked fine after getting the correct replacement.
Oxygen sensors have a tremendous effect on the performance and economy. Most O2 sensors are too old which is a problem, the signal is weaker and lags behind the ECM which causes driving issues. I was taught to replace the O2 every 50 k miles or 24 months, this may be extreme but their optimal condition is needed for the best performance and economy of the Corvette. When my O2 sensor failed I had no lights warning me of it, the car would go into open mode to stay drive-able. Verifying that the O2 sensor is working is hard as the signal is between .1 and .9 volts and oscillates back and forth very quickly. Watching it work with a scanner will show it failed or is weak. I still replace my 02's every few years before they fail when least expected (or needed). The O2 sensor only works after it is properly warmed up, older units have a tendency to force the car into open loop when sitting at a light for a period of time.
It is good that people like you explain what solved your Corvette's issues! That is how we all learn here at the Corvette Forum! I appreciate your time and effort.
Best regards,
Chris
On the Idle Air Control the shape of the pintle is critical and if the wrong shaped Pintle (The tip that controls the air flow) is used then is used the IAC doesn't work very well. All to often people don't compare the new one with the existing one from the Corvette. When I bought mine from a NAPA store they had two or three variations on the pintle and none matched the one that came with my 1988 C4 Coupe. I finally after looking for a while found the right tip for my Corvette and it worked fine after getting the correct replacement.
Oxygen sensors have a tremendous effect on the performance and economy. Most O2 sensors are too old which is a problem, the signal is weaker and lags behind the ECM which causes driving issues. I was taught to replace the O2 every 50 k miles or 24 months, this may be extreme but their optimal condition is needed for the best performance and economy of the Corvette. When my O2 sensor failed I had no lights warning me of it, the car would go into open mode to stay drive-able. Verifying that the O2 sensor is working is hard as the signal is between .1 and .9 volts and oscillates back and forth very quickly. Watching it work with a scanner will show it failed or is weak. I still replace my 02's every few years before they fail when least expected (or needed). The O2 sensor only works after it is properly warmed up, older units have a tendency to force the car into open loop when sitting at a light for a period of time.
It is good that people like you explain what solved your Corvette's issues! That is how we all learn here at the Corvette Forum! I appreciate your time and effort.
Best regards,
Chris
