Question on LT4 starting and idle
Thread Starter
Instructor
Joined: Dec 2004
Posts: 112
Likes: 2
From: Roselle IL
Question on LT4 starting and idle
Hi everyone,
I have a 1996 LT4 with 33K miles on it that has developed a strange habit lately. It seems that since I refilled my gas tank to full (to avoid the massive increase in gas prices
), the car hesitates when I start it when it is cold.
For instance, I last drove it on Wednesday, and then drove it again tonight (Saturday). The car takes a few seconds of cranking (3-5 seconds) before it started both tonight and Wednesday. In addition, upon starting, it immediately idles at about 700 rpm instead of the usual 1500 or so upon cold start up. Does the summer weather have anything to do with this? Usually, it starts right up without any hesitation.
Once I drive it, it runs great, and starting it a few hours later causes no problem.
Also, I should mention that my A/C is currently blowing out of the top and floor only. Could this have an effect?
Anyone know what this may be?
Thanks
I have a 1996 LT4 with 33K miles on it that has developed a strange habit lately. It seems that since I refilled my gas tank to full (to avoid the massive increase in gas prices
), the car hesitates when I start it when it is cold. For instance, I last drove it on Wednesday, and then drove it again tonight (Saturday). The car takes a few seconds of cranking (3-5 seconds) before it started both tonight and Wednesday. In addition, upon starting, it immediately idles at about 700 rpm instead of the usual 1500 or so upon cold start up. Does the summer weather have anything to do with this? Usually, it starts right up without any hesitation.
Once I drive it, it runs great, and starting it a few hours later causes no problem.
Also, I should mention that my A/C is currently blowing out of the top and floor only. Could this have an effect?
Anyone know what this may be?
Thanks
Thread Starter
Instructor
Joined: Dec 2004
Posts: 112
Likes: 2
From: Roselle IL
Originally Posted by REDC4CORVETTE
Does the cruise control work?
Do you have a good connecton at the IAC?
Do you have a good connecton at the IAC?
I'm ignorant, so where and what is the IAC?
Thanks
Racer
Joined: Apr 2005
Posts: 408
Likes: 0
The hvac blowing out the defrost is a sign of a vacuum leak. These are vacuum controled on the manual ac controls. If you have the electronic ac controls with the little temperature display then I think those vents are not controled by vacuum, but rather by a solenoid.
I would check for any vacuum leaks on the various lines snaking around the engine bay, and especially any that travel into the interior through the firewall, as one of these is surely running to your hvac controls.
A vacuum leak should cause a higher idle however, not a lower one.
The engine idleing lower could just be higher outside temperatures. The engine temp sensor will read pretty low. I think I've seen as low as 80 degrees on the digital display.
The IAC is the idle air controller. This is a valve that controls how much air your engine receives at idle to run. It is located just below the bores on your throttle body. There is a connector running to it. You can see it from the passenger side with the hood up. There is a connector also running to your tps or throttle position sensor, located right next to it on your throttle body also.
I would check for any vacuum leaks on the various lines snaking around the engine bay, and especially any that travel into the interior through the firewall, as one of these is surely running to your hvac controls.
A vacuum leak should cause a higher idle however, not a lower one.
The engine idleing lower could just be higher outside temperatures. The engine temp sensor will read pretty low. I think I've seen as low as 80 degrees on the digital display.
The IAC is the idle air controller. This is a valve that controls how much air your engine receives at idle to run. It is located just below the bores on your throttle body. There is a connector running to it. You can see it from the passenger side with the hood up. There is a connector also running to your tps or throttle position sensor, located right next to it on your throttle body also.
Race Director
Joined: Oct 2002
Posts: 10,864
Likes: 198
From: Southern CA
Originally Posted by megatron
In addition, upon starting, it immediately idles at about 700 rpm instead of the usual 1500 or so upon cold start up.
Thanks
1500 is way too high for a cold start idle.
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Thread Starter
Instructor
Joined: Dec 2004
Posts: 112
Likes: 2
From: Roselle IL
Originally Posted by lt4red
The hvac blowing out the defrost is a sign of a vacuum leak. These are vacuum controled on the manual ac controls. If you have the electronic ac controls with the little temperature display then I think those vents are not controled by vacuum, but rather by a solenoid.
I would check for any vacuum leaks on the various lines snaking around the engine bay, and especially any that travel into the interior through the firewall, as one of these is surely running to your hvac controls.
A vacuum leak should cause a higher idle however, not a lower one.
The engine idleing lower could just be higher outside temperatures. The engine temp sensor will read pretty low. I think I've seen as low as 80 degrees on the digital display.
The IAC is the idle air controller. This is a valve that controls how much air your engine receives at idle to run. It is located just below the bores on your throttle body. There is a connector running to it. You can see it from the passenger side with the hood up. There is a connector also running to your tps or throttle position sensor, located right next to it on your throttle body also.
I would check for any vacuum leaks on the various lines snaking around the engine bay, and especially any that travel into the interior through the firewall, as one of these is surely running to your hvac controls.
A vacuum leak should cause a higher idle however, not a lower one.
The engine idleing lower could just be higher outside temperatures. The engine temp sensor will read pretty low. I think I've seen as low as 80 degrees on the digital display.
The IAC is the idle air controller. This is a valve that controls how much air your engine receives at idle to run. It is located just below the bores on your throttle body. There is a connector running to it. You can see it from the passenger side with the hood up. There is a connector also running to your tps or throttle position sensor, located right next to it on your throttle body also.
Thread Starter
Instructor
Joined: Dec 2004
Posts: 112
Likes: 2
From: Roselle IL
Thanks to everyone for their input. I think I may have just gotten some bad gas (or at least gas my car doesn't like) from BP Amoco. I'll stick to Shell in the future as my car seems to like this brand better.
Thanks
Thanks