99 Mustang GT won't idle - MustangForums.com


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Old 03-17-2017, 12:19 AM   #1
Eric D Jones
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Default 99 Mustang GT won't idle

A few weeks ago I purchased a 99 Mustang GT with a radiator leak. So, naturally, I bought a new radiator and installed it. After the install, the car won't idle. Car starts up fine but then dies immediately unless I give it gas. If I keep trying it then it'll occasionally idle very rough and low—around 800rpm or so.
I can't imagine putting in a new radiator having anything to do with the idling problem, but I still listed it anyway just by some chance it be relevant in some way.

I already replaced the IAC (I've read that is a lot of peoples problem) but it didn't change anything.
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Old 03-17-2017, 05:36 AM   #2
Z28KLR
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Classic symptom of vacuum leak or other source of unmetered air being drawn in.
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Old 03-17-2017, 10:05 AM   #3
Eric D Jones
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Quote:
Originally Posted by Z28KLR View Post
Classic symptom of vacuum leak or other source of unmetered air being drawn in.
That's one of the main things that I thought could be the problem, but I honestly don't really know how to check for vacuum leaks. I've tried inspecting the lines but I can't really tell just by looking at them.
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Old 03-17-2017, 06:11 PM   #4
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This may be a reach but if the rad was leaking and spraying anti-freeze it could have sprayed on some of the electrical connector, (inspect and clean all connectors) the next thing i would check is the TPS, pretty easy to do.
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Old 03-22-2017, 08:55 PM   #5
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Thank you to everyone who has replied. I've replaced a couple vacuum lines that I thought a leak could be coming from, replaced all spark plugs and coils, air filter, cleaned the MAF sensors, and the problem still persists.
Also, I bled the coolant system, I'm fairly certain that I got all the air pockets out
The car won't die if I give it gas, but it kind of shakes and smoke comes somewhere from under the car, I can't tell exactly where.
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