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Old 01-22-2011, 11:30 AM   #1
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Default 98 Bonny no idle when cold

It needs to have the gas pedal goosed to keep it running when cold, but once warmed up it idles OK. What could cause this?

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Old 01-22-2011, 11:32 AM   #2
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Check the idle air control. Clean it good.
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Old 01-22-2011, 12:28 PM   #3
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The idle air control is on top of the throttle body. It'* the one you can take out with out the tamper free screws. When you take it out it should look like a plunger. Use throttle body cleaner.
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Old 01-22-2011, 06:29 PM   #4
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I kind of thought it might be the IAC. We just replaced the upper intake (again) since it was leaking coolant, and the back of the throttle body was nice and gunky. What'* weird is that it took about a week or so after replacing the intake for this to start happening. At first the car would start up, dip to about 500 RPM, then come back to a more normal idle speed. Now you have to hold the gas to keep it alive for a bit. Once you start driving, it'* fine.
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Old 01-23-2011, 05:02 PM   #5
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I went ahead and pulled out the IAC and cleaned it. It looked fine, no buildup just a little black. One thing I've noticed is that the voltage is really low, like 10 or so when you fire it up and goes up a little past 14 while holding the gas. It'* a really old alternator, probably the original. Which would mean it has 210,000 miles on it. Think the car just doesn't have enough charge after starting and the computer gets a little fussy?
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Old 01-23-2011, 05:10 PM   #6
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That could very well be the problem. When the voltage drops the fuel pump slows down. Doing a fuel pressure test will show if this is the case.
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Old 01-23-2011, 11:42 PM   #7
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Actually, I rented a fuel pressure gauge from Autozone and it held steady around 45 psi. It dropped a little when I turned it on, but it leveled back out.

Also, cleaning the IAC didn't seem to solve my problem. I've checked for vacuum leaks and replaced a few hoses, mainly the one that goes to the regulator, but that didn't seem to help either. It'* really weird, you have to drive the car for it to start running correctly. My roommate thinks its running rich when fired up, so once it'* under load it figures things out and drives (and idles) well.
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Old 01-24-2011, 09:02 PM   #8
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If you can get a scan tool on it, read your CTS values (coolant temp sensor). When the car is cold and in open loop, the CTS plays such a massive part on engine fueling. If its bad, its prolly telling the PCM its like -30 degrees out so it fattenes up the injector pulsewidth and you run ruch, idle low and stall,. Once it warms up enough to light off the O2 sensor, it relies more on the O2 to check fueling, it then sees it rich and adjusts as needed.

Is your SES light on?? Even if it isnt, check for codes anyway. Most codes will hard set but dont throw an SES light.
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Old 01-25-2011, 01:25 PM   #9
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Alright, I'll try popping over to Autozone to see if I can read what the CTS is saying. The SES light hasn't come on yet, but the idle thing got a little worse today. I went ahead and started it up, revved it a little, held the gas to keep the engine around 1200 RPM, backed out of my driveway, started driving away, let off the gas to go around a turn and it died. It wouldn't start back up unless I gave it a good amount of gas. I had to kind of hobble it to school. I tried letting it idle in the parking lot, and it was around 600 RPM in drive.

I did a little searching through the forums to see if anyone else had this problem, and it sounds like some people have MAF problems. I unplugged it to see if it changed anything, but it still wouldn't idle (at all).
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Old 01-25-2011, 01:38 PM   #10
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If you suspect a voltage drop, don't forget to check the wiring. It is possible and likely that your power wiring in the engine bay has corroded if you are experiencing voltage drops. Just something else to check while you have the hood open. Look for wires that go from the battery, starter, and alternator.
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