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Old 11-21-2007, 05:38 PM   #1
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1990 Mustang GT Rough Idle

EDIT: 1992 Mustang... if that matters

Hi,

My car has been running a little rough lately, mostly while the motor is cold. It will still hiccup when the engine warms up but not near as bad. Upon start up, the car will idle around 700-800 and jump around. The motor sounds like it has a miss every now and then. It also runs very rich during all this.

Once the motor warms up, it smooths out a lot but will still have a slight miss under part throttle just cruising around. It also still runs rich. WOT is great. I took it to the track and it ran perfect. The only mods on the car are offroad H-pipe and flowmaster catback and a smog pump delete.

I cleaned my MAF, adjusted the TPS to .95 and checked the IAC. All of this seems to be ok. I ran codes on the car and pulled a 67 and 85 on KOEO. KOER pulled 94 and 44.

Any clue on what I should check next? I'm kind of at a loss.

Last edited by XPTB; 11-21-2007 at 05:58 PM.
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Old 11-21-2007, 07:06 PM   #2
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time for cap and rotor change?
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Old 11-22-2007, 02:42 AM   #3
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Could be, the car has 166k miles on it. It is the original distributor from what I can tell. Just not sure if its that since it works great at WOT
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Old 11-22-2007, 10:08 AM   #4
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That would be my first guess..Now that the weather has changed problems will become more pronounced.Check your plugs also.
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Old 11-22-2007, 12:28 PM   #5
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I know plugs and wires are relatively new. I just bought the car and I'm trying to solve the problems the previous owner had. Someone suggested EGR?
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Old 11-22-2007, 03:17 PM   #6
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I disconnected that piece of junk. all that ever did was cause problems.
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Old 11-23-2007, 12:51 PM   #7
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Do you have to have it tuned or anything? I heard you can't just disconnect it without "telling the computer"
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Old 11-23-2007, 01:24 PM   #8
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I had an A9L computer in my gt.After disconnecting it if you have any issues or problems just reflash your computer.You may be right on that but in my experience i never had any issue or problem aftwr disconnecting it.Just make sure you cap your vacumn lines
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Old 12-07-2007, 10:15 PM   #9
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I think my rough idle is vacuum related. I found a few lines that are "capped" off. I do have a smog delete so I don't know if any of these go to that or not. If anyone could help point out what these lines are, that would be excellent.

# 1. Comes out under the Plenum.


#2. I think the red circled one goes to the smog pump. The green one is pretty long, I circled which wire it is going back into the connector.


# 3. This one is really long and is coming out of the passenger side fender. It reaches all the way up to the front of my intake.


Also, this car has a throttle body coolant bypass, but it isn't really bypassed. Previous owner just took the hoses off the TB and plugged them. Should I connect them back together?
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Old 12-07-2007, 11:18 PM   #10
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The white vacuum line with the red circle goes right below the intake tube to a fitting attached to the smog tube. The other long line goes to the back of the intake.
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