View Full Version : My Idle goes up and down

03-28-07, 09:28 PM
I have a 1992 Brougham RWD with a 5.0 TBI. When I turn on the car the engine is idleing just fine, with less then a mintue the motor starts to idle low and then idel up to normal what can be wrong

03-28-07, 09:41 PM
Any trouble codes? Sounds like an idle air control problem to me.

03-28-07, 09:43 PM
No codes, how can I check to make sure

03-29-07, 04:36 PM
There is likely a thermally-activated vacuum switch that is activating after a minute or so of running. Whatever is connected to this switch (or the switch itself) is leaking. You'll need to trace vacuum hoses to locate it. It helps greatly if you have a hand-operated vacuum pump to test the lines and other devices.

04-02-07, 10:49 PM
I changed all the vacuum holes and nothing same problem still, anyother suggestion

04-03-07, 11:52 AM
Have you cleaned the throttle body blades? They will cause this. Too high ignition timing will cause erratic idle as well.

Lean conditions can also cause erratic idle.

04-03-07, 05:07 PM
With the car on park I turn the steering wheel and the car goes to low idle like if it wants to turn off, almost like if I was running out of gas.

04-04-07, 04:09 PM
does any one have pictures or a diagram where I can check to make sure that the vacuum line are at the right place

04-04-07, 04:57 PM
I wish I did, I have nothing on the TBI cars except the 85 4.1L

04-04-07, 11:12 PM
This might be a smooth trick for people in search of a vacuum diagram: I have the Haynes and Chiltons manuals that cover something like 1970 to 1987. I don't think Haynes had a vacuum manual at all and Chiltons had a bunch to choose from. You are supposed to pick the one that looks the most like your car or something. Anyway, nothing really matched mine very well, so I called Haynes and said "Your book is missing the vacuum diagram that I need." The guy on the phone was actually really nice and sent me one by e-mail. It wasn't the greatest diagram, but maybe somebody else should try this and see if you have better luck.

04-05-07, 12:37 AM
Something to look for is PCV hose cracks and any other vacuum line crack. With that age, they are bound to be pretty brittle.

04-05-07, 05:07 PM
OK guys this is the update I purchased the car about a week ago and the owner told me that the car has a full tank, I been driving the car for two days and notes that the fuel gauge does not go down so I drop the gas tank down and I notes that the middle fuel line on the sending unit was lose from the sending unit, so I went too two auto parts and one has the sending unit so I came up with the idea of using JB welding, now do you guys thing that JB welding would work and do you guys thing this can be my idle problem also. When I'm at a red light the car turns off unless I accelerate a little then I stays on.

04-05-07, 08:21 PM
How is the fuel pressure? Can you check it?

Is vacuum line to Fuel Pressure Regulator (FPR) good? Put a vacuum pump on the line and a gauge on the port and check pressure with and without vacuum (you can use engine as "pump" too). I like pump because I can check the leakdown of the FPR too.

04-13-07, 01:42 PM
will JB welding does not work so I had to order a new sending unit I put it on and my fuel gauge is marking half a tank so now its wroking correct but I still have idle problems, I removed the idle control valve and cleaned it up a little but nothing, is the pin on the idle control valve supposed to be hard and stiff

04-15-07, 04:26 PM
I play with the timing and was able to set it where the car stop giving idle problems, so I think I found the problem:bouncy: