Idle dips and rises

S

surfaaron

Active LVC Member
Joined
Jul 23, 2004
Messages
115
Reaction score
0
Location
seattle washington
When I start up in the morning if I sit for a couple of minutes idleing the idle will dip(4or5hundred) and then rise(7or 8hundred) . I can put it into gear and it seems fine. Then I can be driving later in the day and be at a stop and it will do it again but more agressive and almost die or completly die. It always starts back. Any ideas.
 
Assuming you haven't done so already, it wouldn't hurt to service the engine.. New plugs, air cleaner, fuel filter, change the oil and oil filter. Dirty filters, especially gas and air could contribute to it hunting for the proper RPM.

A clogged fuel cap vent might do it.. a vacuum in the gas tank might restrict fuel flow somewhat... but my mind is wandering here..

----------
There may exist a slight vacuum leak. Vacuum is high when the throttle is closed (like at a stop sign or when warming up). A vacuum leak will throw things off, and it's difficult to maintain a steady, low RPM.

Once the throttle opens manifold vacuum drops (or rises, depending on your point of view) to near atmospheric, and a vacuum leak is more or less undetectable.
--------

Check anything that looks like a vacuum hose along with it's connections to the engine and to other components, for cracks, crimps looseness, etc..

If no luck, a vacuum component might be damaged. Some have a thin rubber membrane inside that distorts under vacuum, and that distortion mechanically pulls on something. If the membrane is old, brittle and cracked it leaks to some degree, and whatever it controls is then out of control.
These components' can be checked for integrity with a hand-held vacuum pump (maybe $15 at a tool store) carefully applied to it's inlet or hose.
 
Thanks Elesse for the ideas. I will give it all a check and let you know how it goes. The module sure had made a difference in how the car runs. Would be nice to figure out these other things as well.
 
I agree with E on the scheduled maintenance items.

Two big sources of surging at idle are the TPS and O2 sensors. If they're original, they need to be replaced.
 
I have done a complete tune up less than 3k ago and replaced the o2 snensors 10 or 15k ago . I think I am going to replace the tps. It looks to be the original one and I have 103k on the car. I may need some help figuring out how to use my multimeter to set it though. Not really that good with electronics. I am going to try to do it on thurs. I will let you know how it goes.
 
Tps

DSCF3107.sized.jpg

surfaaron said:
...I may need some help figuring out how to use my multimeter to set it though. Not really that good with electronics. I am going to try to do it on thurs. I will let you know how it goes.
Click to expand...
If you don't have a multimeter, then mark the position of where the screw sits in the large slot on the current TPS and transfer that mark to the new TPS and tighten the screw there.

That's the "Broke Dude" way of replacing it in a pinch :)
 
I have a multimeter just not sure if I am using it right. What setting do I want it to be on? The tps should be at .96-.98? Use the green wire with a paper clip or ? stuck down in the connection to get the reading?
 
I replaced the TPS and set it to.98. Idle is much better. Still has a little bump at idle but no hesitation and sits at 600 perfect. I am going to replace the o2 sensors next. Just wondering the best place to get them from at the best price. Does it matter if they come with the factory type plug or just pig tails?
 
surfaaron said:
This is what I have. Just not sure of what settings to us. Dont know a lot about using a multimeter.
Click to expand...

Multimeters come in handy.. check batteries for a charge.. an AC electrical outlet for power. There are lots of ways to use them. I see yours has a transistor identifier and checker.. useful if you're into electronics.

Google "how to use a multimeter" .. lots of hits.. lots of stuff to say about it.

You have two leads, one is red and one black. The black goes in the hole marked COM.. short for "common".
The red lead goes in either of the other two.. Voma (for measuring Volts, Ohms, and "ma" small amounts of DC current (milli-amps, or Amperage) , or the 10ADC hole, for up to 10 amps of DC current. (That's the only thing the 10ADC hole is used for.)

The dial..
DCV is Direct Current Volts (DC is basically battery power).
Use ACV to measure alternating current volts (AC like in a wall socket.)
Voltage can be thought of as the degree of electrical "pressure". High pressure is high voltage. Spark plugs need very high voltage to spark, like 30,000 volts.

DCA is DC Amperage.. Amperage is the "volume of flow" or amount of electricity flowing through a wire.
(10A is for 10 amps DC. Thats a lot of amps.. This setting is not fused. You'll toast the meter if you're not careful.
Use that special 10ADC hole for the red lead when dial is set to 10A)

Amps is sometimes called current.. think "flow of electricity" when you see either term. Flowing current like flowing water.. it's about the amount of water or electricity flowing past a point.

hFE is for measuring transistors.

the funny little symbol after that is for testing diodes..
------

That Omega symbol is for testing continuity. (it measures "ohms" or "resistance"). The dial offers scales from 200 ohms (very little resistance) to 2000k ohms (2,000,000 ohms.. very high resistance). Use the 200 setting for most common tasks like when searching for a faulty connection.

An ohms reading tells you if a wire is continuous or broken. A broken wire measures infinity or a very high number. A short length of unbroken wire (the wire is "continuous") measures Zero or a very low number, like 2 or 3 ohms..
A good connection between any two things.. two wires.. a wire and the frame of the car, etc.. will measure Zero.

A slightly bad, dirty connection will measure somewhere between Zero and infinity..
--------

IF you want to measure your battery voltage, or voltage flowing through wires in a car, set the dial to DCV , picking a scale a bit above what you expect.
You expect about 12 volts so use the 20 (it'll read 20 volts maximum scale) Apply more than 20 volts and the screen will probably show an error.

-----------
Be careful measuring amps.. it's too much to explain it here, but that thing has fuses.. they burn out when measuring amps improperly.. you won't need to measure amps on the car except in special circumstances.
 
i dunno.. never had to buy one. I'd probably call a Ford dealer or the Big Auto Parts Store Near You..

O2 sensors don't seem like the type of thing that needs to be redesigned and modified very often. And the hole they screw into has to be standard no matter the model car.. Since Ford doesn't manufacture them themselves, whoever does make the one for the Mark probably designed it to fit 20 years and 50 types of car.. but i'm guessing there.
 
if you buy motorcraft o2 sensors you will see the bosch logo next to the ford logo printed on the sensor.
I suggest doing both sensors at same time
 
You must log in or register to reply here.

Members online

No members online now.
Total: 134 (members: 0, guests: 134)
Back
Top